File: | lib/Transforms/Scalar/SimpleLoopUnswitch.cpp |
Warning: | line 2361, column 24 The left operand of '>=' is a garbage value |
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1 | ///===- SimpleLoopUnswitch.cpp - Hoist loop-invariant control flow ---------===// | |||
2 | // | |||
3 | // The LLVM Compiler Infrastructure | |||
4 | // | |||
5 | // This file is distributed under the University of Illinois Open Source | |||
6 | // License. See LICENSE.TXT for details. | |||
7 | // | |||
8 | //===----------------------------------------------------------------------===// | |||
9 | ||||
10 | #include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h" | |||
11 | #include "llvm/ADT/DenseMap.h" | |||
12 | #include "llvm/ADT/STLExtras.h" | |||
13 | #include "llvm/ADT/Sequence.h" | |||
14 | #include "llvm/ADT/SetVector.h" | |||
15 | #include "llvm/ADT/SmallPtrSet.h" | |||
16 | #include "llvm/ADT/SmallVector.h" | |||
17 | #include "llvm/ADT/Statistic.h" | |||
18 | #include "llvm/ADT/Twine.h" | |||
19 | #include "llvm/Analysis/AssumptionCache.h" | |||
20 | #include "llvm/Analysis/CFG.h" | |||
21 | #include "llvm/Analysis/CodeMetrics.h" | |||
22 | #include "llvm/Analysis/InstructionSimplify.h" | |||
23 | #include "llvm/Analysis/LoopAnalysisManager.h" | |||
24 | #include "llvm/Analysis/LoopInfo.h" | |||
25 | #include "llvm/Analysis/LoopIterator.h" | |||
26 | #include "llvm/Analysis/LoopPass.h" | |||
27 | #include "llvm/Analysis/Utils/Local.h" | |||
28 | #include "llvm/IR/BasicBlock.h" | |||
29 | #include "llvm/IR/Constant.h" | |||
30 | #include "llvm/IR/Constants.h" | |||
31 | #include "llvm/IR/Dominators.h" | |||
32 | #include "llvm/IR/Function.h" | |||
33 | #include "llvm/IR/InstrTypes.h" | |||
34 | #include "llvm/IR/Instruction.h" | |||
35 | #include "llvm/IR/Instructions.h" | |||
36 | #include "llvm/IR/IntrinsicInst.h" | |||
37 | #include "llvm/IR/Use.h" | |||
38 | #include "llvm/IR/Value.h" | |||
39 | #include "llvm/Pass.h" | |||
40 | #include "llvm/Support/Casting.h" | |||
41 | #include "llvm/Support/Debug.h" | |||
42 | #include "llvm/Support/ErrorHandling.h" | |||
43 | #include "llvm/Support/GenericDomTree.h" | |||
44 | #include "llvm/Support/raw_ostream.h" | |||
45 | #include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h" | |||
46 | #include "llvm/Transforms/Utils/BasicBlockUtils.h" | |||
47 | #include "llvm/Transforms/Utils/Cloning.h" | |||
48 | #include "llvm/Transforms/Utils/LoopUtils.h" | |||
49 | #include "llvm/Transforms/Utils/ValueMapper.h" | |||
50 | #include <algorithm> | |||
51 | #include <cassert> | |||
52 | #include <iterator> | |||
53 | #include <numeric> | |||
54 | #include <utility> | |||
55 | ||||
56 | #define DEBUG_TYPE"simple-loop-unswitch" "simple-loop-unswitch" | |||
57 | ||||
58 | using namespace llvm; | |||
59 | ||||
60 | STATISTIC(NumBranches, "Number of branches unswitched")static llvm::Statistic NumBranches = {"simple-loop-unswitch", "NumBranches", "Number of branches unswitched", {0}, {false} }; | |||
61 | STATISTIC(NumSwitches, "Number of switches unswitched")static llvm::Statistic NumSwitches = {"simple-loop-unswitch", "NumSwitches", "Number of switches unswitched", {0}, {false} }; | |||
62 | STATISTIC(NumTrivial, "Number of unswitches that are trivial")static llvm::Statistic NumTrivial = {"simple-loop-unswitch", "NumTrivial" , "Number of unswitches that are trivial", {0}, {false}}; | |||
63 | ||||
64 | static cl::opt<bool> EnableNonTrivialUnswitch( | |||
65 | "enable-nontrivial-unswitch", cl::init(false), cl::Hidden, | |||
66 | cl::desc("Forcibly enables non-trivial loop unswitching rather than " | |||
67 | "following the configuration passed into the pass.")); | |||
68 | ||||
69 | static cl::opt<int> | |||
70 | UnswitchThreshold("unswitch-threshold", cl::init(50), cl::Hidden, | |||
71 | cl::desc("The cost threshold for unswitching a loop.")); | |||
72 | ||||
73 | /// Collect all of the loop invariant input values transitively used by the | |||
74 | /// homogeneous instruction graph from a given root. | |||
75 | /// | |||
76 | /// This essentially walks from a root recursively through loop variant operands | |||
77 | /// which have the exact same opcode and finds all inputs which are loop | |||
78 | /// invariant. For some operations these can be re-associated and unswitched out | |||
79 | /// of the loop entirely. | |||
80 | static TinyPtrVector<Value *> | |||
81 | collectHomogenousInstGraphLoopInvariants(Loop &L, Instruction &Root, | |||
82 | LoopInfo &LI) { | |||
83 | assert(!L.isLoopInvariant(&Root) &&(static_cast <bool> (!L.isLoopInvariant(&Root) && "Only need to walk the graph if root itself is not invariant." ) ? void (0) : __assert_fail ("!L.isLoopInvariant(&Root) && \"Only need to walk the graph if root itself is not invariant.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 84, __extension__ __PRETTY_FUNCTION__)) | |||
84 | "Only need to walk the graph if root itself is not invariant.")(static_cast <bool> (!L.isLoopInvariant(&Root) && "Only need to walk the graph if root itself is not invariant." ) ? void (0) : __assert_fail ("!L.isLoopInvariant(&Root) && \"Only need to walk the graph if root itself is not invariant.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 84, __extension__ __PRETTY_FUNCTION__)); | |||
85 | TinyPtrVector<Value *> Invariants; | |||
86 | ||||
87 | // Build a worklist and recurse through operators collecting invariants. | |||
88 | SmallVector<Instruction *, 4> Worklist; | |||
89 | SmallPtrSet<Instruction *, 8> Visited; | |||
90 | Worklist.push_back(&Root); | |||
91 | Visited.insert(&Root); | |||
92 | do { | |||
93 | Instruction &I = *Worklist.pop_back_val(); | |||
94 | for (Value *OpV : I.operand_values()) { | |||
95 | // Skip constants as unswitching isn't interesting for them. | |||
96 | if (isa<Constant>(OpV)) | |||
97 | continue; | |||
98 | ||||
99 | // Add it to our result if loop invariant. | |||
100 | if (L.isLoopInvariant(OpV)) { | |||
101 | Invariants.push_back(OpV); | |||
102 | continue; | |||
103 | } | |||
104 | ||||
105 | // If not an instruction with the same opcode, nothing we can do. | |||
106 | Instruction *OpI = dyn_cast<Instruction>(OpV); | |||
107 | if (!OpI || OpI->getOpcode() != Root.getOpcode()) | |||
108 | continue; | |||
109 | ||||
110 | // Visit this operand. | |||
111 | if (Visited.insert(OpI).second) | |||
112 | Worklist.push_back(OpI); | |||
113 | } | |||
114 | } while (!Worklist.empty()); | |||
115 | ||||
116 | return Invariants; | |||
117 | } | |||
118 | ||||
119 | static void replaceLoopInvariantUses(Loop &L, Value *Invariant, | |||
120 | Constant &Replacement) { | |||
121 | assert(!isa<Constant>(Invariant) && "Why are we unswitching on a constant?")(static_cast <bool> (!isa<Constant>(Invariant) && "Why are we unswitching on a constant?") ? void (0) : __assert_fail ("!isa<Constant>(Invariant) && \"Why are we unswitching on a constant?\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 121, __extension__ __PRETTY_FUNCTION__)); | |||
122 | ||||
123 | // Replace uses of LIC in the loop with the given constant. | |||
124 | for (auto UI = Invariant->use_begin(), UE = Invariant->use_end(); UI != UE;) { | |||
125 | // Grab the use and walk past it so we can clobber it in the use list. | |||
126 | Use *U = &*UI++; | |||
127 | Instruction *UserI = dyn_cast<Instruction>(U->getUser()); | |||
128 | ||||
129 | // Replace this use within the loop body. | |||
130 | if (UserI && L.contains(UserI)) | |||
131 | U->set(&Replacement); | |||
132 | } | |||
133 | } | |||
134 | ||||
135 | /// Check that all the LCSSA PHI nodes in the loop exit block have trivial | |||
136 | /// incoming values along this edge. | |||
137 | static bool areLoopExitPHIsLoopInvariant(Loop &L, BasicBlock &ExitingBB, | |||
138 | BasicBlock &ExitBB) { | |||
139 | for (Instruction &I : ExitBB) { | |||
140 | auto *PN = dyn_cast<PHINode>(&I); | |||
141 | if (!PN) | |||
142 | // No more PHIs to check. | |||
143 | return true; | |||
144 | ||||
145 | // If the incoming value for this edge isn't loop invariant the unswitch | |||
146 | // won't be trivial. | |||
147 | if (!L.isLoopInvariant(PN->getIncomingValueForBlock(&ExitingBB))) | |||
148 | return false; | |||
149 | } | |||
150 | llvm_unreachable("Basic blocks should never be empty!")::llvm::llvm_unreachable_internal("Basic blocks should never be empty!" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 150); | |||
151 | } | |||
152 | ||||
153 | /// Insert code to test a set of loop invariant values, and conditionally branch | |||
154 | /// on them. | |||
155 | static void buildPartialUnswitchConditionalBranch(BasicBlock &BB, | |||
156 | ArrayRef<Value *> Invariants, | |||
157 | bool Direction, | |||
158 | BasicBlock &UnswitchedSucc, | |||
159 | BasicBlock &NormalSucc) { | |||
160 | IRBuilder<> IRB(&BB); | |||
161 | Value *Cond = Invariants.front(); | |||
162 | for (Value *Invariant : | |||
163 | make_range(std::next(Invariants.begin()), Invariants.end())) | |||
164 | if (Direction) | |||
165 | Cond = IRB.CreateOr(Cond, Invariant); | |||
166 | else | |||
167 | Cond = IRB.CreateAnd(Cond, Invariant); | |||
168 | ||||
169 | IRB.CreateCondBr(Cond, Direction ? &UnswitchedSucc : &NormalSucc, | |||
170 | Direction ? &NormalSucc : &UnswitchedSucc); | |||
171 | } | |||
172 | ||||
173 | /// Rewrite the PHI nodes in an unswitched loop exit basic block. | |||
174 | /// | |||
175 | /// Requires that the loop exit and unswitched basic block are the same, and | |||
176 | /// that the exiting block was a unique predecessor of that block. Rewrites the | |||
177 | /// PHI nodes in that block such that what were LCSSA PHI nodes become trivial | |||
178 | /// PHI nodes from the old preheader that now contains the unswitched | |||
179 | /// terminator. | |||
180 | static void rewritePHINodesForUnswitchedExitBlock(BasicBlock &UnswitchedBB, | |||
181 | BasicBlock &OldExitingBB, | |||
182 | BasicBlock &OldPH) { | |||
183 | for (PHINode &PN : UnswitchedBB.phis()) { | |||
184 | // When the loop exit is directly unswitched we just need to update the | |||
185 | // incoming basic block. We loop to handle weird cases with repeated | |||
186 | // incoming blocks, but expect to typically only have one operand here. | |||
187 | for (auto i : seq<int>(0, PN.getNumOperands())) { | |||
188 | assert(PN.getIncomingBlock(i) == &OldExitingBB &&(static_cast <bool> (PN.getIncomingBlock(i) == &OldExitingBB && "Found incoming block different from unique predecessor!" ) ? void (0) : __assert_fail ("PN.getIncomingBlock(i) == &OldExitingBB && \"Found incoming block different from unique predecessor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 189, __extension__ __PRETTY_FUNCTION__)) | |||
189 | "Found incoming block different from unique predecessor!")(static_cast <bool> (PN.getIncomingBlock(i) == &OldExitingBB && "Found incoming block different from unique predecessor!" ) ? void (0) : __assert_fail ("PN.getIncomingBlock(i) == &OldExitingBB && \"Found incoming block different from unique predecessor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 189, __extension__ __PRETTY_FUNCTION__)); | |||
190 | PN.setIncomingBlock(i, &OldPH); | |||
191 | } | |||
192 | } | |||
193 | } | |||
194 | ||||
195 | /// Rewrite the PHI nodes in the loop exit basic block and the split off | |||
196 | /// unswitched block. | |||
197 | /// | |||
198 | /// Because the exit block remains an exit from the loop, this rewrites the | |||
199 | /// LCSSA PHI nodes in it to remove the unswitched edge and introduces PHI | |||
200 | /// nodes into the unswitched basic block to select between the value in the | |||
201 | /// old preheader and the loop exit. | |||
202 | static void rewritePHINodesForExitAndUnswitchedBlocks(BasicBlock &ExitBB, | |||
203 | BasicBlock &UnswitchedBB, | |||
204 | BasicBlock &OldExitingBB, | |||
205 | BasicBlock &OldPH, | |||
206 | bool FullUnswitch) { | |||
207 | assert(&ExitBB != &UnswitchedBB &&(static_cast <bool> (&ExitBB != &UnswitchedBB && "Must have different loop exit and unswitched blocks!") ? void (0) : __assert_fail ("&ExitBB != &UnswitchedBB && \"Must have different loop exit and unswitched blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 208, __extension__ __PRETTY_FUNCTION__)) | |||
208 | "Must have different loop exit and unswitched blocks!")(static_cast <bool> (&ExitBB != &UnswitchedBB && "Must have different loop exit and unswitched blocks!") ? void (0) : __assert_fail ("&ExitBB != &UnswitchedBB && \"Must have different loop exit and unswitched blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 208, __extension__ __PRETTY_FUNCTION__)); | |||
209 | Instruction *InsertPt = &*UnswitchedBB.begin(); | |||
210 | for (PHINode &PN : ExitBB.phis()) { | |||
211 | auto *NewPN = PHINode::Create(PN.getType(), /*NumReservedValues*/ 2, | |||
212 | PN.getName() + ".split", InsertPt); | |||
213 | ||||
214 | // Walk backwards over the old PHI node's inputs to minimize the cost of | |||
215 | // removing each one. We have to do this weird loop manually so that we | |||
216 | // create the same number of new incoming edges in the new PHI as we expect | |||
217 | // each case-based edge to be included in the unswitched switch in some | |||
218 | // cases. | |||
219 | // FIXME: This is really, really gross. It would be much cleaner if LLVM | |||
220 | // allowed us to create a single entry for a predecessor block without | |||
221 | // having separate entries for each "edge" even though these edges are | |||
222 | // required to produce identical results. | |||
223 | for (int i = PN.getNumIncomingValues() - 1; i >= 0; --i) { | |||
224 | if (PN.getIncomingBlock(i) != &OldExitingBB) | |||
225 | continue; | |||
226 | ||||
227 | Value *Incoming = PN.getIncomingValue(i); | |||
228 | if (FullUnswitch) | |||
229 | // No more edge from the old exiting block to the exit block. | |||
230 | PN.removeIncomingValue(i); | |||
231 | ||||
232 | NewPN->addIncoming(Incoming, &OldPH); | |||
233 | } | |||
234 | ||||
235 | // Now replace the old PHI with the new one and wire the old one in as an | |||
236 | // input to the new one. | |||
237 | PN.replaceAllUsesWith(NewPN); | |||
238 | NewPN->addIncoming(&PN, &ExitBB); | |||
239 | } | |||
240 | } | |||
241 | ||||
242 | /// Hoist the current loop up to the innermost loop containing a remaining exit. | |||
243 | /// | |||
244 | /// Because we've removed an exit from the loop, we may have changed the set of | |||
245 | /// loops reachable and need to move the current loop up the loop nest or even | |||
246 | /// to an entirely separate nest. | |||
247 | static void hoistLoopToNewParent(Loop &L, BasicBlock &Preheader, | |||
248 | DominatorTree &DT, LoopInfo &LI) { | |||
249 | // If the loop is already at the top level, we can't hoist it anywhere. | |||
250 | Loop *OldParentL = L.getParentLoop(); | |||
251 | if (!OldParentL) | |||
252 | return; | |||
253 | ||||
254 | SmallVector<BasicBlock *, 4> Exits; | |||
255 | L.getExitBlocks(Exits); | |||
256 | Loop *NewParentL = nullptr; | |||
257 | for (auto *ExitBB : Exits) | |||
258 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) | |||
259 | if (!NewParentL || NewParentL->contains(ExitL)) | |||
260 | NewParentL = ExitL; | |||
261 | ||||
262 | if (NewParentL == OldParentL) | |||
263 | return; | |||
264 | ||||
265 | // The new parent loop (if different) should always contain the old one. | |||
266 | if (NewParentL) | |||
267 | assert(NewParentL->contains(OldParentL) &&(static_cast <bool> (NewParentL->contains(OldParentL ) && "Can only hoist this loop up the nest!") ? void ( 0) : __assert_fail ("NewParentL->contains(OldParentL) && \"Can only hoist this loop up the nest!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 268, __extension__ __PRETTY_FUNCTION__)) | |||
268 | "Can only hoist this loop up the nest!")(static_cast <bool> (NewParentL->contains(OldParentL ) && "Can only hoist this loop up the nest!") ? void ( 0) : __assert_fail ("NewParentL->contains(OldParentL) && \"Can only hoist this loop up the nest!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 268, __extension__ __PRETTY_FUNCTION__)); | |||
269 | ||||
270 | // The preheader will need to move with the body of this loop. However, | |||
271 | // because it isn't in this loop we also need to update the primary loop map. | |||
272 | assert(OldParentL == LI.getLoopFor(&Preheader) &&(static_cast <bool> (OldParentL == LI.getLoopFor(&Preheader ) && "Parent loop of this loop should contain this loop's preheader!" ) ? void (0) : __assert_fail ("OldParentL == LI.getLoopFor(&Preheader) && \"Parent loop of this loop should contain this loop's preheader!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 273, __extension__ __PRETTY_FUNCTION__)) | |||
273 | "Parent loop of this loop should contain this loop's preheader!")(static_cast <bool> (OldParentL == LI.getLoopFor(&Preheader ) && "Parent loop of this loop should contain this loop's preheader!" ) ? void (0) : __assert_fail ("OldParentL == LI.getLoopFor(&Preheader) && \"Parent loop of this loop should contain this loop's preheader!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 273, __extension__ __PRETTY_FUNCTION__)); | |||
274 | LI.changeLoopFor(&Preheader, NewParentL); | |||
275 | ||||
276 | // Remove this loop from its old parent. | |||
277 | OldParentL->removeChildLoop(&L); | |||
278 | ||||
279 | // Add the loop either to the new parent or as a top-level loop. | |||
280 | if (NewParentL) | |||
281 | NewParentL->addChildLoop(&L); | |||
282 | else | |||
283 | LI.addTopLevelLoop(&L); | |||
284 | ||||
285 | // Remove this loops blocks from the old parent and every other loop up the | |||
286 | // nest until reaching the new parent. Also update all of these | |||
287 | // no-longer-containing loops to reflect the nesting change. | |||
288 | for (Loop *OldContainingL = OldParentL; OldContainingL != NewParentL; | |||
289 | OldContainingL = OldContainingL->getParentLoop()) { | |||
290 | llvm::erase_if(OldContainingL->getBlocksVector(), | |||
291 | [&](const BasicBlock *BB) { | |||
292 | return BB == &Preheader || L.contains(BB); | |||
293 | }); | |||
294 | ||||
295 | OldContainingL->getBlocksSet().erase(&Preheader); | |||
296 | for (BasicBlock *BB : L.blocks()) | |||
297 | OldContainingL->getBlocksSet().erase(BB); | |||
298 | ||||
299 | // Because we just hoisted a loop out of this one, we have essentially | |||
300 | // created new exit paths from it. That means we need to form LCSSA PHI | |||
301 | // nodes for values used in the no-longer-nested loop. | |||
302 | formLCSSA(*OldContainingL, DT, &LI, nullptr); | |||
303 | ||||
304 | // We shouldn't need to form dedicated exits because the exit introduced | |||
305 | // here is the (just split by unswitching) preheader. As such, it is | |||
306 | // necessarily dedicated. | |||
307 | assert(OldContainingL->hasDedicatedExits() &&(static_cast <bool> (OldContainingL->hasDedicatedExits () && "Unexpected predecessor of hoisted loop preheader!" ) ? void (0) : __assert_fail ("OldContainingL->hasDedicatedExits() && \"Unexpected predecessor of hoisted loop preheader!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 308, __extension__ __PRETTY_FUNCTION__)) | |||
308 | "Unexpected predecessor of hoisted loop preheader!")(static_cast <bool> (OldContainingL->hasDedicatedExits () && "Unexpected predecessor of hoisted loop preheader!" ) ? void (0) : __assert_fail ("OldContainingL->hasDedicatedExits() && \"Unexpected predecessor of hoisted loop preheader!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 308, __extension__ __PRETTY_FUNCTION__)); | |||
309 | } | |||
310 | } | |||
311 | ||||
312 | /// Unswitch a trivial branch if the condition is loop invariant. | |||
313 | /// | |||
314 | /// This routine should only be called when loop code leading to the branch has | |||
315 | /// been validated as trivial (no side effects). This routine checks if the | |||
316 | /// condition is invariant and one of the successors is a loop exit. This | |||
317 | /// allows us to unswitch without duplicating the loop, making it trivial. | |||
318 | /// | |||
319 | /// If this routine fails to unswitch the branch it returns false. | |||
320 | /// | |||
321 | /// If the branch can be unswitched, this routine splits the preheader and | |||
322 | /// hoists the branch above that split. Preserves loop simplified form | |||
323 | /// (splitting the exit block as necessary). It simplifies the branch within | |||
324 | /// the loop to an unconditional branch but doesn't remove it entirely. Further | |||
325 | /// cleanup can be done with some simplify-cfg like pass. | |||
326 | /// | |||
327 | /// If `SE` is not null, it will be updated based on the potential loop SCEVs | |||
328 | /// invalidated by this. | |||
329 | static bool unswitchTrivialBranch(Loop &L, BranchInst &BI, DominatorTree &DT, | |||
330 | LoopInfo &LI, ScalarEvolution *SE) { | |||
331 | assert(BI.isConditional() && "Can only unswitch a conditional branch!")(static_cast <bool> (BI.isConditional() && "Can only unswitch a conditional branch!" ) ? void (0) : __assert_fail ("BI.isConditional() && \"Can only unswitch a conditional branch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 331, __extension__ __PRETTY_FUNCTION__)); | |||
332 | LLVM_DEBUG(dbgs() << " Trying to unswitch branch: " << BI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Trying to unswitch branch: " << BI << "\n"; } } while (false); | |||
333 | ||||
334 | // The loop invariant values that we want to unswitch. | |||
335 | TinyPtrVector<Value *> Invariants; | |||
336 | ||||
337 | // When true, we're fully unswitching the branch rather than just unswitching | |||
338 | // some input conditions to the branch. | |||
339 | bool FullUnswitch = false; | |||
340 | ||||
341 | if (L.isLoopInvariant(BI.getCondition())) { | |||
342 | Invariants.push_back(BI.getCondition()); | |||
343 | FullUnswitch = true; | |||
344 | } else { | |||
345 | if (auto *CondInst = dyn_cast<Instruction>(BI.getCondition())) | |||
346 | Invariants = collectHomogenousInstGraphLoopInvariants(L, *CondInst, LI); | |||
