Bug Summary

File:lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp
Warning:line 538, column 3
1st function call argument is an uninitialized value

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name HexagonVectorLoopCarriedReuse.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-9/lib/clang/9.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-9~svn362543/build-llvm/lib/Target/Hexagon -I /build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon -I /build/llvm-toolchain-snapshot-9~svn362543/build-llvm/include -I /build/llvm-toolchain-snapshot-9~svn362543/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/include/clang/9.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-9/lib/clang/9.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-9~svn362543/build-llvm/lib/Target/Hexagon -fdebug-prefix-map=/build/llvm-toolchain-snapshot-9~svn362543=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2019-06-05-060531-1271-1 -x c++ /build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp -faddrsig
1//===- HexagonVectorLoopCarriedReuse.cpp ----------------------------------===//
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 removes the computation of provably redundant expressions that have
10// been computed earlier in a previous iteration. It relies on the use of PHIs
11// to identify loop carried dependences. This is scalar replacement for vector
12// types.
13//
14//-----------------------------------------------------------------------------
15// Motivation: Consider the case where we have the following loop structure.
16//
17// Loop:
18// t0 = a[i];
19// t1 = f(t0);
20// t2 = g(t1);
21// ...
22// t3 = a[i+1];
23// t4 = f(t3);
24// t5 = g(t4);
25// t6 = op(t2, t5)
26// cond_branch <Loop>
27//
28// This can be converted to
29// t00 = a[0];
30// t10 = f(t00);
31// t20 = g(t10);
32// Loop:
33// t2 = t20;
34// t3 = a[i+1];
35// t4 = f(t3);
36// t5 = g(t4);
37// t6 = op(t2, t5)
38// t20 = t5
39// cond_branch <Loop>
40//
41// SROA does a good job of reusing a[i+1] as a[i] in the next iteration.
42// Such a loop comes to this pass in the following form.
43//
44// LoopPreheader:
45// X0 = a[0];
46// Loop:
47// X2 = PHI<(X0, LoopPreheader), (X1, Loop)>
48// t1 = f(X2) <-- I1
49// t2 = g(t1)
50// ...
51// X1 = a[i+1]
52// t4 = f(X1) <-- I2
53// t5 = g(t4)
54// t6 = op(t2, t5)
55// cond_branch <Loop>
56//
57// In this pass, we look for PHIs such as X2 whose incoming values come only
58// from the Loop Preheader and over the backedge and additionaly, both these
59// values are the results of the same operation in terms of opcode. We call such
60// a PHI node a dependence chain or DepChain. In this case, the dependence of X2
61// over X1 is carried over only one iteration and so the DepChain is only one
62// PHI node long.
63//
64// Then, we traverse the uses of the PHI (X2) and the uses of the value of the
65// PHI coming over the backedge (X1). We stop at the first pair of such users
66// I1 (of X2) and I2 (of X1) that meet the following conditions.
67// 1. I1 and I2 are the same operation, but with different operands.
68// 2. X2 and X1 are used at the same operand number in the two instructions.
69// 3. All other operands Op1 of I1 and Op2 of I2 are also such that there is a
70// a DepChain from Op1 to Op2 of the same length as that between X2 and X1.
71//
72// We then make the following transformation
73// LoopPreheader:
74// X0 = a[0];
75// Y0 = f(X0);
76// Loop:
77// X2 = PHI<(X0, LoopPreheader), (X1, Loop)>
78// Y2 = PHI<(Y0, LoopPreheader), (t4, Loop)>
79// t1 = f(X2) <-- Will be removed by DCE.
80// t2 = g(Y2)
81// ...
82// X1 = a[i+1]
83// t4 = f(X1)
84// t5 = g(t4)
85// t6 = op(t2, t5)
86// cond_branch <Loop>
87//
88// We proceed until we cannot find any more such instructions I1 and I2.
89//
90// --- DepChains & Loop carried dependences ---
91// Consider a single basic block loop such as
92//
93// LoopPreheader:
94// X0 = ...
95// Y0 = ...
96// Loop:
97// X2 = PHI<(X0, LoopPreheader), (X1, Loop)>
98// Y2 = PHI<(Y0, LoopPreheader), (X2, Loop)>
99// ...
