1 //===- Local.cpp - Functions to perform local transformations -------------===//
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 family of functions perform various local transformations to the
11 // program.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "llvm/Transforms/Utils/Local.h"
16 #include "llvm/ADT/APInt.h"
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/ADT/DenseMapInfo.h"
19 #include "llvm/ADT/DenseSet.h"
20 #include "llvm/ADT/Hashing.h"
21 #include "llvm/ADT/None.h"
22 #include "llvm/ADT/Optional.h"
23 #include "llvm/ADT/STLExtras.h"
24 #include "llvm/ADT/SetVector.h"
25 #include "llvm/ADT/SmallPtrSet.h"
26 #include "llvm/ADT/SmallVector.h"
27 #include "llvm/ADT/Statistic.h"
28 #include "llvm/ADT/TinyPtrVector.h"
29 #include "llvm/Analysis/ConstantFolding.h"
30 #include "llvm/Analysis/EHPersonalities.h"
31 #include "llvm/Analysis/InstructionSimplify.h"
32 #include "llvm/Analysis/LazyValueInfo.h"
33 #include "llvm/Analysis/MemoryBuiltins.h"
34 #include "llvm/Analysis/TargetLibraryInfo.h"
35 #include "llvm/Analysis/ValueTracking.h"
36 #include "llvm/BinaryFormat/Dwarf.h"
37 #include "llvm/IR/Argument.h"
38 #include "llvm/IR/Attributes.h"
39 #include "llvm/IR/BasicBlock.h"
40 #include "llvm/IR/CFG.h"
41 #include "llvm/IR/CallSite.h"
42 #include "llvm/IR/Constant.h"
43 #include "llvm/IR/ConstantRange.h"
44 #include "llvm/IR/Constants.h"
45 #include "llvm/IR/DIBuilder.h"
46 #include "llvm/IR/DataLayout.h"
47 #include "llvm/IR/DebugInfoMetadata.h"
48 #include "llvm/IR/DebugLoc.h"
49 #include "llvm/IR/DerivedTypes.h"
50 #include "llvm/IR/Dominators.h"
51 #include "llvm/IR/Function.h"
52 #include "llvm/IR/GetElementPtrTypeIterator.h"
53 #include "llvm/IR/GlobalObject.h"
54 #include "llvm/IR/IRBuilder.h"
55 #include "llvm/IR/InstrTypes.h"
56 #include "llvm/IR/Instruction.h"
57 #include "llvm/IR/Instructions.h"
58 #include "llvm/IR/IntrinsicInst.h"
59 #include "llvm/IR/Intrinsics.h"
60 #include "llvm/IR/LLVMContext.h"
61 #include "llvm/IR/MDBuilder.h"
62 #include "llvm/IR/Metadata.h"
63 #include "llvm/IR/Module.h"
64 #include "llvm/IR/Operator.h"
65 #include "llvm/IR/PatternMatch.h"
66 #include "llvm/IR/Type.h"
67 #include "llvm/IR/Use.h"
68 #include "llvm/IR/User.h"
69 #include "llvm/IR/Value.h"
70 #include "llvm/IR/ValueHandle.h"
71 #include "llvm/Support/Casting.h"
72 #include "llvm/Support/Debug.h"
73 #include "llvm/Support/ErrorHandling.h"
74 #include "llvm/Support/KnownBits.h"
75 #include "llvm/Support/raw_ostream.h"
76 #include "llvm/Transforms/Utils/ValueMapper.h"
77 #include <algorithm>
78 #include <cassert>
79 #include <climits>
80 #include <cstdint>
81 #include <iterator>
82 #include <map>
83 #include <utility>
84
85 using namespace llvm;
86 using namespace llvm::PatternMatch;
87
88 #define DEBUG_TYPE "local"
89
90 STATISTIC(NumRemoved, "Number of unreachable basic blocks removed");
91
92 //===----------------------------------------------------------------------===//
93 // Local constant propagation.
94 //
95
96 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
97 /// constant value, convert it into an unconditional branch to the constant
98 /// destination. This is a nontrivial operation because the successors of this
99 /// basic block must have their PHI nodes updated.
100 /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
101 /// conditions and indirectbr addresses this might make dead if
102 /// DeleteDeadConditions is true.
ConstantFoldTerminator(BasicBlock * BB,bool DeleteDeadConditions,const TargetLibraryInfo * TLI,DeferredDominance * DDT)103 bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
104 const TargetLibraryInfo *TLI,
105 DeferredDominance *DDT) {
106 TerminatorInst *T = BB->getTerminator();
107 IRBuilder<> Builder(T);
108
109 // Branch - See if we are conditional jumping on constant
110 if (auto *BI = dyn_cast<BranchInst>(T)) {
111 if (BI->isUnconditional()) return false; // Can't optimize uncond branch
112 BasicBlock *Dest1 = BI->getSuccessor(0);
113 BasicBlock *Dest2 = BI->getSuccessor(1);
114
115 if (auto *Cond = dyn_cast<ConstantInt>(BI->getCondition())) {
116 // Are we branching on constant?
117 // YES. Change to unconditional branch...
118 BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2;
119 BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1;
120
121 // Let the basic block know that we are letting go of it. Based on this,
122 // it will adjust it's PHI nodes.
123 OldDest->removePredecessor(BB);
124
125 // Replace the conditional branch with an unconditional one.
126 Builder.CreateBr(Destination);
127 BI->eraseFromParent();
128 if (DDT)
129 DDT->deleteEdge(BB, OldDest);
130 return true;
131 }
132
133 if (Dest2 == Dest1) { // Conditional branch to same location?
134 // This branch matches something like this:
135 // br bool %cond, label %Dest, label %Dest
136 // and changes it into: br label %Dest
137
138 // Let the basic block know that we are letting go of one copy of it.
139 assert(BI->getParent() && "Terminator not inserted in block!");
140 Dest1->removePredecessor(BI->getParent());
141
142 // Replace the conditional branch with an unconditional one.
143 Builder.CreateBr(Dest1);
144 Value *Cond = BI->getCondition();
145 BI->eraseFromParent();
146 if (DeleteDeadConditions)
147 RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
148 return true;
149 }
150 return false;
151 }
152
153 if (auto *SI = dyn_cast<SwitchInst>(T)) {
154 // If we are switching on a constant, we can convert the switch to an
155 // unconditional branch.
156 auto *CI = dyn_cast<ConstantInt>(SI->getCondition());
157 BasicBlock *DefaultDest = SI->getDefaultDest();
158 BasicBlock *TheOnlyDest = DefaultDest;
159
160 // If the default is unreachable, ignore it when searching for TheOnlyDest.
161 if (isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg()) &&
162 SI->getNumCases() > 0) {
163 TheOnlyDest = SI->case_begin()->getCaseSuccessor();
164 }
165
166 // Figure out which case it goes to.
167 for (auto i = SI->case_begin(), e = SI->case_end(); i != e;) {
168 // Found case matching a constant operand?
169 if (i->getCaseValue() == CI) {
170 TheOnlyDest = i->getCaseSuccessor();
171 break;
172 }
173
174 // Check to see if this branch is going to the same place as the default
175 // dest. If so, eliminate it as an explicit compare.
176 if (i->getCaseSuccessor() == DefaultDest) {
177 MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
178 unsigned NCases = SI->getNumCases();
179 // Fold the case metadata into the default if there will be any branches
180 // left, unless the metadata doesn't match the switch.
181 if (NCases > 1 && MD && MD->getNumOperands() == 2 + NCases) {
182 // Collect branch weights into a vector.
183 SmallVector<uint32_t, 8> Weights;
184 for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e;
185 ++MD_i) {
186 auto *CI = mdconst::extract<ConstantInt>(MD->getOperand(MD_i));
187 Weights.push_back(CI->getValue().getZExtValue());
188 }
189 // Merge weight of this case to the default weight.
190 unsigned idx = i->getCaseIndex();
191 Weights[0] += Weights[idx+1];
192 // Remove weight for this case.
193 std::swap(Weights[idx+1], Weights.back());
194 Weights.pop_back();
195 SI->setMetadata(LLVMContext::MD_prof,
196 MDBuilder(BB->getContext()).
197 createBranchWeights(Weights));
198 }
199 // Remove this entry.
200 BasicBlock *ParentBB = SI->getParent();
201 DefaultDest->removePredecessor(ParentBB);
202 i = SI->removeCase(i);
203 e = SI->case_end();
204 if (DDT)
205 DDT->deleteEdge(ParentBB, DefaultDest);
206 continue;
207 }
208
209 // Otherwise, check to see if the switch only branches to one destination.
210 // We do this by reseting "TheOnlyDest" to null when we find two non-equal
211 // destinations.
212 if (i->getCaseSuccessor() != TheOnlyDest)
213 TheOnlyDest = nullptr;
214
215 // Increment this iterator as we haven't removed the case.
216 ++i;
217 }
218
219 if (CI && !TheOnlyDest) {
220 // Branching on a constant, but not any of the cases, go to the default
221 // successor.
222 TheOnlyDest = SI->getDefaultDest();
223 }
224
225 // If we found a single destination that we can fold the switch into, do so
226 // now.
227 if (TheOnlyDest) {
228 // Insert the new branch.
229 Builder.CreateBr(TheOnlyDest);
230 BasicBlock *BB = SI->getParent();
231 std::vector <DominatorTree::UpdateType> Updates;
232 if (DDT)
233 Updates.reserve(SI->getNumSuccessors() - 1);
234
235 // Remove entries from PHI nodes which we no longer branch to...
236 for (BasicBlock *Succ : SI->successors()) {
237 // Found case matching a constant operand?
238 if (Succ == TheOnlyDest) {
239 TheOnlyDest = nullptr; // Don't modify the first branch to TheOnlyDest
240 } else {
241 Succ->removePredecessor(BB);
242 if (DDT)
243 Updates.push_back({DominatorTree::Delete, BB, Succ});
244 }
245 }
246
247 // Delete the old switch.
248 Value *Cond = SI->getCondition();
249 SI->eraseFromParent();
250 if (DeleteDeadConditions)
251 RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
252 if (DDT)
253 DDT->applyUpdates(Updates);
254 return true;
255 }
256
257 if (SI->getNumCases() == 1) {
258 // Otherwise, we can fold this switch into a conditional branch
259 // instruction if it has only one non-default destination.
