Bug Summary

File:lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
Warning:line 1561, column 28
Called C++ object pointer is null

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 InstCombineLoadStoreAlloca.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-eagerly-assume -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 -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-7/lib/clang/7.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-7~svn338205/build-llvm/lib/Transforms/InstCombine -I /build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine -I /build/llvm-toolchain-snapshot-7~svn338205/build-llvm/include -I /build/llvm-toolchain-snapshot-7~svn338205/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/x86_64-linux-gnu/c++/8 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/x86_64-linux-gnu/c++/8 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/backward -internal-isystem /usr/include/clang/7.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-7/lib/clang/7.0.0/include -internal-externc-isystem /usr/lib/gcc/x86_64-linux-gnu/8/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-class-memaccess -Wno-comment -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-7~svn338205/build-llvm/lib/Transforms/InstCombine -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2018-07-29-043837-17923-1 -x c++ /build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp -faddrsig
1//===- InstCombineLoadStoreAlloca.cpp -------------------------------------===//
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// This file implements the visit functions for load, store and alloca.
11//
12//===----------------------------------------------------------------------===//
13
14#include "InstCombineInternal.h"
15#include "llvm/ADT/MapVector.h"
16#include "llvm/ADT/SmallString.h"
17#include "llvm/ADT/Statistic.h"
18#include "llvm/Analysis/Loads.h"
19#include "llvm/Transforms/Utils/Local.h"
20#include "llvm/IR/ConstantRange.h"
21#include "llvm/IR/DataLayout.h"
22#include "llvm/IR/IntrinsicInst.h"
23#include "llvm/IR/LLVMContext.h"
24#include "llvm/IR/MDBuilder.h"
25#include "llvm/IR/PatternMatch.h"
26#include "llvm/Transforms/Utils/BasicBlockUtils.h"
27using namespace llvm;
28using namespace PatternMatch;
29
30#define DEBUG_TYPE"instcombine" "instcombine"
31
32STATISTIC(NumDeadStore, "Number of dead stores eliminated")static llvm::Statistic NumDeadStore = {"instcombine", "NumDeadStore"
, "Number of dead stores eliminated", {0}, {false}}
;
33STATISTIC(NumGlobalCopies, "Number of allocas copied from constant global")static llvm::Statistic NumGlobalCopies = {"instcombine", "NumGlobalCopies"
, "Number of allocas copied from constant global", {0}, {false
}}
;
34
35/// pointsToConstantGlobal - Return true if V (possibly indirectly) points to
36/// some part of a constant global variable. This intentionally only accepts
37/// constant expressions because we can't rewrite arbitrary instructions.
38static bool pointsToConstantGlobal(Value *V) {
39 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
40 return GV->isConstant();
41
42 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
43 if (CE->getOpcode() == Instruction::BitCast ||
44 CE->getOpcode() == Instruction::AddrSpaceCast ||
45 CE->getOpcode() == Instruction::GetElementPtr)
46 return pointsToConstantGlobal(CE->getOperand(0));
47 }
48 return false;
49}
50
51/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
52/// pointer to an alloca. Ignore any reads of the pointer, return false if we
53/// see any stores or other unknown uses. If we see pointer arithmetic, keep
54/// track of whether it moves the pointer (with IsOffset) but otherwise traverse
55/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
56/// the alloca, and if the source pointer is a pointer to a constant global, we
57/// can optimize this.
58static bool
59isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
60 SmallVectorImpl<Instruction *> &ToDelete) {
61 // We track lifetime intrinsics as we encounter them. If we decide to go
62 // ahead and replace the value with the global, this lets the caller quickly
63 // eliminate the markers.
64
65 SmallVector<std::pair<Value *, bool>, 35> ValuesToInspect;
66 ValuesToInspect.emplace_back(V, false);
67 while (!ValuesToInspect.empty()) {
68 auto ValuePair = ValuesToInspect.pop_back_val();
69 const bool IsOffset = ValuePair.second;
70 for (auto &U : ValuePair.first->uses()) {
71 auto *I = cast<Instruction>(U.getUser());
72
73 if (auto *LI = dyn_cast<LoadInst>(I)) {
74 // Ignore non-volatile loads, they are always ok.
75 if (!LI->isSimple()) return false;
76 continue;
77 }
78
79 if (isa<BitCastInst>(I) || isa<AddrSpaceCastInst>(I)) {
80 // If uses of the bitcast are ok, we are ok.
81 ValuesToInspect.emplace_back(I, IsOffset);
82 continue;
83 }
84 if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
85 // If the GEP has all zero indices, it doesn't offset the pointer. If it
86 // doesn't, it does.
87 ValuesToInspect.emplace_back(I, IsOffset || !GEP->hasAllZeroIndices());
88 continue;
89 }
90
91 if (auto CS = CallSite(I)) {
92 // If this is the function being called then we treat it like a load and
93 // ignore it.
94 if (CS.isCallee(&U))
95 continue;
96
97 unsigned DataOpNo = CS.getDataOperandNo(&U);
98 bool IsArgOperand = CS.isArgOperand(&U);
99
100 // Inalloca arguments are clobbered by the call.
101 if (IsArgOperand && CS.isInAllocaArgument(DataOpNo))
102 return false;
103
104 // If this is a readonly/readnone call site, then we know it is just a
105 // load (but one that potentially returns the value itself), so we can
106 // ignore it if we know that the value isn't captured.
107 if (CS.onlyReadsMemory() &&
108 (CS.getInstruction()->use_empty() || CS.doesNotCapture(DataOpNo)))
109 continue;
110
111 // If this is being passed as a byval argument, the caller is making a
112 // copy, so it is only a read of the alloca.
113 if (IsArgOperand && CS.isByValArgument(DataOpNo))
114 continue;
115 }
116
117 // Lifetime intrinsics can be handled by the caller.
118 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
119 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
120 II->getIntrinsicID() == Intrinsic::lifetime_end) {
121 assert(II->use_empty() && "Lifetime markers have no result to use!")(static_cast <bool> (II->use_empty() && "Lifetime markers have no result to use!"
) ? void (0) : __assert_fail ("II->use_empty() && \"Lifetime markers have no result to use!\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 121, __extension__ __PRETTY_FUNCTION__))
;
122 ToDelete.push_back(II);
123 continue;
124 }
125 }
126
127 // If this is isn't our memcpy/memmove, reject it as something we can't
128 // handle.
129 MemTransferInst *MI = dyn_cast<MemTransferInst>(I);
130 if (!MI)
131 return false;
132
133 // If the transfer is using the alloca as a source of the transfer, then
134 // ignore it since it is a load (unless the transfer is volatile).
135 if (U.getOperandNo() == 1) {
136 if (MI->isVolatile()) return false;
137 continue;
138 }
139
140 // If we already have seen a copy, reject the second one.
141 if (TheCopy) return false;
142
143 // If the pointer has been offset from the start of the alloca, we can't
144 // safely handle this.
145 if (IsOffset) return false;
146
147 // If the memintrinsic isn't using the alloca as the dest, reject it.
148 if (U.getOperandNo() != 0) return false;
149
150 // If the source of the memcpy/move is not a constant global, reject it.
151 if (!pointsToConstantGlobal(MI->getSource()))
152 return false;
153
154 // Otherwise, the transform is safe. Remember the copy instruction.
155 TheCopy = MI;
156 }
157 }
158 return true;
159}
160
161/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
162/// modified by a copy from a constant global. If we can prove this, we can
163/// replace any uses of the alloca with uses of the global directly.
164static MemTransferInst *
165isOnlyCopiedFromConstantGlobal(AllocaInst *AI,
166 SmallVectorImpl<Instruction *> &ToDelete) {
167 MemTransferInst *TheCopy = nullptr;
168 if (isOnlyCopiedFromConstantGlobal(AI, TheCopy, ToDelete))
169 return TheCopy;
170 return nullptr;
171}
172
173/// Returns true if V is dereferenceable for size of alloca.
174static bool isDereferenceableForAllocaSize(const Value *V, const AllocaInst *AI,
175 const DataLayout &DL) {
176 if (AI->isArrayAllocation())
177 return false;
178 uint64_t AllocaSize = DL.getTypeStoreSize(AI->getAllocatedType());
179 if (!AllocaSize)
180 return false;
181 return isDereferenceableAndAlignedPointer(V, AI->getAlignment(),
182 APInt(64, AllocaSize), DL);
183}
184
185static Instruction *simplifyAllocaArraySize(InstCombiner &IC, AllocaInst &AI) {
186 // Check for array size of 1 (scalar allocation).
187 if (!AI.isArrayAllocation()) {
188 // i32 1 is the canonical array size for scalar allocations.
189 if (AI.getArraySize()->getType()->isIntegerTy(32))
190 return nullptr;
191
192 // Canonicalize it.
193 Value *V = IC.Builder.getInt32(1);
194 AI.setOperand(0, V);
195 return &AI;
196 }
197
198 // Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1
199 if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {
200 Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getZExtValue());
201 AllocaInst *New = IC.Builder.CreateAlloca(NewTy, nullptr, AI.getName());
202 New->setAlignment(AI.getAlignment());
203
204 // Scan to the end of the allocation instructions, to skip over a block of
205 // allocas if possible...also skip interleaved debug info
206 //
207 BasicBlock::iterator It(New);
208 while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It))
209 ++It;
210
211 // Now that I is pointing to the first non-allocation-inst in the block,
212 // insert our getelementptr instruction...
213 //
214 Type *IdxTy = IC.getDataLayout().getIntPtrType(AI.getType());
215 Value *NullIdx = Constant::getNullValue(IdxTy);
216 Value *Idx[2] = {NullIdx, NullIdx};
217 Instruction *GEP =
218 GetElementPtrInst::CreateInBounds(New, Idx, New->getName() + ".sub");
219 IC.InsertNewInstBefore(GEP, *It);
220
221 // Now make everything use the getelementptr instead of the original
222 // allocation.
