LLVM  10.0.0svn
LCSSA.cpp
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1 //===-- LCSSA.cpp - Convert loops into loop-closed SSA form ---------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This pass transforms loops by placing phi nodes at the end of the loops for
10 // all values that are live across the loop boundary. For example, it turns
11 // the left into the right code:
12 //
13 // for (...) for (...)
14 // if (c) if (c)
15 // X1 = ... X1 = ...
16 // else else
17 // X2 = ... X2 = ...
18 // X3 = phi(X1, X2) X3 = phi(X1, X2)
19 // ... = X3 + 4 X4 = phi(X3)
20 // ... = X4 + 4
21 //
22 // This is still valid LLVM; the extra phi nodes are purely redundant, and will
23 // be trivially eliminated by InstCombine. The major benefit of this
24 // transformation is that it makes many other loop optimizations, such as
25 // LoopUnswitching, simpler.
26 //
27 //===----------------------------------------------------------------------===//
28 
30 #include "llvm/ADT/STLExtras.h"
31 #include "llvm/ADT/Statistic.h"
36 #include "llvm/Analysis/LoopPass.h"
40 #include "llvm/IR/Constants.h"
41 #include "llvm/IR/Dominators.h"
42 #include "llvm/IR/Function.h"
43 #include "llvm/IR/Instructions.h"
44 #include "llvm/IR/IntrinsicInst.h"
46 #include "llvm/Pass.h"
47 #include "llvm/Transforms/Utils.h"
51 using namespace llvm;
52 
53 #define DEBUG_TYPE "lcssa"
54 
55 STATISTIC(NumLCSSA, "Number of live out of a loop variables");
56 
57 #ifdef EXPENSIVE_CHECKS
58 static bool VerifyLoopLCSSA = true;
59 #else
60 static bool VerifyLoopLCSSA = false;
61 #endif
63  VerifyLoopLCSSAFlag("verify-loop-lcssa", cl::location(VerifyLoopLCSSA),
64  cl::Hidden,
65  cl::desc("Verify loop lcssa form (time consuming)"));
66 
67 /// Return true if the specified block is in the list.
68 static bool isExitBlock(BasicBlock *BB,
69  const SmallVectorImpl<BasicBlock *> &ExitBlocks) {
70  return is_contained(ExitBlocks, BB);
71 }
72 
73 /// For every instruction from the worklist, check to see if it has any uses
74 /// that are outside the current loop. If so, insert LCSSA PHI nodes and
75 /// rewrite the uses.
77  DominatorTree &DT, LoopInfo &LI) {
78  SmallVector<Use *, 16> UsesToRewrite;
79  SmallSetVector<PHINode *, 16> PHIsToRemove;
80  PredIteratorCache PredCache;
81  bool Changed = false;
82 
83  // Cache the Loop ExitBlocks across this loop. We expect to get a lot of
84  // instructions within the same loops, computing the exit blocks is
85  // expensive, and we're not mutating the loop structure.
87 
88  while (!Worklist.empty()) {
89  UsesToRewrite.clear();
90 
91  Instruction *I = Worklist.pop_back_val();
92  assert(!I->getType()->isTokenTy() && "Tokens shouldn't be in the worklist");
93  BasicBlock *InstBB = I->getParent();
94  Loop *L = LI.getLoopFor(InstBB);
95  assert(L && "Instruction belongs to a BB that's not part of a loop");
96  if (!LoopExitBlocks.count(L))
97  L->getExitBlocks(LoopExitBlocks[L]);
98  assert(LoopExitBlocks.count(L));
99  const SmallVectorImpl<BasicBlock *> &ExitBlocks = LoopExitBlocks[L];
100 
101  if (ExitBlocks.empty())
102  continue;
103 
104  for (Use &U : I->uses()) {
105  Instruction *User = cast<Instruction>(U.getUser());
106  BasicBlock *UserBB = User->getParent();
107  if (auto *PN = dyn_cast<PHINode>(User))
108  UserBB = PN->getIncomingBlock(U);
109 
110  if (InstBB != UserBB && !L->contains(UserBB))
111  UsesToRewrite.push_back(&U);
112  }
113 
114  // If there are no uses outside the loop, exit with no change.