100// X1 = ...
101// ...
102// cond_branch <Loop>
103//
104// Then there is a dependence between X2 and X1 that goes back one iteration,
105// i.e. X1 is used as X2 in the very next iteration. We represent this as a
106// DepChain from X2 to X1 (X2->X1).
107// Similarly, there is a dependence between Y2 and X1 that goes back two
108// iterations. X1 is used as Y2 two iterations after it is computed. This is
109// represented by a DepChain as (Y2->X2->X1).
110//
111// A DepChain has the following properties.
112// 1. Num of edges in DepChain = Number of Instructions in DepChain = Number of
113// iterations of carried dependence + 1.
114// 2. All instructions in the DepChain except the last are PHIs.
115//
116//===----------------------------------------------------------------------===//
117
118#include "llvm/ADT/SetVector.h"
119#include "llvm/ADT/SmallVector.h"
120#include "llvm/ADT/Statistic.h"
121#include "llvm/Analysis/LoopInfo.h"
122#include "llvm/Analysis/LoopPass.h"
123#include "llvm/IR/BasicBlock.h"
124#include "llvm/IR/DerivedTypes.h"
125#include "llvm/IR/IRBuilder.h"
126#include "llvm/IR/Instruction.h"
127#include "llvm/IR/Instructions.h"
128#include "llvm/IR/IntrinsicInst.h"
129#include "llvm/IR/Intrinsics.h"
130#include "llvm/IR/Use.h"
131#include "llvm/IR/User.h"
132#include "llvm/IR/Value.h"
133#include "llvm/Pass.h"
134#include "llvm/Support/Casting.h"
135#include "llvm/Support/CommandLine.h"
136#include "llvm/Support/Compiler.h"
137#include "llvm/Support/Debug.h"
138#include "llvm/Support/raw_ostream.h"
139#include "llvm/Transforms/Scalar.h"
140#include "llvm/Transforms/Utils.h"
141#include <algorithm>
142#include <cassert>
143#include <cstddef>
144#include <map>
145#include <memory>
146#include <set>
147
148using namespace llvm;
149
150#define DEBUG_TYPE"hexagon-vlcr" "hexagon-vlcr"
151
152STATISTIC(HexagonNumVectorLoopCarriedReuse,static llvm::Statistic HexagonNumVectorLoopCarriedReuse = {"hexagon-vlcr"
, "HexagonNumVectorLoopCarriedReuse", "Number of values that were reused from a previous iteration."
, {0}, {false}}
153 "Number of values that were reused from a previous iteration.")static llvm::Statistic HexagonNumVectorLoopCarriedReuse = {"hexagon-vlcr"
, "HexagonNumVectorLoopCarriedReuse", "Number of values that were reused from a previous iteration."
, {0}, {false}};
154
155static cl::opt<int> HexagonVLCRIterationLim("hexagon-vlcr-iteration-lim",
156 cl::Hidden,
157 cl::desc("Maximum distance of loop carried dependences that are handled"),
158 cl::init(2), cl::ZeroOrMore);
159
160namespace llvm {
161
162void initializeHexagonVectorLoopCarriedReusePass(PassRegistry&);
163Pass *createHexagonVectorLoopCarriedReusePass();
164
165} // end namespace llvm
166
167namespace {
168
169 // See info about DepChain in the comments at the top of this file.