347 | if (Invariants.empty()) | |||
348 | // Couldn't find invariant inputs! | |||
349 | return false; | |||
350 | } | |||
351 | ||||
352 | // Check that one of the branch's successors exits, and which one. | |||
353 | bool ExitDirection = true; | |||
354 | int LoopExitSuccIdx = 0; | |||
355 | auto *LoopExitBB = BI.getSuccessor(0); | |||
356 | if (L.contains(LoopExitBB)) { | |||
357 | ExitDirection = false; | |||
358 | LoopExitSuccIdx = 1; | |||
359 | LoopExitBB = BI.getSuccessor(1); | |||
360 | if (L.contains(LoopExitBB)) | |||
361 | return false; | |||
362 | } | |||
363 | auto *ContinueBB = BI.getSuccessor(1 - LoopExitSuccIdx); | |||
364 | auto *ParentBB = BI.getParent(); | |||
365 | if (!areLoopExitPHIsLoopInvariant(L, *ParentBB, *LoopExitBB)) | |||
366 | return false; | |||
367 | ||||
368 | // When unswitching only part of the branch's condition, we need the exit | |||
369 | // block to be reached directly from the partially unswitched input. This can | |||
370 | // be done when the exit block is along the true edge and the branch condition | |||
371 | // is a graph of `or` operations, or the exit block is along the false edge | |||
372 | // and the condition is a graph of `and` operations. | |||
373 | if (!FullUnswitch) { | |||
374 | if (ExitDirection) { | |||
375 | if (cast<Instruction>(BI.getCondition())->getOpcode() != Instruction::Or) | |||
376 | return false; | |||
377 | } else { | |||
378 | if (cast<Instruction>(BI.getCondition())->getOpcode() != Instruction::And) | |||
379 | return false; | |||
380 | } | |||
381 | } | |||
382 | ||||
383 | LLVM_DEBUG({do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: " << BI << "\n"; for (Value *Invariant : Invariants ) { dbgs() << " " << *Invariant << " == true" ; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs () << "\n"; } }; } } while (false) | |||
384 | dbgs() << " unswitching trivial invariant conditions for: " << BIdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: " << BI << "\n"; for (Value *Invariant : Invariants ) { dbgs() << " " << *Invariant << " == true" ; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs () << "\n"; } }; } } while (false) | |||
385 | << "\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: " << BI << "\n"; for (Value *Invariant : Invariants ) { dbgs() << " " << *Invariant << " == true" ; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs () << "\n"; } }; } } while (false) | |||
386 | for (Value *Invariant : Invariants) {do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: " << BI << "\n"; for (Value *Invariant : Invariants ) { dbgs() << " " << *Invariant << " == true" ; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs () << "\n"; } }; } } while (false) | |||
387 | dbgs() << " " << *Invariant << " == true";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: " << BI << "\n"; for (Value *Invariant : Invariants ) { dbgs() << " " << *Invariant << " == true" ; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs () << "\n"; } }; } } while (false) | |||
388 | if (Invariant != Invariants.back())do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: " << BI << "\n"; for (Value *Invariant : Invariants ) { dbgs() << " " << *Invariant << " == true" ; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs () << "\n"; } }; } } while (false) | |||
389 | dbgs() << " ||";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: " << BI << "\n"; for (Value *Invariant : Invariants ) { dbgs() << " " << *Invariant << " == true" ; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs () << "\n"; } }; } } while (false) | |||
390 | dbgs() << "\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: " << BI << "\n"; for (Value *Invariant : Invariants ) { dbgs() << " " << *Invariant << " == true" ; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs () << "\n"; } }; } } while (false) | |||
391 | }do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: " << BI << "\n"; for (Value *Invariant : Invariants ) { dbgs() << " " << *Invariant << " == true" ; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs () << "\n"; } }; } } while (false) | |||
392 | })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { { dbgs() << " unswitching trivial invariant conditions for: " << BI << "\n"; for (Value *Invariant : Invariants ) { dbgs() << " " << *Invariant << " == true" ; if (Invariant != Invariants.back()) dbgs() << " ||"; dbgs () << "\n"; } }; } } while (false); | |||
393 | ||||
394 | // If we have scalar evolutions, we need to invalidate them including this | |||
395 | // loop and the loop containing the exit block. | |||
396 | if (SE) { | |||
397 | if (Loop *ExitL = LI.getLoopFor(LoopExitBB)) | |||
398 | SE->forgetLoop(ExitL); | |||
399 | else | |||
400 | // Forget the entire nest as this exits the entire nest. | |||
401 | SE->forgetTopmostLoop(&L); | |||
402 | } | |||
403 | ||||
404 | // Split the preheader, so that we know that there is a safe place to insert | |||
405 | // the conditional branch. We will change the preheader to have a conditional | |||
406 | // branch on LoopCond. | |||
407 | BasicBlock *OldPH = L.getLoopPreheader(); | |||
408 | BasicBlock *NewPH = SplitEdge(OldPH, L.getHeader(), &DT, &LI); | |||
409 | ||||
410 | // Now that we have a place to insert the conditional branch, create a place | |||
411 | // to branch to: this is the exit block out of the loop that we are | |||
412 | // unswitching. We need to split this if there are other loop predecessors. | |||
413 | // Because the loop is in simplified form, *any* other predecessor is enough. | |||
414 | BasicBlock *UnswitchedBB; | |||
415 | if (FullUnswitch && LoopExitBB->getUniquePredecessor()) { | |||
416 | assert(LoopExitBB->getUniquePredecessor() == BI.getParent() &&(static_cast <bool> (LoopExitBB->getUniquePredecessor () == BI.getParent() && "A branch's parent isn't a predecessor!" ) ? void (0) : __assert_fail ("LoopExitBB->getUniquePredecessor() == BI.getParent() && \"A branch's parent isn't a predecessor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 417, __extension__ __PRETTY_FUNCTION__)) | |||
417 | "A branch's parent isn't a predecessor!")(static_cast <bool> (LoopExitBB->getUniquePredecessor () == BI.getParent() && "A branch's parent isn't a predecessor!" ) ? void (0) : __assert_fail ("LoopExitBB->getUniquePredecessor() == BI.getParent() && \"A branch's parent isn't a predecessor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 417, __extension__ __PRETTY_FUNCTION__)); | |||
418 | UnswitchedBB = LoopExitBB; | |||
419 | } else { | |||
420 | UnswitchedBB = SplitBlock(LoopExitBB, &LoopExitBB->front(), &DT, &LI); | |||
421 | } | |||
422 | ||||
423 | // Actually move the invariant uses into the unswitched position. If possible, | |||
424 | // we do this by moving the instructions, but when doing partial unswitching | |||
425 | // we do it by building a new merge of the values in the unswitched position. | |||
426 | OldPH->getTerminator()->eraseFromParent(); | |||
427 | if (FullUnswitch) { | |||
428 | // If fully unswitching, we can use the existing branch instruction. | |||
429 | // Splice it into the old PH to gate reaching the new preheader and re-point | |||
430 | // its successors. | |||
431 | OldPH->getInstList().splice(OldPH->end(), BI.getParent()->getInstList(), | |||
432 | BI); | |||
433 | BI.setSuccessor(LoopExitSuccIdx, UnswitchedBB); | |||
434 | BI.setSuccessor(1 - LoopExitSuccIdx, NewPH); | |||
435 | ||||
436 | // Create a new unconditional branch that will continue the loop as a new | |||
437 | // terminator. | |||
438 | BranchInst::Create(ContinueBB, ParentBB); | |||
439 | } else { | |||
440 | // Only unswitching a subset of inputs to the condition, so we will need to | |||
441 | // build a new branch that merges the invariant inputs. | |||
442 | if (ExitDirection) | |||
443 | assert(cast<Instruction>(BI.getCondition())->getOpcode() ==(static_cast <bool> (cast<Instruction>(BI.getCondition ())->getOpcode() == Instruction::Or && "Must have an `or` of `i1`s for the condition!" ) ? void (0) : __assert_fail ("cast<Instruction>(BI.getCondition())->getOpcode() == Instruction::Or && \"Must have an `or` of `i1`s for the condition!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 445, __extension__ __PRETTY_FUNCTION__)) | |||
444 | Instruction::Or &&(static_cast <bool> (cast<Instruction>(BI.getCondition ())->getOpcode() == Instruction::Or && "Must have an `or` of `i1`s for the condition!" ) ? void (0) : __assert_fail ("cast<Instruction>(BI.getCondition())->getOpcode() == Instruction::Or && \"Must have an `or` of `i1`s for the condition!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 445, __extension__ __PRETTY_FUNCTION__)) | |||
445 | "Must have an `or` of `i1`s for the condition!")(static_cast <bool> (cast<Instruction>(BI.getCondition ())->getOpcode() == Instruction::Or && "Must have an `or` of `i1`s for the condition!" ) ? void (0) : __assert_fail ("cast<Instruction>(BI.getCondition())->getOpcode() == Instruction::Or && \"Must have an `or` of `i1`s for the condition!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 445, __extension__ __PRETTY_FUNCTION__)); | |||
446 | else | |||
447 | assert(cast<Instruction>(BI.getCondition())->getOpcode() ==(static_cast <bool> (cast<Instruction>(BI.getCondition ())->getOpcode() == Instruction::And && "Must have an `and` of `i1`s for the condition!" ) ? void (0) : __assert_fail ("cast<Instruction>(BI.getCondition())->getOpcode() == Instruction::And && \"Must have an `and` of `i1`s for the condition!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 449, __extension__ __PRETTY_FUNCTION__)) | |||
448 | Instruction::And &&(static_cast <bool> (cast<Instruction>(BI.getCondition ())->getOpcode() == Instruction::And && "Must have an `and` of `i1`s for the condition!" ) ? void (0) : __assert_fail ("cast<Instruction>(BI.getCondition())->getOpcode() == Instruction::And && \"Must have an `and` of `i1`s for the condition!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 449, __extension__ __PRETTY_FUNCTION__)) | |||
449 | "Must have an `and` of `i1`s for the condition!")(static_cast <bool> (cast<Instruction>(BI.getCondition ())->getOpcode() == Instruction::And && "Must have an `and` of `i1`s for the condition!" ) ? void (0) : __assert_fail ("cast<Instruction>(BI.getCondition())->getOpcode() == Instruction::And && \"Must have an `and` of `i1`s for the condition!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 449, __extension__ __PRETTY_FUNCTION__)); | |||
450 | buildPartialUnswitchConditionalBranch(*OldPH, Invariants, ExitDirection, | |||
451 | *UnswitchedBB, *NewPH); | |||
452 | } | |||
453 | ||||
454 | // Rewrite the relevant PHI nodes. | |||
455 | if (UnswitchedBB == LoopExitBB) | |||
456 | rewritePHINodesForUnswitchedExitBlock(*UnswitchedBB, *ParentBB, *OldPH); | |||
457 | else | |||
458 | rewritePHINodesForExitAndUnswitchedBlocks(*LoopExitBB, *UnswitchedBB, | |||
459 | *ParentBB, *OldPH, FullUnswitch); | |||
460 | ||||
461 | // Now we need to update the dominator tree. | |||
462 | SmallVector<DominatorTree::UpdateType, 2> DTUpdates; | |||
463 | DTUpdates.push_back({DT.Insert, OldPH, UnswitchedBB}); | |||
464 | if (FullUnswitch) | |||
465 | DTUpdates.push_back({DT.Delete, ParentBB, LoopExitBB}); | |||
466 | DT.applyUpdates(DTUpdates); | |||
467 | ||||
468 | // The constant we can replace all of our invariants with inside the loop | |||
469 | // body. If any of the invariants have a value other than this the loop won't | |||
470 | // be entered. | |||
471 | ConstantInt *Replacement = ExitDirection | |||
472 | ? ConstantInt::getFalse(BI.getContext()) | |||
473 | : ConstantInt::getTrue(BI.getContext()); | |||
474 | ||||
475 | // Since this is an i1 condition we can also trivially replace uses of it | |||
476 | // within the loop with a constant. | |||
477 | for (Value *Invariant : Invariants) | |||
478 | replaceLoopInvariantUses(L, Invariant, *Replacement); | |||
479 | ||||
480 | // If this was full unswitching, we may have changed the nesting relationship | |||
481 | // for this loop so hoist it to its correct parent if needed. | |||
482 | if (FullUnswitch) | |||
483 | hoistLoopToNewParent(L, *NewPH, DT, LI); | |||
484 | ||||
485 | ++NumTrivial; | |||
486 | ++NumBranches; | |||
487 | return true; | |||
488 | } | |||
489 | ||||
490 | /// Unswitch a trivial switch if the condition is loop invariant. | |||
491 | /// | |||
492 | /// This routine should only be called when loop code leading to the switch has | |||
493 | /// been validated as trivial (no side effects). This routine checks if the | |||
494 | /// condition is invariant and that at least one of the successors is a loop | |||
495 | /// exit. This allows us to unswitch without duplicating the loop, making it | |||
496 | /// trivial. | |||
497 | /// | |||
498 | /// If this routine fails to unswitch the switch it returns false. | |||
499 | /// | |||
500 | /// If the switch can be unswitched, this routine splits the preheader and | |||
501 | /// copies the switch above that split. If the default case is one of the | |||
502 | /// exiting cases, it copies the non-exiting cases and points them at the new | |||
503 | /// preheader. If the default case is not exiting, it copies the exiting cases | |||
504 | /// and points the default at the preheader. It preserves loop simplified form | |||
505 | /// (splitting the exit blocks as necessary). It simplifies the switch within | |||
506 | /// the loop by removing now-dead cases. If the default case is one of those | |||
507 | /// unswitched, it replaces its destination with a new basic block containing | |||
508 | /// only unreachable. Such basic blocks, while technically loop exits, are not | |||
509 | /// considered for unswitching so this is a stable transform and the same | |||
510 | /// switch will not be revisited. If after unswitching there is only a single | |||
511 | /// in-loop successor, the switch is further simplified to an unconditional | |||
512 | /// branch. Still more cleanup can be done with some simplify-cfg like pass. | |||
513 | /// | |||
514 | /// If `SE` is not null, it will be updated based on the potential loop SCEVs | |||
515 | /// invalidated by this. | |||
516 | static bool unswitchTrivialSwitch(Loop &L, SwitchInst &SI, DominatorTree &DT, | |||
517 | LoopInfo &LI, ScalarEvolution *SE) { | |||
518 | LLVM_DEBUG(dbgs() << " Trying to unswitch switch: " << SI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Trying to unswitch switch: " << SI << "\n"; } } while (false); | |||
519 | Value *LoopCond = SI.getCondition(); | |||
520 | ||||
521 | // If this isn't switching on an invariant condition, we can't unswitch it. | |||
522 | if (!L.isLoopInvariant(LoopCond)) | |||
523 | return false; | |||
524 | ||||
525 | auto *ParentBB = SI.getParent(); | |||
526 | ||||
527 | SmallVector<int, 4> ExitCaseIndices; | |||
528 | for (auto Case : SI.cases()) { | |||
529 | auto *SuccBB = Case.getCaseSuccessor(); | |||
530 | if (!L.contains(SuccBB) && | |||
531 | areLoopExitPHIsLoopInvariant(L, *ParentBB, *SuccBB)) | |||
532 | ExitCaseIndices.push_back(Case.getCaseIndex()); | |||
533 | } | |||
534 | BasicBlock *DefaultExitBB = nullptr; | |||
535 | if (!L.contains(SI.getDefaultDest()) && | |||
536 | areLoopExitPHIsLoopInvariant(L, *ParentBB, *SI.getDefaultDest()) && | |||
537 | !isa<UnreachableInst>(SI.getDefaultDest()->getTerminator())) | |||
538 | DefaultExitBB = SI.getDefaultDest(); | |||
539 | else if (ExitCaseIndices.empty()) | |||
540 | return false; | |||
541 | ||||
542 | LLVM_DEBUG(dbgs() << " unswitching trivial cases...\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " unswitching trivial cases...\n" ; } } while (false); | |||
543 | ||||
544 | // We may need to invalidate SCEVs for the outermost loop reached by any of | |||
545 | // the exits. | |||
546 | Loop *OuterL = &L; | |||
547 | ||||
548 | if (DefaultExitBB) { | |||
549 | // Clear out the default destination temporarily to allow accurate | |||
550 | // predecessor lists to be examined below. | |||
551 | SI.setDefaultDest(nullptr); | |||
552 | // Check the loop containing this exit. | |||
553 | Loop *ExitL = LI.getLoopFor(DefaultExitBB); | |||
554 | if (!ExitL || ExitL->contains(OuterL)) | |||
555 | OuterL = ExitL; | |||
556 | } | |||
557 | ||||
558 | // Store the exit cases into a separate data structure and remove them from | |||
559 | // the switch. | |||
560 | SmallVector<std::pair<ConstantInt *, BasicBlock *>, 4> ExitCases; | |||
561 | ExitCases.reserve(ExitCaseIndices.size()); | |||
562 | // We walk the case indices backwards so that we remove the last case first | |||
563 | // and don't disrupt the earlier indices. | |||
564 | for (unsigned Index : reverse(ExitCaseIndices)) { | |||
565 | auto CaseI = SI.case_begin() + Index; | |||
566 | // Compute the outer loop from this exit. | |||
567 | Loop *ExitL = LI.getLoopFor(CaseI->getCaseSuccessor()); | |||
568 | if (!ExitL || ExitL->contains(OuterL)) | |||
569 | OuterL = ExitL; | |||
570 | // Save the value of this case. | |||
571 | ExitCases.push_back({CaseI->getCaseValue(), CaseI->getCaseSuccessor()}); | |||
572 | // Delete the unswitched cases. | |||
573 | SI.removeCase(CaseI); | |||
574 | } | |||
575 | ||||
576 | if (SE) { | |||
577 | if (OuterL) | |||
578 | SE->forgetLoop(OuterL); | |||
579 | else | |||
580 | SE->forgetTopmostLoop(&L); | |||
581 | } | |||
582 | ||||
583 | // Check if after this all of the remaining cases point at the same | |||
584 | // successor. | |||
585 | BasicBlock *CommonSuccBB = nullptr; | |||
586 | if (SI.getNumCases() > 0 && | |||
587 | std::all_of(std::next(SI.case_begin()), SI.case_end(), | |||
588 | [&SI](const SwitchInst::CaseHandle &Case) { | |||
589 | return Case.getCaseSuccessor() == | |||
590 | SI.case_begin()->getCaseSuccessor(); | |||
591 | })) | |||
592 | CommonSuccBB = SI.case_begin()->getCaseSuccessor(); | |||
593 | if (!DefaultExitBB) { | |||
594 | // If we're not unswitching the default, we need it to match any cases to | |||
595 | // have a common successor or if we have no cases it is the common | |||
596 | // successor. | |||
597 | if (SI.getNumCases() == 0) | |||
598 | CommonSuccBB = SI.getDefaultDest(); | |||
599 | else if (SI.getDefaultDest() != CommonSuccBB) | |||
600 | CommonSuccBB = nullptr; | |||
601 | } | |||
602 | ||||
603 | // Split the preheader, so that we know that there is a safe place to insert | |||
604 | // the switch. | |||
605 | BasicBlock *OldPH = L.getLoopPreheader(); | |||
606 | BasicBlock *NewPH = SplitEdge(OldPH, L.getHeader(), &DT, &LI); | |||
607 | OldPH->getTerminator()->eraseFromParent(); | |||
608 | ||||
609 | // Now add the unswitched switch. | |||
610 | auto *NewSI = SwitchInst::Create(LoopCond, NewPH, ExitCases.size(), OldPH); | |||
611 | ||||
612 | // Rewrite the IR for the unswitched basic blocks. This requires two steps. | |||
613 | // First, we split any exit blocks with remaining in-loop predecessors. Then | |||
614 | // we update the PHIs in one of two ways depending on if there was a split. | |||
615 | // We walk in reverse so that we split in the same order as the cases | |||
616 | // appeared. This is purely for convenience of reading the resulting IR, but | |||
617 | // it doesn't cost anything really. | |||
618 | SmallPtrSet<BasicBlock *, 2> UnswitchedExitBBs; | |||
619 | SmallDenseMap<BasicBlock *, BasicBlock *, 2> SplitExitBBMap; | |||
620 | // Handle the default exit if necessary. | |||
621 | // FIXME: It'd be great if we could merge this with the loop below but LLVM's | |||
622 | // ranges aren't quite powerful enough yet. | |||
623 | if (DefaultExitBB) { | |||
624 | if (pred_empty(DefaultExitBB)) { | |||
625 | UnswitchedExitBBs.insert(DefaultExitBB); | |||
626 | rewritePHINodesForUnswitchedExitBlock(*DefaultExitBB, *ParentBB, *OldPH); | |||
627 | } else { | |||
628 | auto *SplitBB = | |||
629 | SplitBlock(DefaultExitBB, &DefaultExitBB->front(), &DT, &LI); | |||
630 | rewritePHINodesForExitAndUnswitchedBlocks( | |||
631 | *DefaultExitBB, *SplitBB, *ParentBB, *OldPH, /*FullUnswitch*/ true); | |||
632 | DefaultExitBB = SplitExitBBMap[DefaultExitBB] = SplitBB; | |||
633 | } | |||
634 | } | |||
635 | // Note that we must use a reference in the for loop so that we update the | |||
636 | // container. | |||
637 | for (auto &CasePair : reverse(ExitCases)) { | |||
638 | // Grab a reference to the exit block in the pair so that we can update it. | |||
639 | BasicBlock *ExitBB = CasePair.second; | |||
640 | ||||
641 | // If this case is the last edge into the exit block, we can simply reuse it | |||
642 | // as it will no longer be a loop exit. No mapping necessary. | |||
643 | if (pred_empty(ExitBB)) { | |||
644 | // Only rewrite once. | |||
645 | if (UnswitchedExitBBs.insert(ExitBB).second) | |||
646 | rewritePHINodesForUnswitchedExitBlock(*ExitBB, *ParentBB, *OldPH); | |||
647 | continue; | |||
648 | } | |||
649 | ||||
650 | // Otherwise we need to split the exit block so that we retain an exit | |||
651 | // block from the loop and a target for the unswitched condition. | |||
652 | BasicBlock *&SplitExitBB = SplitExitBBMap[ExitBB]; | |||
653 | if (!SplitExitBB) { | |||
654 | // If this is the first time we see this, do the split and remember it. | |||
655 | SplitExitBB = SplitBlock(ExitBB, &ExitBB->front(), &DT, &LI); | |||
656 | rewritePHINodesForExitAndUnswitchedBlocks( | |||
657 | *ExitBB, *SplitExitBB, *ParentBB, *OldPH, /*FullUnswitch*/ true); | |||
658 | } | |||
659 | // Update the case pair to point to the split block. | |||
660 | CasePair.second = SplitExitBB; | |||
661 | } | |||
662 | ||||
663 | // Now add the unswitched cases. We do this in reverse order as we built them | |||
664 | // in reverse order. | |||
665 | for (auto CasePair : reverse(ExitCases)) { | |||
666 | ConstantInt *CaseVal = CasePair.first; | |||
667 | BasicBlock *UnswitchedBB = CasePair.second; | |||
668 | ||||
669 | NewSI->addCase(CaseVal, UnswitchedBB); | |||
670 | } | |||
671 | ||||