115  if (UsesToRewrite.empty())
116  continue;
117 
118  ++NumLCSSA; // We are applying the transformation
119 
120  // Invoke instructions are special in that their result value is not
121  // available along their unwind edge. The code below tests to see whether
122  // DomBB dominates the value, so adjust DomBB to the normal destination
123  // block, which is effectively where the value is first usable.
124  BasicBlock *DomBB = InstBB;
125  if (auto *Inv = dyn_cast<InvokeInst>(I))
126  DomBB = Inv->getNormalDest();
127 
128  DomTreeNode *DomNode = DT.getNode(DomBB);
129 
130  SmallVector<PHINode *, 16> AddedPHIs;
131  SmallVector<PHINode *, 8> PostProcessPHIs;
132 
133  SmallVector<PHINode *, 4> InsertedPHIs;
134  SSAUpdater SSAUpdate(&InsertedPHIs);
135  SSAUpdate.Initialize(I->getType(), I->getName());
136 
137  // Insert the LCSSA phi's into all of the exit blocks dominated by the
138  // value, and add them to the Phi's map.
139  for (BasicBlock *ExitBB : ExitBlocks) {
140  if (!DT.dominates(DomNode, DT.getNode(ExitBB)))
141  continue;
142 
143  // If we already inserted something for this BB, don't reprocess it.
144  if (SSAUpdate.HasValueForBlock(ExitBB))
145  continue;
146 
147  PHINode *PN = PHINode::Create(I->getType(), PredCache.size(ExitBB),
148  I->getName() + ".lcssa", &ExitBB->front());
149  // Get the debug location from the original instruction.
150  PN->setDebugLoc(I->getDebugLoc());
151  // Add inputs from inside the loop for this PHI.
152  for (BasicBlock *Pred : PredCache.get(ExitBB)) {
153  PN->addIncoming(I, Pred);
154 
155  // If the exit block has a predecessor not within the loop, arrange for
156  // the incoming value use corresponding to that predecessor to be
157  // rewritten in terms of a different LCSSA PHI.
158  if (!L->contains(Pred))
159  UsesToRewrite.push_back(
161  PN->getNumIncomingValues() - 1)));
162  }
163 
164  AddedPHIs.push_back(PN);
165 
166  // Remember that this phi makes the value alive in this block.
167  SSAUpdate.AddAvailableValue(ExitBB, PN);
168 
169  // LoopSimplify might fail to simplify some loops (e.g. when indirect
170  // branches are involved). In such situations, it might happen that an
171  // exit for Loop L1 is the header of a disjoint Loop L2. Thus, when we
172  // create PHIs in such an exit block, we are also inserting PHIs into L2's
173  // header. This could break LCSSA form for L2 because these inserted PHIs
174  // can also have uses outside of L2. Remember all PHIs in such situation
175  // as to revisit than later on. FIXME: Remove this if indirectbr support
176  // into LoopSimplify gets improved.
177  if (auto *OtherLoop = LI.getLoopFor(ExitBB))
178  if (!L->contains(OtherLoop))
179  PostProcessPHIs.push_back(PN);
180  }
181 
182  // Rewrite all uses outside the loop in terms of the new PHIs we just
183  // inserted.
184  for (Use *UseToRewrite : UsesToRewrite) {
185  // If this use is in an exit block, rewrite to use the newly inserted PHI.
186  // This is required for correctness because SSAUpdate doesn't handle uses
187  // in the same block. It assumes the PHI we inserted is at the end of the
188  // block.
189  Instruction *User = cast<Instruction>(UseToRewrite->getUser());
190  BasicBlock *UserBB = User->getParent();
191  if (auto *PN = dyn_cast<PHINode>(User))
192  UserBB = PN->getIncomingBlock(*UseToRewrite);
193 
194  if (isa<PHINode>(UserBB->begin()) && isExitBlock(UserBB, ExitBlocks)) {
195  // Tell the VHs that the uses changed. This updates SCEV's caches.