170 using ChainOfDependences = SmallVector<Instruction *, 4>;
171
172 class DepChain {
173 ChainOfDependences Chain;
174
175 public:
176 bool isIdentical(DepChain &Other) const {
177 if (Other.size() != size())
178 return false;
179 ChainOfDependences &OtherChain = Other.getChain();
180 for (int i = 0; i < size(); ++i) {
181 if (Chain[i] != OtherChain[i])
182 return false;
183 }
184 return true;
185 }
186
187 ChainOfDependences &getChain() {
188 return Chain;
189 }
190
191 int size() const {
192 return Chain.size();
193 }
194
195 void clear() {
196 Chain.clear();
197 }
198
199 void push_back(Instruction *I) {
200 Chain.push_back(I);
201 }
202
203 int iterations() const {
204 return size() - 1;
205 }
206
207 Instruction *front() const {
208 return Chain.front();
209 }
210
211 Instruction *back() const {
212 return Chain.back();
213 }
214
215 Instruction *&operator[](const int index) {
216 return Chain[index];
217 }
218
219 friend raw_ostream &operator<< (raw_ostream &OS, const DepChain &D);
220 };
221
222 LLVM_ATTRIBUTE_UNUSED__attribute__((__unused__))
223 raw_ostream &operator<<(raw_ostream &OS, const DepChain &D) {
224 const ChainOfDependences &CD = D.Chain;
225 int ChainSize = CD.size();
226 OS << "**DepChain Start::**\n";
227 for (int i = 0; i < ChainSize -1; ++i) {
228 OS << *(CD[i]) << " -->\n";
229 }
230 OS << *CD[ChainSize-1] << "\n";
231 return OS;
232 }
233
234 struct ReuseValue {
235 Instruction *Inst2Replace = nullptr;
236
237 // In the new PHI node that we'll construct this is the value that'll be
238 // used over the backedge. This is teh value that gets reused from a
239 // previous iteration.
240 Instruction *BackedgeInst = nullptr;
241
242 ReuseValue() = default;
243
244 void reset() { Inst2Replace = nullptr; BackedgeInst = nullptr; }
245 bool isDefined() { return Inst2Replace != nullptr; }
246 };
247
248 LLVM_ATTRIBUTE_UNUSED__attribute__((__unused__))
249 raw_ostream &operator<<(raw_ostream &OS, const ReuseValue &RU) {
250 OS << "** ReuseValue ***\n";
251 OS << "Instruction to Replace: " << *(RU.Inst2Replace) << "\n";
252 OS << "Backedge Instruction: " << *(RU.BackedgeInst) << "\n";
253 return OS;
254 }
255
256 class HexagonVectorLoopCarriedReuse : public LoopPass {
257 public:
258 static char ID;
259
260 explicit HexagonVectorLoopCarriedReuse() : LoopPass(ID) {
261 PassRegistry *PR = PassRegistry::getPassRegistry();
262 initializeHexagonVectorLoopCarriedReusePass(*PR);
263 }
264
265 StringRef getPassName() const override {
266 return "Hexagon-specific loop carried reuse for HVX vectors";
267 }
268
269 void getAnalysisUsage(AnalysisUsage &AU) const override {
270 AU.addRequired<LoopInfoWrapperPass>();
271 AU.addRequiredID(LoopSimplifyID);
272 AU.addRequiredID(LCSSAID);
273 AU.addPreservedID(LCSSAID);
274 AU.setPreservesCFG();
275 }
276
277 bool runOnLoop(Loop *L, LPPassManager &LPM) override;
278
279 private:
280 SetVector<DepChain *> Dependences;
281 std::set<Instruction *> ReplacedInsts;
282 Loop *CurLoop;
283 ReuseValue ReuseCandidate;
284
285 bool doVLCR();
286 void findLoopCarriedDeps();
287 void findValueToReuse();
288 void findDepChainFromPHI(Instruction *I, DepChain &D);
289 void reuseValue();
290 Value *findValueInBlock(Value *Op, BasicBlock *BB);
291 bool isDepChainBtwn(Instruction *I1, Instruction *I2, int Iters);
292 DepChain *getDepChainBtwn(Instruction *I1, Instruction *I2);
293 bool isEquivalentOperation(Instruction *I1, Instruction *I2);
294 bool canReplace(Instruction *I);