260 auto FirstCase = *SI->case_begin();
261 Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
262 FirstCase.getCaseValue(), "cond");
263
264 // Insert the new branch.
265 BranchInst *NewBr = Builder.CreateCondBr(Cond,
266 FirstCase.getCaseSuccessor(),
267 SI->getDefaultDest());
268 MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
269 if (MD && MD->getNumOperands() == 3) {
270 ConstantInt *SICase =
271 mdconst::dyn_extract<ConstantInt>(MD->getOperand(2));
272 ConstantInt *SIDef =
273 mdconst::dyn_extract<ConstantInt>(MD->getOperand(1));
274 assert(SICase && SIDef);
275 // The TrueWeight should be the weight for the single case of SI.
276 NewBr->setMetadata(LLVMContext::MD_prof,
277 MDBuilder(BB->getContext()).
278 createBranchWeights(SICase->getValue().getZExtValue(),
279 SIDef->getValue().getZExtValue()));
280 }
281
282 // Update make.implicit metadata to the newly-created conditional branch.
283 MDNode *MakeImplicitMD = SI->getMetadata(LLVMContext::MD_make_implicit);
284 if (MakeImplicitMD)
285 NewBr->setMetadata(LLVMContext::MD_make_implicit, MakeImplicitMD);
286
287 // Delete the old switch.
288 SI->eraseFromParent();
289 return true;
290 }
291 return false;
292 }
293
294 if (auto *IBI = dyn_cast<IndirectBrInst>(T)) {
295 // indirectbr blockaddress(@F, @BB) -> br label @BB
296 if (auto *BA =
297 dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
298 BasicBlock *TheOnlyDest = BA->getBasicBlock();
299 std::vector <DominatorTree::UpdateType> Updates;
300 if (DDT)
301 Updates.reserve(IBI->getNumDestinations() - 1);
302
303 // Insert the new branch.
304 Builder.CreateBr(TheOnlyDest);
305
306 for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
307 if (IBI->getDestination(i) == TheOnlyDest) {
308 TheOnlyDest = nullptr;
309 } else {
310 BasicBlock *ParentBB = IBI->getParent();
311 BasicBlock *DestBB = IBI->getDestination(i);
312 DestBB->removePredecessor(ParentBB);
313 if (DDT)
314 Updates.push_back({DominatorTree::Delete, ParentBB, DestBB});
315 }
316 }
317 Value *Address = IBI->getAddress();
318 IBI->eraseFromParent();
319 if (DeleteDeadConditions)
320 RecursivelyDeleteTriviallyDeadInstructions(Address, TLI);
321
322 // If we didn't find our destination in the IBI successor list, then we
323 // have undefined behavior. Replace the unconditional branch with an
324 // 'unreachable' instruction.
325 if (TheOnlyDest) {
326 BB->getTerminator()->eraseFromParent();
327 new UnreachableInst(BB->getContext(), BB);
328 }
329
330 if (DDT)
331 DDT->applyUpdates(Updates);
332 return true;
333 }
334 }
335
336 return false;
337 }
338
339 //===----------------------------------------------------------------------===//
340 // Local dead code elimination.
341 //
342
343 /// isInstructionTriviallyDead - Return true if the result produced by the
344 /// instruction is not used, and the instruction has no side effects.
345 ///
isInstructionTriviallyDead(Instruction * I,const TargetLibraryInfo * TLI)346 bool llvm::isInstructionTriviallyDead(Instruction *I,
347 const TargetLibraryInfo *TLI) {
348 if (!I->use_empty())
349 return false;
350 return wouldInstructionBeTriviallyDead(I, TLI);
351 }
352
wouldInstructionBeTriviallyDead(Instruction * I,const TargetLibraryInfo * TLI)353 bool llvm::wouldInstructionBeTriviallyDead(Instruction *I,
354 const TargetLibraryInfo *TLI) {
355 if (isa<TerminatorInst>(I))
356 return false;
357
358 // We don't want the landingpad-like instructions removed by anything this
359 // general.
360 if (I->isEHPad())
361 return false;
362
363 // We don't want debug info removed by anything this general, unless
364 // debug info is empty.
365 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
366 if (DDI->getAddress())
367 return false;
368 return true;
369 }
370 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
371 if (DVI->getValue())
372 return false;
373 return true;
374 }
375 if (DbgLabelInst *DLI = dyn_cast<DbgLabelInst>(I)) {
376 if (DLI->getLabel())
377 return false;
378 return true;
379 }
380
381 if (!I->mayHaveSideEffects())
382 return true;
383
384 // Special case intrinsics that "may have side effects" but can be deleted
385 // when dead.
386 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
387 // Safe to delete llvm.stacksave and launder.invariant.group if dead.
388 if (II->getIntrinsicID() == Intrinsic::stacksave ||
389 II->getIntrinsicID() == Intrinsic::launder_invariant_group)
390 return true;
391
392 // Lifetime intrinsics are dead when their right-hand is undef.
393 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
394 II->getIntrinsicID() == Intrinsic::lifetime_end)
395 return isa<UndefValue>(II->getArgOperand(1));
396
397 // Assumptions are dead if their condition is trivially true. Guards on
398 // true are operationally no-ops. In the future we can consider more
399 // sophisticated tradeoffs for guards considering potential for check
400 // widening, but for now we keep things simple.
401 if (II->getIntrinsicID() == Intrinsic::assume ||
402 II->getIntrinsicID() == Intrinsic::experimental_guard) {
403 if (ConstantInt *Cond = dyn_cast<ConstantInt>(II->getArgOperand(0)))
404 return !Cond->isZero();
405
406 return false;
407 }
408 }
409
410 if (isAllocLikeFn(I, TLI))
411 return true;
412
413 if (CallInst *CI = isFreeCall(I, TLI))
414 if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
415 return C->isNullValue() || isa<UndefValue>(C);
416
417 if (CallSite CS = CallSite(I))
418 if (isMathLibCallNoop(CS, TLI))
419 return true;
420
421 return false;
422 }
423
424 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
425 /// trivially dead instruction, delete it. If that makes any of its operands
426 /// trivially dead, delete them too, recursively. Return true if any
427 /// instructions were deleted.
428 bool
RecursivelyDeleteTriviallyDeadInstructions(Value * V,const TargetLibraryInfo * TLI)429 llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V,
430 const TargetLibraryInfo *TLI) {
431 Instruction *I = dyn_cast<Instruction>(V);
432 if (!I || !I->use_empty() || !isInstructionTriviallyDead(I, TLI))
433 return false;
434
435 SmallVector<Instruction*, 16> DeadInsts;
436 DeadInsts.push_back(I);
437 RecursivelyDeleteTriviallyDeadInstructions(DeadInsts, TLI);
438
439 return true;
440 }
441
RecursivelyDeleteTriviallyDeadInstructions(SmallVectorImpl<Instruction * > & DeadInsts,const TargetLibraryInfo * TLI)442 void llvm::RecursivelyDeleteTriviallyDeadInstructions(
443 SmallVectorImpl<Instruction *> &DeadInsts, const TargetLibraryInfo *TLI) {
444 // Process the dead instruction list until empty.
445 while (!DeadInsts.empty()) {
446 Instruction &I = *DeadInsts.pop_back_val();
447 assert(I.use_empty() && "Instructions with uses are not dead.");
448 assert(isInstructionTriviallyDead(&I, TLI) &&
449 "Live instruction found in dead worklist!");
450
451 // Don't lose the debug info while deleting the instructions.
452 salvageDebugInfo(I);
453
454 // Null out all of the instruction's operands to see if any operand becomes
455 // dead as we go.
456 for (Use &OpU : I.operands()) {
457 Value *OpV = OpU.get();
458 OpU.set(nullptr);
459
460 if (!OpV->use_empty())
461 continue;
462
463 // If the operand is an instruction that became dead as we nulled out the
464 // operand, and if it is 'trivially' dead, delete it in a future loop
465 // iteration.
466 if (Instruction *OpI = dyn_cast<Instruction>(OpV))
467 if (isInstructionTriviallyDead(OpI, TLI))
468 DeadInsts.push_back(OpI);
469 }
470
471 I.eraseFromParent();
472 }
473 }
474
475 /// areAllUsesEqual - Check whether the uses of a value are all the same.
476 /// This is similar to Instruction::hasOneUse() except this will also return
477 /// true when there are no uses or multiple uses that all refer to the same
478 /// value.
areAllUsesEqual(Instruction * I)479 static bool areAllUsesEqual(Instruction *I) {
480 Value::user_iterator UI = I->user_begin();
481 Value::user_iterator UE = I->user_end();
482 if (UI == UE)
483 return true;
484
485 User *TheUse = *UI;
486 for (++UI; UI != UE; ++UI) {
487 if (*UI != TheUse)
488 return false;
489 }
490 return true;
491 }
492
493 /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
494 /// dead PHI node, due to being a def-use chain of single-use nodes that
495 /// either forms a cycle or is terminated by a trivially dead instruction,
496 /// delete it. If that makes any of its operands trivially dead, delete them
497 /// too, recursively. Return true if a change was made.
RecursivelyDeleteDeadPHINode(PHINode * PN,const TargetLibraryInfo * TLI)498 bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN,
499 const TargetLibraryInfo *TLI) {
500 SmallPtrSet<Instruction*, 4> Visited;
501 for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects();
502 I = cast<Instruction>(*I->user_begin())) {
503 if (I->use_empty())
504 return RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
505
506 // If we find an instruction more than once, we're on a cycle that
507 // won't prove fruitful.
508 if (!Visited.insert(I).second) {
509 // Break the cycle and delete the instruction and its operands.
510 I->replaceAllUsesWith(UndefValue::get(I->getType()));
511 (void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
512 return true;
513 }
514 }
515 return false;
516 }
517
518 static bool
simplifyAndDCEInstruction(Instruction * I,SmallSetVector<Instruction *,16> & WorkList,const DataLayout & DL,const TargetLibraryInfo * TLI)519 simplifyAndDCEInstruction(Instruction *I,
520 SmallSetVector<Instruction *, 16> &WorkList,
521 const DataLayout &DL,
522 const TargetLibraryInfo *TLI) {
523 if (isInstructionTriviallyDead(I, TLI)) {
524 salvageDebugInfo(*I);
525
526 // Null out all of the instruction's operands to see if any operand becomes
527 // dead as we go.