672 | // If the default was unswitched, re-point it and add explicit cases for | |||
673 | // entering the loop. | |||
674 | if (DefaultExitBB) { | |||
675 | NewSI->setDefaultDest(DefaultExitBB); | |||
676 | ||||
677 | // We removed all the exit cases, so we just copy the cases to the | |||
678 | // unswitched switch. | |||
679 | for (auto Case : SI.cases()) | |||
680 | NewSI->addCase(Case.getCaseValue(), NewPH); | |||
681 | } | |||
682 | ||||
683 | // If we ended up with a common successor for every path through the switch | |||
684 | // after unswitching, rewrite it to an unconditional branch to make it easy | |||
685 | // to recognize. Otherwise we potentially have to recognize the default case | |||
686 | // pointing at unreachable and other complexity. | |||
687 | if (CommonSuccBB) { | |||
688 | BasicBlock *BB = SI.getParent(); | |||
689 | // We may have had multiple edges to this common successor block, so remove | |||
690 | // them as predecessors. We skip the first one, either the default or the | |||
691 | // actual first case. | |||
692 | bool SkippedFirst = DefaultExitBB == nullptr; | |||
693 | for (auto Case : SI.cases()) { | |||
694 | assert(Case.getCaseSuccessor() == CommonSuccBB &&(static_cast <bool> (Case.getCaseSuccessor() == CommonSuccBB && "Non-common successor!") ? void (0) : __assert_fail ("Case.getCaseSuccessor() == CommonSuccBB && \"Non-common successor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 695, __extension__ __PRETTY_FUNCTION__)) | |||
695 | "Non-common successor!")(static_cast <bool> (Case.getCaseSuccessor() == CommonSuccBB && "Non-common successor!") ? void (0) : __assert_fail ("Case.getCaseSuccessor() == CommonSuccBB && \"Non-common successor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 695, __extension__ __PRETTY_FUNCTION__)); | |||
696 | (void)Case; | |||
697 | if (!SkippedFirst) { | |||
698 | SkippedFirst = true; | |||
699 | continue; | |||
700 | } | |||
701 | CommonSuccBB->removePredecessor(BB, | |||
702 | /*DontDeleteUselessPHIs*/ true); | |||
703 | } | |||
704 | // Now nuke the switch and replace it with a direct branch. | |||
705 | SI.eraseFromParent(); | |||
706 | BranchInst::Create(CommonSuccBB, BB); | |||
707 | } else if (DefaultExitBB) { | |||
708 | assert(SI.getNumCases() > 0 &&(static_cast <bool> (SI.getNumCases() > 0 && "If we had no cases we'd have a common successor!") ? void ( 0) : __assert_fail ("SI.getNumCases() > 0 && \"If we had no cases we'd have a common successor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 709, __extension__ __PRETTY_FUNCTION__)) | |||
709 | "If we had no cases we'd have a common successor!")(static_cast <bool> (SI.getNumCases() > 0 && "If we had no cases we'd have a common successor!") ? void ( 0) : __assert_fail ("SI.getNumCases() > 0 && \"If we had no cases we'd have a common successor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 709, __extension__ __PRETTY_FUNCTION__)); | |||
710 | // Move the last case to the default successor. This is valid as if the | |||
711 | // default got unswitched it cannot be reached. This has the advantage of | |||
712 | // being simple and keeping the number of edges from this switch to | |||
713 | // successors the same, and avoiding any PHI update complexity. | |||
714 | auto LastCaseI = std::prev(SI.case_end()); | |||
715 | SI.setDefaultDest(LastCaseI->getCaseSuccessor()); | |||
716 | SI.removeCase(LastCaseI); | |||
717 | } | |||
718 | ||||
719 | // Walk the unswitched exit blocks and the unswitched split blocks and update | |||
720 | // the dominator tree based on the CFG edits. While we are walking unordered | |||
721 | // containers here, the API for applyUpdates takes an unordered list of | |||
722 | // updates and requires them to not contain duplicates. | |||
723 | SmallVector<DominatorTree::UpdateType, 4> DTUpdates; | |||
724 | for (auto *UnswitchedExitBB : UnswitchedExitBBs) { | |||
725 | DTUpdates.push_back({DT.Delete, ParentBB, UnswitchedExitBB}); | |||
726 | DTUpdates.push_back({DT.Insert, OldPH, UnswitchedExitBB}); | |||
727 | } | |||
728 | for (auto SplitUnswitchedPair : SplitExitBBMap) { | |||
729 | auto *UnswitchedBB = SplitUnswitchedPair.second; | |||
730 | DTUpdates.push_back({DT.Delete, ParentBB, UnswitchedBB}); | |||
731 | DTUpdates.push_back({DT.Insert, OldPH, UnswitchedBB}); | |||
732 | } | |||
733 | DT.applyUpdates(DTUpdates); | |||
734 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel ::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 734, __extension__ __PRETTY_FUNCTION__)); | |||
735 | ||||
736 | // We may have changed the nesting relationship for this loop so hoist it to | |||
737 | // its correct parent if needed. | |||
738 | hoistLoopToNewParent(L, *NewPH, DT, LI); | |||
739 | ||||
740 | ++NumTrivial; | |||
741 | ++NumSwitches; | |||
742 | return true; | |||
743 | } | |||
744 | ||||
745 | /// This routine scans the loop to find a branch or switch which occurs before | |||
746 | /// any side effects occur. These can potentially be unswitched without | |||
747 | /// duplicating the loop. If a branch or switch is successfully unswitched the | |||
748 | /// scanning continues to see if subsequent branches or switches have become | |||
749 | /// trivial. Once all trivial candidates have been unswitched, this routine | |||
750 | /// returns. | |||
751 | /// | |||
752 | /// The return value indicates whether anything was unswitched (and therefore | |||
753 | /// changed). | |||
754 | /// | |||
755 | /// If `SE` is not null, it will be updated based on the potential loop SCEVs | |||
756 | /// invalidated by this. | |||
757 | static bool unswitchAllTrivialConditions(Loop &L, DominatorTree &DT, | |||
758 | LoopInfo &LI, ScalarEvolution *SE) { | |||
759 | bool Changed = false; | |||
760 | ||||
761 | // If loop header has only one reachable successor we should keep looking for | |||
762 | // trivial condition candidates in the successor as well. An alternative is | |||
763 | // to constant fold conditions and merge successors into loop header (then we | |||
764 | // only need to check header's terminator). The reason for not doing this in | |||
765 | // LoopUnswitch pass is that it could potentially break LoopPassManager's | |||
766 | // invariants. Folding dead branches could either eliminate the current loop | |||
767 | // or make other loops unreachable. LCSSA form might also not be preserved | |||
768 | // after deleting branches. The following code keeps traversing loop header's | |||
769 | // successors until it finds the trivial condition candidate (condition that | |||
770 | // is not a constant). Since unswitching generates branches with constant | |||
771 | // conditions, this scenario could be very common in practice. | |||
772 | BasicBlock *CurrentBB = L.getHeader(); | |||
773 | SmallPtrSet<BasicBlock *, 8> Visited; | |||
774 | Visited.insert(CurrentBB); | |||
775 | do { | |||
776 | // Check if there are any side-effecting instructions (e.g. stores, calls, | |||
777 | // volatile loads) in the part of the loop that the code *would* execute | |||
778 | // without unswitching. | |||
779 | if (llvm::any_of(*CurrentBB, | |||
780 | [](Instruction &I) { return I.mayHaveSideEffects(); })) | |||
781 | return Changed; | |||
782 | ||||
783 | TerminatorInst *CurrentTerm = CurrentBB->getTerminator(); | |||
784 | ||||
785 | if (auto *SI = dyn_cast<SwitchInst>(CurrentTerm)) { | |||
786 | // Don't bother trying to unswitch past a switch with a constant | |||
787 | // condition. This should be removed prior to running this pass by | |||
788 | // simplify-cfg. | |||
789 | if (isa<Constant>(SI->getCondition())) | |||
790 | return Changed; | |||
791 | ||||
792 | if (!unswitchTrivialSwitch(L, *SI, DT, LI, SE)) | |||
793 | // Couldn't unswitch this one so we're done. | |||
794 | return Changed; | |||
795 | ||||
796 | // Mark that we managed to unswitch something. | |||
797 | Changed = true; | |||
798 | ||||
799 | // If unswitching turned the terminator into an unconditional branch then | |||
800 | // we can continue. The unswitching logic specifically works to fold any | |||
801 | // cases it can into an unconditional branch to make it easier to | |||
802 | // recognize here. | |||
803 | auto *BI = dyn_cast<BranchInst>(CurrentBB->getTerminator()); | |||
804 | if (!BI || BI->isConditional()) | |||
805 | return Changed; | |||
806 | ||||
807 | CurrentBB = BI->getSuccessor(0); | |||
808 | continue; | |||
809 | } | |||
810 | ||||
811 | auto *BI = dyn_cast<BranchInst>(CurrentTerm); | |||
812 | if (!BI) | |||
813 | // We do not understand other terminator instructions. | |||
814 | return Changed; | |||
815 | ||||
816 | // Don't bother trying to unswitch past an unconditional branch or a branch | |||
817 | // with a constant value. These should be removed by simplify-cfg prior to | |||
818 | // running this pass. | |||
819 | if (!BI->isConditional() || isa<Constant>(BI->getCondition())) | |||
820 | return Changed; | |||
821 | ||||
822 | // Found a trivial condition candidate: non-foldable conditional branch. If | |||
823 | // we fail to unswitch this, we can't do anything else that is trivial. | |||
824 | if (!unswitchTrivialBranch(L, *BI, DT, LI, SE)) | |||
825 | return Changed; | |||
826 | ||||
827 | // Mark that we managed to unswitch something. | |||
828 | Changed = true; | |||
829 | ||||
830 | // If we only unswitched some of the conditions feeding the branch, we won't | |||
831 | // have collapsed it to a single successor. | |||
832 | BI = cast<BranchInst>(CurrentBB->getTerminator()); | |||
833 | if (BI->isConditional()) | |||
834 | return Changed; | |||
835 | ||||
836 | // Follow the newly unconditional branch into its successor. | |||
837 | CurrentBB = BI->getSuccessor(0); | |||
838 | ||||
839 | // When continuing, if we exit the loop or reach a previous visited block, | |||
840 | // then we can not reach any trivial condition candidates (unfoldable | |||
841 | // branch instructions or switch instructions) and no unswitch can happen. | |||
842 | } while (L.contains(CurrentBB) && Visited.insert(CurrentBB).second); | |||
843 | ||||
844 | return Changed; | |||
845 | } | |||
846 | ||||
847 | /// Build the cloned blocks for an unswitched copy of the given loop. | |||
848 | /// | |||
849 | /// The cloned blocks are inserted before the loop preheader (`LoopPH`) and | |||
850 | /// after the split block (`SplitBB`) that will be used to select between the | |||
851 | /// cloned and original loop. | |||
852 | /// | |||
853 | /// This routine handles cloning all of the necessary loop blocks and exit | |||
854 | /// blocks including rewriting their instructions and the relevant PHI nodes. | |||
855 | /// Any loop blocks or exit blocks which are dominated by a different successor | |||
856 | /// than the one for this clone of the loop blocks can be trivially skipped. We | |||
857 | /// use the `DominatingSucc` map to determine whether a block satisfies that | |||
858 | /// property with a simple map lookup. | |||
859 | /// | |||
860 | /// It also correctly creates the unconditional branch in the cloned | |||
861 | /// unswitched parent block to only point at the unswitched successor. | |||
862 | /// | |||
863 | /// This does not handle most of the necessary updates to `LoopInfo`. Only exit | |||
864 | /// block splitting is correctly reflected in `LoopInfo`, essentially all of | |||
865 | /// the cloned blocks (and their loops) are left without full `LoopInfo` | |||
866 | /// updates. This also doesn't fully update `DominatorTree`. It adds the cloned | |||
867 | /// blocks to them but doesn't create the cloned `DominatorTree` structure and | |||
868 | /// instead the caller must recompute an accurate DT. It *does* correctly | |||
869 | /// update the `AssumptionCache` provided in `AC`. | |||
870 | static BasicBlock *buildClonedLoopBlocks( | |||
871 | Loop &L, BasicBlock *LoopPH, BasicBlock *SplitBB, | |||
872 | ArrayRef<BasicBlock *> ExitBlocks, BasicBlock *ParentBB, | |||
873 | BasicBlock *UnswitchedSuccBB, BasicBlock *ContinueSuccBB, | |||
874 | const SmallDenseMap<BasicBlock *, BasicBlock *, 16> &DominatingSucc, | |||
875 | ValueToValueMapTy &VMap, | |||
876 | SmallVectorImpl<DominatorTree::UpdateType> &DTUpdates, AssumptionCache &AC, | |||
877 | DominatorTree &DT, LoopInfo &LI) { | |||
878 | SmallVector<BasicBlock *, 4> NewBlocks; | |||
879 | NewBlocks.reserve(L.getNumBlocks() + ExitBlocks.size()); | |||
880 | ||||
881 | // We will need to clone a bunch of blocks, wrap up the clone operation in | |||
882 | // a helper. | |||
883 | auto CloneBlock = [&](BasicBlock *OldBB) { | |||
884 | // Clone the basic block and insert it before the new preheader. | |||
885 | BasicBlock *NewBB = CloneBasicBlock(OldBB, VMap, ".us", OldBB->getParent()); | |||
886 | NewBB->moveBefore(LoopPH); | |||
887 | ||||
888 | // Record this block and the mapping. | |||
889 | NewBlocks.push_back(NewBB); | |||
890 | VMap[OldBB] = NewBB; | |||
891 | ||||
892 | return NewBB; | |||
893 | }; | |||
894 | ||||
895 | // We skip cloning blocks when they have a dominating succ that is not the | |||
896 | // succ we are cloning for. | |||
897 | auto SkipBlock = [&](BasicBlock *BB) { | |||
898 | auto It = DominatingSucc.find(BB); | |||
899 | return It != DominatingSucc.end() && It->second != UnswitchedSuccBB; | |||
900 | }; | |||
901 | ||||
902 | // First, clone the preheader. | |||
903 | auto *ClonedPH = CloneBlock(LoopPH); | |||
904 | ||||
905 | // Then clone all the loop blocks, skipping the ones that aren't necessary. | |||
906 | for (auto *LoopBB : L.blocks()) | |||
907 | if (!SkipBlock(LoopBB)) | |||
908 | CloneBlock(LoopBB); | |||
909 | ||||
910 | // Split all the loop exit edges so that when we clone the exit blocks, if | |||
911 | // any of the exit blocks are *also* a preheader for some other loop, we | |||
912 | // don't create multiple predecessors entering the loop header. | |||
913 | for (auto *ExitBB : ExitBlocks) { | |||
914 | if (SkipBlock(ExitBB)) | |||
915 | continue; | |||
916 | ||||
917 | // When we are going to clone an exit, we don't need to clone all the | |||
918 | // instructions in the exit block and we want to ensure we have an easy | |||
919 | // place to merge the CFG, so split the exit first. This is always safe to | |||
920 | // do because there cannot be any non-loop predecessors of a loop exit in | |||
921 | // loop simplified form. | |||
922 | auto *MergeBB = SplitBlock(ExitBB, &ExitBB->front(), &DT, &LI); | |||
923 | ||||
924 | // Rearrange the names to make it easier to write test cases by having the | |||
925 | // exit block carry the suffix rather than the merge block carrying the | |||
926 | // suffix. | |||
927 | MergeBB->takeName(ExitBB); | |||
928 | ExitBB->setName(Twine(MergeBB->getName()) + ".split"); | |||
929 | ||||
930 | // Now clone the original exit block. | |||
931 | auto *ClonedExitBB = CloneBlock(ExitBB); | |||
932 | assert(ClonedExitBB->getTerminator()->getNumSuccessors() == 1 &&(static_cast <bool> (ClonedExitBB->getTerminator()-> getNumSuccessors() == 1 && "Exit block should have been split to have one successor!" ) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getNumSuccessors() == 1 && \"Exit block should have been split to have one successor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 933, __extension__ __PRETTY_FUNCTION__)) | |||
933 | "Exit block should have been split to have one successor!")(static_cast <bool> (ClonedExitBB->getTerminator()-> getNumSuccessors() == 1 && "Exit block should have been split to have one successor!" ) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getNumSuccessors() == 1 && \"Exit block should have been split to have one successor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 933, __extension__ __PRETTY_FUNCTION__)); | |||
934 | assert(ClonedExitBB->getTerminator()->getSuccessor(0) == MergeBB &&(static_cast <bool> (ClonedExitBB->getTerminator()-> getSuccessor(0) == MergeBB && "Cloned exit block has the wrong successor!" ) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getSuccessor(0) == MergeBB && \"Cloned exit block has the wrong successor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 935, __extension__ __PRETTY_FUNCTION__)) | |||
935 | "Cloned exit block has the wrong successor!")(static_cast <bool> (ClonedExitBB->getTerminator()-> getSuccessor(0) == MergeBB && "Cloned exit block has the wrong successor!" ) ? void (0) : __assert_fail ("ClonedExitBB->getTerminator()->getSuccessor(0) == MergeBB && \"Cloned exit block has the wrong successor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 935, __extension__ __PRETTY_FUNCTION__)); | |||
936 | ||||
937 | // Remap any cloned instructions and create a merge phi node for them. | |||
938 | for (auto ZippedInsts : llvm::zip_first( | |||
939 | llvm::make_range(ExitBB->begin(), std::prev(ExitBB->end())), | |||
940 | llvm::make_range(ClonedExitBB->begin(), | |||
941 | std::prev(ClonedExitBB->end())))) { | |||
942 | Instruction &I = std::get<0>(ZippedInsts); | |||
943 | Instruction &ClonedI = std::get<1>(ZippedInsts); | |||
944 | ||||
945 | // The only instructions in the exit block should be PHI nodes and | |||
946 | // potentially a landing pad. | |||
947 | assert((static_cast <bool> ((isa<PHINode>(I) || isa<LandingPadInst >(I) || isa<CatchPadInst>(I)) && "Bad instruction in exit block!" ) ? void (0) : __assert_fail ("(isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) && \"Bad instruction in exit block!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 949, __extension__ __PRETTY_FUNCTION__)) | |||
948 | (isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) &&(static_cast <bool> ((isa<PHINode>(I) || isa<LandingPadInst >(I) || isa<CatchPadInst>(I)) && "Bad instruction in exit block!" ) ? void (0) : __assert_fail ("(isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) && \"Bad instruction in exit block!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 949, __extension__ __PRETTY_FUNCTION__)) | |||
949 | "Bad instruction in exit block!")(static_cast <bool> ((isa<PHINode>(I) || isa<LandingPadInst >(I) || isa<CatchPadInst>(I)) && "Bad instruction in exit block!" ) ? void (0) : __assert_fail ("(isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) && \"Bad instruction in exit block!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 949, __extension__ __PRETTY_FUNCTION__)); | |||
950 | // We should have a value map between the instruction and its clone. | |||
951 | assert(VMap.lookup(&I) == &ClonedI && "Mismatch in the value map!")(static_cast <bool> (VMap.lookup(&I) == &ClonedI && "Mismatch in the value map!") ? void (0) : __assert_fail ("VMap.lookup(&I) == &ClonedI && \"Mismatch in the value map!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 951, __extension__ __PRETTY_FUNCTION__)); | |||
952 | ||||
953 | auto *MergePN = | |||
954 | PHINode::Create(I.getType(), /*NumReservedValues*/ 2, ".us-phi", | |||
955 | &*MergeBB->getFirstInsertionPt()); | |||
956 | I.replaceAllUsesWith(MergePN); | |||
957 | MergePN->addIncoming(&I, ExitBB); | |||
958 | MergePN->addIncoming(&ClonedI, ClonedExitBB); | |||
959 | } | |||
960 | } | |||
961 | ||||
962 | // Rewrite the instructions in the cloned blocks to refer to the instructions | |||
963 | // in the cloned blocks. We have to do this as a second pass so that we have | |||
964 | // everything available. Also, we have inserted new instructions which may | |||
965 | // include assume intrinsics, so we update the assumption cache while | |||
966 | // processing this. | |||
967 | for (auto *ClonedBB : NewBlocks) | |||
968 | for (Instruction &I : *ClonedBB) { | |||
969 | RemapInstruction(&I, VMap, | |||
970 | RF_NoModuleLevelChanges | RF_IgnoreMissingLocals); | |||
971 | if (auto *II = dyn_cast<IntrinsicInst>(&I)) | |||
972 | if (II->getIntrinsicID() == Intrinsic::assume) | |||
973 | AC.registerAssumption(II); | |||
974 | } | |||
975 | ||||
976 | // Update any PHI nodes in the cloned successors of the skipped blocks to not | |||
977 | // have spurious incoming values. | |||
978 | for (auto *LoopBB : L.blocks()) | |||
979 | if (SkipBlock(LoopBB)) | |||
980 | for (auto *SuccBB : successors(LoopBB)) | |||
981 | if (auto *ClonedSuccBB = cast_or_null<BasicBlock>(VMap.lookup(SuccBB))) | |||
982 | for (PHINode &PN : ClonedSuccBB->phis()) | |||
983 | PN.removeIncomingValue(LoopBB, /*DeletePHIIfEmpty*/ false); | |||
984 | ||||
985 | // Remove the cloned parent as a predecessor of any successor we ended up | |||
986 | // cloning other than the unswitched one. | |||
987 | auto *ClonedParentBB = cast<BasicBlock>(VMap.lookup(ParentBB)); | |||
988 | for (auto *SuccBB : successors(ParentBB)) { | |||
989 | if (SuccBB == UnswitchedSuccBB) | |||
990 | continue; | |||
991 | ||||
992 | auto *ClonedSuccBB = cast_or_null<BasicBlock>(VMap.lookup(SuccBB)); | |||
993 | if (!ClonedSuccBB) | |||
994 | continue; | |||
995 | ||||
996 | ClonedSuccBB->removePredecessor(ClonedParentBB, | |||
997 | /*DontDeleteUselessPHIs*/ true); | |||
998 | } | |||
999 | ||||
1000 | // Replace the cloned branch with an unconditional branch to the cloned | |||
1001 | // unswitched successor. | |||
1002 | auto *ClonedSuccBB = cast<BasicBlock>(VMap.lookup(UnswitchedSuccBB)); | |||
1003 | ClonedParentBB->getTerminator()->eraseFromParent(); | |||
1004 | BranchInst::Create(ClonedSuccBB, ClonedParentBB); | |||
1005 | ||||
1006 | // If there are duplicate entries in the PHI nodes because of multiple edges | |||
1007 | // to the unswitched successor, we need to nuke all but one as we replaced it | |||
1008 | // with a direct branch. | |||
1009 | for (PHINode &PN : ClonedSuccBB->phis()) { | |||
1010 | bool Found = false; | |||
1011 | // Loop over the incoming operands backwards so we can easily delete as we | |||
1012 | // go without invalidating the index. | |||
1013 | for (int i = PN.getNumOperands() - 1; i >= 0; --i) { | |||
1014 | if (PN.getIncomingBlock(i) != ClonedParentBB) | |||
1015 | continue; | |||
1016 | if (!Found) { | |||
1017 | Found = true; | |||
1018 | continue; | |||
1019 | } | |||