295 };
296
297} // end anonymous namespace
298
299char HexagonVectorLoopCarriedReuse::ID = 0;
300
301INITIALIZE_PASS_BEGIN(HexagonVectorLoopCarriedReuse, "hexagon-vlcr",static void *initializeHexagonVectorLoopCarriedReusePassOnce(
PassRegistry &Registry) {
302 "Hexagon-specific predictive commoning for HVX vectors", false, false)static void *initializeHexagonVectorLoopCarriedReusePassOnce(
PassRegistry &Registry) {
303INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry);
304INITIALIZE_PASS_DEPENDENCY(LoopSimplify)initializeLoopSimplifyPass(Registry);
305INITIALIZE_PASS_DEPENDENCY(LCSSAWrapperPass)initializeLCSSAWrapperPassPass(Registry);
306INITIALIZE_PASS_END(HexagonVectorLoopCarriedReuse, "hexagon-vlcr",PassInfo *PI = new PassInfo( "Hexagon-specific predictive commoning for HVX vectors"
, "hexagon-vlcr", &HexagonVectorLoopCarriedReuse::ID, PassInfo
::NormalCtor_t(callDefaultCtor<HexagonVectorLoopCarriedReuse
>), false, false); Registry.registerPass(*PI, true); return
PI; } static llvm::once_flag InitializeHexagonVectorLoopCarriedReusePassFlag
; void llvm::initializeHexagonVectorLoopCarriedReusePass(PassRegistry
&Registry) { llvm::call_once(InitializeHexagonVectorLoopCarriedReusePassFlag
, initializeHexagonVectorLoopCarriedReusePassOnce, std::ref(Registry
)); }
307 "Hexagon-specific predictive commoning for HVX vectors", false, false)PassInfo *PI = new PassInfo( "Hexagon-specific predictive commoning for HVX vectors"
, "hexagon-vlcr", &HexagonVectorLoopCarriedReuse::ID, PassInfo
::NormalCtor_t(callDefaultCtor<HexagonVectorLoopCarriedReuse
>), false, false); Registry.registerPass(*PI, true); return
PI; } static llvm::once_flag InitializeHexagonVectorLoopCarriedReusePassFlag
; void llvm::initializeHexagonVectorLoopCarriedReusePass(PassRegistry
&Registry) { llvm::call_once(InitializeHexagonVectorLoopCarriedReusePassFlag
, initializeHexagonVectorLoopCarriedReusePassOnce, std::ref(Registry
)); }
308
309bool HexagonVectorLoopCarriedReuse::runOnLoop(Loop *L, LPPassManager &LPM) {
310 if (skipLoop(L))
1
Assuming the condition is false
→
2
←
Taking false branch
→
311 return false;
312
313 if (!L->getLoopPreheader())
3
←
Assuming the condition is false
→
4
←
Taking false branch
→
314 return false;
315
316 // Work only on innermost loops.
317 if (!L->getSubLoops().empty())
5
←
Assuming the condition is false
→
6
←
Taking false branch
→
318 return false;
319
320 // Work only on single basic blocks loops.
321 if (L->getNumBlocks() != 1)
7
←
Assuming the condition is false
→
8
←
Taking false branch
→
322 return false;
323
324 CurLoop = L;
325
326 return doVLCR();
9
←
Calling 'HexagonVectorLoopCarriedReuse::doVLCR'
→
327}
328
329bool HexagonVectorLoopCarriedReuse::isEquivalentOperation(Instruction *I1,
330 Instruction *I2) {
331 if (!I1->isSameOperationAs(I2))
332 return false;
333 // This check is in place specifically for intrinsics. isSameOperationAs will
334 // return two for any two hexagon intrinsics because they are essentially the
335 // same instruciton (CallInst). We need to scratch the surface to see if they
336 // are calls to the same function.
337 if (CallInst *C1 = dyn_cast<CallInst>(I1)) {
338 if (CallInst *C2 = dyn_cast<CallInst>(I2)) {
339 if (C1->getCalledFunction() != C2->getCalledFunction())
340 return false;
341 }
342 }
343
344 // If both the Instructions are of Vector Type and any of the element
345 // is integer constant, check their values too for equivalence.