196  if (UseToRewrite->get()->hasValueHandle())
197  ValueHandleBase::ValueIsRAUWd(*UseToRewrite, &UserBB->front());
198  UseToRewrite->set(&UserBB->front());
199  continue;
200  }
201 
202  // If we added a single PHI, it must dominate all uses and we can directly
203  // rename it.
204  if (AddedPHIs.size() == 1) {
205  // Tell the VHs that the uses changed. This updates SCEV's caches.
206  // We might call ValueIsRAUWd multiple times for the same value.
207  if (UseToRewrite->get()->hasValueHandle())
208  ValueHandleBase::ValueIsRAUWd(*UseToRewrite, AddedPHIs[0]);
209  UseToRewrite->set(AddedPHIs[0]);
210  continue;
211  }
212 
213  // Otherwise, do full PHI insertion.
214  SSAUpdate.RewriteUse(*UseToRewrite);
215  }
216 
218  llvm::findDbgValues(DbgValues, I);
219 
220  // Update pre-existing debug value uses that reside outside the loop.
221  auto &Ctx = I->getContext();
222  for (auto DVI : DbgValues) {
223  BasicBlock *UserBB = DVI->getParent();
224  if (InstBB == UserBB || L->contains(UserBB))
225  continue;
226  // We currently only handle debug values residing in blocks that were
227  // traversed while rewriting the uses. If we inserted just a single PHI,
228  // we will handle all relevant debug values.
229  Value *V = AddedPHIs.size() == 1 ? AddedPHIs[0]
230  : SSAUpdate.FindValueForBlock(UserBB);
231  if (V)
232  DVI->setOperand(0, MetadataAsValue::get(Ctx, ValueAsMetadata::get(V)));
233  }
234 
235  // SSAUpdater might have inserted phi-nodes inside other loops. We'll need
236  // to post-process them to keep LCSSA form.
237  for (PHINode *InsertedPN : InsertedPHIs) {
238  if (auto *OtherLoop = LI.getLoopFor(InsertedPN->getParent()))
239  if (!L->contains(OtherLoop))
240  PostProcessPHIs.push_back(InsertedPN);
241  }
242 
243  // Post process PHI instructions that were inserted into another disjoint
244  // loop and update their exits properly.
245  for (auto *PostProcessPN : PostProcessPHIs)
246  if (!PostProcessPN->use_empty())
247  Worklist.push_back(PostProcessPN);
248 
249  // Keep track of PHI nodes that we want to remove because they did not have
250  // any uses rewritten. If the new PHI is used, store it so that we can
251  // try to propagate dbg.value intrinsics to it.
252  SmallVector<PHINode *, 2> NeedDbgValues;
253  for (PHINode *PN : AddedPHIs)
254  if (PN->use_empty())
255  PHIsToRemove.insert(PN);
256  else
257  NeedDbgValues.push_back(PN);
258  insertDebugValuesForPHIs(InstBB, NeedDbgValues);
259  Changed = true;
260  }
261  // Remove PHI nodes that did not have any uses rewritten. We need to redo the
262  // use_empty() check here, because even if the PHI node wasn't used when added
263  // to PHIsToRemove, later added PHI nodes can be using it. This cleanup is
264  // not guaranteed to handle trees/cycles of PHI nodes that only are used by
265  // each other. Such situations has only been noticed when the input IR
266  // contains unreachable code, and leaving some extra redundant PHI nodes in
267  // such situations is considered a minor problem.
268  for (PHINode *PN : PHIsToRemove)
269  if (PN->use_empty())
270  PN->eraseFromParent();
271  return Changed;
272 }
273 
274 // Compute the set of BasicBlocks in the loop `L` dominating at least one exit.
276  Loop &L, DominatorTree &DT, SmallVector<BasicBlock *, 8> &ExitBlocks,
277  SmallSetVector<BasicBlock *, 8> &BlocksDominatingExits) {
278  SmallVector<BasicBlock *, 8> BBWorklist;
279 
280  // We start from the exit blocks, as every block trivially dominates itself
281  // (not strictly).