1020 | PN.removeIncomingValue(i, /*DeletePHIIfEmpty*/ false); | |||
1021 | } | |||
1022 | } | |||
1023 | ||||
1024 | // Record the domtree updates for the new blocks. | |||
1025 | SmallPtrSet<BasicBlock *, 4> SuccSet; | |||
1026 | for (auto *ClonedBB : NewBlocks) { | |||
1027 | for (auto *SuccBB : successors(ClonedBB)) | |||
1028 | if (SuccSet.insert(SuccBB).second) | |||
1029 | DTUpdates.push_back({DominatorTree::Insert, ClonedBB, SuccBB}); | |||
1030 | SuccSet.clear(); | |||
1031 | } | |||
1032 | ||||
1033 | return ClonedPH; | |||
1034 | } | |||
1035 | ||||
1036 | /// Recursively clone the specified loop and all of its children. | |||
1037 | /// | |||
1038 | /// The target parent loop for the clone should be provided, or can be null if | |||
1039 | /// the clone is a top-level loop. While cloning, all the blocks are mapped | |||
1040 | /// with the provided value map. The entire original loop must be present in | |||
1041 | /// the value map. The cloned loop is returned. | |||
1042 | static Loop *cloneLoopNest(Loop &OrigRootL, Loop *RootParentL, | |||
1043 | const ValueToValueMapTy &VMap, LoopInfo &LI) { | |||
1044 | auto AddClonedBlocksToLoop = [&](Loop &OrigL, Loop &ClonedL) { | |||
1045 | assert(ClonedL.getBlocks().empty() && "Must start with an empty loop!")(static_cast <bool> (ClonedL.getBlocks().empty() && "Must start with an empty loop!") ? void (0) : __assert_fail ("ClonedL.getBlocks().empty() && \"Must start with an empty loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1045, __extension__ __PRETTY_FUNCTION__)); | |||
1046 | ClonedL.reserveBlocks(OrigL.getNumBlocks()); | |||
1047 | for (auto *BB : OrigL.blocks()) { | |||
1048 | auto *ClonedBB = cast<BasicBlock>(VMap.lookup(BB)); | |||
1049 | ClonedL.addBlockEntry(ClonedBB); | |||
1050 | if (LI.getLoopFor(BB) == &OrigL) | |||
1051 | LI.changeLoopFor(ClonedBB, &ClonedL); | |||
1052 | } | |||
1053 | }; | |||
1054 | ||||
1055 | // We specially handle the first loop because it may get cloned into | |||
1056 | // a different parent and because we most commonly are cloning leaf loops. | |||
1057 | Loop *ClonedRootL = LI.AllocateLoop(); | |||
1058 | if (RootParentL) | |||
1059 | RootParentL->addChildLoop(ClonedRootL); | |||
1060 | else | |||
1061 | LI.addTopLevelLoop(ClonedRootL); | |||
1062 | AddClonedBlocksToLoop(OrigRootL, *ClonedRootL); | |||
1063 | ||||
1064 | if (OrigRootL.empty()) | |||
1065 | return ClonedRootL; | |||
1066 | ||||
1067 | // If we have a nest, we can quickly clone the entire loop nest using an | |||
1068 | // iterative approach because it is a tree. We keep the cloned parent in the | |||
1069 | // data structure to avoid repeatedly querying through a map to find it. | |||
1070 | SmallVector<std::pair<Loop *, Loop *>, 16> LoopsToClone; | |||
1071 | // Build up the loops to clone in reverse order as we'll clone them from the | |||
1072 | // back. | |||
1073 | for (Loop *ChildL : llvm::reverse(OrigRootL)) | |||
1074 | LoopsToClone.push_back({ClonedRootL, ChildL}); | |||
1075 | do { | |||
1076 | Loop *ClonedParentL, *L; | |||
1077 | std::tie(ClonedParentL, L) = LoopsToClone.pop_back_val(); | |||
1078 | Loop *ClonedL = LI.AllocateLoop(); | |||
1079 | ClonedParentL->addChildLoop(ClonedL); | |||
1080 | AddClonedBlocksToLoop(*L, *ClonedL); | |||
1081 | for (Loop *ChildL : llvm::reverse(*L)) | |||
1082 | LoopsToClone.push_back({ClonedL, ChildL}); | |||
1083 | } while (!LoopsToClone.empty()); | |||
1084 | ||||
1085 | return ClonedRootL; | |||
1086 | } | |||
1087 | ||||
1088 | /// Build the cloned loops of an original loop from unswitching. | |||
1089 | /// | |||
1090 | /// Because unswitching simplifies the CFG of the loop, this isn't a trivial | |||
1091 | /// operation. We need to re-verify that there even is a loop (as the backedge | |||
1092 | /// may not have been cloned), and even if there are remaining backedges the | |||
1093 | /// backedge set may be different. However, we know that each child loop is | |||
1094 | /// undisturbed, we only need to find where to place each child loop within | |||
1095 | /// either any parent loop or within a cloned version of the original loop. | |||
1096 | /// | |||
1097 | /// Because child loops may end up cloned outside of any cloned version of the | |||
1098 | /// original loop, multiple cloned sibling loops may be created. All of them | |||
1099 | /// are returned so that the newly introduced loop nest roots can be | |||
1100 | /// identified. | |||
1101 | static void buildClonedLoops(Loop &OrigL, ArrayRef<BasicBlock *> ExitBlocks, | |||
1102 | const ValueToValueMapTy &VMap, LoopInfo &LI, | |||
1103 | SmallVectorImpl<Loop *> &NonChildClonedLoops) { | |||
1104 | Loop *ClonedL = nullptr; | |||
1105 | ||||
1106 | auto *OrigPH = OrigL.getLoopPreheader(); | |||
1107 | auto *OrigHeader = OrigL.getHeader(); | |||
1108 | ||||
1109 | auto *ClonedPH = cast<BasicBlock>(VMap.lookup(OrigPH)); | |||
1110 | auto *ClonedHeader = cast<BasicBlock>(VMap.lookup(OrigHeader)); | |||
1111 | ||||
1112 | // We need to know the loops of the cloned exit blocks to even compute the | |||
1113 | // accurate parent loop. If we only clone exits to some parent of the | |||
1114 | // original parent, we want to clone into that outer loop. We also keep track | |||
1115 | // of the loops that our cloned exit blocks participate in. | |||
1116 | Loop *ParentL = nullptr; | |||
1117 | SmallVector<BasicBlock *, 4> ClonedExitsInLoops; | |||
1118 | SmallDenseMap<BasicBlock *, Loop *, 16> ExitLoopMap; | |||
1119 | ClonedExitsInLoops.reserve(ExitBlocks.size()); | |||
1120 | for (auto *ExitBB : ExitBlocks) | |||
1121 | if (auto *ClonedExitBB = cast_or_null<BasicBlock>(VMap.lookup(ExitBB))) | |||
1122 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) { | |||
1123 | ExitLoopMap[ClonedExitBB] = ExitL; | |||
1124 | ClonedExitsInLoops.push_back(ClonedExitBB); | |||
1125 | if (!ParentL || (ParentL != ExitL && ParentL->contains(ExitL))) | |||
1126 | ParentL = ExitL; | |||
1127 | } | |||
1128 | assert((!ParentL || ParentL == OrigL.getParentLoop() ||(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop () || ParentL->contains(OrigL.getParentLoop())) && "The computed parent loop should always contain (or be) the parent of " "the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1131, __extension__ __PRETTY_FUNCTION__)) | |||
1129 | ParentL->contains(OrigL.getParentLoop())) &&(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop () || ParentL->contains(OrigL.getParentLoop())) && "The computed parent loop should always contain (or be) the parent of " "the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1131, __extension__ __PRETTY_FUNCTION__)) | |||
1130 | "The computed parent loop should always contain (or be) the parent of "(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop () || ParentL->contains(OrigL.getParentLoop())) && "The computed parent loop should always contain (or be) the parent of " "the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1131, __extension__ __PRETTY_FUNCTION__)) | |||
1131 | "the original loop.")(static_cast <bool> ((!ParentL || ParentL == OrigL.getParentLoop () || ParentL->contains(OrigL.getParentLoop())) && "The computed parent loop should always contain (or be) the parent of " "the original loop.") ? void (0) : __assert_fail ("(!ParentL || ParentL == OrigL.getParentLoop() || ParentL->contains(OrigL.getParentLoop())) && \"The computed parent loop should always contain (or be) the parent of \" \"the original loop.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1131, __extension__ __PRETTY_FUNCTION__)); | |||
1132 | ||||
1133 | // We build the set of blocks dominated by the cloned header from the set of | |||
1134 | // cloned blocks out of the original loop. While not all of these will | |||
1135 | // necessarily be in the cloned loop, it is enough to establish that they | |||
1136 | // aren't in unreachable cycles, etc. | |||
1137 | SmallSetVector<BasicBlock *, 16> ClonedLoopBlocks; | |||
1138 | for (auto *BB : OrigL.blocks()) | |||
1139 | if (auto *ClonedBB = cast_or_null<BasicBlock>(VMap.lookup(BB))) | |||
1140 | ClonedLoopBlocks.insert(ClonedBB); | |||
1141 | ||||
1142 | // Rebuild the set of blocks that will end up in the cloned loop. We may have | |||
1143 | // skipped cloning some region of this loop which can in turn skip some of | |||
1144 | // the backedges so we have to rebuild the blocks in the loop based on the | |||
1145 | // backedges that remain after cloning. | |||
1146 | SmallVector<BasicBlock *, 16> Worklist; | |||
1147 | SmallPtrSet<BasicBlock *, 16> BlocksInClonedLoop; | |||
1148 | for (auto *Pred : predecessors(ClonedHeader)) { | |||
1149 | // The only possible non-loop header predecessor is the preheader because | |||
1150 | // we know we cloned the loop in simplified form. | |||
1151 | if (Pred == ClonedPH) | |||
1152 | continue; | |||
1153 | ||||
1154 | // Because the loop was in simplified form, the only non-loop predecessor | |||
1155 | // should be the preheader. | |||
1156 | assert(ClonedLoopBlocks.count(Pred) && "Found a predecessor of the loop "(static_cast <bool> (ClonedLoopBlocks.count(Pred) && "Found a predecessor of the loop " "header other than the preheader " "that is not part of the loop!") ? void (0) : __assert_fail ( "ClonedLoopBlocks.count(Pred) && \"Found a predecessor of the loop \" \"header other than the preheader \" \"that is not part of the loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1158, __extension__ __PRETTY_FUNCTION__)) | |||
1157 | "header other than the preheader "(static_cast <bool> (ClonedLoopBlocks.count(Pred) && "Found a predecessor of the loop " "header other than the preheader " "that is not part of the loop!") ? void (0) : __assert_fail ( "ClonedLoopBlocks.count(Pred) && \"Found a predecessor of the loop \" \"header other than the preheader \" \"that is not part of the loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1158, __extension__ __PRETTY_FUNCTION__)) | |||
1158 | "that is not part of the loop!")(static_cast <bool> (ClonedLoopBlocks.count(Pred) && "Found a predecessor of the loop " "header other than the preheader " "that is not part of the loop!") ? void (0) : __assert_fail ( "ClonedLoopBlocks.count(Pred) && \"Found a predecessor of the loop \" \"header other than the preheader \" \"that is not part of the loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1158, __extension__ __PRETTY_FUNCTION__)); | |||
1159 | ||||
1160 | // Insert this block into the loop set and on the first visit (and if it | |||
1161 | // isn't the header we're currently walking) put it into the worklist to | |||
1162 | // recurse through. | |||
1163 | if (BlocksInClonedLoop.insert(Pred).second && Pred != ClonedHeader) | |||
1164 | Worklist.push_back(Pred); | |||
1165 | } | |||
1166 | ||||
1167 | // If we had any backedges then there *is* a cloned loop. Put the header into | |||
1168 | // the loop set and then walk the worklist backwards to find all the blocks | |||
1169 | // that remain within the loop after cloning. | |||
1170 | if (!BlocksInClonedLoop.empty()) { | |||
1171 | BlocksInClonedLoop.insert(ClonedHeader); | |||
1172 | ||||
1173 | while (!Worklist.empty()) { | |||
1174 | BasicBlock *BB = Worklist.pop_back_val(); | |||
1175 | assert(BlocksInClonedLoop.count(BB) &&(static_cast <bool> (BlocksInClonedLoop.count(BB) && "Didn't put block into the loop set!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count(BB) && \"Didn't put block into the loop set!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1176, __extension__ __PRETTY_FUNCTION__)) | |||
1176 | "Didn't put block into the loop set!")(static_cast <bool> (BlocksInClonedLoop.count(BB) && "Didn't put block into the loop set!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count(BB) && \"Didn't put block into the loop set!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1176, __extension__ __PRETTY_FUNCTION__)); | |||
1177 | ||||
1178 | // Insert any predecessors that are in the possible set into the cloned | |||
1179 | // set, and if the insert is successful, add them to the worklist. Note | |||
1180 | // that we filter on the blocks that are definitely reachable via the | |||
1181 | // backedge to the loop header so we may prune out dead code within the | |||
1182 | // cloned loop. | |||
1183 | for (auto *Pred : predecessors(BB)) | |||
1184 | if (ClonedLoopBlocks.count(Pred) && | |||
1185 | BlocksInClonedLoop.insert(Pred).second) | |||
1186 | Worklist.push_back(Pred); | |||
1187 | } | |||
1188 | ||||
1189 | ClonedL = LI.AllocateLoop(); | |||
1190 | if (ParentL) { | |||
1191 | ParentL->addBasicBlockToLoop(ClonedPH, LI); | |||
1192 | ParentL->addChildLoop(ClonedL); | |||
1193 | } else { | |||
1194 | LI.addTopLevelLoop(ClonedL); | |||
1195 | } | |||
1196 | NonChildClonedLoops.push_back(ClonedL); | |||
1197 | ||||
1198 | ClonedL->reserveBlocks(BlocksInClonedLoop.size()); | |||
1199 | // We don't want to just add the cloned loop blocks based on how we | |||
1200 | // discovered them. The original order of blocks was carefully built in | |||
1201 | // a way that doesn't rely on predecessor ordering. Rather than re-invent | |||
1202 | // that logic, we just re-walk the original blocks (and those of the child | |||
1203 | // loops) and filter them as we add them into the cloned loop. | |||
1204 | for (auto *BB : OrigL.blocks()) { | |||
1205 | auto *ClonedBB = cast_or_null<BasicBlock>(VMap.lookup(BB)); | |||
1206 | if (!ClonedBB || !BlocksInClonedLoop.count(ClonedBB)) | |||
1207 | continue; | |||
1208 | ||||
1209 | // Directly add the blocks that are only in this loop. | |||
1210 | if (LI.getLoopFor(BB) == &OrigL) { | |||
1211 | ClonedL->addBasicBlockToLoop(ClonedBB, LI); | |||
1212 | continue; | |||
1213 | } | |||
1214 | ||||
1215 | // We want to manually add it to this loop and parents. | |||
1216 | // Registering it with LoopInfo will happen when we clone the top | |||
1217 | // loop for this block. | |||
1218 | for (Loop *PL = ClonedL; PL; PL = PL->getParentLoop()) | |||
1219 | PL->addBlockEntry(ClonedBB); | |||
1220 | } | |||
1221 | ||||
1222 | // Now add each child loop whose header remains within the cloned loop. All | |||
1223 | // of the blocks within the loop must satisfy the same constraints as the | |||
1224 | // header so once we pass the header checks we can just clone the entire | |||
1225 | // child loop nest. | |||
1226 | for (Loop *ChildL : OrigL) { | |||
1227 | auto *ClonedChildHeader = | |||
1228 | cast_or_null<BasicBlock>(VMap.lookup(ChildL->getHeader())); | |||
1229 | if (!ClonedChildHeader || !BlocksInClonedLoop.count(ClonedChildHeader)) | |||
1230 | continue; | |||
1231 | ||||
1232 | #ifndef NDEBUG | |||
1233 | // We should never have a cloned child loop header but fail to have | |||
1234 | // all of the blocks for that child loop. | |||
1235 | for (auto *ChildLoopBB : ChildL->blocks()) | |||
1236 | assert(BlocksInClonedLoop.count((static_cast <bool> (BlocksInClonedLoop.count( cast< BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer " "loop but not all of its blocks!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1239, __extension__ __PRETTY_FUNCTION__)) | |||
1237 | cast<BasicBlock>(VMap.lookup(ChildLoopBB))) &&(static_cast <bool> (BlocksInClonedLoop.count( cast< BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer " "loop but not all of its blocks!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1239, __extension__ __PRETTY_FUNCTION__)) | |||
1238 | "Child cloned loop has a header within the cloned outer "(static_cast <bool> (BlocksInClonedLoop.count( cast< BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer " "loop but not all of its blocks!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1239, __extension__ __PRETTY_FUNCTION__)) | |||
1239 | "loop but not all of its blocks!")(static_cast <bool> (BlocksInClonedLoop.count( cast< BasicBlock>(VMap.lookup(ChildLoopBB))) && "Child cloned loop has a header within the cloned outer " "loop but not all of its blocks!") ? void (0) : __assert_fail ("BlocksInClonedLoop.count( cast<BasicBlock>(VMap.lookup(ChildLoopBB))) && \"Child cloned loop has a header within the cloned outer \" \"loop but not all of its blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1239, __extension__ __PRETTY_FUNCTION__)); | |||
1240 | #endif | |||
1241 | ||||
1242 | cloneLoopNest(*ChildL, ClonedL, VMap, LI); | |||
1243 | } | |||
1244 | } | |||
1245 | ||||
1246 | // Now that we've handled all the components of the original loop that were | |||
1247 | // cloned into a new loop, we still need to handle anything from the original | |||
1248 | // loop that wasn't in a cloned loop. | |||
1249 | ||||
1250 | // Figure out what blocks are left to place within any loop nest containing | |||
1251 | // the unswitched loop. If we never formed a loop, the cloned PH is one of | |||
1252 | // them. | |||
1253 | SmallPtrSet<BasicBlock *, 16> UnloopedBlockSet; | |||
1254 | if (BlocksInClonedLoop.empty()) | |||
1255 | UnloopedBlockSet.insert(ClonedPH); | |||
1256 | for (auto *ClonedBB : ClonedLoopBlocks) | |||
1257 | if (!BlocksInClonedLoop.count(ClonedBB)) | |||
1258 | UnloopedBlockSet.insert(ClonedBB); | |||
1259 | ||||
1260 | // Copy the cloned exits and sort them in ascending loop depth, we'll work | |||
1261 | // backwards across these to process them inside out. The order shouldn't | |||
1262 | // matter as we're just trying to build up the map from inside-out; we use | |||
1263 | // the map in a more stably ordered way below. | |||
1264 | auto OrderedClonedExitsInLoops = ClonedExitsInLoops; | |||
1265 | llvm::sort(OrderedClonedExitsInLoops.begin(), OrderedClonedExitsInLoops.end(), | |||
1266 | [&](BasicBlock *LHS, BasicBlock *RHS) { | |||
1267 | return ExitLoopMap.lookup(LHS)->getLoopDepth() < | |||
1268 | ExitLoopMap.lookup(RHS)->getLoopDepth(); | |||
1269 | }); | |||
1270 | ||||
1271 | // Populate the existing ExitLoopMap with everything reachable from each | |||
1272 | // exit, starting from the inner most exit. | |||
1273 | while (!UnloopedBlockSet.empty() && !OrderedClonedExitsInLoops.empty()) { | |||
1274 | assert(Worklist.empty() && "Didn't clear worklist!")(static_cast <bool> (Worklist.empty() && "Didn't clear worklist!" ) ? void (0) : __assert_fail ("Worklist.empty() && \"Didn't clear worklist!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1274, __extension__ __PRETTY_FUNCTION__)); | |||
1275 | ||||
1276 | BasicBlock *ExitBB = OrderedClonedExitsInLoops.pop_back_val(); | |||
1277 | Loop *ExitL = ExitLoopMap.lookup(ExitBB); | |||
1278 | ||||
1279 | // Walk the CFG back until we hit the cloned PH adding everything reachable | |||
1280 | // and in the unlooped set to this exit block's loop. | |||
1281 | Worklist.push_back(ExitBB); | |||
1282 | do { | |||
1283 | BasicBlock *BB = Worklist.pop_back_val(); | |||
1284 | // We can stop recursing at the cloned preheader (if we get there). | |||
1285 | if (BB == ClonedPH) | |||
1286 | continue; | |||
1287 | ||||
1288 | for (BasicBlock *PredBB : predecessors(BB)) { | |||
1289 | // If this pred has already been moved to our set or is part of some | |||
1290 | // (inner) loop, no update needed. | |||
1291 | if (!UnloopedBlockSet.erase(PredBB)) { | |||
1292 | assert((static_cast <bool> ((BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && "Predecessor not mapped to a loop!" ) ? void (0) : __assert_fail ("(BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && \"Predecessor not mapped to a loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1294, __extension__ __PRETTY_FUNCTION__)) | |||
1293 | (BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) &&(static_cast <bool> ((BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && "Predecessor not mapped to a loop!" ) ? void (0) : __assert_fail ("(BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && \"Predecessor not mapped to a loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1294, __extension__ __PRETTY_FUNCTION__)) | |||
1294 | "Predecessor not mapped to a loop!")(static_cast <bool> ((BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && "Predecessor not mapped to a loop!" ) ? void (0) : __assert_fail ("(BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) && \"Predecessor not mapped to a loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1294, __extension__ __PRETTY_FUNCTION__)); | |||
1295 | continue; | |||
1296 | } | |||
1297 | ||||
1298 | // We just insert into the loop set here. We'll add these blocks to the | |||
1299 | // exit loop after we build up the set in an order that doesn't rely on | |||
1300 | // predecessor order (which in turn relies on use list order). | |||
1301 | bool Inserted = ExitLoopMap.insert({PredBB, ExitL}).second; | |||
1302 | (void)Inserted; | |||
1303 | assert(Inserted && "Should only visit an unlooped block once!")(static_cast <bool> (Inserted && "Should only visit an unlooped block once!" ) ? void (0) : __assert_fail ("Inserted && \"Should only visit an unlooped block once!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1303, __extension__ __PRETTY_FUNCTION__)); | |||
1304 | ||||
1305 | // And recurse through to its predecessors. | |||
1306 | Worklist.push_back(PredBB); | |||
1307 | } | |||
1308 | } while (!Worklist.empty()); | |||
1309 | } | |||
1310 | ||||
1311 | // Now that the ExitLoopMap gives as mapping for all the non-looping cloned | |||
1312 | // blocks to their outer loops, walk the cloned blocks and the cloned exits | |||
1313 | // in their original order adding them to the correct loop. | |||
1314 | ||||
1315 | // We need a stable insertion order. We use the order of the original loop | |||
1316 | // order and map into the correct parent loop. | |||
1317 | for (auto *BB : llvm::concat<BasicBlock *const>( | |||
1318 | makeArrayRef(ClonedPH), ClonedLoopBlocks, ClonedExitsInLoops)) | |||
1319 | if (Loop *OuterL = ExitLoopMap.lookup(BB)) | |||
1320 | OuterL->addBasicBlockToLoop(BB, LI); | |||
1321 | ||||
1322 | #ifndef NDEBUG | |||
1323 | for (auto &BBAndL : ExitLoopMap) { | |||
1324 | auto *BB = BBAndL.first; | |||