346 if (I1->getType()->isVectorTy() && I2->getType()->isVectorTy()) {
347 unsigned NumOperands = I1->getNumOperands();
348 for (unsigned i = 0; i < NumOperands; ++i) {
349 ConstantInt *C1 = dyn_cast<ConstantInt>(I1->getOperand(i));
350 ConstantInt *C2 = dyn_cast<ConstantInt>(I2->getOperand(i));
351 if(!C1) continue;
352 assert(C2)((C2) ? static_cast<void> (0) : __assert_fail ("C2", "/build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp"
, 352, __PRETTY_FUNCTION__));
353 if (C1->getSExtValue() != C2->getSExtValue())
354 return false;
355 }
356 }
357
358 return true;
359}
360
361bool HexagonVectorLoopCarriedReuse::canReplace(Instruction *I) {
362 const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I);
363 if (II &&
364 (II->getIntrinsicID() == Intrinsic::hexagon_V6_hi ||
365 II->getIntrinsicID() == Intrinsic::hexagon_V6_lo)) {
366 LLVM_DEBUG(dbgs() << "Not considering for reuse: " << *II << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Not considering for reuse: "
<< *II << "\n"; } } while (false);
367 return false;
368 }
369 return true;
370}
371void HexagonVectorLoopCarriedReuse::findValueToReuse() {
372 for (auto *D : Dependences) {
373 LLVM_DEBUG(dbgs() << "Processing dependence " << *(D->front()) << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Processing dependence " <<
*(D->front()) << "\n"; } } while (false);
374 if (D->iterations() > HexagonVLCRIterationLim) {
375 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << ".. Skipping because number of iterations > than the limit\n"
; } } while (false)
376 dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << ".. Skipping because number of iterations > than the limit\n"
; } } while (false)
377 << ".. Skipping because number of iterations > than the limit\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << ".. Skipping because number of iterations > than the limit\n"
; } } while (false);
378 continue;
379 }
380
381 PHINode *PN = cast<PHINode>(D->front());
382 Instruction *BEInst = D->back();
383 int Iters = D->iterations();
384 BasicBlock *BB = PN->getParent();
385 LLVM_DEBUG(dbgs() << "Checking if any uses of " << *PNdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Checking if any uses of "
<< *PN << " can be reused\n"; } } while (false)
386 << " can be reused\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Checking if any uses of "
<< *PN << " can be reused\n"; } } while (false);
387
388 SmallVector<Instruction *, 4> PNUsers;
389 for (auto UI = PN->use_begin(), E = PN->use_end(); UI != E; ++UI) {
390 Use &U = *UI;
391 Instruction *User = cast<Instruction>(U.getUser());
392
393 if (User->getParent() != BB)
394 continue;
395 if (ReplacedInsts.count(User)) {
396 LLVM_DEBUG(dbgs() << *Userdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << *User << " has already been replaced. Skipping...\n"
; } } while (false)
397 << " has already been replaced. Skipping...\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << *User << " has already been replaced. Skipping...\n"
; } } while (false);
398 continue;
399 }
400 if (isa<PHINode>(User))
401 continue;
402 if (User->mayHaveSideEffects())
403 continue;
404 if (!canReplace(User))
405 continue;
406
407 PNUsers.push_back(User);
408 }
409 LLVM_DEBUG(dbgs() << PNUsers.size() << " use(s) of the PHI in the block\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << PNUsers.size() << " use(s) of the PHI in the block\n"
; } } while (false);
410
411 // For each interesting use I of PN, find an Instruction BEUser that
412 // performs the same operation as I on BEInst and whose other operands,
413 // if any, can also be rematerialized in OtherBB. We stop when we find the
414 // first such Instruction BEUser. This is because once BEUser is
415 // rematerialized in OtherBB, we may find more such "fixup" opportunities
416 // in this block. So, we'll start over again.
417 for (Instruction *I : PNUsers) {
418 for (auto UI = BEInst->use_begin(), E = BEInst->use_end(); UI != E;
419 ++UI) {
420 Use &U = *UI;
421 Instruction *BEUser = cast<Instruction>(U.getUser());
422
423 if (BEUser->getParent() != BB)
424 continue;
425 if (!isEquivalentOperation(I, BEUser))
426 continue;
427
428 int NumOperands = I->getNumOperands();
429
430 for (int OpNo = 0; OpNo < NumOperands; ++OpNo) {
431 Value *Op = I->getOperand(OpNo);
432 Value *BEOp = BEUser->getOperand(OpNo);
433
434 Instruction *OpInst = dyn_cast<Instruction>(Op);
435 if (!OpInst) {
436 if (Op == BEOp)
437 continue;
438 // Do not allow reuse to occur when the operands may be different
439 // values.