223 return IC.replaceInstUsesWith(AI, GEP);
224 }
225
226 if (isa<UndefValue>(AI.getArraySize()))
227 return IC.replaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
228
229 // Ensure that the alloca array size argument has type intptr_t, so that
230 // any casting is exposed early.
231 Type *IntPtrTy = IC.getDataLayout().getIntPtrType(AI.getType());
232 if (AI.getArraySize()->getType() != IntPtrTy) {
233 Value *V = IC.Builder.CreateIntCast(AI.getArraySize(), IntPtrTy, false);
234 AI.setOperand(0, V);
235 return &AI;
236 }
237
238 return nullptr;
239}
240
241namespace {
242// If I and V are pointers in different address space, it is not allowed to
243// use replaceAllUsesWith since I and V have different types. A
244// non-target-specific transformation should not use addrspacecast on V since
245// the two address space may be disjoint depending on target.
246//
247// This class chases down uses of the old pointer until reaching the load
248// instructions, then replaces the old pointer in the load instructions with
249// the new pointer. If during the chasing it sees bitcast or GEP, it will
250// create new bitcast or GEP with the new pointer and use them in the load
251// instruction.
252class PointerReplacer {
253public:
254 PointerReplacer(InstCombiner &IC) : IC(IC) {}
255 void replacePointer(Instruction &I, Value *V);
256
257private:
258 void findLoadAndReplace(Instruction &I);
259 void replace(Instruction *I);
260 Value *getReplacement(Value *I);
261
262 SmallVector<Instruction *, 4> Path;
263 MapVector<Value *, Value *> WorkMap;
264 InstCombiner &IC;
265};
266} // end anonymous namespace
267
268void PointerReplacer::findLoadAndReplace(Instruction &I) {
269 for (auto U : I.users()) {
270 auto *Inst = dyn_cast<Instruction>(&*U);
271 if (!Inst)
272 return;
273 LLVM_DEBUG(dbgs() << "Found pointer user: " << *U << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("instcombine")) { dbgs() << "Found pointer user: " <<
*U << '\n'; } } while (false)
;
274 if (isa<LoadInst>(Inst)) {
275 for (auto P : Path)
276 replace(P);
277 replace(Inst);
278 } else if (isa<GetElementPtrInst>(Inst) || isa<BitCastInst>(Inst)) {
279 Path.push_back(Inst);
280 findLoadAndReplace(*Inst);
281 Path.pop_back();
282 } else {
283 return;
284 }
285 }
286}
287
288Value *PointerReplacer::getReplacement(Value *V) {
289 auto Loc = WorkMap.find(V);
290 if (Loc != WorkMap.end())
291 return Loc->second;
292 return nullptr;
293}
294
295void PointerReplacer::replace(Instruction *I) {
296 if (getReplacement(I))
297 return;
298
299 if (auto *LT = dyn_cast<LoadInst>(I)) {
300 auto *V = getReplacement(LT->getPointerOperand());
301 assert(V && "Operand not replaced")(static_cast <bool> (V && "Operand not replaced"
) ? void (0) : __assert_fail ("V && \"Operand not replaced\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 301, __extension__ __PRETTY_FUNCTION__))
;
302 auto *NewI = new LoadInst(V);
303 NewI->takeName(LT);
304 IC.InsertNewInstWith(NewI, *LT);
305 IC.replaceInstUsesWith(*LT, NewI);
306 WorkMap[LT] = NewI;
307 } else if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
308 auto *V = getReplacement(GEP->getPointerOperand());
309 assert(V && "Operand not replaced")(static_cast <bool> (V && "Operand not replaced"
) ? void (0) : __assert_fail ("V && \"Operand not replaced\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 309, __extension__ __PRETTY_FUNCTION__))
;
310 SmallVector<Value *, 8> Indices;
311 Indices.append(GEP->idx_begin(), GEP->idx_end());
312 auto *NewI = GetElementPtrInst::Create(
313 V->getType()->getPointerElementType(), V, Indices);
314 IC.InsertNewInstWith(NewI, *GEP);
315 NewI->takeName(GEP);
316 WorkMap[GEP] = NewI;
317 } else if (auto *BC = dyn_cast<BitCastInst>(I)) {
318 auto *V = getReplacement(BC->getOperand(0));
319 assert(V && "Operand not replaced")(static_cast <bool> (V && "Operand not replaced"
) ? void (0) : __assert_fail ("V && \"Operand not replaced\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 319, __extension__ __PRETTY_FUNCTION__))
;
320 auto *NewT = PointerType::get(BC->getType()->getPointerElementType(),
321 V->getType()->getPointerAddressSpace());
322 auto *NewI = new BitCastInst(V, NewT);
323 IC.InsertNewInstWith(NewI, *BC);
324 NewI->takeName(BC);
325 WorkMap[BC] = NewI;
326 } else {
327 llvm_unreachable("should never reach here")::llvm::llvm_unreachable_internal("should never reach here", "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 327)
;
328 }
329}
330
331void PointerReplacer::replacePointer(Instruction &I, Value *V) {
332#ifndef NDEBUG
333 auto *PT = cast<PointerType>(I.getType());
334 auto *NT = cast<PointerType>(V->getType());
335 assert(PT != NT && PT->getElementType() == NT->getElementType() &&(static_cast <bool> (PT != NT && PT->getElementType
() == NT->getElementType() && "Invalid usage") ? void
(0) : __assert_fail ("PT != NT && PT->getElementType() == NT->getElementType() && \"Invalid usage\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 336, __extension__ __PRETTY_FUNCTION__))
336 "Invalid usage")(static_cast <bool> (PT != NT && PT->getElementType
() == NT->getElementType() && "Invalid usage") ? void
(0) : __assert_fail ("PT != NT && PT->getElementType() == NT->getElementType() && \"Invalid usage\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 336, __extension__ __PRETTY_FUNCTION__))
;
337#endif
338 WorkMap[&I] = V;
339 findLoadAndReplace(I);
340}
341
342Instruction *InstCombiner::visitAllocaInst(AllocaInst &AI) {
343 if (auto *I = simplifyAllocaArraySize(*this, AI))
344 return I;
345
346 if (AI.getAllocatedType()->isSized()) {
347 // If the alignment is 0 (unspecified), assign it the preferred alignment.
348 if (AI.getAlignment() == 0)
349 AI.setAlignment(DL.getPrefTypeAlignment(AI.getAllocatedType()));
350
351 // Move all alloca's of zero byte objects to the entry block and merge them
352 // together. Note that we only do this for alloca's, because malloc should
353 // allocate and return a unique pointer, even for a zero byte allocation.
354 if (DL.getTypeAllocSize(AI.getAllocatedType()) == 0) {
355 // For a zero sized alloca there is no point in doing an array allocation.
356 // This is helpful if the array size is a complicated expression not used
357 // elsewhere.
358 if (AI.isArrayAllocation()) {
359 AI.setOperand(0, ConstantInt::get(AI.getArraySize()->getType(), 1));
360 return &AI;
361 }
362
363 // Get the first instruction in the entry block.
364 BasicBlock &EntryBlock = AI.getParent()->getParent()->getEntryBlock();
365 Instruction *FirstInst = EntryBlock.getFirstNonPHIOrDbg();
366 if (FirstInst != &AI) {
367 // If the entry block doesn't start with a zero-size alloca then move
368 // this one to the start of the entry block. There is no problem with
369 // dominance as the array size was forced to a constant earlier already.
370 AllocaInst *EntryAI = dyn_cast<AllocaInst>(FirstInst);
371 if (!EntryAI || !EntryAI->getAllocatedType()->isSized() ||
372 DL.getTypeAllocSize(EntryAI->getAllocatedType()) != 0) {
373 AI.moveBefore(FirstInst);
374 return &AI;
375 }
376
377 // If the alignment of the entry block alloca is 0 (unspecified),
378 // assign it the preferred alignment.
379 if (EntryAI->getAlignment() == 0)
380 EntryAI->setAlignment(
381 DL.getPrefTypeAlignment(EntryAI->getAllocatedType()));
382 // Replace this zero-sized alloca with the one at the start of the entry
383 // block after ensuring that the address will be aligned enough for both
384 // types.
385 unsigned MaxAlign = std::max(EntryAI->getAlignment(),
386 AI.getAlignment());
387 EntryAI->setAlignment(MaxAlign);
388 if (AI.getType() != EntryAI->getType())
389 return new BitCastInst(EntryAI, AI.getType());
390 return replaceInstUsesWith(AI, EntryAI);
391 }
392 }
393 }
394
395 if (AI.getAlignment()) {
396 // Check to see if this allocation is only modified by a memcpy/memmove from
397 // a constant global whose alignment is equal to or exceeds that of the
398 // allocation. If this is the case, we can change all users to use
399 // the constant global instead. This is commonly produced by the CFE by
400 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
401 // is only subsequently read.