528 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
529 Value *OpV = I->getOperand(i);
530 I->setOperand(i, nullptr);
531
532 if (!OpV->use_empty() || I == OpV)
533 continue;
534
535 // If the operand is an instruction that became dead as we nulled out the
536 // operand, and if it is 'trivially' dead, delete it in a future loop
537 // iteration.
538 if (Instruction *OpI = dyn_cast<Instruction>(OpV))
539 if (isInstructionTriviallyDead(OpI, TLI))
540 WorkList.insert(OpI);
541 }
542
543 I->eraseFromParent();
544
545 return true;
546 }
547
548 if (Value *SimpleV = SimplifyInstruction(I, DL)) {
549 // Add the users to the worklist. CAREFUL: an instruction can use itself,
550 // in the case of a phi node.
551 for (User *U : I->users()) {
552 if (U != I) {
553 WorkList.insert(cast<Instruction>(U));
554 }
555 }
556
557 // Replace the instruction with its simplified value.
558 bool Changed = false;
559 if (!I->use_empty()) {
560 I->replaceAllUsesWith(SimpleV);
561 Changed = true;
562 }
563 if (isInstructionTriviallyDead(I, TLI)) {
564 I->eraseFromParent();
565 Changed = true;
566 }
567 return Changed;
568 }
569 return false;
570 }
571
572 /// SimplifyInstructionsInBlock - Scan the specified basic block and try to
573 /// simplify any instructions in it and recursively delete dead instructions.
574 ///
575 /// This returns true if it changed the code, note that it can delete
576 /// instructions in other blocks as well in this block.
SimplifyInstructionsInBlock(BasicBlock * BB,const TargetLibraryInfo * TLI)577 bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB,
578 const TargetLibraryInfo *TLI) {
579 bool MadeChange = false;
580 const DataLayout &DL = BB->getModule()->getDataLayout();
581
582 #ifndef NDEBUG
583 // In debug builds, ensure that the terminator of the block is never replaced
584 // or deleted by these simplifications. The idea of simplification is that it
585 // cannot introduce new instructions, and there is no way to replace the
586 // terminator of a block without introducing a new instruction.
587 AssertingVH<Instruction> TerminatorVH(&BB->back());
588 #endif
589
590 SmallSetVector<Instruction *, 16> WorkList;
591 // Iterate over the original function, only adding insts to the worklist
592 // if they actually need to be revisited. This avoids having to pre-init
593 // the worklist with the entire function's worth of instructions.
594 for (BasicBlock::iterator BI = BB->begin(), E = std::prev(BB->end());
595 BI != E;) {
596 assert(!BI->isTerminator());
597 Instruction *I = &*BI;
598 ++BI;
599
600 // We're visiting this instruction now, so make sure it's not in the
601 // worklist from an earlier visit.
602 if (!WorkList.count(I))
603 MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI);
604 }
605
606 while (!WorkList.empty()) {
607 Instruction *I = WorkList.pop_back_val();
608 MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI);
609 }
610 return MadeChange;
611 }
612
613 //===----------------------------------------------------------------------===//
614 // Control Flow Graph Restructuring.
615 //
616
617 /// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
618 /// method is called when we're about to delete Pred as a predecessor of BB. If
619 /// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
620 ///
621 /// Unlike the removePredecessor method, this attempts to simplify uses of PHI
622 /// nodes that collapse into identity values. For example, if we have:
623 /// x = phi(1, 0, 0, 0)
624 /// y = and x, z
625 ///
626 /// .. and delete the predecessor corresponding to the '1', this will attempt to
627 /// recursively fold the and to 0.
RemovePredecessorAndSimplify(BasicBlock * BB,BasicBlock * Pred,DeferredDominance * DDT)628 void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
629 DeferredDominance *DDT) {
630 // This only adjusts blocks with PHI nodes.
631 if (!isa<PHINode>(BB->begin()))
632 return;
633
634 // Remove the entries for Pred from the PHI nodes in BB, but do not simplify
635 // them down. This will leave us with single entry phi nodes and other phis
636 // that can be removed.
637 BB->removePredecessor(Pred, true);
638
639 WeakTrackingVH PhiIt = &BB->front();
640 while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) {
641 PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt));
642 Value *OldPhiIt = PhiIt;
643
644 if (!recursivelySimplifyInstruction(PN))
645 continue;
646
647 // If recursive simplification ended up deleting the next PHI node we would
648 // iterate to, then our iterator is invalid, restart scanning from the top
649 // of the block.
650 if (PhiIt != OldPhiIt) PhiIt = &BB->front();
651 }
652 if (DDT)
653 DDT->deleteEdge(Pred, BB);
654 }
655
656 /// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its
657 /// predecessor is known to have one successor (DestBB!). Eliminate the edge
658 /// between them, moving the instructions in the predecessor into DestBB and
659 /// deleting the predecessor block.
MergeBasicBlockIntoOnlyPred(BasicBlock * DestBB,DominatorTree * DT,DeferredDominance * DDT)660 void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, DominatorTree *DT,
661 DeferredDominance *DDT) {
662 assert(!(DT && DDT) && "Cannot call with both DT and DDT.");
663
664 // If BB has single-entry PHI nodes, fold them.
665 while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
666 Value *NewVal = PN->getIncomingValue(0);
667 // Replace self referencing PHI with undef, it must be dead.
668 if (NewVal == PN) NewVal = UndefValue::get(PN->getType());
669 PN->replaceAllUsesWith(NewVal);
670 PN->eraseFromParent();
671 }
672
673 BasicBlock *PredBB = DestBB->getSinglePredecessor();
674 assert(PredBB && "Block doesn't have a single predecessor!");
675
676 bool ReplaceEntryBB = false;
677 if (PredBB == &DestBB->getParent()->getEntryBlock())
678 ReplaceEntryBB = true;
679
680 // Deferred DT update: Collect all the edges that enter PredBB. These
681 // dominator edges will be redirected to DestBB.
682 std::vector <DominatorTree::UpdateType> Updates;
683 if (DDT && !ReplaceEntryBB) {
684 Updates.reserve(1 + (2 * pred_size(PredBB)));
685 Updates.push_back({DominatorTree::Delete, PredBB, DestBB});
686 for (auto I = pred_begin(PredBB), E = pred_end(PredBB); I != E; ++I) {
687 Updates.push_back({DominatorTree::Delete, *I, PredBB});
688 // This predecessor of PredBB may already have DestBB as a successor.
689 if (llvm::find(successors(*I), DestBB) == succ_end(*I))
690 Updates.push_back({DominatorTree::Insert, *I, DestBB});
691 }
692 }
693
694 // Zap anything that took the address of DestBB. Not doing this will give the
695 // address an invalid value.
696 if (DestBB->hasAddressTaken()) {
697 BlockAddress *BA = BlockAddress::get(DestBB);
698 Constant *Replacement =
699 ConstantInt::get(Type::getInt32Ty(BA->getContext()), 1);
700 BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
701 BA->getType()));
702 BA->destroyConstant();
703 }
704
705 // Anything that branched to PredBB now branches to DestBB.
706 PredBB->replaceAllUsesWith(DestBB);
707
708 // Splice all the instructions from PredBB to DestBB.
709 PredBB->getTerminator()->eraseFromParent();
710 DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
711
712 // If the PredBB is the entry block of the function, move DestBB up to
713 // become the entry block after we erase PredBB.
714 if (ReplaceEntryBB)
715 DestBB->moveAfter(PredBB);
716
717 if (DT) {
718 // For some irreducible CFG we end up having forward-unreachable blocks
719 // so check if getNode returns a valid node before updating the domtree.
720 if (DomTreeNode *DTN = DT->getNode(PredBB)) {
721 BasicBlock *PredBBIDom = DTN->getIDom()->getBlock();
722 DT->changeImmediateDominator(DestBB, PredBBIDom);
723 DT->eraseNode(PredBB);
724 }
725 }
726
727 if (DDT) {
728 DDT->deleteBB(PredBB); // Deferred deletion of BB.
729 if (ReplaceEntryBB)
730 // The entry block was removed and there is no external interface for the
731 // dominator tree to be notified of this change. In this corner-case we
732 // recalculate the entire tree.
733 DDT->recalculate(*(DestBB->getParent()));
734 else
735 DDT->applyUpdates(Updates);
736 } else {
737 PredBB->eraseFromParent(); // Nuke BB.
738 }
739 }
740
741 /// CanMergeValues - Return true if we can choose one of these values to use
742 /// in place of the other. Note that we will always choose the non-undef
743 /// value to keep.
CanMergeValues(Value * First,Value * Second)744 static bool CanMergeValues(Value *First, Value *Second) {
745 return First == Second || isa<UndefValue>(First) || isa<UndefValue>(Second);
746 }
747
748 /// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
749 /// almost-empty BB ending in an unconditional branch to Succ, into Succ.
750 ///
751 /// Assumption: Succ is the single successor for BB.
CanPropagatePredecessorsForPHIs(BasicBlock * BB,BasicBlock * Succ)752 static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
753 assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
754
755 LLVM_DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
756 << Succ->getName() << "\n");
757 // Shortcut, if there is only a single predecessor it must be BB and merging
758 // is always safe
759 if (Succ->getSinglePredecessor()) return true;
760
761 // Make a list of the predecessors of BB
762 SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
763
764 // Look at all the phi nodes in Succ, to see if they present a conflict when
765 // merging these blocks
766 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
767 PHINode *PN = cast<PHINode>(I);
768
769 // If the incoming value from BB is again a PHINode in
770 // BB which has the same incoming value for *PI as PN does, we can
771 // merge the phi nodes and then the blocks can still be merged
772 PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
773 if (BBPN && BBPN->getParent() == BB) {
774 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
775 BasicBlock *IBB = PN->getIncomingBlock(PI);
776 if (BBPreds.count(IBB) &&
777 !CanMergeValues(BBPN->getIncomingValueForBlock(IBB),
778 PN->getIncomingValue(PI))) {
779 LLVM_DEBUG(dbgs()
780 << "Can't fold, phi node " << PN->getName() << " in "
781 << Succ->getName() << " is conflicting with "
782 << BBPN->getName() << " with regard to common predecessor "
783 << IBB->getName() << "\n");
784 return false;
785 }
786 }
787 } else {
788 Value* Val = PN->getIncomingValueForBlock(BB);
789 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
790 // See if the incoming value for the common predecessor is equal to the
791 // one for BB, in which case this phi node will not prevent the merging
792 // of the block.