440 BEUser = nullptr;
441 break;
442 }
443
444 Instruction *BEOpInst = dyn_cast<Instruction>(BEOp);
445
446 if (!isDepChainBtwn(OpInst, BEOpInst, Iters)) {
447 BEUser = nullptr;
448 break;
449 }
450 }
451 if (BEUser) {
452 LLVM_DEBUG(dbgs() << "Found Value for reuse.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Found Value for reuse.\n"
; } } while (false);
453 ReuseCandidate.Inst2Replace = I;
454 ReuseCandidate.BackedgeInst = BEUser;
455 return;
456 } else
457 ReuseCandidate.reset();
458 }
459 }
460 }
461 ReuseCandidate.reset();
462}
463
464Value *HexagonVectorLoopCarriedReuse::findValueInBlock(Value *Op,
465 BasicBlock *BB) {
466 PHINode *PN = dyn_cast<PHINode>(Op);
467 assert(PN)((PN) ? static_cast<void> (0) : __assert_fail ("PN", "/build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp"
, 467, __PRETTY_FUNCTION__));
468 Value *ValueInBlock = PN->getIncomingValueForBlock(BB);
469 return ValueInBlock;
470}
471
472void HexagonVectorLoopCarriedReuse::reuseValue() {
473 LLVM_DEBUG(dbgs() << ReuseCandidate)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << ReuseCandidate; } } while
(false);
18
←
Assuming 'DebugFlag' is 0
→
19
←
Loop condition is false. Exiting loop
→
474 Instruction *Inst2Replace = ReuseCandidate.Inst2Replace;
475 Instruction *BEInst = ReuseCandidate.BackedgeInst;
476 int NumOperands = Inst2Replace->getNumOperands();
477 std::map<Instruction *, DepChain *> DepChains;
478 int Iterations = -1;
479 BasicBlock *LoopPH = CurLoop->getLoopPreheader();
480
481 for (int i = 0; i < NumOperands; ++i) {
20
←
Loop condition is false. Execution continues on line 498
→
482 Instruction *I = dyn_cast<Instruction>(Inst2Replace->getOperand(i));
483 if(!I)
484 continue;
485 else {
486 Instruction *J = cast<Instruction>(BEInst->getOperand(i));
487 DepChain *D = getDepChainBtwn(I, J);
488
489 assert(D &&((D && "No DepChain between corresponding operands in ReuseCandidate\n"
) ? static_cast<void> (0) : __assert_fail ("D && \"No DepChain between corresponding operands in ReuseCandidate\\n\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp"
, 490, __PRETTY_FUNCTION__))
490 "No DepChain between corresponding operands in ReuseCandidate\n")((D && "No DepChain between corresponding operands in ReuseCandidate\n"
) ? static_cast<void> (0) : __assert_fail ("D && \"No DepChain between corresponding operands in ReuseCandidate\\n\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp"
, 490, __PRETTY_FUNCTION__));
491 if (Iterations == -1)
492 Iterations = D->iterations();
493 assert(Iterations == D->iterations() && "Iterations mismatch")((Iterations == D->iterations() && "Iterations mismatch"
) ? static_cast<void> (0) : __assert_fail ("Iterations == D->iterations() && \"Iterations mismatch\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp"
, 493, __PRETTY_FUNCTION__));
494 DepChains[I] = D;
495 }
496 }
497
498 LLVM_DEBUG(dbgs() << "reuseValue is making the following changes\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "reuseValue is making the following changes\n"
; } } while (false);
21
←
Assuming 'DebugFlag' is 0
→
22
←
Loop condition is false. Exiting loop
→
499
500 SmallVector<Instruction *, 4> InstsInPreheader;
501 for (int i = 0; i < Iterations; ++i) {
23
←
Loop condition is false. Execution continues on line 522
→
502 Instruction *InstInPreheader = Inst2Replace->clone();
503 SmallVector<Value *, 4> Ops;
504 for (int j = 0; j < NumOperands; ++j) {
505 Instruction *I = dyn_cast<Instruction>(Inst2Replace->getOperand(j));
506 if (!I)
507 continue;
508 // Get the DepChain corresponding to this operand.
509 DepChain &D = *DepChains[I];
510 // Get the PHI for the iteration number and find
511 // the incoming value from the Loop Preheader for
512 // that PHI.