402 SmallVector<Instruction *, 4> ToDelete;
403 if (MemTransferInst *Copy = isOnlyCopiedFromConstantGlobal(&AI, ToDelete)) {
404 unsigned SourceAlign = getOrEnforceKnownAlignment(
405 Copy->getSource(), AI.getAlignment(), DL, &AI, &AC, &DT);
406 if (AI.getAlignment() <= SourceAlign &&
407 isDereferenceableForAllocaSize(Copy->getSource(), &AI, DL)) {
408 LLVM_DEBUG(dbgs() << "Found alloca equal to global: " << AI << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("instcombine")) { dbgs() << "Found alloca equal to global: "
<< AI << '\n'; } } while (false)
;
409 LLVM_DEBUG(dbgs() << " memcpy = " << *Copy << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("instcombine")) { dbgs() << " memcpy = " << *Copy
<< '\n'; } } while (false)
;
410 for (unsigned i = 0, e = ToDelete.size(); i != e; ++i)
411 eraseInstFromFunction(*ToDelete[i]);
412 Constant *TheSrc = cast<Constant>(Copy->getSource());
413 auto *SrcTy = TheSrc->getType();
414 auto *DestTy = PointerType::get(AI.getType()->getPointerElementType(),
415 SrcTy->getPointerAddressSpace());
416 Constant *Cast =
417 ConstantExpr::getPointerBitCastOrAddrSpaceCast(TheSrc, DestTy);
418 if (AI.getType()->getPointerAddressSpace() ==
419 SrcTy->getPointerAddressSpace()) {
420 Instruction *NewI = replaceInstUsesWith(AI, Cast);
421 eraseInstFromFunction(*Copy);
422 ++NumGlobalCopies;
423 return NewI;
424 } else {
425 PointerReplacer PtrReplacer(*this);
426 PtrReplacer.replacePointer(AI, Cast);
427 ++NumGlobalCopies;
428 }
429 }
430 }
431 }
432
433 // At last, use the generic allocation site handler to aggressively remove
434 // unused allocas.
435 return visitAllocSite(AI);
436}
437
438// Are we allowed to form a atomic load or store of this type?
439static bool isSupportedAtomicType(Type *Ty) {
440 return Ty->isIntOrPtrTy() || Ty->isFloatingPointTy();
441}
442
443/// Helper to combine a load to a new type.
444///
445/// This just does the work of combining a load to a new type. It handles
446/// metadata, etc., and returns the new instruction. The \c NewTy should be the
447/// loaded *value* type. This will convert it to a pointer, cast the operand to
448/// that pointer type, load it, etc.
449///
450/// Note that this will create all of the instructions with whatever insert
451/// point the \c InstCombiner currently is using.
452static LoadInst *combineLoadToNewType(InstCombiner &IC, LoadInst &LI, Type *NewTy,
453 const Twine &Suffix = "") {
454 assert((!LI.isAtomic() || isSupportedAtomicType(NewTy)) &&(static_cast <bool> ((!LI.isAtomic() || isSupportedAtomicType
(NewTy)) && "can't fold an atomic load to requested type"
) ? void (0) : __assert_fail ("(!LI.isAtomic() || isSupportedAtomicType(NewTy)) && \"can't fold an atomic load to requested type\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 455, __extension__ __PRETTY_FUNCTION__))
455 "can't fold an atomic load to requested type")(static_cast <bool> ((!LI.isAtomic() || isSupportedAtomicType
(NewTy)) && "can't fold an atomic load to requested type"
) ? void (0) : __assert_fail ("(!LI.isAtomic() || isSupportedAtomicType(NewTy)) && \"can't fold an atomic load to requested type\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 455, __extension__ __PRETTY_FUNCTION__))
;
456
457 Value *Ptr = LI.getPointerOperand();
458 unsigned AS = LI.getPointerAddressSpace();
459 SmallVector<std::pair<unsigned, MDNode *>, 8> MD;
460 LI.getAllMetadata(MD);
461
462 Value *NewPtr = nullptr;
463 if (!(match(Ptr, m_BitCast(m_Value(NewPtr))) &&
464 NewPtr->getType()->getPointerElementType() == NewTy &&
465 NewPtr->getType()->getPointerAddressSpace() == AS))
466 NewPtr = IC.Builder.CreateBitCast(Ptr, NewTy->getPointerTo(AS));
467
468 LoadInst *NewLoad = IC.Builder.CreateAlignedLoad(
469 NewPtr, LI.getAlignment(), LI.isVolatile(), LI.getName() + Suffix);
470 NewLoad->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
471 MDBuilder MDB(NewLoad->getContext());
472 for (const auto &MDPair : MD) {
473 unsigned ID = MDPair.first;
474 MDNode *N = MDPair.second;
475 // Note, essentially every kind of metadata should be preserved here! This
476 // routine is supposed to clone a load instruction changing *only its type*.
477 // The only metadata it makes sense to drop is metadata which is invalidated
478 // when the pointer type changes. This should essentially never be the case
479 // in LLVM, but we explicitly switch over only known metadata to be
480 // conservatively correct. If you are adding metadata to LLVM which pertains
481 // to loads, you almost certainly want to add it here.
482 switch (ID) {
483 case LLVMContext::MD_dbg:
484 case LLVMContext::MD_tbaa:
485 case LLVMContext::MD_prof:
486 case LLVMContext::MD_fpmath:
487 case LLVMContext::MD_tbaa_struct:
488 case LLVMContext::MD_invariant_load:
489 case LLVMContext::MD_alias_scope:
490 case LLVMContext::MD_noalias:
491 case LLVMContext::MD_nontemporal:
492 case LLVMContext::MD_mem_parallel_loop_access:
493 // All of these directly apply.
494 NewLoad->setMetadata(ID, N);
495 break;
496
497 case LLVMContext::MD_nonnull:
498 copyNonnullMetadata(LI, N, *NewLoad);
499 break;
500 case LLVMContext::MD_align:
501 case LLVMContext::MD_dereferenceable:
502 case LLVMContext::MD_dereferenceable_or_null:
503 // These only directly apply if the new type is also a pointer.
504 if (NewTy->isPointerTy())
505 NewLoad->setMetadata(ID, N);
506 break;
507 case LLVMContext::MD_range:
508 copyRangeMetadata(IC.getDataLayout(), LI, N, *NewLoad);
509 break;
510 }
511 }
512 return NewLoad;
513}
514
515/// Combine a store to a new type.
516///
517/// Returns the newly created store instruction.
518static StoreInst *combineStoreToNewValue(InstCombiner &IC, StoreInst &SI, Value *V) {
519 assert((!SI.isAtomic() || isSupportedAtomicType(V->getType())) &&(static_cast <bool> ((!SI.isAtomic() || isSupportedAtomicType
(V->getType())) && "can't fold an atomic store of requested type"
) ? void (0) : __assert_fail ("(!SI.isAtomic() || isSupportedAtomicType(V->getType())) && \"can't fold an atomic store of requested type\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 520, __extension__ __PRETTY_FUNCTION__))
520 "can't fold an atomic store of requested type")(static_cast <bool> ((!SI.isAtomic() || isSupportedAtomicType
(V->getType())) && "can't fold an atomic store of requested type"
) ? void (0) : __assert_fail ("(!SI.isAtomic() || isSupportedAtomicType(V->getType())) && \"can't fold an atomic store of requested type\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 520, __extension__ __PRETTY_FUNCTION__))
;
521
522 Value *Ptr = SI.getPointerOperand();
523 unsigned AS = SI.getPointerAddressSpace();
524 SmallVector<std::pair<unsigned, MDNode *>, 8> MD;
525 SI.getAllMetadata(MD);
526
527 StoreInst *NewStore = IC.Builder.CreateAlignedStore(
528 V, IC.Builder.CreateBitCast(Ptr, V->getType()->getPointerTo(AS)),
529 SI.getAlignment(), SI.isVolatile());
530 NewStore->setAtomic(SI.getOrdering(), SI.getSyncScopeID());
531 for (const auto &MDPair : MD) {
532 unsigned ID = MDPair.first;
533 MDNode *N = MDPair.second;
534 // Note, essentially every kind of metadata should be preserved here! This
535 // routine is supposed to clone a store instruction changing *only its
536 // type*. The only metadata it makes sense to drop is metadata which is
537 // invalidated when the pointer type changes. This should essentially
538 // never be the case in LLVM, but we explicitly switch over only known
539 // metadata to be conservatively correct. If you are adding metadata to
540 // LLVM which pertains to stores, you almost certainly want to add it
541 // here.
542 switch (ID) {
543 case LLVMContext::MD_dbg:
544 case LLVMContext::MD_tbaa:
545 case LLVMContext::MD_prof:
546 case LLVMContext::MD_fpmath:
547 case LLVMContext::MD_tbaa_struct:
548 case LLVMContext::MD_alias_scope:
549 case LLVMContext::MD_noalias:
550 case LLVMContext::MD_nontemporal:
551 case LLVMContext::MD_mem_parallel_loop_access:
552 // All of these directly apply.
553 NewStore->setMetadata(ID, N);
554 break;
555
556 case LLVMContext::MD_invariant_load:
557 case LLVMContext::MD_nonnull:
558 case LLVMContext::MD_range:
559 case LLVMContext::MD_align:
560 case LLVMContext::MD_dereferenceable:
561 case LLVMContext::MD_dereferenceable_or_null:
562 // These don't apply for stores.
563 break;
564 }
565 }
566
567 return NewStore;
568}
569
570/// Returns true if instruction represent minmax pattern like:
571/// select ((cmp load V1, load V2), V1, V2).
572static bool isMinMaxWithLoads(Value *V) {
573 assert(V->getType()->isPointerTy() && "Expected pointer type.")(static_cast <bool> (V->getType()->isPointerTy() &&
"Expected pointer type.") ? void (0) : __assert_fail ("V->getType()->isPointerTy() && \"Expected pointer type.\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 573, __extension__ __PRETTY_FUNCTION__))
;
574 // Ignore possible ty* to ixx* bitcast.
575 V = peekThroughBitcast(V);
576 // Check that select is select ((cmp load V1, load V2), V1, V2) - minmax
577 // pattern.