1325 | auto *OuterL = BBAndL.second; | |||
1326 | assert(LI.getLoopFor(BB) == OuterL &&(static_cast <bool> (LI.getLoopFor(BB) == OuterL && "Failed to put all blocks into outer loops!") ? void (0) : __assert_fail ("LI.getLoopFor(BB) == OuterL && \"Failed to put all blocks into outer loops!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1327, __extension__ __PRETTY_FUNCTION__)) | |||
1327 | "Failed to put all blocks into outer loops!")(static_cast <bool> (LI.getLoopFor(BB) == OuterL && "Failed to put all blocks into outer loops!") ? void (0) : __assert_fail ("LI.getLoopFor(BB) == OuterL && \"Failed to put all blocks into outer loops!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1327, __extension__ __PRETTY_FUNCTION__)); | |||
1328 | } | |||
1329 | #endif | |||
1330 | ||||
1331 | // Now that all the blocks are placed into the correct containing loop in the | |||
1332 | // absence of child loops, find all the potentially cloned child loops and | |||
1333 | // clone them into whatever outer loop we placed their header into. | |||
1334 | for (Loop *ChildL : OrigL) { | |||
1335 | auto *ClonedChildHeader = | |||
1336 | cast_or_null<BasicBlock>(VMap.lookup(ChildL->getHeader())); | |||
1337 | if (!ClonedChildHeader || BlocksInClonedLoop.count(ClonedChildHeader)) | |||
1338 | continue; | |||
1339 | ||||
1340 | #ifndef NDEBUG | |||
1341 | for (auto *ChildLoopBB : ChildL->blocks()) | |||
1342 | assert(VMap.count(ChildLoopBB) &&(static_cast <bool> (VMap.count(ChildLoopBB) && "Cloned a child loop header but not all of that loops blocks!" ) ? void (0) : __assert_fail ("VMap.count(ChildLoopBB) && \"Cloned a child loop header but not all of that loops blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1343, __extension__ __PRETTY_FUNCTION__)) | |||
1343 | "Cloned a child loop header but not all of that loops blocks!")(static_cast <bool> (VMap.count(ChildLoopBB) && "Cloned a child loop header but not all of that loops blocks!" ) ? void (0) : __assert_fail ("VMap.count(ChildLoopBB) && \"Cloned a child loop header but not all of that loops blocks!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1343, __extension__ __PRETTY_FUNCTION__)); | |||
1344 | #endif | |||
1345 | ||||
1346 | NonChildClonedLoops.push_back(cloneLoopNest( | |||
1347 | *ChildL, ExitLoopMap.lookup(ClonedChildHeader), VMap, LI)); | |||
1348 | } | |||
1349 | } | |||
1350 | ||||
1351 | static void | |||
1352 | deleteDeadClonedBlocks(Loop &L, ArrayRef<BasicBlock *> ExitBlocks, | |||
1353 | ArrayRef<std::unique_ptr<ValueToValueMapTy>> VMaps, | |||
1354 | DominatorTree &DT) { | |||
1355 | // Find all the dead clones, and remove them from their successors. | |||
1356 | SmallVector<BasicBlock *, 16> DeadBlocks; | |||
1357 | for (BasicBlock *BB : llvm::concat<BasicBlock *const>(L.blocks(), ExitBlocks)) | |||
1358 | for (auto &VMap : VMaps) | |||
1359 | if (BasicBlock *ClonedBB = cast_or_null<BasicBlock>(VMap->lookup(BB))) | |||
1360 | if (!DT.isReachableFromEntry(ClonedBB)) { | |||
1361 | for (BasicBlock *SuccBB : successors(ClonedBB)) | |||
1362 | SuccBB->removePredecessor(ClonedBB); | |||
1363 | DeadBlocks.push_back(ClonedBB); | |||
1364 | } | |||
1365 | ||||
1366 | // Drop any remaining references to break cycles. | |||
1367 | for (BasicBlock *BB : DeadBlocks) | |||
1368 | BB->dropAllReferences(); | |||
1369 | // Erase them from the IR. | |||
1370 | for (BasicBlock *BB : DeadBlocks) | |||
1371 | BB->eraseFromParent(); | |||
1372 | } | |||
1373 | ||||
1374 | static void | |||
1375 | deleteDeadBlocksFromLoop(Loop &L, | |||
1376 | SmallVectorImpl<BasicBlock *> &ExitBlocks, | |||
1377 | DominatorTree &DT, LoopInfo &LI) { | |||
1378 | // Find all the dead blocks, and remove them from their successors. | |||
1379 | SmallVector<BasicBlock *, 16> DeadBlocks; | |||
1380 | for (BasicBlock *BB : llvm::concat<BasicBlock *const>(L.blocks(), ExitBlocks)) | |||
1381 | if (!DT.isReachableFromEntry(BB)) { | |||
1382 | for (BasicBlock *SuccBB : successors(BB)) | |||
1383 | SuccBB->removePredecessor(BB); | |||
1384 | DeadBlocks.push_back(BB); | |||
1385 | } | |||
1386 | ||||
1387 | SmallPtrSet<BasicBlock *, 16> DeadBlockSet(DeadBlocks.begin(), | |||
1388 | DeadBlocks.end()); | |||
1389 | ||||
1390 | // Filter out the dead blocks from the exit blocks list so that it can be | |||
1391 | // used in the caller. | |||
1392 | llvm::erase_if(ExitBlocks, | |||
1393 | [&](BasicBlock *BB) { return DeadBlockSet.count(BB); }); | |||
1394 | ||||
1395 | // Walk from this loop up through its parents removing all of the dead blocks. | |||
1396 | for (Loop *ParentL = &L; ParentL; ParentL = ParentL->getParentLoop()) { | |||
1397 | for (auto *BB : DeadBlocks) | |||
1398 | ParentL->getBlocksSet().erase(BB); | |||
1399 | llvm::erase_if(ParentL->getBlocksVector(), | |||
1400 | [&](BasicBlock *BB) { return DeadBlockSet.count(BB); }); | |||
1401 | } | |||
1402 | ||||
1403 | // Now delete the dead child loops. This raw delete will clear them | |||
1404 | // recursively. | |||
1405 | llvm::erase_if(L.getSubLoopsVector(), [&](Loop *ChildL) { | |||
1406 | if (!DeadBlockSet.count(ChildL->getHeader())) | |||
1407 | return false; | |||
1408 | ||||
1409 | assert(llvm::all_of(ChildL->blocks(),(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1414, __extension__ __PRETTY_FUNCTION__)) | |||
1410 | [&](BasicBlock *ChildBB) {(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1414, __extension__ __PRETTY_FUNCTION__)) | |||
1411 | return DeadBlockSet.count(ChildBB);(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1414, __extension__ __PRETTY_FUNCTION__)) | |||
1412 | }) &&(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1414, __extension__ __PRETTY_FUNCTION__)) | |||
1413 | "If the child loop header is dead all blocks in the child loop must "(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1414, __extension__ __PRETTY_FUNCTION__)) | |||
1414 | "be dead as well!")(static_cast <bool> (llvm::all_of(ChildL->blocks(), [ &](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB ); }) && "If the child loop header is dead all blocks in the child loop must " "be dead as well!") ? void (0) : __assert_fail ("llvm::all_of(ChildL->blocks(), [&](BasicBlock *ChildBB) { return DeadBlockSet.count(ChildBB); }) && \"If the child loop header is dead all blocks in the child loop must \" \"be dead as well!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1414, __extension__ __PRETTY_FUNCTION__)); | |||
1415 | LI.destroy(ChildL); | |||
1416 | return true; | |||
1417 | }); | |||
1418 | ||||
1419 | // Remove the loop mappings for the dead blocks and drop all the references | |||
1420 | // from these blocks to others to handle cyclic references as we start | |||
1421 | // deleting the blocks themselves. | |||
1422 | for (auto *BB : DeadBlocks) { | |||
1423 | // Check that the dominator tree has already been updated. | |||
1424 | assert(!DT.getNode(BB) && "Should already have cleared domtree!")(static_cast <bool> (!DT.getNode(BB) && "Should already have cleared domtree!" ) ? void (0) : __assert_fail ("!DT.getNode(BB) && \"Should already have cleared domtree!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1424, __extension__ __PRETTY_FUNCTION__)); | |||
1425 | LI.changeLoopFor(BB, nullptr); | |||
1426 | BB->dropAllReferences(); | |||
1427 | } | |||
1428 | ||||
1429 | // Actually delete the blocks now that they've been fully unhooked from the | |||
1430 | // IR. | |||
1431 | for (auto *BB : DeadBlocks) | |||
1432 | BB->eraseFromParent(); | |||
1433 | } | |||
1434 | ||||
1435 | /// Recompute the set of blocks in a loop after unswitching. | |||
1436 | /// | |||
1437 | /// This walks from the original headers predecessors to rebuild the loop. We | |||
1438 | /// take advantage of the fact that new blocks can't have been added, and so we | |||
1439 | /// filter by the original loop's blocks. This also handles potentially | |||
1440 | /// unreachable code that we don't want to explore but might be found examining | |||
1441 | /// the predecessors of the header. | |||
1442 | /// | |||
1443 | /// If the original loop is no longer a loop, this will return an empty set. If | |||
1444 | /// it remains a loop, all the blocks within it will be added to the set | |||
1445 | /// (including those blocks in inner loops). | |||
1446 | static SmallPtrSet<const BasicBlock *, 16> recomputeLoopBlockSet(Loop &L, | |||
1447 | LoopInfo &LI) { | |||
1448 | SmallPtrSet<const BasicBlock *, 16> LoopBlockSet; | |||
1449 | ||||
1450 | auto *PH = L.getLoopPreheader(); | |||
1451 | auto *Header = L.getHeader(); | |||
1452 | ||||
1453 | // A worklist to use while walking backwards from the header. | |||
1454 | SmallVector<BasicBlock *, 16> Worklist; | |||
1455 | ||||
1456 | // First walk the predecessors of the header to find the backedges. This will | |||
1457 | // form the basis of our walk. | |||
1458 | for (auto *Pred : predecessors(Header)) { | |||
1459 | // Skip the preheader. | |||
1460 | if (Pred == PH) | |||
1461 | continue; | |||
1462 | ||||
1463 | // Because the loop was in simplified form, the only non-loop predecessor | |||
1464 | // is the preheader. | |||
1465 | assert(L.contains(Pred) && "Found a predecessor of the loop header other "(static_cast <bool> (L.contains(Pred) && "Found a predecessor of the loop header other " "than the preheader that is not part of the " "loop!") ? void (0) : __assert_fail ("L.contains(Pred) && \"Found a predecessor of the loop header other \" \"than the preheader that is not part of the \" \"loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1467, __extension__ __PRETTY_FUNCTION__)) | |||
1466 | "than the preheader that is not part of the "(static_cast <bool> (L.contains(Pred) && "Found a predecessor of the loop header other " "than the preheader that is not part of the " "loop!") ? void (0) : __assert_fail ("L.contains(Pred) && \"Found a predecessor of the loop header other \" \"than the preheader that is not part of the \" \"loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1467, __extension__ __PRETTY_FUNCTION__)) | |||
1467 | "loop!")(static_cast <bool> (L.contains(Pred) && "Found a predecessor of the loop header other " "than the preheader that is not part of the " "loop!") ? void (0) : __assert_fail ("L.contains(Pred) && \"Found a predecessor of the loop header other \" \"than the preheader that is not part of the \" \"loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1467, __extension__ __PRETTY_FUNCTION__)); | |||
1468 | ||||
1469 | // Insert this block into the loop set and on the first visit and, if it | |||
1470 | // isn't the header we're currently walking, put it into the worklist to | |||
1471 | // recurse through. | |||
1472 | if (LoopBlockSet.insert(Pred).second && Pred != Header) | |||
1473 | Worklist.push_back(Pred); | |||
1474 | } | |||
1475 | ||||
1476 | // If no backedges were found, we're done. | |||
1477 | if (LoopBlockSet.empty()) | |||
1478 | return LoopBlockSet; | |||
1479 | ||||
1480 | // We found backedges, recurse through them to identify the loop blocks. | |||
1481 | while (!Worklist.empty()) { | |||
1482 | BasicBlock *BB = Worklist.pop_back_val(); | |||
1483 | assert(LoopBlockSet.count(BB) && "Didn't put block into the loop set!")(static_cast <bool> (LoopBlockSet.count(BB) && "Didn't put block into the loop set!" ) ? void (0) : __assert_fail ("LoopBlockSet.count(BB) && \"Didn't put block into the loop set!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1483, __extension__ __PRETTY_FUNCTION__)); | |||
1484 | ||||
1485 | // No need to walk past the header. | |||
1486 | if (BB == Header) | |||
1487 | continue; | |||
1488 | ||||
1489 | // Because we know the inner loop structure remains valid we can use the | |||
1490 | // loop structure to jump immediately across the entire nested loop. | |||
1491 | // Further, because it is in loop simplified form, we can directly jump | |||
1492 | // to its preheader afterward. | |||
1493 | if (Loop *InnerL = LI.getLoopFor(BB)) | |||
1494 | if (InnerL != &L) { | |||
1495 | assert(L.contains(InnerL) &&(static_cast <bool> (L.contains(InnerL) && "Should not reach a loop *outside* this loop!" ) ? void (0) : __assert_fail ("L.contains(InnerL) && \"Should not reach a loop *outside* this loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1496, __extension__ __PRETTY_FUNCTION__)) | |||
1496 | "Should not reach a loop *outside* this loop!")(static_cast <bool> (L.contains(InnerL) && "Should not reach a loop *outside* this loop!" ) ? void (0) : __assert_fail ("L.contains(InnerL) && \"Should not reach a loop *outside* this loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1496, __extension__ __PRETTY_FUNCTION__)); | |||
1497 | // The preheader is the only possible predecessor of the loop so | |||
1498 | // insert it into the set and check whether it was already handled. | |||
1499 | auto *InnerPH = InnerL->getLoopPreheader(); | |||
1500 | assert(L.contains(InnerPH) && "Cannot contain an inner loop block "(static_cast <bool> (L.contains(InnerPH) && "Cannot contain an inner loop block " "but not contain the inner loop " "preheader!") ? void (0) : __assert_fail ("L.contains(InnerPH) && \"Cannot contain an inner loop block \" \"but not contain the inner loop \" \"preheader!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1502, __extension__ __PRETTY_FUNCTION__)) | |||
1501 | "but not contain the inner loop "(static_cast <bool> (L.contains(InnerPH) && "Cannot contain an inner loop block " "but not contain the inner loop " "preheader!") ? void (0) : __assert_fail ("L.contains(InnerPH) && \"Cannot contain an inner loop block \" \"but not contain the inner loop \" \"preheader!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1502, __extension__ __PRETTY_FUNCTION__)) | |||
1502 | "preheader!")(static_cast <bool> (L.contains(InnerPH) && "Cannot contain an inner loop block " "but not contain the inner loop " "preheader!") ? void (0) : __assert_fail ("L.contains(InnerPH) && \"Cannot contain an inner loop block \" \"but not contain the inner loop \" \"preheader!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1502, __extension__ __PRETTY_FUNCTION__)); | |||
1503 | if (!LoopBlockSet.insert(InnerPH).second) | |||
1504 | // The only way to reach the preheader is through the loop body | |||
1505 | // itself so if it has been visited the loop is already handled. | |||
1506 | continue; | |||
1507 | ||||
1508 | // Insert all of the blocks (other than those already present) into | |||
1509 | // the loop set. We expect at least the block that led us to find the | |||
1510 | // inner loop to be in the block set, but we may also have other loop | |||
1511 | // blocks if they were already enqueued as predecessors of some other | |||
1512 | // outer loop block. | |||
1513 | for (auto *InnerBB : InnerL->blocks()) { | |||
1514 | if (InnerBB == BB) { | |||
1515 | assert(LoopBlockSet.count(InnerBB) &&(static_cast <bool> (LoopBlockSet.count(InnerBB) && "Block should already be in the set!") ? void (0) : __assert_fail ("LoopBlockSet.count(InnerBB) && \"Block should already be in the set!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1516, __extension__ __PRETTY_FUNCTION__)) | |||
1516 | "Block should already be in the set!")(static_cast <bool> (LoopBlockSet.count(InnerBB) && "Block should already be in the set!") ? void (0) : __assert_fail ("LoopBlockSet.count(InnerBB) && \"Block should already be in the set!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1516, __extension__ __PRETTY_FUNCTION__)); | |||
1517 | continue; | |||
1518 | } | |||
1519 | ||||
1520 | LoopBlockSet.insert(InnerBB); | |||
1521 | } | |||
1522 | ||||
1523 | // Add the preheader to the worklist so we will continue past the | |||
1524 | // loop body. | |||
1525 | Worklist.push_back(InnerPH); | |||
1526 | continue; | |||
1527 | } | |||
1528 | ||||
1529 | // Insert any predecessors that were in the original loop into the new | |||
1530 | // set, and if the insert is successful, add them to the worklist. | |||
1531 | for (auto *Pred : predecessors(BB)) | |||
1532 | if (L.contains(Pred) && LoopBlockSet.insert(Pred).second) | |||
1533 | Worklist.push_back(Pred); | |||
1534 | } | |||
1535 | ||||
1536 | assert(LoopBlockSet.count(Header) && "Cannot fail to add the header!")(static_cast <bool> (LoopBlockSet.count(Header) && "Cannot fail to add the header!") ? void (0) : __assert_fail ("LoopBlockSet.count(Header) && \"Cannot fail to add the header!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1536, __extension__ __PRETTY_FUNCTION__)); | |||
1537 | ||||
1538 | // We've found all the blocks participating in the loop, return our completed | |||
1539 | // set. | |||
1540 | return LoopBlockSet; | |||
1541 | } | |||
1542 | ||||
1543 | /// Rebuild a loop after unswitching removes some subset of blocks and edges. | |||
1544 | /// | |||
1545 | /// The removal may have removed some child loops entirely but cannot have | |||
1546 | /// disturbed any remaining child loops. However, they may need to be hoisted | |||
1547 | /// to the parent loop (or to be top-level loops). The original loop may be | |||
1548 | /// completely removed. | |||
1549 | /// | |||
1550 | /// The sibling loops resulting from this update are returned. If the original | |||
1551 | /// loop remains a valid loop, it will be the first entry in this list with all | |||
1552 | /// of the newly sibling loops following it. | |||
1553 | /// | |||
1554 | /// Returns true if the loop remains a loop after unswitching, and false if it | |||
1555 | /// is no longer a loop after unswitching (and should not continue to be | |||
1556 | /// referenced). | |||
1557 | static bool rebuildLoopAfterUnswitch(Loop &L, ArrayRef<BasicBlock *> ExitBlocks, | |||
1558 | LoopInfo &LI, | |||
1559 | SmallVectorImpl<Loop *> &HoistedLoops) { | |||
1560 | auto *PH = L.getLoopPreheader(); | |||
1561 | ||||
1562 | // Compute the actual parent loop from the exit blocks. Because we may have | |||
1563 | // pruned some exits the loop may be different from the original parent. | |||
1564 | Loop *ParentL = nullptr; | |||
1565 | SmallVector<Loop *, 4> ExitLoops; | |||
1566 | SmallVector<BasicBlock *, 4> ExitsInLoops; | |||
1567 | ExitsInLoops.reserve(ExitBlocks.size()); | |||
1568 | for (auto *ExitBB : ExitBlocks) | |||
1569 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) { | |||
1570 | ExitLoops.push_back(ExitL); | |||
1571 | ExitsInLoops.push_back(ExitBB); | |||
1572 | if (!ParentL || (ParentL != ExitL && ParentL->contains(ExitL))) | |||
1573 | ParentL = ExitL; | |||
1574 | } | |||
1575 | ||||
1576 | // Recompute the blocks participating in this loop. This may be empty if it | |||
1577 | // is no longer a loop. | |||
1578 | auto LoopBlockSet = recomputeLoopBlockSet(L, LI); | |||
1579 | ||||
1580 | // If we still have a loop, we need to re-set the loop's parent as the exit | |||
1581 | // block set changing may have moved it within the loop nest. Note that this | |||
1582 | // can only happen when this loop has a parent as it can only hoist the loop | |||
1583 | // *up* the nest. | |||
1584 | if (!LoopBlockSet.empty() && L.getParentLoop() != ParentL) { | |||
1585 | // Remove this loop's (original) blocks from all of the intervening loops. | |||
1586 | for (Loop *IL = L.getParentLoop(); IL != ParentL; | |||
1587 | IL = IL->getParentLoop()) { | |||
1588 | IL->getBlocksSet().erase(PH); | |||
1589 | for (auto *BB : L.blocks()) | |||
1590 | IL->getBlocksSet().erase(BB); | |||
1591 | llvm::erase_if(IL->getBlocksVector(), [&](BasicBlock *BB) { | |||
1592 | return BB == PH || L.contains(BB); | |||
1593 | }); | |||
1594 | } | |||
1595 | ||||
1596 | LI.changeLoopFor(PH, ParentL); | |||
1597 | L.getParentLoop()->removeChildLoop(&L); | |||
1598 | if (ParentL) | |||
1599 | ParentL->addChildLoop(&L); | |||
1600 | else | |||
1601 | LI.addTopLevelLoop(&L); | |||
1602 | } | |||
1603 | ||||
1604 | // Now we update all the blocks which are no longer within the loop. | |||
1605 | auto &Blocks = L.getBlocksVector(); | |||
1606 | auto BlocksSplitI = | |||
1607 | LoopBlockSet.empty() | |||
1608 | ? Blocks.begin() | |||
1609 | : std::stable_partition( | |||
1610 | Blocks.begin(), Blocks.end(), | |||
1611 | [&](BasicBlock *BB) { return LoopBlockSet.count(BB); }); | |||
1612 | ||||
1613 | // Before we erase the list of unlooped blocks, build a set of them. | |||
1614 | SmallPtrSet<BasicBlock *, 16> UnloopedBlocks(BlocksSplitI, Blocks.end()); | |||
1615 | if (LoopBlockSet.empty()) | |||
1616 | UnloopedBlocks.insert(PH); | |||
1617 | ||||
1618 | // Now erase these blocks from the loop. | |||
1619 | for (auto *BB : make_range(BlocksSplitI, Blocks.end())) | |||
1620 | L.getBlocksSet().erase(BB); | |||
1621 | Blocks.erase(BlocksSplitI, Blocks.end()); | |||
1622 | ||||
1623 | // Sort the exits in ascending loop depth, we'll work backwards across these | |||
1624 | // to process them inside out. | |||
1625 | std::stable_sort(ExitsInLoops.begin(), ExitsInLoops.end(), | |||
1626 | [&](BasicBlock *LHS, BasicBlock *RHS) { | |||
1627 | return LI.getLoopDepth(LHS) < LI.getLoopDepth(RHS); | |||
1628 | }); | |||
1629 | ||||
1630 | // We'll build up a set for each exit loop. | |||
1631 | SmallPtrSet<BasicBlock *, 16> NewExitLoopBlocks; | |||
1632 | Loop *PrevExitL = L.getParentLoop(); // The deepest possible exit loop. | |||
1633 | ||||
1634 | auto RemoveUnloopedBlocksFromLoop = | |||
1635 | [](Loop &L, SmallPtrSetImpl<BasicBlock *> &UnloopedBlocks) { | |||
1636 | for (auto *BB : UnloopedBlocks) | |||
1637 | L.getBlocksSet().erase(BB); | |||
1638 | llvm::erase_if(L.getBlocksVector(), [&](BasicBlock *BB) { | |||
1639 | return UnloopedBlocks.count(BB); | |||
1640 | }); | |||
1641 | }; | |||
1642 | ||||
1643 | SmallVector<BasicBlock *, 16> Worklist; | |||
1644 | while (!UnloopedBlocks.empty() && !ExitsInLoops.empty()) { | |||
1645 | assert(Worklist.empty() && "Didn't clear worklist!")(static_cast <bool> (Worklist.empty() && "Didn't clear worklist!" ) ? void (0) : __assert_fail ("Worklist.empty() && \"Didn't clear worklist!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1645, __extension__ __PRETTY_FUNCTION__)); | |||