513 Value *ValInPreheader = findValueInBlock(D[i], LoopPH);
514 InstInPreheader->setOperand(j, ValInPreheader);
515 }
516 InstsInPreheader.push_back(InstInPreheader);
517 InstInPreheader->setName(Inst2Replace->getName() + ".hexagon.vlcr");
518 InstInPreheader->insertBefore(LoopPH->getTerminator());
519 LLVM_DEBUG(dbgs() << "Added " << *InstInPreheader << " to "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Added " << *InstInPreheader
<< " to " << LoopPH->getName() << "\n";
} } while (false)
520 << LoopPH->getName() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Added " << *InstInPreheader
<< " to " << LoopPH->getName() << "\n";
} } while (false);
521 }
522 BasicBlock *BB = BEInst->getParent();
523 IRBuilder<> IRB(BB);
524 IRB.SetInsertPoint(BB->getFirstNonPHI());
525 Value *BEVal = BEInst;
526 PHINode *NewPhi;
24
←
'NewPhi' declared without an initial value
→
527 for (int i = Iterations-1; i >=0 ; --i) {
25
←
Loop condition is false. Execution continues on line 538
→
528 Instruction *InstInPreheader = InstsInPreheader[i];
529 NewPhi = IRB.CreatePHI(InstInPreheader->getType(), 2);
530 NewPhi->addIncoming(InstInPreheader, LoopPH);
531 NewPhi->addIncoming(BEVal, BB);
532 LLVM_DEBUG(dbgs() << "Adding " << *NewPhi << " to " << BB->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Adding " << *NewPhi
<< " to " << BB->getName() << "\n"; } }
while (false)
533 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Adding " << *NewPhi
<< " to " << BB->getName() << "\n"; } }
while (false);
534 BEVal = NewPhi;
535 }
536 // We are in LCSSA form. So, a value defined inside the Loop is used only
537 // inside the loop. So, the following is safe.
538 Inst2Replace->replaceAllUsesWith(NewPhi);
26
←
1st function call argument is an uninitialized value
539 ReplacedInsts.insert(Inst2Replace);
540 ++HexagonNumVectorLoopCarriedReuse;
541}
542
543bool HexagonVectorLoopCarriedReuse::doVLCR() {
544 assert(CurLoop->getSubLoops().empty() &&((CurLoop->getSubLoops().empty() && "Can do VLCR on the innermost loop only"
) ? static_cast<void> (0) : __assert_fail ("CurLoop->getSubLoops().empty() && \"Can do VLCR on the innermost loop only\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp"
, 545, __PRETTY_FUNCTION__))
10
←
Assuming the condition is true
→
11
←
'?' condition is true
→
545 "Can do VLCR on the innermost loop only")((CurLoop->getSubLoops().empty() && "Can do VLCR on the innermost loop only"
) ? static_cast<void> (0) : __assert_fail ("CurLoop->getSubLoops().empty() && \"Can do VLCR on the innermost loop only\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp"
, 545, __PRETTY_FUNCTION__));
546 assert((CurLoop->getNumBlocks() == 1) &&(((CurLoop->getNumBlocks() == 1) && "Can do VLCR only on single block loops"
) ? static_cast<void> (0) : __assert_fail ("(CurLoop->getNumBlocks() == 1) && \"Can do VLCR only on single block loops\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp"
, 547, __PRETTY_FUNCTION__))
12
←
Assuming the condition is true
→
13
←
'?' condition is true
→
547 "Can do VLCR only on single block loops")(((CurLoop->getNumBlocks() == 1) && "Can do VLCR only on single block loops"
) ? static_cast<void> (0) : __assert_fail ("(CurLoop->getNumBlocks() == 1) && \"Can do VLCR only on single block loops\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp"
, 547, __PRETTY_FUNCTION__));
548
549 bool Changed = false;
550 bool Continue;
551
552 LLVM_DEBUG(dbgs() << "Working on Loop: " << *CurLoop->getHeader() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Working on Loop: " <<
*CurLoop->getHeader() << "\n"; } } while (false);
14
←
Assuming 'DebugFlag' is 0
→
15
←
Loop condition is false. Exiting loop
→
553 do {
554 // Reset datastructures.