282  for (BasicBlock *BB : ExitBlocks)
283  BBWorklist.push_back(BB);
284 
285  while (!BBWorklist.empty()) {
286  BasicBlock *BB = BBWorklist.pop_back_val();
287 
288  // Check if this is a loop header. If this is the case, we're done.
289  if (L.getHeader() == BB)
290  continue;
291 
292  // Otherwise, add its immediate predecessor in the dominator tree to the
293  // worklist, unless we visited it already.
294  BasicBlock *IDomBB = DT.getNode(BB)->getIDom()->getBlock();
295 
296  // Exit blocks can have an immediate dominator not beloinging to the
297  // loop. For an exit block to be immediately dominated by another block
298  // outside the loop, it implies not all paths from that dominator, to the
299  // exit block, go through the loop.
300  // Example:
301  //
302  // |---- A
303  // | |
304  // | B<--
305  // | | |
306  // |---> C --
307  // |
308  // D
309  //
310  // C is the exit block of the loop and it's immediately dominated by A,
311  // which doesn't belong to the loop.
312  if (!L.contains(IDomBB))
313  continue;
314 
315  if (BlocksDominatingExits.insert(IDomBB))
316  BBWorklist.push_back(IDomBB);
317  }
318 }
319 
321  ScalarEvolution *SE) {
322  bool Changed = false;
323 
324 #ifdef EXPENSIVE_CHECKS
325  // Verify all sub-loops are in LCSSA form already.
326  for (Loop *SubLoop: L)
327  assert(SubLoop->isRecursivelyLCSSAForm(DT, *LI) && "Subloop not in LCSSA!");
328 #endif
329 
330  SmallVector<BasicBlock *, 8> ExitBlocks;
331  L.getExitBlocks(ExitBlocks);
332  if (ExitBlocks.empty())
333  return false;
334 
335  SmallSetVector<BasicBlock *, 8> BlocksDominatingExits;
336 
337  // We want to avoid use-scanning leveraging dominance informations.
338  // If a block doesn't dominate any of the loop exits, the none of the values
339  // defined in the loop can be used outside.
340  // We compute the set of blocks fullfilling the conditions in advance
341  // walking the dominator tree upwards until we hit a loop header.
342  computeBlocksDominatingExits(L, DT, ExitBlocks, BlocksDominatingExits);
343 
345 
346  // Look at all the instructions in the loop, checking to see if they have uses
347  // outside the loop. If so, put them into the worklist to rewrite those uses.
348  for (BasicBlock *BB : BlocksDominatingExits) {
349  // Skip blocks that are part of any sub-loops, they must be in LCSSA
350  // already.
351  if (LI->getLoopFor(BB) != &L)
352  continue;
353  for (Instruction &I : *BB) {
354  // Reject two common cases fast: instructions with no uses (like stores)
355  // and instructions with one use that is in the same block as this.
356  if (I.use_empty() ||
357  (I.hasOneUse() && I.user_back()->getParent() == BB &&
358  !isa<PHINode>(I.user_back())))
359  continue;
360 
361  // Tokens cannot be used in PHI nodes, so we skip over them.
362  // We can run into tokens which are live out of a loop with catchswitch
363  // instructions in Windows EH if the catchswitch has one catchpad which
364  // is inside the loop and another which is not.
365  if (I.getType()->isTokenTy())
366  continue;
367 
368  Worklist.push_back(&I);
369  }
370  }
371  Changed = formLCSSAForInstructions(Worklist, DT, *LI);
372 
373  // If we modified the code, remove any caches about the loop from SCEV to
374  // avoid dangling entries.
375  // FIXME: This is a big hammer, can we clear the cache more selectively?
376  if (SE && Changed)
377  SE->forgetLoop(&L);
378 
379  assert(L.isLCSSAForm(DT));
380 
381  return Changed;
382 }
383 
384 /// Process a loop nest depth first.
386  ScalarEvolution *SE) {
387  bool Changed = false;
388 
389  // Recurse depth-first through inner loops.