1646 | assert(NewExitLoopBlocks.empty() && "Didn't clear loop set!")(static_cast <bool> (NewExitLoopBlocks.empty() && "Didn't clear loop set!") ? void (0) : __assert_fail ("NewExitLoopBlocks.empty() && \"Didn't clear loop set!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1646, __extension__ __PRETTY_FUNCTION__)); | |||
1647 | ||||
1648 | // Grab the next exit block, in decreasing loop depth order. | |||
1649 | BasicBlock *ExitBB = ExitsInLoops.pop_back_val(); | |||
1650 | Loop &ExitL = *LI.getLoopFor(ExitBB); | |||
1651 | assert(ExitL.contains(&L) && "Exit loop must contain the inner loop!")(static_cast <bool> (ExitL.contains(&L) && "Exit loop must contain the inner loop!" ) ? void (0) : __assert_fail ("ExitL.contains(&L) && \"Exit loop must contain the inner loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1651, __extension__ __PRETTY_FUNCTION__)); | |||
1652 | ||||
1653 | // Erase all of the unlooped blocks from the loops between the previous | |||
1654 | // exit loop and this exit loop. This works because the ExitInLoops list is | |||
1655 | // sorted in increasing order of loop depth and thus we visit loops in | |||
1656 | // decreasing order of loop depth. | |||
1657 | for (; PrevExitL != &ExitL; PrevExitL = PrevExitL->getParentLoop()) | |||
1658 | RemoveUnloopedBlocksFromLoop(*PrevExitL, UnloopedBlocks); | |||
1659 | ||||
1660 | // Walk the CFG back until we hit the cloned PH adding everything reachable | |||
1661 | // and in the unlooped set to this exit block's loop. | |||
1662 | Worklist.push_back(ExitBB); | |||
1663 | do { | |||
1664 | BasicBlock *BB = Worklist.pop_back_val(); | |||
1665 | // We can stop recursing at the cloned preheader (if we get there). | |||
1666 | if (BB == PH) | |||
1667 | continue; | |||
1668 | ||||
1669 | for (BasicBlock *PredBB : predecessors(BB)) { | |||
1670 | // If this pred has already been moved to our set or is part of some | |||
1671 | // (inner) loop, no update needed. | |||
1672 | if (!UnloopedBlocks.erase(PredBB)) { | |||
1673 | assert((NewExitLoopBlocks.count(PredBB) ||(static_cast <bool> ((NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && "Predecessor not in a nested loop (or already visited)!" ) ? void (0) : __assert_fail ("(NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && \"Predecessor not in a nested loop (or already visited)!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1675, __extension__ __PRETTY_FUNCTION__)) | |||
1674 | ExitL.contains(LI.getLoopFor(PredBB))) &&(static_cast <bool> ((NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && "Predecessor not in a nested loop (or already visited)!" ) ? void (0) : __assert_fail ("(NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && \"Predecessor not in a nested loop (or already visited)!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1675, __extension__ __PRETTY_FUNCTION__)) | |||
1675 | "Predecessor not in a nested loop (or already visited)!")(static_cast <bool> ((NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && "Predecessor not in a nested loop (or already visited)!" ) ? void (0) : __assert_fail ("(NewExitLoopBlocks.count(PredBB) || ExitL.contains(LI.getLoopFor(PredBB))) && \"Predecessor not in a nested loop (or already visited)!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1675, __extension__ __PRETTY_FUNCTION__)); | |||
1676 | continue; | |||
1677 | } | |||
1678 | ||||
1679 | // We just insert into the loop set here. We'll add these blocks to the | |||
1680 | // exit loop after we build up the set in a deterministic order rather | |||
1681 | // than the predecessor-influenced visit order. | |||
1682 | bool Inserted = NewExitLoopBlocks.insert(PredBB).second; | |||
1683 | (void)Inserted; | |||
1684 | assert(Inserted && "Should only visit an unlooped block once!")(static_cast <bool> (Inserted && "Should only visit an unlooped block once!" ) ? void (0) : __assert_fail ("Inserted && \"Should only visit an unlooped block once!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1684, __extension__ __PRETTY_FUNCTION__)); | |||
1685 | ||||
1686 | // And recurse through to its predecessors. | |||
1687 | Worklist.push_back(PredBB); | |||
1688 | } | |||
1689 | } while (!Worklist.empty()); | |||
1690 | ||||
1691 | // If blocks in this exit loop were directly part of the original loop (as | |||
1692 | // opposed to a child loop) update the map to point to this exit loop. This | |||
1693 | // just updates a map and so the fact that the order is unstable is fine. | |||
1694 | for (auto *BB : NewExitLoopBlocks) | |||
1695 | if (Loop *BBL = LI.getLoopFor(BB)) | |||
1696 | if (BBL == &L || !L.contains(BBL)) | |||
1697 | LI.changeLoopFor(BB, &ExitL); | |||
1698 | ||||
1699 | // We will remove the remaining unlooped blocks from this loop in the next | |||
1700 | // iteration or below. | |||
1701 | NewExitLoopBlocks.clear(); | |||
1702 | } | |||
1703 | ||||
1704 | // Any remaining unlooped blocks are no longer part of any loop unless they | |||
1705 | // are part of some child loop. | |||
1706 | for (; PrevExitL; PrevExitL = PrevExitL->getParentLoop()) | |||
1707 | RemoveUnloopedBlocksFromLoop(*PrevExitL, UnloopedBlocks); | |||
1708 | for (auto *BB : UnloopedBlocks) | |||
1709 | if (Loop *BBL = LI.getLoopFor(BB)) | |||
1710 | if (BBL == &L || !L.contains(BBL)) | |||
1711 | LI.changeLoopFor(BB, nullptr); | |||
1712 | ||||
1713 | // Sink all the child loops whose headers are no longer in the loop set to | |||
1714 | // the parent (or to be top level loops). We reach into the loop and directly | |||
1715 | // update its subloop vector to make this batch update efficient. | |||
1716 | auto &SubLoops = L.getSubLoopsVector(); | |||
1717 | auto SubLoopsSplitI = | |||
1718 | LoopBlockSet.empty() | |||
1719 | ? SubLoops.begin() | |||
1720 | : std::stable_partition( | |||
1721 | SubLoops.begin(), SubLoops.end(), [&](Loop *SubL) { | |||
1722 | return LoopBlockSet.count(SubL->getHeader()); | |||
1723 | }); | |||
1724 | for (auto *HoistedL : make_range(SubLoopsSplitI, SubLoops.end())) { | |||
1725 | HoistedLoops.push_back(HoistedL); | |||
1726 | HoistedL->setParentLoop(nullptr); | |||
1727 | ||||
1728 | // To compute the new parent of this hoisted loop we look at where we | |||
1729 | // placed the preheader above. We can't lookup the header itself because we | |||
1730 | // retained the mapping from the header to the hoisted loop. But the | |||
1731 | // preheader and header should have the exact same new parent computed | |||
1732 | // based on the set of exit blocks from the original loop as the preheader | |||
1733 | // is a predecessor of the header and so reached in the reverse walk. And | |||
1734 | // because the loops were all in simplified form the preheader of the | |||
1735 | // hoisted loop can't be part of some *other* loop. | |||
1736 | if (auto *NewParentL = LI.getLoopFor(HoistedL->getLoopPreheader())) | |||
1737 | NewParentL->addChildLoop(HoistedL); | |||
1738 | else | |||
1739 | LI.addTopLevelLoop(HoistedL); | |||
1740 | } | |||
1741 | SubLoops.erase(SubLoopsSplitI, SubLoops.end()); | |||
1742 | ||||
1743 | // Actually delete the loop if nothing remained within it. | |||
1744 | if (Blocks.empty()) { | |||
1745 | assert(SubLoops.empty() &&(static_cast <bool> (SubLoops.empty() && "Failed to remove all subloops from the original loop!" ) ? void (0) : __assert_fail ("SubLoops.empty() && \"Failed to remove all subloops from the original loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1746, __extension__ __PRETTY_FUNCTION__)) | |||
1746 | "Failed to remove all subloops from the original loop!")(static_cast <bool> (SubLoops.empty() && "Failed to remove all subloops from the original loop!" ) ? void (0) : __assert_fail ("SubLoops.empty() && \"Failed to remove all subloops from the original loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1746, __extension__ __PRETTY_FUNCTION__)); | |||
1747 | if (Loop *ParentL = L.getParentLoop()) | |||
1748 | ParentL->removeChildLoop(llvm::find(*ParentL, &L)); | |||
1749 | else | |||
1750 | LI.removeLoop(llvm::find(LI, &L)); | |||
1751 | LI.destroy(&L); | |||
1752 | return false; | |||
1753 | } | |||
1754 | ||||
1755 | return true; | |||
1756 | } | |||
1757 | ||||
1758 | /// Helper to visit a dominator subtree, invoking a callable on each node. | |||
1759 | /// | |||
1760 | /// Returning false at any point will stop walking past that node of the tree. | |||
1761 | template <typename CallableT> | |||
1762 | void visitDomSubTree(DominatorTree &DT, BasicBlock *BB, CallableT Callable) { | |||
1763 | SmallVector<DomTreeNode *, 4> DomWorklist; | |||
1764 | DomWorklist.push_back(DT[BB]); | |||
1765 | #ifndef NDEBUG | |||
1766 | SmallPtrSet<DomTreeNode *, 4> Visited; | |||
1767 | Visited.insert(DT[BB]); | |||
1768 | #endif | |||
1769 | do { | |||
1770 | DomTreeNode *N = DomWorklist.pop_back_val(); | |||
1771 | ||||
1772 | // Visit this node. | |||
1773 | if (!Callable(N->getBlock())) | |||
1774 | continue; | |||
1775 | ||||
1776 | // Accumulate the child nodes. | |||
1777 | for (DomTreeNode *ChildN : *N) { | |||
1778 | assert(Visited.insert(ChildN).second &&(static_cast <bool> (Visited.insert(ChildN).second && "Cannot visit a node twice when walking a tree!") ? void (0) : __assert_fail ("Visited.insert(ChildN).second && \"Cannot visit a node twice when walking a tree!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1779, __extension__ __PRETTY_FUNCTION__)) | |||
1779 | "Cannot visit a node twice when walking a tree!")(static_cast <bool> (Visited.insert(ChildN).second && "Cannot visit a node twice when walking a tree!") ? void (0) : __assert_fail ("Visited.insert(ChildN).second && \"Cannot visit a node twice when walking a tree!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1779, __extension__ __PRETTY_FUNCTION__)); | |||
1780 | DomWorklist.push_back(ChildN); | |||
1781 | } | |||
1782 | } while (!DomWorklist.empty()); | |||
1783 | } | |||
1784 | ||||
1785 | static bool unswitchNontrivialInvariants( | |||
1786 | Loop &L, TerminatorInst &TI, ArrayRef<Value *> Invariants, | |||
1787 | DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC, | |||
1788 | function_ref<void(bool, ArrayRef<Loop *>)> UnswitchCB, | |||
1789 | ScalarEvolution *SE) { | |||
1790 | auto *ParentBB = TI.getParent(); | |||
1791 | BranchInst *BI = dyn_cast<BranchInst>(&TI); | |||
1792 | SwitchInst *SI = BI ? nullptr : cast<SwitchInst>(&TI); | |||
1793 | ||||
1794 | // We can only unswitch switches, conditional branches with an invariant | |||
1795 | // condition, or combining invariant conditions with an instruction. | |||
1796 | assert((SI || BI->isConditional()) &&(static_cast <bool> ((SI || BI->isConditional()) && "Can only unswitch switches and conditional branch!") ? void (0) : __assert_fail ("(SI || BI->isConditional()) && \"Can only unswitch switches and conditional branch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1797, __extension__ __PRETTY_FUNCTION__)) | |||
1797 | "Can only unswitch switches and conditional branch!")(static_cast <bool> ((SI || BI->isConditional()) && "Can only unswitch switches and conditional branch!") ? void (0) : __assert_fail ("(SI || BI->isConditional()) && \"Can only unswitch switches and conditional branch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1797, __extension__ __PRETTY_FUNCTION__)); | |||
1798 | bool FullUnswitch = SI || BI->getCondition() == Invariants[0]; | |||
1799 | if (FullUnswitch) | |||
1800 | assert(Invariants.size() == 1 &&(static_cast <bool> (Invariants.size() == 1 && "Cannot have other invariants with full unswitching!" ) ? void (0) : __assert_fail ("Invariants.size() == 1 && \"Cannot have other invariants with full unswitching!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1801, __extension__ __PRETTY_FUNCTION__)) | |||
1801 | "Cannot have other invariants with full unswitching!")(static_cast <bool> (Invariants.size() == 1 && "Cannot have other invariants with full unswitching!" ) ? void (0) : __assert_fail ("Invariants.size() == 1 && \"Cannot have other invariants with full unswitching!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1801, __extension__ __PRETTY_FUNCTION__)); | |||
1802 | else | |||
1803 | assert(isa<Instruction>(BI->getCondition()) &&(static_cast <bool> (isa<Instruction>(BI->getCondition ()) && "Partial unswitching requires an instruction as the condition!" ) ? void (0) : __assert_fail ("isa<Instruction>(BI->getCondition()) && \"Partial unswitching requires an instruction as the condition!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1804, __extension__ __PRETTY_FUNCTION__)) | |||
1804 | "Partial unswitching requires an instruction as the condition!")(static_cast <bool> (isa<Instruction>(BI->getCondition ()) && "Partial unswitching requires an instruction as the condition!" ) ? void (0) : __assert_fail ("isa<Instruction>(BI->getCondition()) && \"Partial unswitching requires an instruction as the condition!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1804, __extension__ __PRETTY_FUNCTION__)); | |||
1805 | ||||
1806 | // Constant and BBs tracking the cloned and continuing successor. When we are | |||
1807 | // unswitching the entire condition, this can just be trivially chosen to | |||
1808 | // unswitch towards `true`. However, when we are unswitching a set of | |||
1809 | // invariants combined with `and` or `or`, the combining operation determines | |||
1810 | // the best direction to unswitch: we want to unswitch the direction that will | |||
1811 | // collapse the branch. | |||
1812 | bool Direction = true; | |||
1813 | int ClonedSucc = 0; | |||
1814 | if (!FullUnswitch) { | |||
1815 | if (cast<Instruction>(BI->getCondition())->getOpcode() != Instruction::Or) { | |||
1816 | assert(cast<Instruction>(BI->getCondition())->getOpcode() ==(static_cast <bool> (cast<Instruction>(BI->getCondition ())->getOpcode() == Instruction::And && "Only `or` and `and` instructions can combine invariants being " "unswitched.") ? void (0) : __assert_fail ("cast<Instruction>(BI->getCondition())->getOpcode() == Instruction::And && \"Only `or` and `and` instructions can combine invariants being \" \"unswitched.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1819, __extension__ __PRETTY_FUNCTION__)) | |||
1817 | Instruction::And &&(static_cast <bool> (cast<Instruction>(BI->getCondition ())->getOpcode() == Instruction::And && "Only `or` and `and` instructions can combine invariants being " "unswitched.") ? void (0) : __assert_fail ("cast<Instruction>(BI->getCondition())->getOpcode() == Instruction::And && \"Only `or` and `and` instructions can combine invariants being \" \"unswitched.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1819, __extension__ __PRETTY_FUNCTION__)) | |||
1818 | "Only `or` and `and` instructions can combine invariants being "(static_cast <bool> (cast<Instruction>(BI->getCondition ())->getOpcode() == Instruction::And && "Only `or` and `and` instructions can combine invariants being " "unswitched.") ? void (0) : __assert_fail ("cast<Instruction>(BI->getCondition())->getOpcode() == Instruction::And && \"Only `or` and `and` instructions can combine invariants being \" \"unswitched.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1819, __extension__ __PRETTY_FUNCTION__)) | |||
1819 | "unswitched.")(static_cast <bool> (cast<Instruction>(BI->getCondition ())->getOpcode() == Instruction::And && "Only `or` and `and` instructions can combine invariants being " "unswitched.") ? void (0) : __assert_fail ("cast<Instruction>(BI->getCondition())->getOpcode() == Instruction::And && \"Only `or` and `and` instructions can combine invariants being \" \"unswitched.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1819, __extension__ __PRETTY_FUNCTION__)); | |||
1820 | Direction = false; | |||
1821 | ClonedSucc = 1; | |||
1822 | } | |||
1823 | } | |||
1824 | ||||
1825 | BasicBlock *RetainedSuccBB = | |||
1826 | BI ? BI->getSuccessor(1 - ClonedSucc) : SI->getDefaultDest(); | |||
1827 | SmallSetVector<BasicBlock *, 4> UnswitchedSuccBBs; | |||
1828 | if (BI) | |||
1829 | UnswitchedSuccBBs.insert(BI->getSuccessor(ClonedSucc)); | |||
1830 | else | |||
1831 | for (auto Case : SI->cases()) | |||
1832 | if (Case.getCaseSuccessor() != RetainedSuccBB) | |||
1833 | UnswitchedSuccBBs.insert(Case.getCaseSuccessor()); | |||
1834 | ||||
1835 | assert(!UnswitchedSuccBBs.count(RetainedSuccBB) &&(static_cast <bool> (!UnswitchedSuccBBs.count(RetainedSuccBB ) && "Should not unswitch the same successor we are retaining!" ) ? void (0) : __assert_fail ("!UnswitchedSuccBBs.count(RetainedSuccBB) && \"Should not unswitch the same successor we are retaining!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1836, __extension__ __PRETTY_FUNCTION__)) | |||
1836 | "Should not unswitch the same successor we are retaining!")(static_cast <bool> (!UnswitchedSuccBBs.count(RetainedSuccBB ) && "Should not unswitch the same successor we are retaining!" ) ? void (0) : __assert_fail ("!UnswitchedSuccBBs.count(RetainedSuccBB) && \"Should not unswitch the same successor we are retaining!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1836, __extension__ __PRETTY_FUNCTION__)); | |||
1837 | ||||
1838 | // The branch should be in this exact loop. Any inner loop's invariant branch | |||
1839 | // should be handled by unswitching that inner loop. The caller of this | |||
1840 | // routine should filter out any candidates that remain (but were skipped for | |||
1841 | // whatever reason). | |||
1842 | assert(LI.getLoopFor(ParentBB) == &L && "Branch in an inner loop!")(static_cast <bool> (LI.getLoopFor(ParentBB) == &L && "Branch in an inner loop!") ? void (0) : __assert_fail ("LI.getLoopFor(ParentBB) == &L && \"Branch in an inner loop!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1842, __extension__ __PRETTY_FUNCTION__)); | |||
1843 | ||||
1844 | SmallVector<BasicBlock *, 4> ExitBlocks; | |||
1845 | L.getUniqueExitBlocks(ExitBlocks); | |||
1846 | ||||
1847 | // We cannot unswitch if exit blocks contain a cleanuppad instruction as we | |||
1848 | // don't know how to split those exit blocks. | |||
1849 | // FIXME: We should teach SplitBlock to handle this and remove this | |||
1850 | // restriction. | |||
1851 | for (auto *ExitBB : ExitBlocks) | |||
1852 | if (isa<CleanupPadInst>(ExitBB->getFirstNonPHI())) | |||
1853 | return false; | |||
1854 | ||||
1855 | // Compute the parent loop now before we start hacking on things. | |||
1856 | Loop *ParentL = L.getParentLoop(); | |||
1857 | ||||
1858 | // Compute the outer-most loop containing one of our exit blocks. This is the | |||
1859 | // furthest up our loopnest which can be mutated, which we will use below to | |||
1860 | // update things. | |||
1861 | Loop *OuterExitL = &L; | |||
1862 | for (auto *ExitBB : ExitBlocks) { | |||
1863 | Loop *NewOuterExitL = LI.getLoopFor(ExitBB); | |||
1864 | if (!NewOuterExitL) { | |||
1865 | // We exited the entire nest with this block, so we're done. | |||
1866 | OuterExitL = nullptr; | |||
1867 | break; | |||
1868 | } | |||
1869 | if (NewOuterExitL != OuterExitL && NewOuterExitL->contains(OuterExitL)) | |||
1870 | OuterExitL = NewOuterExitL; | |||
1871 | } | |||
1872 | ||||
1873 | // At this point, we're definitely going to unswitch something so invalidate | |||
1874 | // any cached information in ScalarEvolution for the outer most loop | |||
1875 | // containing an exit block and all nested loops. | |||
1876 | if (SE) { | |||
1877 | if (OuterExitL) | |||
1878 | SE->forgetLoop(OuterExitL); | |||
1879 | else | |||
1880 | SE->forgetTopmostLoop(&L); | |||
1881 | } | |||
1882 | ||||
1883 | // If the edge from this terminator to a successor dominates that successor, | |||
1884 | // store a map from each block in its dominator subtree to it. This lets us | |||
1885 | // tell when cloning for a particular successor if a block is dominated by | |||
1886 | // some *other* successor with a single data structure. We use this to | |||
1887 | // significantly reduce cloning. | |||
1888 | SmallDenseMap<BasicBlock *, BasicBlock *, 16> DominatingSucc; | |||
1889 | for (auto *SuccBB : llvm::concat<BasicBlock *const>( | |||
1890 | makeArrayRef(RetainedSuccBB), UnswitchedSuccBBs)) | |||
1891 | if (SuccBB->getUniquePredecessor() || | |||
1892 | llvm::all_of(predecessors(SuccBB), [&](BasicBlock *PredBB) { | |||
1893 | return PredBB == ParentBB || DT.dominates(SuccBB, PredBB); | |||
1894 | })) | |||
1895 | visitDomSubTree(DT, SuccBB, [&](BasicBlock *BB) { | |||
1896 | DominatingSucc[BB] = SuccBB; | |||
1897 | return true; | |||
1898 | }); | |||
1899 | ||||
1900 | // Split the preheader, so that we know that there is a safe place to insert | |||
1901 | // the conditional branch. We will change the preheader to have a conditional | |||
1902 | // branch on LoopCond. The original preheader will become the split point | |||
1903 | // between the unswitched versions, and we will have a new preheader for the | |||
1904 | // original loop. | |||
1905 | BasicBlock *SplitBB = L.getLoopPreheader(); | |||
1906 | BasicBlock *LoopPH = SplitEdge(SplitBB, L.getHeader(), &DT, &LI); | |||
1907 | ||||
1908 | // Keep track of the dominator tree updates needed. | |||
1909 | SmallVector<DominatorTree::UpdateType, 4> DTUpdates; | |||
1910 | ||||
1911 | // Clone the loop for each unswitched successor. | |||
1912 | SmallVector<std::unique_ptr<ValueToValueMapTy>, 4> VMaps; | |||
1913 | VMaps.reserve(UnswitchedSuccBBs.size()); | |||
1914 | SmallDenseMap<BasicBlock *, BasicBlock *, 4> ClonedPHs; | |||
1915 | for (auto *SuccBB : UnswitchedSuccBBs) { | |||
1916 | VMaps.emplace_back(new ValueToValueMapTy()); | |||
1917 | ClonedPHs[SuccBB] = buildClonedLoopBlocks( | |||
1918 | L, LoopPH, SplitBB, ExitBlocks, ParentBB, SuccBB, RetainedSuccBB, | |||
1919 | DominatingSucc, *VMaps.back(), DTUpdates, AC, DT, LI); | |||
1920 | } | |||
1921 | ||||
1922 | // The stitching of the branched code back together depends on whether we're | |||