555 Dependences.clear();
556 Continue = false;
557
558 findLoopCarriedDeps();
559 findValueToReuse();
560 if (ReuseCandidate.isDefined()) {
16
←
Taking true branch
→
561 reuseValue();
17
←
Calling 'HexagonVectorLoopCarriedReuse::reuseValue'
→
562 Changed = true;
563 Continue = true;
564 }
565 llvm::for_each(Dependences, std::default_delete<DepChain>());
566 } while (Continue);
567 return Changed;
568}
569
570void HexagonVectorLoopCarriedReuse::findDepChainFromPHI(Instruction *I,
571 DepChain &D) {
572 PHINode *PN = dyn_cast<PHINode>(I);
573 if (!PN) {
574 D.push_back(I);
575 return;
576 } else {
577 auto NumIncomingValues = PN->getNumIncomingValues();
578 if (NumIncomingValues != 2) {
579 D.clear();
580 return;
581 }
582
583 BasicBlock *BB = PN->getParent();
584 if (BB != CurLoop->getHeader()) {
585 D.clear();
586 return;
587 }
588
589 Value *BEVal = PN->getIncomingValueForBlock(BB);
590 Instruction *BEInst = dyn_cast<Instruction>(BEVal);
591 // This is a single block loop with a preheader, so at least
592 // one value should come over the backedge.
593 assert(BEInst && "There should be a value over the backedge")((BEInst && "There should be a value over the backedge"
) ? static_cast<void> (0) : __assert_fail ("BEInst && \"There should be a value over the backedge\""
, "/build/llvm-toolchain-snapshot-9~svn362543/lib/Target/Hexagon/HexagonVectorLoopCarriedReuse.cpp"
, 593, __PRETTY_FUNCTION__));
594
595 Value *PreHdrVal =
596 PN->getIncomingValueForBlock(CurLoop->getLoopPreheader());
597 if(!PreHdrVal || !isa<Instruction>(PreHdrVal)) {
598 D.clear();
599 return;
600 }
601 D.push_back(PN);
602 findDepChainFromPHI(BEInst, D);
603 }
604}
605
606bool HexagonVectorLoopCarriedReuse::isDepChainBtwn(Instruction *I1,
607 Instruction *I2,
608 int Iters) {
609 for (auto *D : Dependences) {
610 if (D->front() == I1 && D->back() == I2 && D->iterations() == Iters)
611 return true;
612 }
613 return false;
614}
615
616DepChain *HexagonVectorLoopCarriedReuse::getDepChainBtwn(Instruction *I1,
617 Instruction *I2) {
618 for (auto *D : Dependences) {
619 if (D->front() == I1 && D->back() == I2)
620 return D;
621 }
622 return nullptr;
623}
624
625void HexagonVectorLoopCarriedReuse::findLoopCarriedDeps() {
626 BasicBlock *BB = CurLoop->getHeader();
627 for (auto I = BB->begin(), E = BB->end(); I != E && isa<PHINode>(I); ++I) {
628 auto *PN = cast<PHINode>(I);
629 if (!isa<VectorType>(PN->getType()))
630 continue;
631
632 DepChain *D = new DepChain();
633 findDepChainFromPHI(PN, *D);
634 if (D->size() != 0)
635 Dependences.insert(D);
636 else
637 delete D;
638 }
639 LLVM_DEBUG(dbgs() << "Found " << Dependences.size() << " dependences\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { dbgs() << "Found " << Dependences
.size() << " dependences\n"; } } while (false);
640 LLVM_DEBUG(for (size_t i = 0; i < Dependences.size();do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { for (size_t i = 0; i < Dependences.size
(); ++i) { dbgs() << *Dependences[i] << "\n"; }; }
} while (false)
641 ++i) { dbgs() << *Dependences[i] << "\n"; })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("hexagon-vlcr")) { for (size_t i = 0; i < Dependences.size
(); ++i) { dbgs() << *Dependences[i] << "\n"; }; }
} while (false);
642}
643
644Pass *llvm::createHexagonVectorLoopCarriedReusePass() {
645 return new HexagonVectorLoopCarriedReuse();
646}