390  for (Loop *SubLoop : L.getSubLoops())
391  Changed |= formLCSSARecursively(*SubLoop, DT, LI, SE);
392 
393  Changed |= formLCSSA(L, DT, LI, SE);
394  return Changed;
395 }
396 
397 /// Process all loops in the function, inner-most out.
399  ScalarEvolution *SE) {
400  bool Changed = false;
401  for (auto &L : *LI)
402  Changed |= formLCSSARecursively(*L, DT, LI, SE);
403  return Changed;
404 }
405 
406 namespace {
407 struct LCSSAWrapperPass : public FunctionPass {
408  static char ID; // Pass identification, replacement for typeid
409  LCSSAWrapperPass() : FunctionPass(ID) {
411  }
412 
413  // Cached analysis information for the current function.
414  DominatorTree *DT;
415  LoopInfo *LI;
416  ScalarEvolution *SE;
417 
418  bool runOnFunction(Function &F) override;
419  void verifyAnalysis() const override {
420  // This check is very expensive. On the loop intensive compiles it may cause
421  // up to 10x slowdown. Currently it's disabled by default. LPPassManager
422  // always does limited form of the LCSSA verification. Similar reasoning
423  // was used for the LoopInfo verifier.
424  if (VerifyLoopLCSSA) {
425  assert(all_of(*LI,
426  [&](Loop *L) {
427  return L->isRecursivelyLCSSAForm(*DT, *LI);
428  }) &&
429  "LCSSA form is broken!");
430  }
431  };
432 
433  /// This transformation requires natural loop information & requires that
434  /// loop preheaders be inserted into the CFG. It maintains both of these,
435  /// as well as the CFG. It also requires dominator information.
436  void getAnalysisUsage(AnalysisUsage &AU) const override {
437  AU.setPreservesCFG();
438 
449 
450  // This is needed to perform LCSSA verification inside LPPassManager
453  }
454 };
455 }
456 
457 char LCSSAWrapperPass::ID = 0;
458 INITIALIZE_PASS_BEGIN(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass",
459  false, false)
463 INITIALIZE_PASS_END(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass",
464  false, false)
465 
466 Pass *llvm::createLCSSAPass() { return new LCSSAWrapperPass(); }
468 
469 /// Transform \p F into loop-closed SSA form.
471  LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
472  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
473  auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
474  SE = SEWP ? &SEWP->getSE() : nullptr;
475 
476  return formLCSSAOnAllLoops(LI, *DT, SE);
477 }
478 
480  auto &LI = AM.getResult<LoopAnalysis>(F);
481  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
482  auto *SE = AM.getCachedResult<ScalarEvolutionAnalysis>(F);
483  if (!formLCSSAOnAllLoops(&LI, DT, SE))
484  return PreservedAnalyses::all();
485 
487  PA.preserveSet<CFGAnalyses>();
488  PA.preserve<BasicAA>();
489  PA.preserve<GlobalsAA>();
490  PA.preserve<SCEVAA>();
492  // BPI maps terminators to probabilities, since we don't modify the CFG, no
493  // updates are needed to preserve it.
496  return PA;
497 }
Legacy wrapper pass to provide the GlobalsAAResult object.
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:80
void initializeLCSSAWrapperPassPass(PassRegistry &)
iterator_range< use_iterator > uses()
Definition: Value.h:374
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
Helper class for SSA formation on a set of values defined in multiple blocks.
Definition: SSAUpdater.h:38
void addIncoming(Value *V, BasicBlock *BB)
Add an incoming value to the end of the PHI list.
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:776
This class represents lattice values for constants.
Definition: AllocatorList.h:23
This is the interface for a simple mod/ref and alias analysis over globals.
void Initialize(Type *Ty, StringRef Name)
Reset this object to get ready for a new set of SSA updates with type &#39;Ty&#39;.
Definition: SSAUpdater.cpp:53
bool isRecursivelyLCSSAForm(DominatorTree &DT, const LoopInfo &LI) const
Return true if this Loop and all inner subloops are in LCSSA form.