1923 | // doing full unswitching or not with the exception that we always want to | |||
1924 | // nuke the initial terminator placed in the split block. | |||
1925 | SplitBB->getTerminator()->eraseFromParent(); | |||
1926 | if (FullUnswitch) { | |||
1927 | // First we need to unhook the successor relationship as we'll be replacing | |||
1928 | // the terminator with a direct branch. This is much simpler for branches | |||
1929 | // than switches so we handle those first. | |||
1930 | if (BI) { | |||
1931 | // Remove the parent as a predecessor of the unswitched successor. | |||
1932 | assert(UnswitchedSuccBBs.size() == 1 &&(static_cast <bool> (UnswitchedSuccBBs.size() == 1 && "Only one possible unswitched block for a branch!") ? void ( 0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1933, __extension__ __PRETTY_FUNCTION__)) | |||
1933 | "Only one possible unswitched block for a branch!")(static_cast <bool> (UnswitchedSuccBBs.size() == 1 && "Only one possible unswitched block for a branch!") ? void ( 0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1933, __extension__ __PRETTY_FUNCTION__)); | |||
1934 | BasicBlock *UnswitchedSuccBB = *UnswitchedSuccBBs.begin(); | |||
1935 | UnswitchedSuccBB->removePredecessor(ParentBB, | |||
1936 | /*DontDeleteUselessPHIs*/ true); | |||
1937 | DTUpdates.push_back({DominatorTree::Delete, ParentBB, UnswitchedSuccBB}); | |||
1938 | } else { | |||
1939 | // Note that we actually want to remove the parent block as a predecessor | |||
1940 | // of *every* case successor. The case successor is either unswitched, | |||
1941 | // completely eliminating an edge from the parent to that successor, or it | |||
1942 | // is a duplicate edge to the retained successor as the retained successor | |||
1943 | // is always the default successor and as we'll replace this with a direct | |||
1944 | // branch we no longer need the duplicate entries in the PHI nodes. | |||
1945 | assert(SI->getDefaultDest() == RetainedSuccBB &&(static_cast <bool> (SI->getDefaultDest() == RetainedSuccBB && "Not retaining default successor!") ? void (0) : __assert_fail ("SI->getDefaultDest() == RetainedSuccBB && \"Not retaining default successor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1946, __extension__ __PRETTY_FUNCTION__)) | |||
1946 | "Not retaining default successor!")(static_cast <bool> (SI->getDefaultDest() == RetainedSuccBB && "Not retaining default successor!") ? void (0) : __assert_fail ("SI->getDefaultDest() == RetainedSuccBB && \"Not retaining default successor!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1946, __extension__ __PRETTY_FUNCTION__)); | |||
1947 | for (auto &Case : SI->cases()) | |||
1948 | Case.getCaseSuccessor()->removePredecessor( | |||
1949 | ParentBB, | |||
1950 | /*DontDeleteUselessPHIs*/ true); | |||
1951 | ||||
1952 | // We need to use the set to populate domtree updates as even when there | |||
1953 | // are multiple cases pointing at the same successor we only want to | |||
1954 | // remove and insert one edge in the domtree. | |||
1955 | for (BasicBlock *SuccBB : UnswitchedSuccBBs) | |||
1956 | DTUpdates.push_back({DominatorTree::Delete, ParentBB, SuccBB}); | |||
1957 | } | |||
1958 | ||||
1959 | // Now that we've unhooked the successor relationship, splice the terminator | |||
1960 | // from the original loop to the split. | |||
1961 | SplitBB->getInstList().splice(SplitBB->end(), ParentBB->getInstList(), TI); | |||
1962 | ||||
1963 | // Now wire up the terminator to the preheaders. | |||
1964 | if (BI) { | |||
1965 | BasicBlock *ClonedPH = ClonedPHs.begin()->second; | |||
1966 | BI->setSuccessor(ClonedSucc, ClonedPH); | |||
1967 | BI->setSuccessor(1 - ClonedSucc, LoopPH); | |||
1968 | DTUpdates.push_back({DominatorTree::Insert, SplitBB, ClonedPH}); | |||
1969 | } else { | |||
1970 | assert(SI && "Must either be a branch or switch!")(static_cast <bool> (SI && "Must either be a branch or switch!" ) ? void (0) : __assert_fail ("SI && \"Must either be a branch or switch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1970, __extension__ __PRETTY_FUNCTION__)); | |||
1971 | ||||
1972 | // Walk the cases and directly update their successors. | |||
1973 | SI->setDefaultDest(LoopPH); | |||
1974 | for (auto &Case : SI->cases()) | |||
1975 | if (Case.getCaseSuccessor() == RetainedSuccBB) | |||
1976 | Case.setSuccessor(LoopPH); | |||
1977 | else | |||
1978 | Case.setSuccessor(ClonedPHs.find(Case.getCaseSuccessor())->second); | |||
1979 | ||||
1980 | // We need to use the set to populate domtree updates as even when there | |||
1981 | // are multiple cases pointing at the same successor we only want to | |||
1982 | // remove and insert one edge in the domtree. | |||
1983 | for (BasicBlock *SuccBB : UnswitchedSuccBBs) | |||
1984 | DTUpdates.push_back( | |||
1985 | {DominatorTree::Insert, SplitBB, ClonedPHs.find(SuccBB)->second}); | |||
1986 | } | |||
1987 | ||||
1988 | // Create a new unconditional branch to the continuing block (as opposed to | |||
1989 | // the one cloned). | |||
1990 | BranchInst::Create(RetainedSuccBB, ParentBB); | |||
1991 | } else { | |||
1992 | assert(BI && "Only branches have partial unswitching.")(static_cast <bool> (BI && "Only branches have partial unswitching." ) ? void (0) : __assert_fail ("BI && \"Only branches have partial unswitching.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1992, __extension__ __PRETTY_FUNCTION__)); | |||
1993 | assert(UnswitchedSuccBBs.size() == 1 &&(static_cast <bool> (UnswitchedSuccBBs.size() == 1 && "Only one possible unswitched block for a branch!") ? void ( 0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1994, __extension__ __PRETTY_FUNCTION__)) | |||
1994 | "Only one possible unswitched block for a branch!")(static_cast <bool> (UnswitchedSuccBBs.size() == 1 && "Only one possible unswitched block for a branch!") ? void ( 0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 1994, __extension__ __PRETTY_FUNCTION__)); | |||
1995 | BasicBlock *ClonedPH = ClonedPHs.begin()->second; | |||
1996 | // When doing a partial unswitch, we have to do a bit more work to build up | |||
1997 | // the branch in the split block. | |||
1998 | buildPartialUnswitchConditionalBranch(*SplitBB, Invariants, Direction, | |||
1999 | *ClonedPH, *LoopPH); | |||
2000 | DTUpdates.push_back({DominatorTree::Insert, SplitBB, ClonedPH}); | |||
2001 | } | |||
2002 | ||||
2003 | // Apply the updates accumulated above to get an up-to-date dominator tree. | |||
2004 | DT.applyUpdates(DTUpdates); | |||
2005 | ||||
2006 | // Now that we have an accurate dominator tree, first delete the dead cloned | |||
2007 | // blocks so that we can accurately build any cloned loops. It is important to | |||
2008 | // not delete the blocks from the original loop yet because we still want to | |||
2009 | // reference the original loop to understand the cloned loop's structure. | |||
2010 | deleteDeadClonedBlocks(L, ExitBlocks, VMaps, DT); | |||
2011 | ||||
2012 | // Build the cloned loop structure itself. This may be substantially | |||
2013 | // different from the original structure due to the simplified CFG. This also | |||
2014 | // handles inserting all the cloned blocks into the correct loops. | |||
2015 | SmallVector<Loop *, 4> NonChildClonedLoops; | |||
2016 | for (std::unique_ptr<ValueToValueMapTy> &VMap : VMaps) | |||
2017 | buildClonedLoops(L, ExitBlocks, *VMap, LI, NonChildClonedLoops); | |||
2018 | ||||
2019 | // Now that our cloned loops have been built, we can update the original loop. | |||
2020 | // First we delete the dead blocks from it and then we rebuild the loop | |||
2021 | // structure taking these deletions into account. | |||
2022 | deleteDeadBlocksFromLoop(L, ExitBlocks, DT, LI); | |||
2023 | SmallVector<Loop *, 4> HoistedLoops; | |||
2024 | bool IsStillLoop = rebuildLoopAfterUnswitch(L, ExitBlocks, LI, HoistedLoops); | |||
2025 | ||||
2026 | // This transformation has a high risk of corrupting the dominator tree, and | |||
2027 | // the below steps to rebuild loop structures will result in hard to debug | |||
2028 | // errors in that case so verify that the dominator tree is sane first. | |||
2029 | // FIXME: Remove this when the bugs stop showing up and rely on existing | |||
2030 | // verification steps. | |||
2031 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel ::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2031, __extension__ __PRETTY_FUNCTION__)); | |||
2032 | ||||
2033 | if (BI) { | |||
2034 | // If we unswitched a branch which collapses the condition to a known | |||
2035 | // constant we want to replace all the uses of the invariants within both | |||
2036 | // the original and cloned blocks. We do this here so that we can use the | |||
2037 | // now updated dominator tree to identify which side the users are on. | |||
2038 | assert(UnswitchedSuccBBs.size() == 1 &&(static_cast <bool> (UnswitchedSuccBBs.size() == 1 && "Only one possible unswitched block for a branch!") ? void ( 0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2039, __extension__ __PRETTY_FUNCTION__)) | |||
2039 | "Only one possible unswitched block for a branch!")(static_cast <bool> (UnswitchedSuccBBs.size() == 1 && "Only one possible unswitched block for a branch!") ? void ( 0) : __assert_fail ("UnswitchedSuccBBs.size() == 1 && \"Only one possible unswitched block for a branch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2039, __extension__ __PRETTY_FUNCTION__)); | |||
2040 | BasicBlock *ClonedPH = ClonedPHs.begin()->second; | |||
2041 | ConstantInt *UnswitchedReplacement = | |||
2042 | Direction ? ConstantInt::getTrue(BI->getContext()) | |||
2043 | : ConstantInt::getFalse(BI->getContext()); | |||
2044 | ConstantInt *ContinueReplacement = | |||
2045 | Direction ? ConstantInt::getFalse(BI->getContext()) | |||
2046 | : ConstantInt::getTrue(BI->getContext()); | |||
2047 | for (Value *Invariant : Invariants) | |||
2048 | for (auto UI = Invariant->use_begin(), UE = Invariant->use_end(); | |||
2049 | UI != UE;) { | |||
2050 | // Grab the use and walk past it so we can clobber it in the use list. | |||
2051 | Use *U = &*UI++; | |||
2052 | Instruction *UserI = dyn_cast<Instruction>(U->getUser()); | |||
2053 | if (!UserI) | |||
2054 | continue; | |||
2055 | ||||
2056 | // Replace it with the 'continue' side if in the main loop body, and the | |||
2057 | // unswitched if in the cloned blocks. | |||
2058 | if (DT.dominates(LoopPH, UserI->getParent())) | |||
2059 | U->set(ContinueReplacement); | |||
2060 | else if (DT.dominates(ClonedPH, UserI->getParent())) | |||
2061 | U->set(UnswitchedReplacement); | |||
2062 | } | |||
2063 | } | |||
2064 | ||||
2065 | // We can change which blocks are exit blocks of all the cloned sibling | |||
2066 | // loops, the current loop, and any parent loops which shared exit blocks | |||
2067 | // with the current loop. As a consequence, we need to re-form LCSSA for | |||
2068 | // them. But we shouldn't need to re-form LCSSA for any child loops. | |||
2069 | // FIXME: This could be made more efficient by tracking which exit blocks are | |||
2070 | // new, and focusing on them, but that isn't likely to be necessary. | |||
2071 | // | |||
2072 | // In order to reasonably rebuild LCSSA we need to walk inside-out across the | |||
2073 | // loop nest and update every loop that could have had its exits changed. We | |||
2074 | // also need to cover any intervening loops. We add all of these loops to | |||
2075 | // a list and sort them by loop depth to achieve this without updating | |||
2076 | // unnecessary loops. | |||
2077 | auto UpdateLoop = [&](Loop &UpdateL) { | |||
2078 | #ifndef NDEBUG | |||
2079 | UpdateL.verifyLoop(); | |||
2080 | for (Loop *ChildL : UpdateL) { | |||
2081 | ChildL->verifyLoop(); | |||
2082 | assert(ChildL->isRecursivelyLCSSAForm(DT, LI) &&(static_cast <bool> (ChildL->isRecursivelyLCSSAForm( DT, LI) && "Perturbed a child loop's LCSSA form!") ? void (0) : __assert_fail ("ChildL->isRecursivelyLCSSAForm(DT, LI) && \"Perturbed a child loop's LCSSA form!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2083, __extension__ __PRETTY_FUNCTION__)) | |||
2083 | "Perturbed a child loop's LCSSA form!")(static_cast <bool> (ChildL->isRecursivelyLCSSAForm( DT, LI) && "Perturbed a child loop's LCSSA form!") ? void (0) : __assert_fail ("ChildL->isRecursivelyLCSSAForm(DT, LI) && \"Perturbed a child loop's LCSSA form!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2083, __extension__ __PRETTY_FUNCTION__)); | |||
2084 | } | |||
2085 | #endif | |||
2086 | // First build LCSSA for this loop so that we can preserve it when | |||
2087 | // forming dedicated exits. We don't want to perturb some other loop's | |||
2088 | // LCSSA while doing that CFG edit. | |||
2089 | formLCSSA(UpdateL, DT, &LI, nullptr); | |||
2090 | ||||
2091 | // For loops reached by this loop's original exit blocks we may | |||
2092 | // introduced new, non-dedicated exits. At least try to re-form dedicated | |||
2093 | // exits for these loops. This may fail if they couldn't have dedicated | |||
2094 | // exits to start with. | |||
2095 | formDedicatedExitBlocks(&UpdateL, &DT, &LI, /*PreserveLCSSA*/ true); | |||
2096 | }; | |||
2097 | ||||
2098 | // For non-child cloned loops and hoisted loops, we just need to update LCSSA | |||
2099 | // and we can do it in any order as they don't nest relative to each other. | |||
2100 | // | |||
2101 | // Also check if any of the loops we have updated have become top-level loops | |||
2102 | // as that will necessitate widening the outer loop scope. | |||
2103 | for (Loop *UpdatedL : | |||
2104 | llvm::concat<Loop *>(NonChildClonedLoops, HoistedLoops)) { | |||
2105 | UpdateLoop(*UpdatedL); | |||
2106 | if (!UpdatedL->getParentLoop()) | |||
2107 | OuterExitL = nullptr; | |||
2108 | } | |||
2109 | if (IsStillLoop) { | |||
2110 | UpdateLoop(L); | |||
2111 | if (!L.getParentLoop()) | |||
2112 | OuterExitL = nullptr; | |||
2113 | } | |||
2114 | ||||
2115 | // If the original loop had exit blocks, walk up through the outer most loop | |||
2116 | // of those exit blocks to update LCSSA and form updated dedicated exits. | |||
2117 | if (OuterExitL != &L) | |||
2118 | for (Loop *OuterL = ParentL; OuterL != OuterExitL; | |||
2119 | OuterL = OuterL->getParentLoop()) | |||
2120 | UpdateLoop(*OuterL); | |||
2121 | ||||
2122 | #ifndef NDEBUG | |||
2123 | // Verify the entire loop structure to catch any incorrect updates before we | |||
2124 | // progress in the pass pipeline. | |||
2125 | LI.verify(DT); | |||
2126 | #endif | |||
2127 | ||||
2128 | // Now that we've unswitched something, make callbacks to report the changes. | |||
2129 | // For that we need to merge together the updated loops and the cloned loops | |||
2130 | // and check whether the original loop survived. | |||
2131 | SmallVector<Loop *, 4> SibLoops; | |||
2132 | for (Loop *UpdatedL : llvm::concat<Loop *>(NonChildClonedLoops, HoistedLoops)) | |||
2133 | if (UpdatedL->getParentLoop() == ParentL) | |||
2134 | SibLoops.push_back(UpdatedL); | |||
2135 | UnswitchCB(IsStillLoop, SibLoops); | |||
2136 | ||||
2137 | ++NumBranches; | |||
2138 | return true; | |||
2139 | } | |||
2140 | ||||
2141 | /// Recursively compute the cost of a dominator subtree based on the per-block | |||
2142 | /// cost map provided. | |||
2143 | /// | |||
2144 | /// The recursive computation is memozied into the provided DT-indexed cost map | |||
2145 | /// to allow querying it for most nodes in the domtree without it becoming | |||
2146 | /// quadratic. | |||
2147 | static int | |||
2148 | computeDomSubtreeCost(DomTreeNode &N, | |||
2149 | const SmallDenseMap<BasicBlock *, int, 4> &BBCostMap, | |||
2150 | SmallDenseMap<DomTreeNode *, int, 4> &DTCostMap) { | |||
2151 | // Don't accumulate cost (or recurse through) blocks not in our block cost | |||
2152 | // map and thus not part of the duplication cost being considered. | |||
2153 | auto BBCostIt = BBCostMap.find(N.getBlock()); | |||
2154 | if (BBCostIt == BBCostMap.end()) | |||
2155 | return 0; | |||
2156 | ||||
2157 | // Lookup this node to see if we already computed its cost. | |||
2158 | auto DTCostIt = DTCostMap.find(&N); | |||
2159 | if (DTCostIt != DTCostMap.end()) | |||
2160 | return DTCostIt->second; | |||
2161 | ||||
2162 | // If not, we have to compute it. We can't use insert above and update | |||
2163 | // because computing the cost may insert more things into the map. | |||
2164 | int Cost = std::accumulate( | |||
2165 | N.begin(), N.end(), BBCostIt->second, [&](int Sum, DomTreeNode *ChildN) { | |||
2166 | return Sum + computeDomSubtreeCost(*ChildN, BBCostMap, DTCostMap); | |||
2167 | }); | |||
2168 | bool Inserted = DTCostMap.insert({&N, Cost}).second; | |||
2169 | (void)Inserted; | |||
2170 | assert(Inserted && "Should not insert a node while visiting children!")(static_cast <bool> (Inserted && "Should not insert a node while visiting children!" ) ? void (0) : __assert_fail ("Inserted && \"Should not insert a node while visiting children!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2170, __extension__ __PRETTY_FUNCTION__)); | |||
2171 | return Cost; | |||
2172 | } | |||
2173 | ||||
2174 | static bool | |||
2175 | unswitchBestCondition(Loop &L, DominatorTree &DT, LoopInfo &LI, | |||
2176 | AssumptionCache &AC, TargetTransformInfo &TTI, | |||
2177 | function_ref<void(bool, ArrayRef<Loop *>)> UnswitchCB, | |||
2178 | ScalarEvolution *SE) { | |||
2179 | // Collect all invariant conditions within this loop (as opposed to an inner | |||
2180 | // loop which would be handled when visiting that inner loop). | |||
2181 | SmallVector<std::pair<TerminatorInst *, TinyPtrVector<Value *>>, 4> | |||
2182 | UnswitchCandidates; | |||
2183 | for (auto *BB : L.blocks()) { | |||
2184 | if (LI.getLoopFor(BB) != &L) | |||
2185 | continue; | |||
2186 | ||||
2187 | if (auto *SI = dyn_cast<SwitchInst>(BB->getTerminator())) { | |||
2188 | // We can only consider fully loop-invariant switch conditions as we need | |||
2189 | // to completely eliminate the switch after unswitching. | |||
2190 | if (!isa<Constant>(SI->getCondition()) && | |||
2191 | L.isLoopInvariant(SI->getCondition())) | |||
2192 | UnswitchCandidates.push_back({SI, {SI->getCondition()}}); | |||
2193 | continue; | |||
2194 | } | |||
2195 | ||||
2196 | auto *BI = dyn_cast<BranchInst>(BB->getTerminator()); | |||
2197 | if (!BI || !BI->isConditional() || isa<Constant>(BI->getCondition()) || | |||
2198 | BI->getSuccessor(0) == BI->getSuccessor(1)) | |||
2199 | continue; | |||
2200 | ||||
2201 | if (L.isLoopInvariant(BI->getCondition())) { | |||
2202 | UnswitchCandidates.push_back({BI, {BI->getCondition()}}); | |||
2203 | continue; | |||
2204 | } | |||
2205 | ||||
2206 | Instruction &CondI = *cast<Instruction>(BI->getCondition()); | |||
2207 | if (CondI.getOpcode() != Instruction::And && | |||
2208 | CondI.getOpcode() != Instruction::Or) | |||
2209 | continue; | |||
2210 | ||||
2211 | TinyPtrVector<Value *> Invariants = | |||
2212 | collectHomogenousInstGraphLoopInvariants(L, CondI, LI); | |||
2213 | if (Invariants.empty()) | |||
2214 | continue; | |||
2215 | ||||
2216 | UnswitchCandidates.push_back({BI, std::move(Invariants)}); | |||
2217 | } | |||
2218 | ||||
2219 | // If we didn't find any candidates, we're done. | |||
2220 | if (UnswitchCandidates.empty()) | |||
2221 | return false; | |||
2222 | ||||
2223 | // Check if there are irreducible CFG cycles in this loop. If so, we cannot | |||
2224 | // easily unswitch non-trivial edges out of the loop. Doing so might turn the | |||
2225 | // irreducible control flow into reducible control flow and introduce new | |||
2226 | // loops "out of thin air". If we ever discover important use cases for doing | |||
2227 | // this, we can add support to loop unswitch, but it is a lot of complexity | |||
2228 | // for what seems little or no real world benefit. | |||
2229 | LoopBlocksRPO RPOT(&L); | |||
2230 | RPOT.perform(&LI); | |||
2231 | if (containsIrreducibleCFG<const BasicBlock *>(RPOT, LI)) | |||
2232 | return false; | |||
2233 | ||||
2234 | LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Considering " << UnswitchCandidates.size() << " non-trivial loop invariant conditions for unswitching.\n" ; } } while (false) | |||
2235 | dbgs() << "Considering " << UnswitchCandidates.size()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Considering " << UnswitchCandidates.size() << " non-trivial loop invariant conditions for unswitching.\n" ; } } while (false) | |||
2236 | << " non-trivial loop invariant conditions for unswitching.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Considering " << UnswitchCandidates.size() << " non-trivial loop invariant conditions for unswitching.\n" ; } } while (false); | |||
2237 | ||||
2238 | // Given that unswitching these terminators will require duplicating parts of | |||
2239 | // the loop, so we need to be able to model that cost. Compute the ephemeral | |||
2240 | // values and set up a data structure to hold per-BB costs. We cache each | |||
2241 | // block's cost so that we don't recompute this when considering different | |||
2242 | // subsets of the loop for duplication during unswitching. | |||
2243 | SmallPtrSet<const Value *, 4> EphValues; | |||
2244 | CodeMetrics::collectEphemeralValues(&L, &AC, EphValues); | |||
2245 | SmallDenseMap<BasicBlock *, int, 4> BBCostMap; | |||
2246 | ||||
2247 | // Compute the cost of each block, as well as the total loop cost. Also, bail | |||
2248 | // out if we see instructions which are incompatible with loop unswitching | |||
2249 | // (convergent, noduplicate, or cross-basic-block tokens). | |||
2250 | // FIXME: We might be able to safely handle some of these in non-duplicated | |||
2251 | // regions. | |||
2252 | int LoopCost = 0; | |||
2253 | for (auto *BB : L.blocks()) { | |||
2254 | int Cost = 0; | |||
2255 | for (auto &I : *BB) { | |||
2256 | if (EphValues.count(&I)) | |||
2257 | continue; | |||
2258 | ||||
2259 | if (I.getType()->isTokenTy() && I.isUsedOutsideOfBlock(BB)) | |||