578 CmpInst::Predicate Pred;
579 Instruction *L1;
580 Instruction *L2;
581 Value *LHS;
582 Value *RHS;
583 if (!match(V, m_Select(m_Cmp(Pred, m_Instruction(L1), m_Instruction(L2)),
584 m_Value(LHS), m_Value(RHS))))
585 return false;
586 return (match(L1, m_Load(m_Specific(LHS))) &&
587 match(L2, m_Load(m_Specific(RHS)))) ||
588 (match(L1, m_Load(m_Specific(RHS))) &&
589 match(L2, m_Load(m_Specific(LHS))));
590}
591
592/// Combine loads to match the type of their uses' value after looking
593/// through intervening bitcasts.
594///
595/// The core idea here is that if the result of a load is used in an operation,
596/// we should load the type most conducive to that operation. For example, when
597/// loading an integer and converting that immediately to a pointer, we should
598/// instead directly load a pointer.
599///
600/// However, this routine must never change the width of a load or the number of
601/// loads as that would introduce a semantic change. This combine is expected to
602/// be a semantic no-op which just allows loads to more closely model the types
603/// of their consuming operations.
604///
605/// Currently, we also refuse to change the precise type used for an atomic load
606/// or a volatile load. This is debatable, and might be reasonable to change
607/// later. However, it is risky in case some backend or other part of LLVM is
608/// relying on the exact type loaded to select appropriate atomic operations.
609static Instruction *combineLoadToOperationType(InstCombiner &IC, LoadInst &LI) {
610 // FIXME: We could probably with some care handle both volatile and ordered
611 // atomic loads here but it isn't clear that this is important.
612 if (!LI.isUnordered())
613 return nullptr;
614
615 if (LI.use_empty())
616 return nullptr;
617
618 // swifterror values can't be bitcasted.
619 if (LI.getPointerOperand()->isSwiftError())
620 return nullptr;
621
622 Type *Ty = LI.getType();
623 const DataLayout &DL = IC.getDataLayout();
624
625 // Try to canonicalize loads which are only ever stored to operate over
626 // integers instead of any other type. We only do this when the loaded type
627 // is sized and has a size exactly the same as its store size and the store
628 // size is a legal integer type.
629 // Do not perform canonicalization if minmax pattern is found (to avoid
630 // infinite loop).
631 if (!Ty->isIntegerTy() && Ty->isSized() &&
632 DL.isLegalInteger(DL.getTypeStoreSizeInBits(Ty)) &&
633 DL.getTypeStoreSizeInBits(Ty) == DL.getTypeSizeInBits(Ty) &&
634 !DL.isNonIntegralPointerType(Ty) &&
635 !isMinMaxWithLoads(
636 peekThroughBitcast(LI.getPointerOperand(), /*OneUseOnly=*/true))) {
637 if (all_of(LI.users(), [&LI](User *U) {
638 auto *SI = dyn_cast<StoreInst>(U);
639 return SI && SI->getPointerOperand() != &LI &&
640 !SI->getPointerOperand()->isSwiftError();
641 })) {
642 LoadInst *NewLoad = combineLoadToNewType(
643 IC, LI,
644 Type::getIntNTy(LI.getContext(), DL.getTypeStoreSizeInBits(Ty)));
645 // Replace all the stores with stores of the newly loaded value.
646 for (auto UI = LI.user_begin(), UE = LI.user_end(); UI != UE;) {
647 auto *SI = cast<StoreInst>(*UI++);
648 IC.Builder.SetInsertPoint(SI);
649 combineStoreToNewValue(IC, *SI, NewLoad);
650 IC.eraseInstFromFunction(*SI);
651 }
652 assert(LI.use_empty() && "Failed to remove all users of the load!")(static_cast <bool> (LI.use_empty() && "Failed to remove all users of the load!"
) ? void (0) : __assert_fail ("LI.use_empty() && \"Failed to remove all users of the load!\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 652, __extension__ __PRETTY_FUNCTION__))
;
653 // Return the old load so the combiner can delete it safely.
654 return &LI;
655 }
656 }
657
658 // Fold away bit casts of the loaded value by loading the desired type.
659 // We can do this for BitCastInsts as well as casts from and to pointer types,
660 // as long as those are noops (i.e., the source or dest type have the same
661 // bitwidth as the target's pointers).
662 if (LI.hasOneUse())
663 if (auto* CI = dyn_cast<CastInst>(LI.user_back()))
664 if (CI->isNoopCast(DL))
665 if (!LI.isAtomic() || isSupportedAtomicType(CI->getDestTy())) {
666 LoadInst *NewLoad = combineLoadToNewType(IC, LI, CI->getDestTy());
667 CI->replaceAllUsesWith(NewLoad);
668 IC.eraseInstFromFunction(*CI);
669 return &LI;
670 }
671
672 // FIXME: We should also canonicalize loads of vectors when their elements are
673 // cast to other types.
674 return nullptr;
675}
676
677static Instruction *unpackLoadToAggregate(InstCombiner &IC, LoadInst &LI) {
678 // FIXME: We could probably with some care handle both volatile and atomic
679 // stores here but it isn't clear that this is important.
680 if (!LI.isSimple())
681 return nullptr;
682
683 Type *T = LI.getType();
684 if (!T->isAggregateType())
685 return nullptr;
686
687 StringRef Name = LI.getName();
688 assert(LI.getAlignment() && "Alignment must be set at this point")(static_cast <bool> (LI.getAlignment() && "Alignment must be set at this point"
) ? void (0) : __assert_fail ("LI.getAlignment() && \"Alignment must be set at this point\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 688, __extension__ __PRETTY_FUNCTION__))
;
689
690 if (auto *ST = dyn_cast<StructType>(T)) {
691 // If the struct only have one element, we unpack.
692 auto NumElements = ST->getNumElements();
693 if (NumElements == 1) {
694 LoadInst *NewLoad = combineLoadToNewType(IC, LI, ST->getTypeAtIndex(0U),
695 ".unpack");
696 AAMDNodes AAMD;
697 LI.getAAMetadata(AAMD);
698 NewLoad->setAAMetadata(AAMD);
699 return IC.replaceInstUsesWith(LI, IC.Builder.CreateInsertValue(
700 UndefValue::get(T), NewLoad, 0, Name));
701 }
702
703 // We don't want to break loads with padding here as we'd loose
704 // the knowledge that padding exists for the rest of the pipeline.
705 const DataLayout &DL = IC.getDataLayout();
706 auto *SL = DL.getStructLayout(ST);
707 if (SL->hasPadding())
708 return nullptr;
709
710 auto Align = LI.getAlignment();
711 if (!Align)
712 Align = DL.getABITypeAlignment(ST);
713
714 auto *Addr = LI.getPointerOperand();
715 auto *IdxType = Type::getInt32Ty(T->getContext());
716 auto *Zero = ConstantInt::get(IdxType, 0);
717
718 Value *V = UndefValue::get(T);
719 for (unsigned i = 0; i < NumElements; i++) {
720 Value *Indices[2] = {
721 Zero,
722 ConstantInt::get(IdxType, i),
723 };
724 auto *Ptr = IC.Builder.CreateInBoundsGEP(ST, Addr, makeArrayRef(Indices),
725 Name + ".elt");
726 auto EltAlign = MinAlign(Align, SL->getElementOffset(i));
727 auto *L = IC.Builder.CreateAlignedLoad(Ptr, EltAlign, Name + ".unpack");
728 // Propagate AA metadata. It'll still be valid on the narrowed load.
729 AAMDNodes AAMD;
730 LI.getAAMetadata(AAMD);
731 L->setAAMetadata(AAMD);
732 V = IC.Builder.CreateInsertValue(V, L, i);
733 }
734
735 V->setName(Name);
736 return IC.replaceInstUsesWith(LI, V);
737 }
738
739 if (auto *AT = dyn_cast<ArrayType>(T)) {
740 auto *ET = AT->getElementType();
741 auto NumElements = AT->getNumElements();
742 if (NumElements == 1) {
743 LoadInst *NewLoad = combineLoadToNewType(IC, LI, ET, ".unpack");
744 AAMDNodes AAMD;
745 LI.getAAMetadata(AAMD);
746 NewLoad->setAAMetadata(AAMD);
747 return IC.replaceInstUsesWith(LI, IC.Builder.CreateInsertValue(
748 UndefValue::get(T), NewLoad, 0, Name));
749 }
750
751 // Bail out if the array is too large. Ideally we would like to optimize
752 // arrays of arbitrary size but this has a terrible impact on compile time.
753 // The threshold here is chosen arbitrarily, maybe needs a little bit of
754 // tuning.
755 if (NumElements > IC.MaxArraySizeForCombine)
756 return nullptr;
757
758 const DataLayout &DL = IC.getDataLayout();
759 auto EltSize = DL.getTypeAllocSize(ET);
760 auto Align = LI.getAlignment();
761 if (!Align)
762 Align = DL.getABITypeAlignment(T);
763
764 auto *Addr = LI.getPointerOperand();
765 auto *IdxType = Type::getInt64Ty(T->getContext());
766 auto *Zero = ConstantInt::get(IdxType, 0);
767
768 Value *V = UndefValue::get(T);
769 uint64_t Offset = 0;
770 for (uint64_t i = 0; i < NumElements; i++) {
771 Value *Indices[2] = {
772 Zero,
773 ConstantInt::get(IdxType, i),
774 };
775 auto *Ptr = IC.Builder.CreateInBoundsGEP(AT, Addr, makeArrayRef(Indices),
776 Name + ".elt");
777 auto *L = IC.Builder.CreateAlignedLoad(Ptr, MinAlign(Align, Offset),
778 Name + ".unpack");
779 AAMDNodes AAMD;
780 LI.getAAMetadata(AAMD);
781 L->setAAMetadata(AAMD);
782 V = IC.Builder.CreateInsertValue(V, L, i);
783 Offset += EltSize;
784 }
785
786 V->setName(Name);
787 return IC.replaceInstUsesWith(LI, V);
788 }
789
790 return nullptr;
791}
792
793// If we can determine that all possible objects pointed to by the provided
794// pointer value are, not only dereferenceable, but also definitively less than
795// or equal to the provided maximum size, then return true. Otherwise, return
796// false (constant global values and allocas fall into this category).