Definition: LoopInfo.cpp:451
void AddAvailableValue(BasicBlock *BB, Value *V)
Indicate that a rewritten value is available in the specified block with the specified value...
Definition: SSAUpdater.cpp:71
The main scalar evolution driver.
LLVMContext & getContext() const
All values hold a context through their type.
Definition: Value.cpp:733
Pass * createLCSSAPass()
Definition: LCSSA.cpp:466
const Use & getOperandUse(unsigned i) const
Definition: User.h:182
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1165
STATISTIC(NumFunctions, "Total number of functions")
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:230
F(f)
static bool isExitBlock(BasicBlock *BB, const SmallVectorImpl< BasicBlock *> &ExitBlocks)
Return true if the specified block is in the list.
Definition: LCSSA.cpp:68
bool formLCSSARecursively(Loop &L, DominatorTree &DT, LoopInfo *LI, ScalarEvolution *SE)
Put a loop nest into LCSSA form.
Definition: LCSSA.cpp:385
static unsigned getOperandNumForIncomingValue(unsigned i)
AnalysisUsage & addRequired()
ArrayRef< BasicBlock * > get(BasicBlock *BB)
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:50
Legacy analysis pass which computes MemorySSA.
Definition: MemorySSA.h:965
This is the interface for a SCEV-based alias analysis.
LoopT * getLoopFor(const BlockT *BB) const
Return the inner most loop that BB lives in.
Definition: LoopInfo.h:928
A Use represents the edge between a Value definition and its users.
Definition: Use.h:55
Analysis pass that exposes the LoopInfo for a function.
Definition: LoopInfo.h:1183
BlockT * getHeader() const
Definition: LoopInfo.h:105
void insertDebugValuesForPHIs(BasicBlock *BB, SmallVectorImpl< PHINode *> &InsertedPHIs)
Propagate dbg.value intrinsics through the newly inserted PHIs.
Definition: Local.cpp:1443
void getExitBlocks(SmallVectorImpl< BlockT *> &ExitBlocks) const
Return all of the successor blocks of this loop.
Definition: LoopInfoImpl.h:62
Analysis pass which computes BranchProbabilityInfo.
void findDbgValues(SmallVectorImpl< DbgValueInst *> &DbgValues, Value *V)
Finds the llvm.dbg.value intrinsics describing a value.
Definition: Local.cpp:1509
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
bool insert(const value_type &X)
Insert a new element into the SetVector.
Definition: SetVector.h:141
PredIteratorCache - This class is an extremely trivial cache for predecessor iterator queries...
Memory SSA
Definition: MemorySSA.cpp:65
AnalysisUsage & addPreservedID(const void *ID)
static void ValueIsRAUWd(Value *Old, Value *New)
Definition: Value.cpp:913
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:144
Legacy analysis pass which computes BranchProbabilityInfo.
Value * FindValueForBlock(BasicBlock *BB) const
Return the value for the specified block if the SSAUpdater has one, otherwise return nullptr...
Definition: SSAUpdater.cpp:66
static MetadataAsValue * get(LLVMContext &Context, Metadata *MD)
Definition: Metadata.cpp:105
NodeT * getBlock() const
static bool runOnFunction(Function &F, bool PostInlining)
bool formLCSSAForInstructions(SmallVectorImpl< Instruction *> &Worklist, DominatorTree &DT, LoopInfo &LI)
Ensures LCSSA form for every instruction from the Worklist in the scope of innermost containing loop...
Definition: LCSSA.cpp:76
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:318
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
size_t size(BasicBlock *BB) const
DomTreeNodeBase * getIDom() const
static cl::opt< bool, true > VerifyLoopLCSSAFlag("verify-loop-lcssa", cl::location(VerifyLoopLCSSA), cl::Hidden, cl::desc("Verify loop lcssa form (time consuming)"))
static bool VerifyLoopLCSSA
Definition: LCSSA.cpp:60
This file contains the declarations for the subclasses of Constant, which represent the different fla...
char & LCSSAID
Definition: LCSSA.cpp:467
Represent the analysis usage information of a pass.
Analysis pass providing a never-invalidated alias analysis result.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:284
Analysis pass providing a never-invalidated alias analysis result.