793 BasicBlock *IBB = PN->getIncomingBlock(PI);
794 if (BBPreds.count(IBB) &&
795 !CanMergeValues(Val, PN->getIncomingValue(PI))) {
796 LLVM_DEBUG(dbgs() << "Can't fold, phi node " << PN->getName()
797 << " in " << Succ->getName()
798 << " is conflicting with regard to common "
799 << "predecessor " << IBB->getName() << "\n");
800 return false;
801 }
802 }
803 }
804 }
805
806 return true;
807 }
808
809 using PredBlockVector = SmallVector<BasicBlock *, 16>;
810 using IncomingValueMap = DenseMap<BasicBlock *, Value *>;
811
812 /// Determines the value to use as the phi node input for a block.
813 ///
814 /// Select between \p OldVal any value that we know flows from \p BB
815 /// to a particular phi on the basis of which one (if either) is not
816 /// undef. Update IncomingValues based on the selected value.
817 ///
818 /// \param OldVal The value we are considering selecting.
819 /// \param BB The block that the value flows in from.
820 /// \param IncomingValues A map from block-to-value for other phi inputs
821 /// that we have examined.
822 ///
823 /// \returns the selected value.
selectIncomingValueForBlock(Value * OldVal,BasicBlock * BB,IncomingValueMap & IncomingValues)824 static Value *selectIncomingValueForBlock(Value *OldVal, BasicBlock *BB,
825 IncomingValueMap &IncomingValues) {
826 if (!isa<UndefValue>(OldVal)) {
827 assert((!IncomingValues.count(BB) ||
828 IncomingValues.find(BB)->second == OldVal) &&
829 "Expected OldVal to match incoming value from BB!");
830
831 IncomingValues.insert(std::make_pair(BB, OldVal));
832 return OldVal;
833 }
834
835 IncomingValueMap::const_iterator It = IncomingValues.find(BB);
836 if (It != IncomingValues.end()) return It->second;
837
838 return OldVal;
839 }
840
841 /// Create a map from block to value for the operands of a
842 /// given phi.
843 ///
844 /// Create a map from block to value for each non-undef value flowing
845 /// into \p PN.
846 ///
847 /// \param PN The phi we are collecting the map for.
848 /// \param IncomingValues [out] The map from block to value for this phi.
gatherIncomingValuesToPhi(PHINode * PN,IncomingValueMap & IncomingValues)849 static void gatherIncomingValuesToPhi(PHINode *PN,
850 IncomingValueMap &IncomingValues) {
851 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
852 BasicBlock *BB = PN->getIncomingBlock(i);
853 Value *V = PN->getIncomingValue(i);
854
855 if (!isa<UndefValue>(V))
856 IncomingValues.insert(std::make_pair(BB, V));
857 }
858 }
859
860 /// Replace the incoming undef values to a phi with the values
861 /// from a block-to-value map.
862 ///
863 /// \param PN The phi we are replacing the undefs in.
864 /// \param IncomingValues A map from block to value.
replaceUndefValuesInPhi(PHINode * PN,const IncomingValueMap & IncomingValues)865 static void replaceUndefValuesInPhi(PHINode *PN,
866 const IncomingValueMap &IncomingValues) {
867 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
868 Value *V = PN->getIncomingValue(i);
869
870 if (!isa<UndefValue>(V)) continue;
871
872 BasicBlock *BB = PN->getIncomingBlock(i);
873 IncomingValueMap::const_iterator It = IncomingValues.find(BB);
874 if (It == IncomingValues.end()) continue;
875
876 PN->setIncomingValue(i, It->second);
877 }
878 }
879
880 /// Replace a value flowing from a block to a phi with
881 /// potentially multiple instances of that value flowing from the
882 /// block's predecessors to the phi.
883 ///
884 /// \param BB The block with the value flowing into the phi.
885 /// \param BBPreds The predecessors of BB.
886 /// \param PN The phi that we are updating.
redirectValuesFromPredecessorsToPhi(BasicBlock * BB,const PredBlockVector & BBPreds,PHINode * PN)887 static void redirectValuesFromPredecessorsToPhi(BasicBlock *BB,
888 const PredBlockVector &BBPreds,
889 PHINode *PN) {
890 Value *OldVal = PN->removeIncomingValue(BB, false);
891 assert(OldVal && "No entry in PHI for Pred BB!");
892
893 IncomingValueMap IncomingValues;
894
895 // We are merging two blocks - BB, and the block containing PN - and
896 // as a result we need to redirect edges from the predecessors of BB
897 // to go to the block containing PN, and update PN
898 // accordingly. Since we allow merging blocks in the case where the
899 // predecessor and successor blocks both share some predecessors,
900 // and where some of those common predecessors might have undef
901 // values flowing into PN, we want to rewrite those values to be
902 // consistent with the non-undef values.
903
904 gatherIncomingValuesToPhi(PN, IncomingValues);
905
906 // If this incoming value is one of the PHI nodes in BB, the new entries
907 // in the PHI node are the entries from the old PHI.
908 if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
909 PHINode *OldValPN = cast<PHINode>(OldVal);
910 for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i) {
911 // Note that, since we are merging phi nodes and BB and Succ might
912 // have common predecessors, we could end up with a phi node with
913 // identical incoming branches. This will be cleaned up later (and
914 // will trigger asserts if we try to clean it up now, without also
915 // simplifying the corresponding conditional branch).
916 BasicBlock *PredBB = OldValPN->getIncomingBlock(i);
917 Value *PredVal = OldValPN->getIncomingValue(i);
918 Value *Selected = selectIncomingValueForBlock(PredVal, PredBB,
919 IncomingValues);
920
921 // And add a new incoming value for this predecessor for the
922 // newly retargeted branch.
923 PN->addIncoming(Selected, PredBB);
924 }
925 } else {
926 for (unsigned i = 0, e = BBPreds.size(); i != e; ++i) {
927 // Update existing incoming values in PN for this
928 // predecessor of BB.
929 BasicBlock *PredBB = BBPreds[i];
930 Value *Selected = selectIncomingValueForBlock(OldVal, PredBB,
931 IncomingValues);
932
933 // And add a new incoming value for this predecessor for the
934 // newly retargeted branch.
935 PN->addIncoming(Selected, PredBB);
936 }
937 }
938
939 replaceUndefValuesInPhi(PN, IncomingValues);
940 }
941
942 /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
943 /// unconditional branch, and contains no instructions other than PHI nodes,
944 /// potential side-effect free intrinsics and the branch. If possible,
945 /// eliminate BB by rewriting all the predecessors to branch to the successor
946 /// block and return true. If we can't transform, return false.
TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock * BB,DeferredDominance * DDT)947 bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
948 DeferredDominance *DDT) {
949 assert(BB != &BB->getParent()->getEntryBlock() &&
950 "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
951
952 // We can't eliminate infinite loops.
953 BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0);
954 if (BB == Succ) return false;
955
956 // Check to see if merging these blocks would cause conflicts for any of the
957 // phi nodes in BB or Succ. If not, we can safely merge.
958 if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
959
960 // Check for cases where Succ has multiple predecessors and a PHI node in BB
961 // has uses which will not disappear when the PHI nodes are merged. It is
962 // possible to handle such cases, but difficult: it requires checking whether
963 // BB dominates Succ, which is non-trivial to calculate in the case where
964 // Succ has multiple predecessors. Also, it requires checking whether
965 // constructing the necessary self-referential PHI node doesn't introduce any
966 // conflicts; this isn't too difficult, but the previous code for doing this
967 // was incorrect.
968 //
969 // Note that if this check finds a live use, BB dominates Succ, so BB is
970 // something like a loop pre-header (or rarely, a part of an irreducible CFG);
971 // folding the branch isn't profitable in that case anyway.
972 if (!Succ->getSinglePredecessor()) {
973 BasicBlock::iterator BBI = BB->begin();
974 while (isa<PHINode>(*BBI)) {
975 for (Use &U : BBI->uses()) {
976 if (PHINode* PN = dyn_cast<PHINode>(U.getUser())) {
977 if (PN->getIncomingBlock(U) != BB)
978 return false;
979 } else {
980 return false;
981 }
982 }
983 ++BBI;
984 }
985 }
986
987 LLVM_DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
988
989 std::vector<DominatorTree::UpdateType> Updates;
990 if (DDT) {
991 Updates.reserve(1 + (2 * pred_size(BB)));
992 Updates.push_back({DominatorTree::Delete, BB, Succ});
993 // All predecessors of BB will be moved to Succ.
994 for (auto I = pred_begin(BB), E = pred_end(BB); I != E; ++I) {
995 Updates.push_back({DominatorTree::Delete, *I, BB});
996 // This predecessor of BB may already have Succ as a successor.
997 if (llvm::find(successors(*I), Succ) == succ_end(*I))
998 Updates.push_back({DominatorTree::Insert, *I, Succ});
999 }
1000 }
1001
1002 if (isa<PHINode>(Succ->begin())) {
1003 // If there is more than one pred of succ, and there are PHI nodes in
1004 // the successor, then we need to add incoming edges for the PHI nodes
1005 //
1006 const PredBlockVector BBPreds(pred_begin(BB), pred_end(BB));
1007
1008 // Loop over all of the PHI nodes in the successor of BB.
1009 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
1010 PHINode *PN = cast<PHINode>(I);
1011
1012 redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN);
1013 }
1014 }
1015
1016 if (Succ->getSinglePredecessor()) {
1017 // BB is the only predecessor of Succ, so Succ will end up with exactly
1018 // the same predecessors BB had.
1019
1020 // Copy over any phi, debug or lifetime instruction.
1021 BB->getTerminator()->eraseFromParent();
1022 Succ->getInstList().splice(Succ->getFirstNonPHI()->getIterator(),
1023 BB->getInstList());
1024 } else {
1025 while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
1026 // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
1027 assert(PN->use_empty() && "There shouldn't be any uses here!");
1028 PN->eraseFromParent();
1029 }
1030 }
1031
1032 // If the unconditional branch we replaced contains llvm.loop metadata, we
1033 // add the metadata to the branch instructions in the predecessors.
1034 unsigned LoopMDKind = BB->getContext().getMDKindID("llvm.loop");
1035 Instruction *TI = BB->getTerminator();
1036 if (TI)
1037 if (MDNode *LoopMD = TI->getMetadata(LoopMDKind))
1038 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
1039 BasicBlock *Pred = *PI;
1040 Pred->getTerminator()->setMetadata(LoopMDKind, LoopMD);
1041 }
1042
1043 // Everything that jumped to BB now goes to Succ.