797//
798// FIXME: This should probably live in ValueTracking (or similar).
799static bool isObjectSizeLessThanOrEq(Value *V, uint64_t MaxSize,
800 const DataLayout &DL) {
801 SmallPtrSet<Value *, 4> Visited;
802 SmallVector<Value *, 4> Worklist(1, V);
803
804 do {
805 Value *P = Worklist.pop_back_val();
806 P = P->stripPointerCasts();
807
808 if (!Visited.insert(P).second)
809 continue;
810
811 if (SelectInst *SI = dyn_cast<SelectInst>(P)) {
812 Worklist.push_back(SI->getTrueValue());
813 Worklist.push_back(SI->getFalseValue());
814 continue;
815 }
816
817 if (PHINode *PN = dyn_cast<PHINode>(P)) {
818 for (Value *IncValue : PN->incoming_values())
819 Worklist.push_back(IncValue);
820 continue;
821 }
822
823 if (GlobalAlias *GA = dyn_cast<GlobalAlias>(P)) {
824 if (GA->isInterposable())
825 return false;
826 Worklist.push_back(GA->getAliasee());
827 continue;
828 }
829
830 // If we know how big this object is, and it is less than MaxSize, continue
831 // searching. Otherwise, return false.
832 if (AllocaInst *AI = dyn_cast<AllocaInst>(P)) {
833 if (!AI->getAllocatedType()->isSized())
834 return false;
835
836 ConstantInt *CS = dyn_cast<ConstantInt>(AI->getArraySize());
837 if (!CS)
838 return false;
839
840 uint64_t TypeSize = DL.getTypeAllocSize(AI->getAllocatedType());
841 // Make sure that, even if the multiplication below would wrap as an
842 // uint64_t, we still do the right thing.
843 if ((CS->getValue().zextOrSelf(128)*APInt(128, TypeSize)).ugt(MaxSize))
844 return false;
845 continue;
846 }
847
848 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
849 if (!GV->hasDefinitiveInitializer() || !GV->isConstant())
850 return false;
851
852 uint64_t InitSize = DL.getTypeAllocSize(GV->getValueType());
853 if (InitSize > MaxSize)
854 return false;
855 continue;
856 }
857
858 return false;
859 } while (!Worklist.empty());
860
861 return true;
862}
863
864// If we're indexing into an object of a known size, and the outer index is
865// not a constant, but having any value but zero would lead to undefined
866// behavior, replace it with zero.
867//
868// For example, if we have:
869// @f.a = private unnamed_addr constant [1 x i32] [i32 12], align 4
870// ...
871// %arrayidx = getelementptr inbounds [1 x i32]* @f.a, i64 0, i64 %x
872// ... = load i32* %arrayidx, align 4
873// Then we know that we can replace %x in the GEP with i64 0.
874//
875// FIXME: We could fold any GEP index to zero that would cause UB if it were
876// not zero. Currently, we only handle the first such index. Also, we could
877// also search through non-zero constant indices if we kept track of the
878// offsets those indices implied.
879static bool canReplaceGEPIdxWithZero(InstCombiner &IC, GetElementPtrInst *GEPI,
880 Instruction *MemI, unsigned &Idx) {
881 if (GEPI->getNumOperands() < 2)
882 return false;
883
884 // Find the first non-zero index of a GEP. If all indices are zero, return
885 // one past the last index.
886 auto FirstNZIdx = [](const GetElementPtrInst *GEPI) {
887 unsigned I = 1;
888 for (unsigned IE = GEPI->getNumOperands(); I != IE; ++I) {
889 Value *V = GEPI->getOperand(I);
890 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V))
891 if (CI->isZero())
892 continue;
893
894 break;
895 }
896
897 return I;
898 };
899
900 // Skip through initial 'zero' indices, and find the corresponding pointer
901 // type. See if the next index is not a constant.
902 Idx = FirstNZIdx(GEPI);
903 if (Idx == GEPI->getNumOperands())
904 return false;
905 if (isa<Constant>(GEPI->getOperand(Idx)))
906 return false;
907
908 SmallVector<Value *, 4> Ops(GEPI->idx_begin(), GEPI->idx_begin() + Idx);
909 Type *AllocTy =
910 GetElementPtrInst::getIndexedType(GEPI->getSourceElementType(), Ops);
911 if (!AllocTy || !AllocTy->isSized())
912 return false;
913 const DataLayout &DL = IC.getDataLayout();
914 uint64_t TyAllocSize = DL.getTypeAllocSize(AllocTy);
915
916 // If there are more indices after the one we might replace with a zero, make
917 // sure they're all non-negative. If any of them are negative, the overall
918 // address being computed might be before the base address determined by the
919 // first non-zero index.
920 auto IsAllNonNegative = [&]() {
921 for (unsigned i = Idx+1, e = GEPI->getNumOperands(); i != e; ++i) {
922 KnownBits Known = IC.computeKnownBits(GEPI->getOperand(i), 0, MemI);
923 if (Known.isNonNegative())
924 continue;
925 return false;
926 }
927
928 return true;
929 };
930
931 // FIXME: If the GEP is not inbounds, and there are extra indices after the
932 // one we'll replace, those could cause the address computation to wrap
933 // (rendering the IsAllNonNegative() check below insufficient). We can do
934 // better, ignoring zero indices (and other indices we can prove small
935 // enough not to wrap).
936 if (Idx+1 != GEPI->getNumOperands() && !GEPI->isInBounds())
937 return false;
938
939 // Note that isObjectSizeLessThanOrEq will return true only if the pointer is
940 // also known to be dereferenceable.
941 return isObjectSizeLessThanOrEq(GEPI->getOperand(0), TyAllocSize, DL) &&
942 IsAllNonNegative();
943}
944
945// If we're indexing into an object with a variable index for the memory
946// access, but the object has only one element, we can assume that the index
947// will always be zero. If we replace the GEP, return it.
948template <typename T>
949static Instruction *replaceGEPIdxWithZero(InstCombiner &IC, Value *Ptr,
950 T &MemI) {
951 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Ptr)) {
952 unsigned Idx;
953 if (canReplaceGEPIdxWithZero(IC, GEPI, &MemI, Idx)) {
954 Instruction *NewGEPI = GEPI->clone();
955 NewGEPI->setOperand(Idx,
956 ConstantInt::get(GEPI->getOperand(Idx)->getType(), 0));
957 NewGEPI->insertBefore(GEPI);
958 MemI.setOperand(MemI.getPointerOperandIndex(), NewGEPI);
959 return NewGEPI;
960 }
961 }
962
963 return nullptr;
964}
965
966static bool canSimplifyNullStoreOrGEP(StoreInst &SI) {
967 if (NullPointerIsDefined(SI.getFunction(), SI.getPointerAddressSpace()))
968 return false;
969
970 auto *Ptr = SI.getPointerOperand();
971 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Ptr))
972 Ptr = GEPI->getOperand(0);
973 return (isa<ConstantPointerNull>(Ptr) &&
974 !NullPointerIsDefined(SI.getFunction(), SI.getPointerAddressSpace()));
975}
976
977static bool canSimplifyNullLoadOrGEP(LoadInst &LI, Value *Op) {
978 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
979 const Value *GEPI0 = GEPI->getOperand(0);
980 if (isa<ConstantPointerNull>(GEPI0) &&
981 !NullPointerIsDefined(LI.getFunction(), GEPI->getPointerAddressSpace()))
982 return true;
983 }
984 if (isa<UndefValue>(Op) ||
985 (isa<ConstantPointerNull>(Op) &&
986 !NullPointerIsDefined(LI.getFunction(), LI.getPointerAddressSpace())))
987 return true;
988 return false;
989}
990
991Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
992 Value *Op = LI.getOperand(0);
993
994 // Try to canonicalize the loaded type.
995 if (Instruction *Res = combineLoadToOperationType(*this, LI))
996 return Res;
997
998 // Attempt to improve the alignment.
999 unsigned KnownAlign = getOrEnforceKnownAlignment(
1000 Op, DL.getPrefTypeAlignment(LI.getType()), DL, &LI, &AC, &DT);
1001 unsigned LoadAlign = LI.getAlignment();
1002 unsigned EffectiveLoadAlign =
1003 LoadAlign != 0 ? LoadAlign : DL.getABITypeAlignment(LI.getType());
1004
1005 if (KnownAlign > EffectiveLoadAlign)
1006 LI.setAlignment(KnownAlign);
1007 else if (LoadAlign == 0)
1008 LI.setAlignment(EffectiveLoadAlign);
1009
1010 // Replace GEP indices if possible.
1011 if (Instruction *NewGEPI = replaceGEPIdxWithZero(*this, Op, LI)) {
1012 Worklist.Add(NewGEPI);
1013 return &LI;
1014 }
1015
1016 if (Instruction *Res = unpackLoadToAggregate(*this, LI))
1017 return Res;
1018
1019 // Do really simple store-to-load forwarding and load CSE, to catch cases
1020 // where there are several consecutive memory accesses to the same location,
1021 // separated by a few arithmetic operations.
1022 BasicBlock::iterator BBI(LI);
1023 bool IsLoadCSE = false;
1024 if (Value *AvailableVal = FindAvailableLoadedValue(
1025 &LI, LI.getParent(), BBI, DefMaxInstsToScan, AA, &IsLoadCSE)) {
1026 if (IsLoadCSE)
1027 combineMetadataForCSE(cast<LoadInst>(AvailableVal), &LI);
1028
1029 return replaceInstUsesWith(
1030 LI, Builder.CreateBitOrPointerCast(AvailableVal, LI.getType(),
1031 LI.getName() + ".cast"));
1032 }
1033
1034 // None of the following transforms are legal for volatile/ordered atomic
1035 // loads. Most of them do apply for unordered atomics.