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
size_t size() const
Definition: SmallVector.h:52
DomTreeNodeBase< NodeT > * getNode(const NodeT *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
char & LoopSimplifyID
static bool formLCSSAOnAllLoops(LoopInfo *LI, DominatorTree &DT, ScalarEvolution *SE)
Process all loops in the function, inner-most out.
Definition: LCSSA.cpp:398
bool formLCSSA(Loop &L, DominatorTree &DT, LoopInfo *LI, ScalarEvolution *SE)
Put loop into LCSSA form.
Definition: LCSSA.cpp:320
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
Definition: LoopInfo.h:115
A SetVector that performs no allocations if smaller than a certain size.
Definition: SetVector.h:297
Legacy wrapper pass to provide the SCEVAAResult object.
static ValueAsMetadata * get(Value *V)
Definition: Metadata.cpp:348
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:837
bool dominates(const Instruction *Def, const Use &U) const
Return true if Def dominates a use in User.
Definition: Dominators.cpp:248
An analysis that produces MemorySSA for a function.
Definition: MemorySSA.h:926
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:374
static PHINode * Create(Type *Ty, unsigned NumReservedValues, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
Constructors - NumReservedValues is a hint for the number of incoming edges that this phi node will h...
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:301
unsigned getNumIncomingValues() const
Return the number of incoming edges.
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: LCSSA.cpp:479
Represents analyses that only rely on functions&#39; control flow.
Definition: PassManager.h:114
Analysis pass that exposes the ScalarEvolution for a function.
lcssa
Definition: LCSSA.cpp:463
const std::vector< LoopT * > & getSubLoops() const
Return the loops contained entirely within this loop.
Definition: LoopInfo.h:136
Analysis pass providing a never-invalidated alias analysis result.
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:321
static void computeBlocksDominatingExits(Loop &L, DominatorTree &DT, SmallVector< BasicBlock *, 8 > &ExitBlocks, SmallSetVector< BasicBlock *, 8 > &BlocksDominatingExits)
Definition: LCSSA.cpp:275
void forgetLoop(const Loop *L)
This method should be called by the client when it has changed a loop in a way that may effect Scalar...
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:55
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:509
bool isTokenTy() const
Return true if this is &#39;token&#39;.
Definition: Type.h:193
void preserveSet()
Mark an analysis set as preserved.
Definition: PassManager.h:189
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:214
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:106
#define I(x, y, z)
Definition: MD5.cpp:58
PassT::Result * getCachedResult(IRUnitT &IR) const
Get the cached result of an analysis pass for a given IR unit.
Definition: PassManager.h:795
void preserve()
Mark an analysis as preserved.
Definition: PassManager.h:174
INITIALIZE_PASS_BEGIN(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass", false, false) INITIALIZE_PASS_END(LCSSAWrapperPass
size_type count(const_arg_type_t< KeyT > Val) const
Return 1 if the specified key is in the map, 0 otherwise.
Definition: DenseMap.h:171
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM_NODISCARD char front() const
front - Get the first character in the string.
Definition: StringRef.h:134
LLVM Value Representation.
Definition: Value.h:73
This file exposes an interface to building/using memory SSA to walk memory instructions using a use/d...
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:1208
This is the interface for LLVM&#39;s primary stateless and local alias analysis.
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:259
A wrapper pass to provide the legacy pass manager access to a suitably prepared AAResults object...
void RewriteUse(Use &U)
Rewrite a use of the symbolic value.
Definition: SSAUpdater.cpp:189
LocationClass< Ty > location(Ty &L)
Definition: CommandLine.h:448
const BasicBlock * getParent() const
Definition: Instruction.h:66
bool HasValueForBlock(BasicBlock *BB) const
Return true if the SSAUpdater already has a value for the specified block.
Definition: SSAUpdater.cpp:62
Legacy wrapper pass to provide the BasicAAResult object.
bool is_contained(R &&Range, const E &Element)
Wrapper function around std::find to detect if an element exists in a container.
Definition: STLExtras.h:1224