1044 BB->replaceAllUsesWith(Succ);
1045 if (!Succ->hasName()) Succ->takeName(BB);
1046
1047 if (DDT) {
1048 DDT->deleteBB(BB); // Deferred deletion of the old basic block.
1049 DDT->applyUpdates(Updates);
1050 } else {
1051 BB->eraseFromParent(); // Delete the old basic block.
1052 }
1053 return true;
1054 }
1055
1056 /// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
1057 /// nodes in this block. This doesn't try to be clever about PHI nodes
1058 /// which differ only in the order of the incoming values, but instcombine
1059 /// orders them so it usually won't matter.
EliminateDuplicatePHINodes(BasicBlock * BB)1060 bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) {
1061 // This implementation doesn't currently consider undef operands
1062 // specially. Theoretically, two phis which are identical except for
1063 // one having an undef where the other doesn't could be collapsed.
1064
1065 struct PHIDenseMapInfo {
1066 static PHINode *getEmptyKey() {
1067 return DenseMapInfo<PHINode *>::getEmptyKey();
1068 }
1069
1070 static PHINode *getTombstoneKey() {
1071 return DenseMapInfo<PHINode *>::getTombstoneKey();
1072 }
1073
1074 static unsigned getHashValue(PHINode *PN) {
1075 // Compute a hash value on the operands. Instcombine will likely have
1076 // sorted them, which helps expose duplicates, but we have to check all
1077 // the operands to be safe in case instcombine hasn't run.
1078 return static_cast<unsigned>(hash_combine(
1079 hash_combine_range(PN->value_op_begin(), PN->value_op_end()),
1080 hash_combine_range(PN->block_begin(), PN->block_end())));
1081 }
1082
1083 static bool isEqual(PHINode *LHS, PHINode *RHS) {
1084 if (LHS == getEmptyKey() || LHS == getTombstoneKey() ||
1085 RHS == getEmptyKey() || RHS == getTombstoneKey())
1086 return LHS == RHS;
1087 return LHS->isIdenticalTo(RHS);
1088 }
1089 };
1090
1091 // Set of unique PHINodes.
1092 DenseSet<PHINode *, PHIDenseMapInfo> PHISet;
1093
1094 // Examine each PHI.
1095 bool Changed = false;
1096 for (auto I = BB->begin(); PHINode *PN = dyn_cast<PHINode>(I++);) {
1097 auto Inserted = PHISet.insert(PN);
1098 if (!Inserted.second) {
1099 // A duplicate. Replace this PHI with its duplicate.
1100 PN->replaceAllUsesWith(*Inserted.first);
1101 PN->eraseFromParent();
1102 Changed = true;
1103
1104 // The RAUW can change PHIs that we already visited. Start over from the
1105 // beginning.
1106 PHISet.clear();
1107 I = BB->begin();
1108 }
1109 }
1110
1111 return Changed;
1112 }
1113
1114 /// enforceKnownAlignment - If the specified pointer points to an object that
1115 /// we control, modify the object's alignment to PrefAlign. This isn't
1116 /// often possible though. If alignment is important, a more reliable approach
1117 /// is to simply align all global variables and allocation instructions to
1118 /// their preferred alignment from the beginning.
enforceKnownAlignment(Value * V,unsigned Align,unsigned PrefAlign,const DataLayout & DL)1119 static unsigned enforceKnownAlignment(Value *V, unsigned Align,
1120 unsigned PrefAlign,
1121 const DataLayout &DL) {
1122 assert(PrefAlign > Align);
1123
1124 V = V->stripPointerCasts();
1125
1126 if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
1127 // TODO: ideally, computeKnownBits ought to have used
1128 // AllocaInst::getAlignment() in its computation already, making
1129 // the below max redundant. But, as it turns out,
1130 // stripPointerCasts recurses through infinite layers of bitcasts,
1131 // while computeKnownBits is not allowed to traverse more than 6
1132 // levels.
1133 Align = std::max(AI->getAlignment(), Align);
1134 if (PrefAlign <= Align)
1135 return Align;
1136
1137 // If the preferred alignment is greater than the natural stack alignment
1138 // then don't round up. This avoids dynamic stack realignment.
1139 if (DL.exceedsNaturalStackAlignment(PrefAlign))
1140 return Align;
1141 AI->setAlignment(PrefAlign);
1142 return PrefAlign;
1143 }
1144
1145 if (auto *GO = dyn_cast<GlobalObject>(V)) {
1146 // TODO: as above, this shouldn't be necessary.
1147 Align = std::max(GO->getAlignment(), Align);
1148 if (PrefAlign <= Align)
1149 return Align;
1150
1151 // If there is a large requested alignment and we can, bump up the alignment
1152 // of the global. If the memory we set aside for the global may not be the
1153 // memory used by the final program then it is impossible for us to reliably
1154 // enforce the preferred alignment.
1155 if (!GO->canIncreaseAlignment())
1156 return Align;
1157
1158 GO->setAlignment(PrefAlign);
1159 return PrefAlign;
1160 }
1161
1162 return Align;
1163 }
1164
getOrEnforceKnownAlignment(Value * V,unsigned PrefAlign,const DataLayout & DL,const Instruction * CxtI,AssumptionCache * AC,const DominatorTree * DT)1165 unsigned llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
1166 const DataLayout &DL,
1167 const Instruction *CxtI,
1168 AssumptionCache *AC,
1169 const DominatorTree *DT) {
1170 assert(V->getType()->isPointerTy() &&
1171 "getOrEnforceKnownAlignment expects a pointer!");
1172
1173 KnownBits Known = computeKnownBits(V, DL, 0, AC, CxtI, DT);
1174 unsigned TrailZ = Known.countMinTrailingZeros();
1175
1176 // Avoid trouble with ridiculously large TrailZ values, such as
1177 // those computed from a null pointer.
1178 TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
1179
1180 unsigned Align = 1u << std::min(Known.getBitWidth() - 1, TrailZ);
1181
1182 // LLVM doesn't support alignments larger than this currently.
1183 Align = std::min(Align, +Value::MaximumAlignment);
1184
1185 if (PrefAlign > Align)
1186 Align = enforceKnownAlignment(V, Align, PrefAlign, DL);
1187
1188 // We don't need to make any adjustment.
1189 return Align;
1190 }
1191
1192 ///===---------------------------------------------------------------------===//
1193 /// Dbg Intrinsic utilities
1194 ///
1195
1196 /// See if there is a dbg.value intrinsic for DIVar before I.
LdStHasDebugValue(DILocalVariable * DIVar,DIExpression * DIExpr,Instruction * I)1197 static bool LdStHasDebugValue(DILocalVariable *DIVar, DIExpression *DIExpr,
1198 Instruction *I) {
1199 // Since we can't guarantee that the original dbg.declare instrinsic
1200 // is removed by LowerDbgDeclare(), we need to make sure that we are
1201 // not inserting the same dbg.value intrinsic over and over.
1202 BasicBlock::InstListType::iterator PrevI(I);
1203 if (PrevI != I->getParent()->getInstList().begin()) {
1204 --PrevI;
1205 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(PrevI))
1206 if (DVI->getValue() == I->getOperand(0) &&
1207 DVI->getVariable() == DIVar &&
1208 DVI->getExpression() == DIExpr)
1209 return true;
1210 }
1211 return false;
1212 }
1213
1214 /// See if there is a dbg.value intrinsic for DIVar for the PHI node.
PhiHasDebugValue(DILocalVariable * DIVar,DIExpression * DIExpr,PHINode * APN)1215 static bool PhiHasDebugValue(DILocalVariable *DIVar,
1216 DIExpression *DIExpr,
1217 PHINode *APN) {
1218 // Since we can't guarantee that the original dbg.declare instrinsic
1219 // is removed by LowerDbgDeclare(), we need to make sure that we are
1220 // not inserting the same dbg.value intrinsic over and over.
1221 SmallVector<DbgValueInst *, 1> DbgValues;
1222 findDbgValues(DbgValues, APN);
1223 for (auto *DVI : DbgValues) {
1224 assert(DVI->getValue() == APN);
1225 if ((DVI->getVariable() == DIVar) && (DVI->getExpression() == DIExpr))
1226 return true;
1227 }
1228 return false;
1229 }
1230
1231 /// Check if the alloc size of \p ValTy is large enough to cover the variable
1232 /// (or fragment of the variable) described by \p DII.
1233 ///
1234 /// This is primarily intended as a helper for the different
1235 /// ConvertDebugDeclareToDebugValue functions. The dbg.declare/dbg.addr that is
1236 /// converted describes an alloca'd variable, so we need to use the
1237 /// alloc size of the value when doing the comparison. E.g. an i1 value will be
1238 /// identified as covering an n-bit fragment, if the store size of i1 is at
1239 /// least n bits.
valueCoversEntireFragment(Type * ValTy,DbgInfoIntrinsic * DII)1240 static bool valueCoversEntireFragment(Type *ValTy, DbgInfoIntrinsic *DII) {
1241 const DataLayout &DL = DII->getModule()->getDataLayout();
1242 uint64_t ValueSize = DL.getTypeAllocSizeInBits(ValTy);
1243 if (auto FragmentSize = DII->getFragmentSizeInBits())
1244 return ValueSize >= *FragmentSize;
1245 // We can't always calculate the size of the DI variable (e.g. if it is a
1246 // VLA). Try to use the size of the alloca that the dbg intrinsic describes
1247 // intead.
1248 if (DII->isAddressOfVariable())
1249 if (auto *AI = dyn_cast_or_null<AllocaInst>(DII->getVariableLocation()))
1250 if (auto FragmentSize = AI->getAllocationSizeInBits(DL))
1251 return ValueSize >= *FragmentSize;
1252 // Could not determine size of variable. Conservatively return false.
1253 return false;
1254 }
1255
1256 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
1257 /// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic.
ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic * DII,StoreInst * SI,DIBuilder & Builder)1258 void llvm::ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
1259 StoreInst *SI, DIBuilder &Builder) {
1260 assert(DII->isAddressOfVariable());
1261 auto *DIVar = DII->getVariable();
1262 assert(DIVar && "Missing variable");
1263 auto *DIExpr = DII->getExpression();
1264 Value *DV = SI->getOperand(0);
1265
1266 if (!valueCoversEntireFragment(SI->getValueOperand()->getType(), DII)) {
1267 // FIXME: If storing to a part of the variable described by the dbg.declare,
1268 // then we want to insert a dbg.value for the corresponding fragment.