1036 if (!LI.isUnordered()) return nullptr;
1037
1038 // load(gep null, ...) -> unreachable
1039 // load null/undef -> unreachable
1040 // TODO: Consider a target hook for valid address spaces for this xforms.
1041 if (canSimplifyNullLoadOrGEP(LI, Op)) {
1042 // Insert a new store to null instruction before the load to indicate
1043 // that this code is not reachable. We do this instead of inserting
1044 // an unreachable instruction directly because we cannot modify the
1045 // CFG.
1046 StoreInst *SI = new StoreInst(UndefValue::get(LI.getType()),
1047 Constant::getNullValue(Op->getType()), &LI);
1048 SI->setDebugLoc(LI.getDebugLoc());
1049 return replaceInstUsesWith(LI, UndefValue::get(LI.getType()));
1050 }
1051
1052 if (Op->hasOneUse()) {
1053 // Change select and PHI nodes to select values instead of addresses: this
1054 // helps alias analysis out a lot, allows many others simplifications, and
1055 // exposes redundancy in the code.
1056 //
1057 // Note that we cannot do the transformation unless we know that the
1058 // introduced loads cannot trap! Something like this is valid as long as
1059 // the condition is always false: load (select bool %C, int* null, int* %G),
1060 // but it would not be valid if we transformed it to load from null
1061 // unconditionally.
1062 //
1063 if (SelectInst *SI = dyn_cast<SelectInst>(Op)) {
1064 // load (select (Cond, &V1, &V2)) --> select(Cond, load &V1, load &V2).
1065 unsigned Align = LI.getAlignment();
1066 if (isSafeToLoadUnconditionally(SI->getOperand(1), Align, DL, SI) &&
1067 isSafeToLoadUnconditionally(SI->getOperand(2), Align, DL, SI)) {
1068 LoadInst *V1 = Builder.CreateLoad(SI->getOperand(1),
1069 SI->getOperand(1)->getName()+".val");
1070 LoadInst *V2 = Builder.CreateLoad(SI->getOperand(2),
1071 SI->getOperand(2)->getName()+".val");
1072 assert(LI.isUnordered() && "implied by above")(static_cast <bool> (LI.isUnordered() && "implied by above"
) ? void (0) : __assert_fail ("LI.isUnordered() && \"implied by above\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 1072, __extension__ __PRETTY_FUNCTION__))
;
1073 V1->setAlignment(Align);
1074 V1->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
1075 V2->setAlignment(Align);
1076 V2->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
1077 return SelectInst::Create(SI->getCondition(), V1, V2);
1078 }
1079
1080 // load (select (cond, null, P)) -> load P
1081 if (isa<ConstantPointerNull>(SI->getOperand(1)) &&
1082 !NullPointerIsDefined(SI->getFunction(),
1083 LI.getPointerAddressSpace())) {
1084 LI.setOperand(0, SI->getOperand(2));
1085 return &LI;
1086 }
1087
1088 // load (select (cond, P, null)) -> load P
1089 if (isa<ConstantPointerNull>(SI->getOperand(2)) &&
1090 !NullPointerIsDefined(SI->getFunction(),
1091 LI.getPointerAddressSpace())) {
1092 LI.setOperand(0, SI->getOperand(1));
1093 return &LI;
1094 }
1095 }
1096 }
1097 return nullptr;
1098}
1099
1100/// Look for extractelement/insertvalue sequence that acts like a bitcast.
1101///
1102/// \returns underlying value that was "cast", or nullptr otherwise.
1103///
1104/// For example, if we have:
1105///
1106/// %E0 = extractelement <2 x double> %U, i32 0
1107/// %V0 = insertvalue [2 x double] undef, double %E0, 0
1108/// %E1 = extractelement <2 x double> %U, i32 1
1109/// %V1 = insertvalue [2 x double] %V0, double %E1, 1
1110///
1111/// and the layout of a <2 x double> is isomorphic to a [2 x double],
1112/// then %V1 can be safely approximated by a conceptual "bitcast" of %U.
1113/// Note that %U may contain non-undef values where %V1 has undef.
1114static Value *likeBitCastFromVector(InstCombiner &IC, Value *V) {
1115 Value *U = nullptr;
1116 while (auto *IV = dyn_cast<InsertValueInst>(V)) {
1117 auto *E = dyn_cast<ExtractElementInst>(IV->getInsertedValueOperand());
1118 if (!E)
1119 return nullptr;
1120 auto *W = E->getVectorOperand();
1121 if (!U)
1122 U = W;
1123 else if (U != W)
1124 return nullptr;
1125 auto *CI = dyn_cast<ConstantInt>(E->getIndexOperand());
1126 if (!CI || IV->getNumIndices() != 1 || CI->getZExtValue() != *IV->idx_begin())
1127 return nullptr;
1128 V = IV->getAggregateOperand();
1129 }
1130 if (!isa<UndefValue>(V) ||!U)
1131 return nullptr;
1132
1133 auto *UT = cast<VectorType>(U->getType());
1134 auto *VT = V->getType();
1135 // Check that types UT and VT are bitwise isomorphic.
1136 const auto &DL = IC.getDataLayout();
1137 if (DL.getTypeStoreSizeInBits(UT) != DL.getTypeStoreSizeInBits(VT)) {
1138 return nullptr;
1139 }
1140 if (auto *AT = dyn_cast<ArrayType>(VT)) {
1141 if (AT->getNumElements() != UT->getNumElements())
1142 return nullptr;
1143 } else {
1144 auto *ST = cast<StructType>(VT);
1145 if (ST->getNumElements() != UT->getNumElements())
1146 return nullptr;
1147 for (const auto *EltT : ST->elements()) {
1148 if (EltT != UT->getElementType())
1149 return nullptr;
1150 }
1151 }
1152 return U;
1153}
1154
1155/// Combine stores to match the type of value being stored.
1156///
1157/// The core idea here is that the memory does not have any intrinsic type and
1158/// where we can we should match the type of a store to the type of value being
1159/// stored.
1160///
1161/// However, this routine must never change the width of a store or the number of
1162/// stores as that would introduce a semantic change. This combine is expected to
1163/// be a semantic no-op which just allows stores to more closely model the types
1164/// of their incoming values.
1165///
1166/// Currently, we also refuse to change the precise type used for an atomic or
1167/// volatile store. This is debatable, and might be reasonable to change later.
1168/// However, it is risky in case some backend or other part of LLVM is relying
1169/// on the exact type stored to select appropriate atomic operations.
1170///
1171/// \returns true if the store was successfully combined away. This indicates
1172/// the caller must erase the store instruction. We have to let the caller erase
1173/// the store instruction as otherwise there is no way to signal whether it was
1174/// combined or not: IC.EraseInstFromFunction returns a null pointer.
1175static bool combineStoreToValueType(InstCombiner &IC, StoreInst &SI) {
1176 // FIXME: We could probably with some care handle both volatile and ordered
1177 // atomic stores here but it isn't clear that this is important.
1178 if (!SI.isUnordered())
1179 return false;
1180
1181 // swifterror values can't be bitcasted.
1182 if (SI.getPointerOperand()->isSwiftError())
1183 return false;
1184
1185 Value *V = SI.getValueOperand();
1186
1187 // Fold away bit casts of the stored value by storing the original type.
1188 if (auto *BC = dyn_cast<BitCastInst>(V)) {
1189 V = BC->getOperand(0);
1190 if (!SI.isAtomic() || isSupportedAtomicType(V->getType())) {
1191 combineStoreToNewValue(IC, SI, V);
1192 return true;
1193 }
1194 }
1195
1196 if (Value *U = likeBitCastFromVector(IC, V))
1197 if (!SI.isAtomic() || isSupportedAtomicType(U->getType())) {
1198 combineStoreToNewValue(IC, SI, U);
1199 return true;
1200 }
1201
1202 // FIXME: We should also canonicalize stores of vectors when their elements
1203 // are cast to other types.
1204 return false;
1205}
1206
1207static bool unpackStoreToAggregate(InstCombiner &IC, StoreInst &SI) {
1208 // FIXME: We could probably with some care handle both volatile and atomic
1209 // stores here but it isn't clear that this is important.
1210 if (!SI.isSimple())
1211 return false;
1212
1213 Value *V = SI.getValueOperand();
1214 Type *T = V->getType();
1215
1216 if (!T->isAggregateType())
1217 return false;
1218
1219 if (auto *ST = dyn_cast<StructType>(T)) {
1220 // If the struct only have one element, we unpack.
1221 unsigned Count = ST->getNumElements();
1222 if (Count == 1) {
1223 V = IC.Builder.CreateExtractValue(V, 0);
1224 combineStoreToNewValue(IC, SI, V);
1225 return true;
1226 }
1227
1228 // We don't want to break loads with padding here as we'd loose
1229 // the knowledge that padding exists for the rest of the pipeline.