2260 | return false; | |||
2261 | if (auto CS = CallSite(&I)) | |||
2262 | if (CS.isConvergent() || CS.cannotDuplicate()) | |||
2263 | return false; | |||
2264 | ||||
2265 | Cost += TTI.getUserCost(&I); | |||
2266 | } | |||
2267 | assert(Cost >= 0 && "Must not have negative costs!")(static_cast <bool> (Cost >= 0 && "Must not have negative costs!" ) ? void (0) : __assert_fail ("Cost >= 0 && \"Must not have negative costs!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2267, __extension__ __PRETTY_FUNCTION__)); | |||
2268 | LoopCost += Cost; | |||
2269 | assert(LoopCost >= 0 && "Must not have negative loop costs!")(static_cast <bool> (LoopCost >= 0 && "Must not have negative loop costs!" ) ? void (0) : __assert_fail ("LoopCost >= 0 && \"Must not have negative loop costs!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2269, __extension__ __PRETTY_FUNCTION__)); | |||
2270 | BBCostMap[BB] = Cost; | |||
2271 | } | |||
2272 | LLVM_DEBUG(dbgs() << " Total loop cost: " << LoopCost << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Total loop cost: " << LoopCost << "\n"; } } while (false); | |||
2273 | ||||
2274 | // Now we find the best candidate by searching for the one with the following | |||
2275 | // properties in order: | |||
2276 | // | |||
2277 | // 1) An unswitching cost below the threshold | |||
2278 | // 2) The smallest number of duplicated unswitch candidates (to avoid | |||
2279 | // creating redundant subsequent unswitching) | |||
2280 | // 3) The smallest cost after unswitching. | |||
2281 | // | |||
2282 | // We prioritize reducing fanout of unswitch candidates provided the cost | |||
2283 | // remains below the threshold because this has a multiplicative effect. | |||
2284 | // | |||
2285 | // This requires memoizing each dominator subtree to avoid redundant work. | |||
2286 | // | |||
2287 | // FIXME: Need to actually do the number of candidates part above. | |||
2288 | SmallDenseMap<DomTreeNode *, int, 4> DTCostMap; | |||
2289 | // Given a terminator which might be unswitched, computes the non-duplicated | |||
2290 | // cost for that terminator. | |||
2291 | auto ComputeUnswitchedCost = [&](TerminatorInst &TI, bool FullUnswitch) { | |||
2292 | BasicBlock &BB = *TI.getParent(); | |||
2293 | SmallPtrSet<BasicBlock *, 4> Visited; | |||
2294 | ||||
2295 | int Cost = LoopCost; | |||
2296 | for (BasicBlock *SuccBB : successors(&BB)) { | |||
2297 | // Don't count successors more than once. | |||
2298 | if (!Visited.insert(SuccBB).second) | |||
2299 | continue; | |||
2300 | ||||
2301 | // If this is a partial unswitch candidate, then it must be a conditional | |||
2302 | // branch with a condition of either `or` or `and`. In that case, one of | |||
2303 | // the successors is necessarily duplicated, so don't even try to remove | |||
2304 | // its cost. | |||
2305 | if (!FullUnswitch) { | |||
2306 | auto &BI = cast<BranchInst>(TI); | |||
2307 | if (cast<Instruction>(BI.getCondition())->getOpcode() == | |||
2308 | Instruction::And) { | |||
2309 | if (SuccBB == BI.getSuccessor(1)) | |||
2310 | continue; | |||
2311 | } else { | |||
2312 | assert(cast<Instruction>(BI.getCondition())->getOpcode() ==(static_cast <bool> (cast<Instruction>(BI.getCondition ())->getOpcode() == Instruction::Or && "Only `and` and `or` conditions can result in a partial " "unswitch!") ? void (0) : __assert_fail ("cast<Instruction>(BI.getCondition())->getOpcode() == Instruction::Or && \"Only `and` and `or` conditions can result in a partial \" \"unswitch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2315, __extension__ __PRETTY_FUNCTION__)) | |||
2313 | Instruction::Or &&(static_cast <bool> (cast<Instruction>(BI.getCondition ())->getOpcode() == Instruction::Or && "Only `and` and `or` conditions can result in a partial " "unswitch!") ? void (0) : __assert_fail ("cast<Instruction>(BI.getCondition())->getOpcode() == Instruction::Or && \"Only `and` and `or` conditions can result in a partial \" \"unswitch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2315, __extension__ __PRETTY_FUNCTION__)) | |||
2314 | "Only `and` and `or` conditions can result in a partial "(static_cast <bool> (cast<Instruction>(BI.getCondition ())->getOpcode() == Instruction::Or && "Only `and` and `or` conditions can result in a partial " "unswitch!") ? void (0) : __assert_fail ("cast<Instruction>(BI.getCondition())->getOpcode() == Instruction::Or && \"Only `and` and `or` conditions can result in a partial \" \"unswitch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2315, __extension__ __PRETTY_FUNCTION__)) | |||
2315 | "unswitch!")(static_cast <bool> (cast<Instruction>(BI.getCondition ())->getOpcode() == Instruction::Or && "Only `and` and `or` conditions can result in a partial " "unswitch!") ? void (0) : __assert_fail ("cast<Instruction>(BI.getCondition())->getOpcode() == Instruction::Or && \"Only `and` and `or` conditions can result in a partial \" \"unswitch!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2315, __extension__ __PRETTY_FUNCTION__)); | |||
2316 | if (SuccBB == BI.getSuccessor(0)) | |||
2317 | continue; | |||
2318 | } | |||
2319 | } | |||
2320 | ||||
2321 | // This successor's domtree will not need to be duplicated after | |||
2322 | // unswitching if the edge to the successor dominates it (and thus the | |||
2323 | // entire tree). This essentially means there is no other path into this | |||
2324 | // subtree and so it will end up live in only one clone of the loop. | |||
2325 | if (SuccBB->getUniquePredecessor() || | |||
2326 | llvm::all_of(predecessors(SuccBB), [&](BasicBlock *PredBB) { | |||
2327 | return PredBB == &BB || DT.dominates(SuccBB, PredBB); | |||
2328 | })) { | |||
2329 | Cost -= computeDomSubtreeCost(*DT[SuccBB], BBCostMap, DTCostMap); | |||
2330 | assert(Cost >= 0 &&(static_cast <bool> (Cost >= 0 && "Non-duplicated cost should never exceed total loop cost!" ) ? void (0) : __assert_fail ("Cost >= 0 && \"Non-duplicated cost should never exceed total loop cost!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2331, __extension__ __PRETTY_FUNCTION__)) | |||
2331 | "Non-duplicated cost should never exceed total loop cost!")(static_cast <bool> (Cost >= 0 && "Non-duplicated cost should never exceed total loop cost!" ) ? void (0) : __assert_fail ("Cost >= 0 && \"Non-duplicated cost should never exceed total loop cost!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2331, __extension__ __PRETTY_FUNCTION__)); | |||
2332 | } | |||
2333 | } | |||
2334 | ||||
2335 | // Now scale the cost by the number of unique successors minus one. We | |||
2336 | // subtract one because there is already at least one copy of the entire | |||
2337 | // loop. This is computing the new cost of unswitching a condition. | |||
2338 | assert(Visited.size() > 1 &&(static_cast <bool> (Visited.size() > 1 && "Cannot unswitch a condition without multiple distinct successors!" ) ? void (0) : __assert_fail ("Visited.size() > 1 && \"Cannot unswitch a condition without multiple distinct successors!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2339, __extension__ __PRETTY_FUNCTION__)) | |||
2339 | "Cannot unswitch a condition without multiple distinct successors!")(static_cast <bool> (Visited.size() > 1 && "Cannot unswitch a condition without multiple distinct successors!" ) ? void (0) : __assert_fail ("Visited.size() > 1 && \"Cannot unswitch a condition without multiple distinct successors!\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2339, __extension__ __PRETTY_FUNCTION__)); | |||
2340 | return Cost * (Visited.size() - 1); | |||
2341 | }; | |||
2342 | TerminatorInst *BestUnswitchTI = nullptr; | |||
2343 | int BestUnswitchCost; | |||
2344 | ArrayRef<Value *> BestUnswitchInvariants; | |||
2345 | for (auto &TerminatorAndInvariants : UnswitchCandidates) { | |||
2346 | TerminatorInst &TI = *TerminatorAndInvariants.first; | |||
2347 | ArrayRef<Value *> Invariants = TerminatorAndInvariants.second; | |||
2348 | BranchInst *BI = dyn_cast<BranchInst>(&TI); | |||
2349 | int CandidateCost = ComputeUnswitchedCost( | |||
2350 | TI, /*FullUnswitch*/ !BI || (Invariants.size() == 1 && | |||
2351 | Invariants[0] == BI->getCondition())); | |||
2352 | LLVM_DEBUG(dbgs() << " Computed cost of " << CandidateCostdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Computed cost of " << CandidateCost << " for unswitch candidate: " << TI << "\n"; } } while (false) | |||
2353 | << " for unswitch candidate: " << TI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Computed cost of " << CandidateCost << " for unswitch candidate: " << TI << "\n"; } } while (false); | |||
2354 | if (!BestUnswitchTI || CandidateCost < BestUnswitchCost) { | |||
2355 | BestUnswitchTI = &TI; | |||
2356 | BestUnswitchCost = CandidateCost; | |||
2357 | BestUnswitchInvariants = Invariants; | |||
2358 | } | |||
2359 | } | |||
2360 | ||||
2361 | if (BestUnswitchCost >= UnswitchThreshold) { | |||
| ||||
2362 | LLVM_DEBUG(dbgs() << "Cannot unswitch, lowest cost found: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Cannot unswitch, lowest cost found: " << BestUnswitchCost << "\n"; } } while (false) | |||
2363 | << BestUnswitchCost << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Cannot unswitch, lowest cost found: " << BestUnswitchCost << "\n"; } } while (false); | |||
2364 | return false; | |||
2365 | } | |||
2366 | ||||
2367 | LLVM_DEBUG(dbgs() << " Trying to unswitch non-trivial (cost = "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Trying to unswitch non-trivial (cost = " << BestUnswitchCost << ") terminator: " << *BestUnswitchTI << "\n"; } } while (false) | |||
2368 | << BestUnswitchCost << ") terminator: " << *BestUnswitchTIdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Trying to unswitch non-trivial (cost = " << BestUnswitchCost << ") terminator: " << *BestUnswitchTI << "\n"; } } while (false) | |||
2369 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << " Trying to unswitch non-trivial (cost = " << BestUnswitchCost << ") terminator: " << *BestUnswitchTI << "\n"; } } while (false); | |||
2370 | return unswitchNontrivialInvariants( | |||
2371 | L, *BestUnswitchTI, BestUnswitchInvariants, DT, LI, AC, UnswitchCB, SE); | |||
2372 | } | |||
2373 | ||||
2374 | /// Unswitch control flow predicated on loop invariant conditions. | |||
2375 | /// | |||
2376 | /// This first hoists all branches or switches which are trivial (IE, do not | |||
2377 | /// require duplicating any part of the loop) out of the loop body. It then | |||
2378 | /// looks at other loop invariant control flows and tries to unswitch those as | |||
2379 | /// well by cloning the loop if the result is small enough. | |||
2380 | /// | |||
2381 | /// The `DT`, `LI`, `AC`, `TTI` parameters are required analyses that are also | |||
2382 | /// updated based on the unswitch. | |||
2383 | /// | |||
2384 | /// If either `NonTrivial` is true or the flag `EnableNonTrivialUnswitch` is | |||
2385 | /// true, we will attempt to do non-trivial unswitching as well as trivial | |||
2386 | /// unswitching. | |||
2387 | /// | |||
2388 | /// The `UnswitchCB` callback provided will be run after unswitching is | |||
2389 | /// complete, with the first parameter set to `true` if the provided loop | |||
2390 | /// remains a loop, and a list of new sibling loops created. | |||
2391 | /// | |||
2392 | /// If `SE` is non-null, we will update that analysis based on the unswitching | |||
2393 | /// done. | |||
2394 | static bool unswitchLoop(Loop &L, DominatorTree &DT, LoopInfo &LI, | |||
2395 | AssumptionCache &AC, TargetTransformInfo &TTI, | |||
2396 | bool NonTrivial, | |||
2397 | function_ref<void(bool, ArrayRef<Loop *>)> UnswitchCB, | |||
2398 | ScalarEvolution *SE) { | |||
2399 | assert(L.isRecursivelyLCSSAForm(DT, LI) &&(static_cast <bool> (L.isRecursivelyLCSSAForm(DT, LI) && "Loops must be in LCSSA form before unswitching.") ? void (0 ) : __assert_fail ("L.isRecursivelyLCSSAForm(DT, LI) && \"Loops must be in LCSSA form before unswitching.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2400, __extension__ __PRETTY_FUNCTION__)) | |||
2400 | "Loops must be in LCSSA form before unswitching.")(static_cast <bool> (L.isRecursivelyLCSSAForm(DT, LI) && "Loops must be in LCSSA form before unswitching.") ? void (0 ) : __assert_fail ("L.isRecursivelyLCSSAForm(DT, LI) && \"Loops must be in LCSSA form before unswitching.\"" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2400, __extension__ __PRETTY_FUNCTION__)); | |||
2401 | bool Changed = false; | |||
2402 | ||||
2403 | // Must be in loop simplified form: we need a preheader and dedicated exits. | |||
2404 | if (!L.isLoopSimplifyForm()) | |||
2405 | return false; | |||
2406 | ||||
2407 | // Try trivial unswitch first before loop over other basic blocks in the loop. | |||
2408 | if (unswitchAllTrivialConditions(L, DT, LI, SE)) { | |||
2409 | // If we unswitched successfully we will want to clean up the loop before | |||
2410 | // processing it further so just mark it as unswitched and return. | |||
2411 | UnswitchCB(/*CurrentLoopValid*/ true, {}); | |||
2412 | return true; | |||
2413 | } | |||
2414 | ||||
2415 | // If we're not doing non-trivial unswitching, we're done. We both accept | |||
2416 | // a parameter but also check a local flag that can be used for testing | |||
2417 | // a debugging. | |||
2418 | if (!NonTrivial && !EnableNonTrivialUnswitch) | |||
2419 | return false; | |||
2420 | ||||
2421 | // For non-trivial unswitching, because it often creates new loops, we rely on | |||
2422 | // the pass manager to iterate on the loops rather than trying to immediately | |||
2423 | // reach a fixed point. There is no substantial advantage to iterating | |||
2424 | // internally, and if any of the new loops are simplified enough to contain | |||
2425 | // trivial unswitching we want to prefer those. | |||
2426 | ||||
2427 | // Try to unswitch the best invariant condition. We prefer this full unswitch to | |||
2428 | // a partial unswitch when possible below the threshold. | |||
2429 | if (unswitchBestCondition(L, DT, LI, AC, TTI, UnswitchCB, SE)) | |||
2430 | return true; | |||
2431 | ||||
2432 | // No other opportunities to unswitch. | |||
2433 | return Changed; | |||
2434 | } | |||
2435 | ||||
2436 | PreservedAnalyses SimpleLoopUnswitchPass::run(Loop &L, LoopAnalysisManager &AM, | |||
2437 | LoopStandardAnalysisResults &AR, | |||
2438 | LPMUpdater &U) { | |||
2439 | Function &F = *L.getHeader()->getParent(); | |||
2440 | (void)F; | |||
2441 | ||||
2442 | LLVM_DEBUG(dbgs() << "Unswitching loop in " << F.getName() << ": " << Ldo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Unswitching loop in " << F.getName() << ": " << L << "\n"; } } while (false) | |||
2443 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Unswitching loop in " << F.getName() << ": " << L << "\n"; } } while (false); | |||
2444 | ||||
2445 | // Save the current loop name in a variable so that we can report it even | |||
2446 | // after it has been deleted. | |||
2447 | std::string LoopName = L.getName(); | |||
2448 | ||||
2449 | auto UnswitchCB = [&L, &U, &LoopName](bool CurrentLoopValid, | |||
2450 | ArrayRef<Loop *> NewLoops) { | |||
2451 | // If we did a non-trivial unswitch, we have added new (cloned) loops. | |||
2452 | if (!NewLoops.empty()) | |||
2453 | U.addSiblingLoops(NewLoops); | |||
2454 | ||||
2455 | // If the current loop remains valid, we should revisit it to catch any | |||
2456 | // other unswitch opportunities. Otherwise, we need to mark it as deleted. | |||
2457 | if (CurrentLoopValid) | |||
2458 | U.revisitCurrentLoop(); | |||
2459 | else | |||
2460 | U.markLoopAsDeleted(L, LoopName); | |||
2461 | }; | |||
2462 | ||||
2463 | if (!unswitchLoop(L, AR.DT, AR.LI, AR.AC, AR.TTI, NonTrivial, UnswitchCB, | |||
2464 | &AR.SE)) | |||
2465 | return PreservedAnalyses::all(); | |||
2466 | ||||
2467 | // Historically this pass has had issues with the dominator tree so verify it | |||
2468 | // in asserts builds. | |||
2469 | assert(AR.DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (AR.DT.verify(DominatorTree::VerificationLevel ::Fast)) ? void (0) : __assert_fail ("AR.DT.verify(DominatorTree::VerificationLevel::Fast)" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2469, __extension__ __PRETTY_FUNCTION__)); | |||
2470 | return getLoopPassPreservedAnalyses(); | |||
2471 | } | |||
2472 | ||||
2473 | namespace { | |||
2474 | ||||
2475 | class SimpleLoopUnswitchLegacyPass : public LoopPass { | |||
2476 | bool NonTrivial; | |||
2477 | ||||
2478 | public: | |||
2479 | static char ID; // Pass ID, replacement for typeid | |||
2480 | ||||
2481 | explicit SimpleLoopUnswitchLegacyPass(bool NonTrivial = false) | |||
2482 | : LoopPass(ID), NonTrivial(NonTrivial) { | |||
2483 | initializeSimpleLoopUnswitchLegacyPassPass( | |||
2484 | *PassRegistry::getPassRegistry()); | |||
2485 | } | |||
2486 | ||||
2487 | bool runOnLoop(Loop *L, LPPassManager &LPM) override; | |||
2488 | ||||
2489 | void getAnalysisUsage(AnalysisUsage &AU) const override { | |||
2490 | AU.addRequired<AssumptionCacheTracker>(); | |||
2491 | AU.addRequired<TargetTransformInfoWrapperPass>(); | |||
2492 | getLoopAnalysisUsage(AU); | |||
2493 | } | |||
2494 | }; | |||
2495 | ||||
2496 | } // end anonymous namespace | |||
2497 | ||||
2498 | bool SimpleLoopUnswitchLegacyPass::runOnLoop(Loop *L, LPPassManager &LPM) { | |||
2499 | if (skipLoop(L)) | |||
| ||||
2500 | return false; | |||
2501 | ||||
2502 | Function &F = *L->getHeader()->getParent(); | |||
2503 | ||||
2504 | LLVM_DEBUG(dbgs() << "Unswitching loop in " << F.getName() << ": " << *Ldo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Unswitching loop in " << F.getName() << ": " << *L << "\n" ; } } while (false) | |||
2505 | << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("simple-loop-unswitch")) { dbgs() << "Unswitching loop in " << F.getName() << ": " << *L << "\n" ; } } while (false); | |||
2506 | ||||
2507 | auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); | |||
2508 | auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); | |||
2509 | auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); | |||
2510 | auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F); | |||
2511 | ||||
2512 | auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>(); | |||
2513 | auto *SE = SEWP ? &SEWP->getSE() : nullptr; | |||
2514 | ||||
2515 | auto UnswitchCB = [&L, &LPM](bool CurrentLoopValid, | |||
2516 | ArrayRef<Loop *> NewLoops) { | |||
2517 | // If we did a non-trivial unswitch, we have added new (cloned) loops. | |||
2518 | for (auto *NewL : NewLoops) | |||
2519 | LPM.addLoop(*NewL); | |||
2520 | ||||
2521 | // If the current loop remains valid, re-add it to the queue. This is | |||
2522 | // a little wasteful as we'll finish processing the current loop as well, | |||
2523 | // but it is the best we can do in the old PM. | |||
2524 | if (CurrentLoopValid) | |||
2525 | LPM.addLoop(*L); | |||
2526 | else | |||
2527 | LPM.markLoopAsDeleted(*L); | |||
2528 | }; | |||
2529 | ||||
2530 | bool Changed = unswitchLoop(*L, DT, LI, AC, TTI, NonTrivial, UnswitchCB, SE); | |||
2531 | ||||
2532 | // If anything was unswitched, also clear any cached information about this | |||
2533 | // loop. | |||
2534 | LPM.deleteSimpleAnalysisLoop(L); | |||
2535 | ||||
2536 | // Historically this pass has had issues with the dominator tree so verify it | |||
2537 | // in asserts builds. | |||
2538 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))(static_cast <bool> (DT.verify(DominatorTree::VerificationLevel ::Fast)) ? void (0) : __assert_fail ("DT.verify(DominatorTree::VerificationLevel::Fast)" , "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp" , 2538, __extension__ __PRETTY_FUNCTION__)); | |||
2539 | ||||
2540 | return Changed; | |||
2541 | } | |||
2542 | ||||
2543 | char SimpleLoopUnswitchLegacyPass::ID = 0; | |||
2544 | INITIALIZE_PASS_BEGIN(SimpleLoopUnswitchLegacyPass, "simple-loop-unswitch",static void *initializeSimpleLoopUnswitchLegacyPassPassOnce(PassRegistry &Registry) { | |||
2545 | "Simple unswitch loops", false, false)static void *initializeSimpleLoopUnswitchLegacyPassPassOnce(PassRegistry &Registry) { | |||
2546 | INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)initializeAssumptionCacheTrackerPass(Registry); | |||
2547 | INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry); | |||
2548 | INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry); | |||
2549 | INITIALIZE_PASS_DEPENDENCY(LoopPass)initializeLoopPassPass(Registry); | |||
2550 | INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry); | |||
2551 | INITIALIZE_PASS_END(SimpleLoopUnswitchLegacyPass, "simple-loop-unswitch",PassInfo *PI = new PassInfo( "Simple unswitch loops", "simple-loop-unswitch" , &SimpleLoopUnswitchLegacyPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<SimpleLoopUnswitchLegacyPass>), false, false); Registry.registerPass(*PI, true); return PI; } static llvm::once_flag InitializeSimpleLoopUnswitchLegacyPassPassFlag ; void llvm::initializeSimpleLoopUnswitchLegacyPassPass(PassRegistry &Registry) { llvm::call_once(InitializeSimpleLoopUnswitchLegacyPassPassFlag , initializeSimpleLoopUnswitchLegacyPassPassOnce, std::ref(Registry )); } | |||
2552 | "Simple unswitch loops", false, false)PassInfo *PI = new PassInfo( "Simple unswitch loops", "simple-loop-unswitch" , &SimpleLoopUnswitchLegacyPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<SimpleLoopUnswitchLegacyPass>), false, false); Registry.registerPass(*PI, true); return PI; } static llvm::once_flag InitializeSimpleLoopUnswitchLegacyPassPassFlag ; void llvm::initializeSimpleLoopUnswitchLegacyPassPass(PassRegistry &Registry) { llvm::call_once(InitializeSimpleLoopUnswitchLegacyPassPassFlag , initializeSimpleLoopUnswitchLegacyPassPassOnce, std::ref(Registry )); } | |||
2553 | ||||
2554 | Pass *llvm::createSimpleLoopUnswitchLegacyPass(bool NonTrivial) { | |||
2555 | return new SimpleLoopUnswitchLegacyPass(NonTrivial); | |||
2556 | } |