1269 LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: "
1270 << *DII << '\n');
1271 // For now, when there is a store to parts of the variable (but we do not
1272 // know which part) we insert an dbg.value instrinsic to indicate that we
1273 // know nothing about the variable's content.
1274 DV = UndefValue::get(DV->getType());
1275 if (!LdStHasDebugValue(DIVar, DIExpr, SI))
1276 Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, DII->getDebugLoc(),
1277 SI);
1278 return;
1279 }
1280
1281 // If an argument is zero extended then use argument directly. The ZExt
1282 // may be zapped by an optimization pass in future.
1283 Argument *ExtendedArg = nullptr;
1284 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
1285 ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0));
1286 if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
1287 ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0));
1288 if (ExtendedArg) {
1289 // If this DII was already describing only a fragment of a variable, ensure
1290 // that fragment is appropriately narrowed here.
1291 // But if a fragment wasn't used, describe the value as the original
1292 // argument (rather than the zext or sext) so that it remains described even
1293 // if the sext/zext is optimized away. This widens the variable description,
1294 // leaving it up to the consumer to know how the smaller value may be
1295 // represented in a larger register.
1296 if (auto Fragment = DIExpr->getFragmentInfo()) {
1297 unsigned FragmentOffset = Fragment->OffsetInBits;
1298 SmallVector<uint64_t, 3> Ops(DIExpr->elements_begin(),
1299 DIExpr->elements_end() - 3);
1300 Ops.push_back(dwarf::DW_OP_LLVM_fragment);
1301 Ops.push_back(FragmentOffset);
1302 const DataLayout &DL = DII->getModule()->getDataLayout();
1303 Ops.push_back(DL.getTypeSizeInBits(ExtendedArg->getType()));
1304 DIExpr = Builder.createExpression(Ops);
1305 }
1306 DV = ExtendedArg;
1307 }
1308 if (!LdStHasDebugValue(DIVar, DIExpr, SI))
1309 Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, DII->getDebugLoc(),
1310 SI);
1311 }
1312
1313 /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
1314 /// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic.
ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic * DII,LoadInst * LI,DIBuilder & Builder)1315 void llvm::ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
1316 LoadInst *LI, DIBuilder &Builder) {
1317 auto *DIVar = DII->getVariable();
1318 auto *DIExpr = DII->getExpression();
1319 assert(DIVar && "Missing variable");
1320
1321 if (LdStHasDebugValue(DIVar, DIExpr, LI))
1322 return;
1323
1324 if (!valueCoversEntireFragment(LI->getType(), DII)) {
1325 // FIXME: If only referring to a part of the variable described by the
1326 // dbg.declare, then we want to insert a dbg.value for the corresponding
1327 // fragment.
1328 LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: "
1329 << *DII << '\n');
1330 return;
1331 }
1332
1333 // We are now tracking the loaded value instead of the address. In the
1334 // future if multi-location support is added to the IR, it might be
1335 // preferable to keep tracking both the loaded value and the original
1336 // address in case the alloca can not be elided.
1337 Instruction *DbgValue = Builder.insertDbgValueIntrinsic(
1338 LI, DIVar, DIExpr, DII->getDebugLoc(), (Instruction *)nullptr);
1339 DbgValue->insertAfter(LI);
1340 }
1341
1342 /// Inserts a llvm.dbg.value intrinsic after a phi that has an associated
1343 /// llvm.dbg.declare or llvm.dbg.addr intrinsic.
ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic * DII,PHINode * APN,DIBuilder & Builder)1344 void llvm::ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
1345 PHINode *APN, DIBuilder &Builder) {
1346 auto *DIVar = DII->getVariable();
1347 auto *DIExpr = DII->getExpression();
1348 assert(DIVar && "Missing variable");
1349
1350 if (PhiHasDebugValue(DIVar, DIExpr, APN))
1351 return;
1352
1353 if (!valueCoversEntireFragment(APN->getType(), DII)) {
1354 // FIXME: If only referring to a part of the variable described by the
1355 // dbg.declare, then we want to insert a dbg.value for the corresponding
1356 // fragment.
1357 LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: "
1358 << *DII << '\n');
1359 return;
1360 }
1361
1362 BasicBlock *BB = APN->getParent();
1363 auto InsertionPt = BB->getFirstInsertionPt();
1364
1365 // The block may be a catchswitch block, which does not have a valid
1366 // insertion point.
1367 // FIXME: Insert dbg.value markers in the successors when appropriate.
1368 if (InsertionPt != BB->end())
1369 Builder.insertDbgValueIntrinsic(APN, DIVar, DIExpr, DII->getDebugLoc(),
1370 &*InsertionPt);
1371 }
1372
1373 /// Determine whether this alloca is either a VLA or an array.
isArray(AllocaInst * AI)1374 static bool isArray(AllocaInst *AI) {
1375 return AI->isArrayAllocation() ||
1376 AI->getType()->getElementType()->isArrayTy();
1377 }
1378
1379 /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
1380 /// of llvm.dbg.value intrinsics.
LowerDbgDeclare(Function & F)1381 bool llvm::LowerDbgDeclare(Function &F) {
1382 DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false);
1383 SmallVector<DbgDeclareInst *, 4> Dbgs;
1384 for (auto &FI : F)
1385 for (Instruction &BI : FI)
1386 if (auto DDI = dyn_cast<DbgDeclareInst>(&BI))
1387 Dbgs.push_back(DDI);
1388
1389 if (Dbgs.empty())
1390 return false;
1391
1392 for (auto &I : Dbgs) {
1393 DbgDeclareInst *DDI = I;
1394 AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress());
1395 // If this is an alloca for a scalar variable, insert a dbg.value
1396 // at each load and store to the alloca and erase the dbg.declare.
1397 // The dbg.values allow tracking a variable even if it is not
1398 // stored on the stack, while the dbg.declare can only describe
1399 // the stack slot (and at a lexical-scope granularity). Later
1400 // passes will attempt to elide the stack slot.
1401 if (!AI || isArray(AI))
1402 continue;
1403
1404 // A volatile load/store means that the alloca can't be elided anyway.
1405 if (llvm::any_of(AI->users(), [](User *U) -> bool {
1406 if (LoadInst *LI = dyn_cast<LoadInst>(U))
1407 return LI->isVolatile();
1408 if (StoreInst *SI = dyn_cast<StoreInst>(U))
1409 return SI->isVolatile();
1410 return false;
1411 }))
1412 continue;
1413
1414 for (auto &AIUse : AI->uses()) {
1415 User *U = AIUse.getUser();
1416 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1417 if (AIUse.getOperandNo() == 1)
1418 ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
1419 } else if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1420 ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
1421 } else if (CallInst *CI = dyn_cast<CallInst>(U)) {
1422 // This is a call by-value or some other instruction that takes a
1423 // pointer to the variable. Insert a *value* intrinsic that describes
1424 // the variable by dereferencing the alloca.
1425 auto *DerefExpr =
1426 DIExpression::append(DDI->getExpression(), dwarf::DW_OP_deref);
1427 DIB.insertDbgValueIntrinsic(AI, DDI->getVariable(), DerefExpr,
1428 DDI->getDebugLoc(), CI);
1429 }
1430 }
1431 DDI->eraseFromParent();
1432 }
1433 return true;
1434 }
1435
1436 /// Propagate dbg.value intrinsics through the newly inserted PHIs.
insertDebugValuesForPHIs(BasicBlock * BB,SmallVectorImpl<PHINode * > & InsertedPHIs)1437 void llvm::insertDebugValuesForPHIs(BasicBlock *BB,
1438 SmallVectorImpl<PHINode *> &InsertedPHIs) {
1439 assert(BB && "No BasicBlock to clone dbg.value(s) from.");
1440 if (InsertedPHIs.size() == 0)
1441 return;
1442
1443 // Map existing PHI nodes to their dbg.values.
1444 ValueToValueMapTy DbgValueMap;
1445 for (auto &I : *BB) {
1446 if (auto DbgII = dyn_cast<DbgInfoIntrinsic>(&I)) {
1447 if (auto *Loc = dyn_cast_or_null<PHINode>(DbgII->getVariableLocation()))
1448 DbgValueMap.insert({Loc, DbgII});
1449 }
1450 }
1451 if (DbgValueMap.size() == 0)
1452 return;
1453
1454 // Then iterate through the new PHIs and look to see if they use one of the
1455 // previously mapped PHIs. If so, insert a new dbg.value intrinsic that will
1456 // propagate the info through the new PHI.
1457 LLVMContext &C = BB->getContext();
1458 for (auto PHI : InsertedPHIs) {
1459 BasicBlock *Parent = PHI->getParent();
1460 // Avoid inserting an intrinsic into an EH block.
1461 if (Parent->getFirstNonPHI()->isEHPad())
1462 continue;
1463 auto PhiMAV = MetadataAsValue::get(C, ValueAsMetadata::get(PHI));
1464 for (auto VI : PHI->operand_values()) {
1465 auto V = DbgValueMap.find(VI);
1466 if (V != DbgValueMap.end()) {
1467 auto *DbgII = cast<DbgInfoIntrinsic>(V->second);
1468 Instruction *NewDbgII = DbgII->clone();
1469 NewDbgII->setOperand(0, PhiMAV);
1470 auto InsertionPt = Parent->getFirstInsertionPt();
1471 assert(InsertionPt != Parent->end() && "Ill-formed basic block");
1472 NewDbgII->insertBefore(&*InsertionPt);
1473 }
1474 }
1475 }
1476 }
1477
1478 /// Finds all intrinsics declaring local variables as living in the memory that
1479 /// 'V' points to. This may include a mix of dbg.declare and
1480 /// dbg.addr intrinsics.
FindDbgAddrUses(Value * V)1481 TinyPtrVector<DbgInfoIntrinsic *> llvm::FindDbgAddrUses(Value *V) {
1482 // This function is hot. Check whether the value has any metadata to avoid a
1483 // DenseMap lookup.