1230 const DataLayout &DL = IC.getDataLayout();
1231 auto *SL = DL.getStructLayout(ST);
1232 if (SL->hasPadding())
1233 return false;
1234
1235 auto Align = SI.getAlignment();
1236 if (!Align)
1237 Align = DL.getABITypeAlignment(ST);
1238
1239 SmallString<16> EltName = V->getName();
1240 EltName += ".elt";
1241 auto *Addr = SI.getPointerOperand();
1242 SmallString<16> AddrName = Addr->getName();
1243 AddrName += ".repack";
1244
1245 auto *IdxType = Type::getInt32Ty(ST->getContext());
1246 auto *Zero = ConstantInt::get(IdxType, 0);
1247 for (unsigned i = 0; i < Count; i++) {
1248 Value *Indices[2] = {
1249 Zero,
1250 ConstantInt::get(IdxType, i),
1251 };
1252 auto *Ptr = IC.Builder.CreateInBoundsGEP(ST, Addr, makeArrayRef(Indices),
1253 AddrName);
1254 auto *Val = IC.Builder.CreateExtractValue(V, i, EltName);
1255 auto EltAlign = MinAlign(Align, SL->getElementOffset(i));
1256 llvm::Instruction *NS = IC.Builder.CreateAlignedStore(Val, Ptr, EltAlign);
1257 AAMDNodes AAMD;
1258 SI.getAAMetadata(AAMD);
1259 NS->setAAMetadata(AAMD);
1260 }
1261
1262 return true;
1263 }
1264
1265 if (auto *AT = dyn_cast<ArrayType>(T)) {
1266 // If the array only have one element, we unpack.
1267 auto NumElements = AT->getNumElements();
1268 if (NumElements == 1) {
1269 V = IC.Builder.CreateExtractValue(V, 0);
1270 combineStoreToNewValue(IC, SI, V);
1271 return true;
1272 }
1273
1274 // Bail out if the array is too large. Ideally we would like to optimize
1275 // arrays of arbitrary size but this has a terrible impact on compile time.
1276 // The threshold here is chosen arbitrarily, maybe needs a little bit of
1277 // tuning.
1278 if (NumElements > IC.MaxArraySizeForCombine)
1279 return false;
1280
1281 const DataLayout &DL = IC.getDataLayout();
1282 auto EltSize = DL.getTypeAllocSize(AT->getElementType());
1283 auto Align = SI.getAlignment();
1284 if (!Align)
1285 Align = DL.getABITypeAlignment(T);
1286
1287 SmallString<16> EltName = V->getName();
1288 EltName += ".elt";
1289 auto *Addr = SI.getPointerOperand();
1290 SmallString<16> AddrName = Addr->getName();
1291 AddrName += ".repack";
1292
1293 auto *IdxType = Type::getInt64Ty(T->getContext());
1294 auto *Zero = ConstantInt::get(IdxType, 0);
1295
1296 uint64_t Offset = 0;
1297 for (uint64_t i = 0; i < NumElements; i++) {
1298 Value *Indices[2] = {
1299 Zero,
1300 ConstantInt::get(IdxType, i),
1301 };
1302 auto *Ptr = IC.Builder.CreateInBoundsGEP(AT, Addr, makeArrayRef(Indices),
1303 AddrName);
1304 auto *Val = IC.Builder.CreateExtractValue(V, i, EltName);
1305 auto EltAlign = MinAlign(Align, Offset);
1306 Instruction *NS = IC.Builder.CreateAlignedStore(Val, Ptr, EltAlign);
1307 AAMDNodes AAMD;
1308 SI.getAAMetadata(AAMD);
1309 NS->setAAMetadata(AAMD);
1310 Offset += EltSize;
1311 }
1312
1313 return true;
1314 }
1315
1316 return false;
1317}
1318
1319/// equivalentAddressValues - Test if A and B will obviously have the same
1320/// value. This includes recognizing that %t0 and %t1 will have the same
1321/// value in code like this:
1322/// %t0 = getelementptr \@a, 0, 3
1323/// store i32 0, i32* %t0
1324/// %t1 = getelementptr \@a, 0, 3
1325/// %t2 = load i32* %t1
1326///
1327static bool equivalentAddressValues(Value *A, Value *B) {
1328 // Test if the values are trivially equivalent.
1329 if (A == B) return true;
1330
1331 // Test if the values come form identical arithmetic instructions.
1332 // This uses isIdenticalToWhenDefined instead of isIdenticalTo because
1333 // its only used to compare two uses within the same basic block, which
1334 // means that they'll always either have the same value or one of them
1335 // will have an undefined value.
1336 if (isa<BinaryOperator>(A) ||
1337 isa<CastInst>(A) ||
1338 isa<PHINode>(A) ||
1339 isa<GetElementPtrInst>(A))
1340 if (Instruction *BI = dyn_cast<Instruction>(B))
1341 if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI))
1342 return true;
1343
1344 // Otherwise they may not be equivalent.
1345 return false;
1346}
1347
1348/// Converts store (bitcast (load (bitcast (select ...)))) to
1349/// store (load (select ...)), where select is minmax:
1350/// select ((cmp load V1, load V2), V1, V2).
1351static bool removeBitcastsFromLoadStoreOnMinMax(InstCombiner &IC,
1352 StoreInst &SI) {
1353 // bitcast?
1354 if (!match(SI.getPointerOperand(), m_BitCast(m_Value())))
1355 return false;
1356 // load? integer?
1357 Value *LoadAddr;
1358 if (!match(SI.getValueOperand(), m_Load(m_BitCast(m_Value(LoadAddr)))))
1359 return false;
1360 auto *LI = cast<LoadInst>(SI.getValueOperand());
1361 if (!LI->getType()->isIntegerTy())
1362 return false;
1363 if (!isMinMaxWithLoads(LoadAddr))
1364 return false;
1365
1366 if (!all_of(LI->users(), [LI, LoadAddr](User *U) {
1367 auto *SI = dyn_cast<StoreInst>(U);
1368 return SI && SI->getPointerOperand() != LI &&
1369 peekThroughBitcast(SI->getPointerOperand()) != LoadAddr &&
1370 !SI->getPointerOperand()->isSwiftError();
1371 }))
1372 return false;
1373
1374 IC.Builder.SetInsertPoint(LI);
1375 LoadInst *NewLI = combineLoadToNewType(
1376 IC, *LI, LoadAddr->getType()->getPointerElementType());
1377 // Replace all the stores with stores of the newly loaded value.
1378 for (auto *UI : LI->users()) {
1379 auto *USI = cast<StoreInst>(UI);
1380 IC.Builder.SetInsertPoint(USI);
1381 combineStoreToNewValue(IC, *USI, NewLI);
1382 }
1383 IC.replaceInstUsesWith(*LI, UndefValue::get(LI->getType()));
1384 IC.eraseInstFromFunction(*LI);
1385 return true;
1386}
1387
1388Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
1389 Value *Val = SI.getOperand(0);
1390 Value *Ptr = SI.getOperand(1);
1391
1392 // Try to canonicalize the stored type.
1393 if (combineStoreToValueType(*this, SI))
1
Taking false branch
1394 return eraseInstFromFunction(SI);
1395
1396 // Attempt to improve the alignment.
1397 unsigned KnownAlign = getOrEnforceKnownAlignment(
1398 Ptr, DL.getPrefTypeAlignment(Val->getType()), DL, &SI, &AC, &DT);
1399 unsigned StoreAlign = SI.getAlignment();
1400 unsigned EffectiveStoreAlign =
1401 StoreAlign != 0 ? StoreAlign : DL.getABITypeAlignment(Val->getType());
2
Assuming 'StoreAlign' is equal to 0
3
'?' condition is false
1402
1403 if (KnownAlign > EffectiveStoreAlign)
4
Assuming 'KnownAlign' is <= 'EffectiveStoreAlign'
5
Taking false branch
1404 SI.setAlignment(KnownAlign);
1405 else if (StoreAlign == 0)
6
Taking true branch
1406 SI.setAlignment(EffectiveStoreAlign);
1407
1408 // Try to canonicalize the stored type.
1409 if (unpackStoreToAggregate(*this, SI))
7
Taking false branch
1410 return eraseInstFromFunction(SI);
1411
1412 if (removeBitcastsFromLoadStoreOnMinMax(*this, SI))
8
Taking false branch
1413 return eraseInstFromFunction(SI);
1414
1415 // Replace GEP indices if possible.
1416 if (Instruction *NewGEPI = replaceGEPIdxWithZero(*this, Ptr, SI)) {
9
Taking false branch
1417 Worklist.Add(NewGEPI);
1418 return &SI;
1419 }
1420
1421 // Don't hack volatile/ordered stores.
1422 // FIXME: Some bits are legal for ordered atomic stores; needs refactoring.
1423 if (!SI.isUnordered()) return nullptr;
10
Taking false branch
1424
1425 // If the RHS is an alloca with a single use, zapify the store, making the
1426 // alloca dead.
1427 if (Ptr->hasOneUse()) {
11
Taking false branch
1428 if (isa<AllocaInst>(Ptr))
1429 return eraseInstFromFunction(SI);
1430 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) {
1431 if (isa<AllocaInst>(GEP->getOperand(0))) {
1432 if (GEP->getOperand(0)->hasOneUse())
1433 return eraseInstFromFunction(SI);
1434 }
1435 }
1436 }
1437
1438 // Do really simple DSE, to catch cases where there are several consecutive
1439 // stores to the same location, separated by a few arithmetic operations. This
1440 // situation often occurs with bitfield accesses.
1441 BasicBlock::iterator BBI(SI);
1442 for (unsigned ScanInsts = 6; BBI != SI.getParent()->begin() && ScanInsts;
12
Loop condition is false. Execution continues on line 1486
1443 --ScanInsts) {
1444 --BBI;
1445 // Don't count debug info directives, lest they affect codegen,
1446 // and we skip pointer-to-pointer bitcasts, which are NOPs.
1447 if (isa<DbgInfoIntrinsic>(BBI) ||
1448 (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) {
1449 ScanInsts++;
1450 continue;
1451 }
1452
1453 if (StoreInst *PrevSI = dyn_cast<StoreInst>(BBI)) {
1454 // Prev store isn't volatile, and stores to the same location?