1484 if (!V->isUsedByMetadata())
1485 return {};
1486 auto *L = LocalAsMetadata::getIfExists(V);
1487 if (!L)
1488 return {};
1489 auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L);
1490 if (!MDV)
1491 return {};
1492
1493 TinyPtrVector<DbgInfoIntrinsic *> Declares;
1494 for (User *U : MDV->users()) {
1495 if (auto *DII = dyn_cast<DbgInfoIntrinsic>(U))
1496 if (DII->isAddressOfVariable())
1497 Declares.push_back(DII);
1498 }
1499
1500 return Declares;
1501 }
1502
findDbgValues(SmallVectorImpl<DbgValueInst * > & DbgValues,Value * V)1503 void llvm::findDbgValues(SmallVectorImpl<DbgValueInst *> &DbgValues, Value *V) {
1504 // This function is hot. Check whether the value has any metadata to avoid a
1505 // DenseMap lookup.
1506 if (!V->isUsedByMetadata())
1507 return;
1508 if (auto *L = LocalAsMetadata::getIfExists(V))
1509 if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
1510 for (User *U : MDV->users())
1511 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(U))
1512 DbgValues.push_back(DVI);
1513 }
1514
findDbgUsers(SmallVectorImpl<DbgInfoIntrinsic * > & DbgUsers,Value * V)1515 void llvm::findDbgUsers(SmallVectorImpl<DbgInfoIntrinsic *> &DbgUsers,
1516 Value *V) {
1517 // This function is hot. Check whether the value has any metadata to avoid a
1518 // DenseMap lookup.
1519 if (!V->isUsedByMetadata())
1520 return;
1521 if (auto *L = LocalAsMetadata::getIfExists(V))
1522 if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
1523 for (User *U : MDV->users())
1524 if (DbgInfoIntrinsic *DII = dyn_cast<DbgInfoIntrinsic>(U))
1525 DbgUsers.push_back(DII);
1526 }
1527
replaceDbgDeclare(Value * Address,Value * NewAddress,Instruction * InsertBefore,DIBuilder & Builder,bool DerefBefore,int Offset,bool DerefAfter)1528 bool llvm::replaceDbgDeclare(Value *Address, Value *NewAddress,
1529 Instruction *InsertBefore, DIBuilder &Builder,
1530 bool DerefBefore, int Offset, bool DerefAfter) {
1531 auto DbgAddrs = FindDbgAddrUses(Address);
1532 for (DbgInfoIntrinsic *DII : DbgAddrs) {
1533 DebugLoc Loc = DII->getDebugLoc();
1534 auto *DIVar = DII->getVariable();
1535 auto *DIExpr = DII->getExpression();
1536 assert(DIVar && "Missing variable");
1537 DIExpr = DIExpression::prepend(DIExpr, DerefBefore, Offset, DerefAfter);
1538 // Insert llvm.dbg.declare immediately before InsertBefore, and remove old
1539 // llvm.dbg.declare.
1540 Builder.insertDeclare(NewAddress, DIVar, DIExpr, Loc, InsertBefore);
1541 if (DII == InsertBefore)
1542 InsertBefore = InsertBefore->getNextNode();
1543 DII->eraseFromParent();
1544 }
1545 return !DbgAddrs.empty();
1546 }
1547
replaceDbgDeclareForAlloca(AllocaInst * AI,Value * NewAllocaAddress,DIBuilder & Builder,bool DerefBefore,int Offset,bool DerefAfter)1548 bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
1549 DIBuilder &Builder, bool DerefBefore,
1550 int Offset, bool DerefAfter) {
1551 return replaceDbgDeclare(AI, NewAllocaAddress, AI->getNextNode(), Builder,
1552 DerefBefore, Offset, DerefAfter);
1553 }
1554
replaceOneDbgValueForAlloca(DbgValueInst * DVI,Value * NewAddress,DIBuilder & Builder,int Offset)1555 static void replaceOneDbgValueForAlloca(DbgValueInst *DVI, Value *NewAddress,
1556 DIBuilder &Builder, int Offset) {
1557 DebugLoc Loc = DVI->getDebugLoc();
1558 auto *DIVar = DVI->getVariable();
1559 auto *DIExpr = DVI->getExpression();
1560 assert(DIVar && "Missing variable");
1561
1562 // This is an alloca-based llvm.dbg.value. The first thing it should do with
1563 // the alloca pointer is dereference it. Otherwise we don't know how to handle
1564 // it and give up.
1565 if (!DIExpr || DIExpr->getNumElements() < 1 ||
1566 DIExpr->getElement(0) != dwarf::DW_OP_deref)
1567 return;
1568
1569 // Insert the offset immediately after the first deref.
1570 // We could just change the offset argument of dbg.value, but it's unsigned...
1571 if (Offset) {
1572 SmallVector<uint64_t, 4> Ops;
1573 Ops.push_back(dwarf::DW_OP_deref);
1574 DIExpression::appendOffset(Ops, Offset);
1575 Ops.append(DIExpr->elements_begin() + 1, DIExpr->elements_end());
1576 DIExpr = Builder.createExpression(Ops);
1577 }
1578
1579 Builder.insertDbgValueIntrinsic(NewAddress, DIVar, DIExpr, Loc, DVI);
1580 DVI->eraseFromParent();
1581 }
1582
replaceDbgValueForAlloca(AllocaInst * AI,Value * NewAllocaAddress,DIBuilder & Builder,int Offset)1583 void llvm::replaceDbgValueForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
1584 DIBuilder &Builder, int Offset) {
1585 if (auto *L = LocalAsMetadata::getIfExists(AI))
1586 if (auto *MDV = MetadataAsValue::getIfExists(AI->getContext(), L))
1587 for (auto UI = MDV->use_begin(), UE = MDV->use_end(); UI != UE;) {
1588 Use &U = *UI++;
1589 if (auto *DVI = dyn_cast<DbgValueInst>(U.getUser()))
1590 replaceOneDbgValueForAlloca(DVI, NewAllocaAddress, Builder, Offset);
1591 }
1592 }
1593
1594 /// Wrap \p V in a ValueAsMetadata instance.
wrapValueInMetadata(LLVMContext & C,Value * V)1595 static MetadataAsValue *wrapValueInMetadata(LLVMContext &C, Value *V) {
1596 return MetadataAsValue::get(C, ValueAsMetadata::get(V));
1597 }
1598
salvageDebugInfo(Instruction & I)1599 bool llvm::salvageDebugInfo(Instruction &I) {
1600 SmallVector<DbgInfoIntrinsic *, 1> DbgUsers;
1601 findDbgUsers(DbgUsers, &I);
1602 if (DbgUsers.empty())
1603 return false;
1604
1605 auto &M = *I.getModule();
1606 auto &DL = M.getDataLayout();
1607 auto &Ctx = I.getContext();
1608 auto wrapMD = [&](Value *V) { return wrapValueInMetadata(Ctx, V); };
1609
1610 auto doSalvage = [&](DbgInfoIntrinsic *DII, SmallVectorImpl<uint64_t> &Ops) {
1611 auto *DIExpr = DII->getExpression();
1612 if (!Ops.empty()) {
1613 // Do not add DW_OP_stack_value for DbgDeclare and DbgAddr, because they
1614 // are implicitly pointing out the value as a DWARF memory location
1615 // description.
1616 bool WithStackValue = isa<DbgValueInst>(DII);
1617 DIExpr = DIExpression::prependOpcodes(DIExpr, Ops, WithStackValue);
1618 }
1619 DII->setOperand(0, wrapMD(I.getOperand(0)));
1620 DII->setOperand(2, MetadataAsValue::get(Ctx, DIExpr));
1621 LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n');
1622 };
1623
1624 auto applyOffset = [&](DbgInfoIntrinsic *DII, uint64_t Offset) {
1625 SmallVector<uint64_t, 8> Ops;
1626 DIExpression::appendOffset(Ops, Offset);
1627 doSalvage(DII, Ops);
1628 };
1629
1630 auto applyOps = [&](DbgInfoIntrinsic *DII,
1631 std::initializer_list<uint64_t> Opcodes) {
1632 SmallVector<uint64_t, 8> Ops(Opcodes);
1633 doSalvage(DII, Ops);
1634 };
1635
1636 if (auto *CI = dyn_cast<CastInst>(&I)) {
1637 if (!CI->isNoopCast(DL))
1638 return false;
1639
1640 // No-op casts are irrelevant for debug info.
1641 MetadataAsValue *CastSrc = wrapMD(I.getOperand(0));
1642 for (auto *DII : DbgUsers) {
1643 DII->setOperand(0, CastSrc);
1644 LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n');
1645 }
1646 return true;
1647 } else if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) {
1648 unsigned BitWidth =
1649 M.getDataLayout().getIndexSizeInBits(GEP->getPointerAddressSpace());
1650 // Rewrite a constant GEP into a DIExpression. Since we are performing
1651 // arithmetic to compute the variable's *value* in the DIExpression, we
1652 // need to mark the expression with a DW_OP_stack_value.
1653 APInt Offset(BitWidth, 0);
1654 if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset))
1655 for (auto *DII : DbgUsers)
1656 applyOffset(DII, Offset.getSExtValue());
1657 return true;
1658 } else if (auto *BI = dyn_cast<BinaryOperator>(&I)) {
1659 // Rewrite binary operations with constant integer operands.
1660 auto *ConstInt = dyn_cast<ConstantInt>(I.getOperand(1));
1661 if (!ConstInt || ConstInt->getBitWidth() > 64)
1662 return false;
1663
1664 uint64_t Val = ConstInt->getSExtValue();
1665 for (auto *DII : DbgUsers) {
1666 switch (BI->getOpcode()) {
1667 case Instruction::Add:
1668 applyOffset(DII, Val);
1669 break;
1670 case Instruction::Sub:
1671 applyOffset(DII, -int64_t(Val));
1672 break;
1673 case Instruction::Mul:
1674 applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_mul});
1675 break;
1676 case Instruction::SDiv:
1677 applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_div});
1678 break;
1679 case Instruction::SRem:
1680 applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_mod});
1681 break;
1682 case Instruction::Or:
1683 applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_or});
1684 break;
1685 case Instruction::And:
1686 applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_and});
1687 break;
1688 case Instruction::Xor:
1689 applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_xor});
1690 break;
1691 case Instruction::Shl:
1692 applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_shl});
1693 break;
1694 case Instruction::LShr:
1695 applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_shr});
1696 break;
1697 case Instruction::AShr:
1698 applyOps(DII, {dwarf::DW_OP_constu, Val, dwarf::DW_OP_shra});
1699 break;
1700 default:
1701 // TODO: Salvage constants from each kind of binop we know about.