1455 if (PrevSI->isUnordered() && equivalentAddressValues(PrevSI->getOperand(1),
1456 SI.getOperand(1))) {
1457 ++NumDeadStore;
1458 ++BBI;
1459 eraseInstFromFunction(*PrevSI);
1460 continue;
1461 }
1462 break;
1463 }
1464
1465 // If this is a load, we have to stop. However, if the loaded value is from
1466 // the pointer we're loading and is producing the pointer we're storing,
1467 // then *this* store is dead (X = load P; store X -> P).
1468 if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
1469 if (LI == Val && equivalentAddressValues(LI->getOperand(0), Ptr)) {
1470 assert(SI.isUnordered() && "can't eliminate ordering operation")(static_cast <bool> (SI.isUnordered() && "can't eliminate ordering operation"
) ? void (0) : __assert_fail ("SI.isUnordered() && \"can't eliminate ordering operation\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 1470, __extension__ __PRETTY_FUNCTION__))
;
1471 return eraseInstFromFunction(SI);
1472 }
1473
1474 // Otherwise, this is a load from some other location. Stores before it
1475 // may not be dead.
1476 break;
1477 }
1478
1479 // Don't skip over loads, throws or things that can modify memory.
1480 if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory() || BBI->mayThrow())
1481 break;
1482 }
1483
1484 // store X, null -> turns into 'unreachable' in SimplifyCFG
1485 // store X, GEP(null, Y) -> turns into 'unreachable' in SimplifyCFG
1486 if (canSimplifyNullStoreOrGEP(SI)) {
13
Taking false branch
1487 if (!isa<UndefValue>(Val)) {
1488 SI.setOperand(0, UndefValue::get(Val->getType()));
1489 if (Instruction *U = dyn_cast<Instruction>(Val))
1490 Worklist.Add(U); // Dropped a use.
1491 }
1492 return nullptr; // Do not modify these!
1493 }
1494
1495 // store undef, Ptr -> noop
1496 if (isa<UndefValue>(Val))
14
Taking false branch
1497 return eraseInstFromFunction(SI);
1498
1499 // If this store is the last instruction in the basic block (possibly
1500 // excepting debug info instructions), and if the block ends with an
1501 // unconditional branch, try to move it to the successor block.
1502 BBI = SI.getIterator();
1503 do {
15
Loop condition is false. Exiting loop
1504 ++BBI;
1505 } while (isa<DbgInfoIntrinsic>(BBI) ||
1506 (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy()));
1507 if (BranchInst *BI = dyn_cast<BranchInst>(BBI))
16
Assuming 'BI' is non-null
17
Taking true branch
1508 if (BI->isUnconditional())
18
Taking true branch
1509 if (SimplifyStoreAtEndOfBlock(SI))
19
Calling 'InstCombiner::SimplifyStoreAtEndOfBlock'
1510 return nullptr; // xform done!
1511
1512 return nullptr;
1513}
1514
1515/// SimplifyStoreAtEndOfBlock - Turn things like:
1516/// if () { *P = v1; } else { *P = v2 }
1517/// into a phi node with a store in the successor.
1518///
1519/// Simplify things like:
1520/// *P = v1; if () { *P = v2; }
1521/// into a phi node with a store in the successor.
1522///
1523bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) {
1524 assert(SI.isUnordered() &&(static_cast <bool> (SI.isUnordered() && "this code has not been auditted for volatile or ordered store case"
) ? void (0) : __assert_fail ("SI.isUnordered() && \"this code has not been auditted for volatile or ordered store case\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 1525, __extension__ __PRETTY_FUNCTION__))
1525 "this code has not been auditted for volatile or ordered store case")(static_cast <bool> (SI.isUnordered() && "this code has not been auditted for volatile or ordered store case"
) ? void (0) : __assert_fail ("SI.isUnordered() && \"this code has not been auditted for volatile or ordered store case\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp"
, 1525, __extension__ __PRETTY_FUNCTION__))
;
1526
1527 BasicBlock *StoreBB = SI.getParent();
1528
1529 // Check to see if the successor block has exactly two incoming edges. If
1530 // so, see if the other predecessor contains a store to the same location.
1531 // if so, insert a PHI node (if needed) and move the stores down.
1532 BasicBlock *DestBB = StoreBB->getTerminator()->getSuccessor(0);
1533
1534 // Determine whether Dest has exactly two predecessors and, if so, compute
1535 // the other predecessor.
1536 pred_iterator PI = pred_begin(DestBB);
1537 BasicBlock *P = *PI;
1538 BasicBlock *OtherBB = nullptr;
20
'OtherBB' initialized to a null pointer value
1539
1540 if (P != StoreBB)
21
Assuming 'P' is equal to 'StoreBB'
22
Taking false branch
1541 OtherBB = P;
1542
1543 if (++PI == pred_end(DestBB))
23
Assuming the condition is false
24
Taking false branch
1544 return false;
1545
1546 P = *PI;
1547 if (P != StoreBB) {
25
Assuming 'P' is equal to 'StoreBB'
26
Taking false branch
1548 if (OtherBB)
1549 return false;
1550 OtherBB = P;
1551 }
1552 if (++PI != pred_end(DestBB))
27
Assuming the condition is false
28
Taking false branch
1553 return false;
1554
1555 // Bail out if all the relevant blocks aren't distinct (this can happen,
1556 // for example, if SI is in an infinite loop)
1557 if (StoreBB == DestBB || OtherBB == DestBB)
29
Assuming 'StoreBB' is not equal to 'DestBB'
30
Assuming 'OtherBB' is not equal to 'DestBB'
31
Taking false branch
1558 return false;
1559
1560 // Verify that the other block ends in a branch and is not otherwise empty.
1561 BasicBlock::iterator BBI(OtherBB->getTerminator());
32
Called C++ object pointer is null
1562 BranchInst *OtherBr = dyn_cast<BranchInst>(BBI);
1563 if (!OtherBr || BBI == OtherBB->begin())
1564 return false;
1565
1566 // If the other block ends in an unconditional branch, check for the 'if then
1567 // else' case. there is an instruction before the branch.
1568 StoreInst *OtherStore = nullptr;
1569 if (OtherBr->isUnconditional()) {
1570 --BBI;
1571 // Skip over debugging info.
1572 while (isa<DbgInfoIntrinsic>(BBI) ||
1573 (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) {
1574 if (BBI==OtherBB->begin())
1575 return false;
1576 --BBI;
1577 }
1578 // If this isn't a store, isn't a store to the same location, or is not the
1579 // right kind of store, bail out.
1580 OtherStore = dyn_cast<StoreInst>(BBI);
1581 if (!OtherStore || OtherStore->getOperand(1) != SI.getOperand(1) ||
1582 !SI.isSameOperationAs(OtherStore))
1583 return false;
1584 } else {
1585 // Otherwise, the other block ended with a conditional branch. If one of the
1586 // destinations is StoreBB, then we have the if/then case.
1587 if (OtherBr->getSuccessor(0) != StoreBB &&
1588 OtherBr->getSuccessor(1) != StoreBB)
1589 return false;
1590
1591 // Okay, we know that OtherBr now goes to Dest and StoreBB, so this is an
1592 // if/then triangle. See if there is a store to the same ptr as SI that
1593 // lives in OtherBB.
1594 for (;; --BBI) {
1595 // Check to see if we find the matching store.
1596 if ((OtherStore = dyn_cast<StoreInst>(BBI))) {
1597 if (OtherStore->getOperand(1) != SI.getOperand(1) ||
1598 !SI.isSameOperationAs(OtherStore))
1599 return false;
1600 break;
1601 }
1602 // If we find something that may be using or overwriting the stored
1603 // value, or if we run out of instructions, we can't do the xform.
1604 if (BBI->mayReadFromMemory() || BBI->mayThrow() ||
1605 BBI->mayWriteToMemory() || BBI == OtherBB->begin())
1606 return false;
1607 }
1608
1609 // In order to eliminate the store in OtherBr, we have to
1610 // make sure nothing reads or overwrites the stored value in
1611 // StoreBB.
1612 for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) {
1613 // FIXME: This should really be AA driven.
1614 if (I->mayReadFromMemory() || I->mayThrow() || I->mayWriteToMemory())
1615 return false;
1616 }
1617 }
1618
1619 // Insert a PHI node now if we need it.
1620 Value *MergedVal = OtherStore->getOperand(0);
1621 if (MergedVal != SI.getOperand(0)) {
1622 PHINode *PN = PHINode::Create(MergedVal->getType(), 2, "storemerge");
1623 PN->addIncoming(SI.getOperand(0), SI.getParent());
1624 PN->addIncoming(OtherStore->getOperand(0), OtherBB);
1625 MergedVal = InsertNewInstBefore(PN, DestBB->front());
1626 }
1627
1628 // Advance to a place where it is safe to insert the new store and
1629 // insert it.
1630 BBI = DestBB->getFirstInsertionPt();
1631 StoreInst *NewSI = new StoreInst(MergedVal, SI.getOperand(1),
1632 SI.isVolatile(),
1633 SI.getAlignment(),
1634 SI.getOrdering(),
1635 SI.getSyncScopeID());
1636 InsertNewInstBefore(NewSI, *BBI);
1637 // The debug locations of the original instructions might differ; merge them.
1638 NewSI->applyMergedLocation(SI.getDebugLoc(), OtherStore->getDebugLoc());
1639
1640 // If the two stores had AA tags, merge them.
1641 AAMDNodes AATags;
1642 SI.getAAMetadata(AATags);
1643 if (AATags) {
1644 OtherStore->getAAMetadata(AATags, /* Merge = */ true);
1645 NewSI->setAAMetadata(AATags);
1646 }
1647
1648 // Nuke the old stores.
1649 eraseInstFromFunction(SI);
1650 eraseInstFromFunction(*OtherStore);
1651 return true;
1652}