1702 return false;
1703 }
1704 }
1705 return true;
1706 } else if (isa<LoadInst>(&I)) {
1707 MetadataAsValue *AddrMD = wrapMD(I.getOperand(0));
1708 for (auto *DII : DbgUsers) {
1709 // Rewrite the load into DW_OP_deref.
1710 auto *DIExpr = DII->getExpression();
1711 DIExpr = DIExpression::prepend(DIExpr, DIExpression::WithDeref);
1712 DII->setOperand(0, AddrMD);
1713 DII->setOperand(2, MetadataAsValue::get(Ctx, DIExpr));
1714 LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n');
1715 }
1716 return true;
1717 }
1718 return false;
1719 }
1720
1721 /// A replacement for a dbg.value expression.
1722 using DbgValReplacement = Optional<DIExpression *>;
1723
1724 /// Point debug users of \p From to \p To using exprs given by \p RewriteExpr,
1725 /// possibly moving/deleting users to prevent use-before-def. Returns true if
1726 /// changes are made.
rewriteDebugUsers(Instruction & From,Value & To,Instruction & DomPoint,DominatorTree & DT,function_ref<DbgValReplacement (DbgInfoIntrinsic & DII)> RewriteExpr)1727 static bool rewriteDebugUsers(
1728 Instruction &From, Value &To, Instruction &DomPoint, DominatorTree &DT,
1729 function_ref<DbgValReplacement(DbgInfoIntrinsic &DII)> RewriteExpr) {
1730 // Find debug users of From.
1731 SmallVector<DbgInfoIntrinsic *, 1> Users;
1732 findDbgUsers(Users, &From);
1733 if (Users.empty())
1734 return false;
1735
1736 // Prevent use-before-def of To.
1737 bool Changed = false;
1738 SmallPtrSet<DbgInfoIntrinsic *, 1> DeleteOrSalvage;
1739 if (isa<Instruction>(&To)) {
1740 bool DomPointAfterFrom = From.getNextNonDebugInstruction() == &DomPoint;
1741
1742 for (auto *DII : Users) {
1743 // It's common to see a debug user between From and DomPoint. Move it
1744 // after DomPoint to preserve the variable update without any reordering.
1745 if (DomPointAfterFrom && DII->getNextNonDebugInstruction() == &DomPoint) {
1746 LLVM_DEBUG(dbgs() << "MOVE: " << *DII << '\n');
1747 DII->moveAfter(&DomPoint);
1748 Changed = true;
1749
1750 // Users which otherwise aren't dominated by the replacement value must
1751 // be salvaged or deleted.
1752 } else if (!DT.dominates(&DomPoint, DII)) {
1753 DeleteOrSalvage.insert(DII);
1754 }
1755 }
1756 }
1757
1758 // Update debug users without use-before-def risk.
1759 for (auto *DII : Users) {
1760 if (DeleteOrSalvage.count(DII))
1761 continue;
1762
1763 LLVMContext &Ctx = DII->getContext();
1764 DbgValReplacement DVR = RewriteExpr(*DII);
1765 if (!DVR)
1766 continue;
1767
1768 DII->setOperand(0, wrapValueInMetadata(Ctx, &To));
1769 DII->setOperand(2, MetadataAsValue::get(Ctx, *DVR));
1770 LLVM_DEBUG(dbgs() << "REWRITE: " << *DII << '\n');
1771 Changed = true;
1772 }
1773
1774 if (!DeleteOrSalvage.empty()) {
1775 // Try to salvage the remaining debug users.
1776 Changed |= salvageDebugInfo(From);
1777
1778 // Delete the debug users which weren't salvaged.
1779 for (auto *DII : DeleteOrSalvage) {
1780 if (DII->getVariableLocation() == &From) {
1781 LLVM_DEBUG(dbgs() << "Erased UseBeforeDef: " << *DII << '\n');
1782 DII->eraseFromParent();
1783 Changed = true;
1784 }
1785 }
1786 }
1787
1788 return Changed;
1789 }
1790
1791 /// Check if a bitcast between a value of type \p FromTy to type \p ToTy would
1792 /// losslessly preserve the bits and semantics of the value. This predicate is
1793 /// symmetric, i.e swapping \p FromTy and \p ToTy should give the same result.
1794 ///
1795 /// Note that Type::canLosslesslyBitCastTo is not suitable here because it
1796 /// allows semantically unequivalent bitcasts, such as <2 x i64> -> <4 x i32>,
1797 /// and also does not allow lossless pointer <-> integer conversions.
isBitCastSemanticsPreserving(const DataLayout & DL,Type * FromTy,Type * ToTy)1798 static bool isBitCastSemanticsPreserving(const DataLayout &DL, Type *FromTy,
1799 Type *ToTy) {
1800 // Trivially compatible types.
1801 if (FromTy == ToTy)
1802 return true;
1803
1804 // Handle compatible pointer <-> integer conversions.
1805 if (FromTy->isIntOrPtrTy() && ToTy->isIntOrPtrTy()) {
1806 bool SameSize = DL.getTypeSizeInBits(FromTy) == DL.getTypeSizeInBits(ToTy);
1807 bool LosslessConversion = !DL.isNonIntegralPointerType(FromTy) &&
1808 !DL.isNonIntegralPointerType(ToTy);
1809 return SameSize && LosslessConversion;
1810 }
1811
1812 // TODO: This is not exhaustive.
1813 return false;
1814 }
1815
replaceAllDbgUsesWith(Instruction & From,Value & To,Instruction & DomPoint,DominatorTree & DT)1816 bool llvm::replaceAllDbgUsesWith(Instruction &From, Value &To,
1817 Instruction &DomPoint, DominatorTree &DT) {
1818 // Exit early if From has no debug users.
1819 if (!From.isUsedByMetadata())
1820 return false;
1821
1822 assert(&From != &To && "Can't replace something with itself");
1823
1824 Type *FromTy = From.getType();
1825 Type *ToTy = To.getType();
1826
1827 auto Identity = [&](DbgInfoIntrinsic &DII) -> DbgValReplacement {
1828 return DII.getExpression();
1829 };
1830
1831 // Handle no-op conversions.
1832 Module &M = *From.getModule();
1833 const DataLayout &DL = M.getDataLayout();
1834 if (isBitCastSemanticsPreserving(DL, FromTy, ToTy))
1835 return rewriteDebugUsers(From, To, DomPoint, DT, Identity);
1836
1837 // Handle integer-to-integer widening and narrowing.
1838 // FIXME: Use DW_OP_convert when it's available everywhere.
1839 if (FromTy->isIntegerTy() && ToTy->isIntegerTy()) {
1840 uint64_t FromBits = FromTy->getPrimitiveSizeInBits();
1841 uint64_t ToBits = ToTy->getPrimitiveSizeInBits();
1842 assert(FromBits != ToBits && "Unexpected no-op conversion");
1843
1844 // When the width of the result grows, assume that a debugger will only
1845 // access the low `FromBits` bits when inspecting the source variable.
1846 if (FromBits < ToBits)
1847 return rewriteDebugUsers(From, To, DomPoint, DT, Identity);
1848
1849 // The width of the result has shrunk. Use sign/zero extension to describe
1850 // the source variable's high bits.
1851 auto SignOrZeroExt = [&](DbgInfoIntrinsic &DII) -> DbgValReplacement {
1852 DILocalVariable *Var = DII.getVariable();
1853
1854 // Without knowing signedness, sign/zero extension isn't possible.
1855 auto Signedness = Var->getSignedness();
1856 if (!Signedness)
1857 return None;
1858
1859 bool Signed = *Signedness == DIBasicType::Signedness::Signed;
1860
1861 if (!Signed) {
1862 // In the unsigned case, assume that a debugger will initialize the
1863 // high bits to 0 and do a no-op conversion.
1864 return Identity(DII);
1865 } else {
1866 // In the signed case, the high bits are given by sign extension, i.e:
1867 // (To >> (ToBits - 1)) * ((2 ^ FromBits) - 1)
1868 // Calculate the high bits and OR them together with the low bits.
1869 SmallVector<uint64_t, 8> Ops({dwarf::DW_OP_dup, dwarf::DW_OP_constu,
1870 (ToBits - 1), dwarf::DW_OP_shr,
1871 dwarf::DW_OP_lit0, dwarf::DW_OP_not,
1872 dwarf::DW_OP_mul, dwarf::DW_OP_or});
1873 return DIExpression::appendToStack(DII.getExpression(), Ops);
1874 }
1875 };
1876 return rewriteDebugUsers(From, To, DomPoint, DT, SignOrZeroExt);
1877 }
1878
1879 // TODO: Floating-point conversions, vectors.
1880 return false;
1881 }
1882
removeAllNonTerminatorAndEHPadInstructions(BasicBlock * BB)1883 unsigned llvm::removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB) {
1884 unsigned NumDeadInst = 0;
1885 // Delete the instructions backwards, as it has a reduced likelihood of
1886 // having to update as many def-use and use-def chains.
1887 Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
1888 while (EndInst != &BB->front()) {
1889 // Delete the next to last instruction.
1890 Instruction *Inst = &*--EndInst->getIterator();
1891 if (!Inst->use_empty() && !Inst->getType()->isTokenTy())
1892 Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
1893 if (Inst->isEHPad() || Inst->getType()->isTokenTy()) {
1894 EndInst = Inst;
1895 continue;
1896 }
1897 if (!isa<DbgInfoIntrinsic>(Inst))
1898 ++NumDeadInst;
1899 Inst->eraseFromParent();
1900 }
1901 return NumDeadInst;
1902 }
1903
changeToUnreachable(Instruction * I,bool UseLLVMTrap,bool PreserveLCSSA,DeferredDominance * DDT)1904 unsigned llvm::changeToUnreachable(Instruction *I, bool UseLLVMTrap,
1905 bool PreserveLCSSA, DeferredDominance *DDT) {
1906 BasicBlock *BB = I->getParent();
1907 std::vector <DominatorTree::UpdateType> Updates;
1908
1909 // Loop over all of the successors, removing BB's entry from any PHI
1910 // nodes.
1911 if (DDT)
1912 Updates.reserve(BB->getTerminator()->getNumSuccessors());
1913 for (BasicBlock *Successor : successors(BB)) {
1914 Successor->removePredecessor(BB, PreserveLCSSA);
1915 if (DDT)
1916 Updates.push_back({DominatorTree::Delete, BB, Successor});
1917 }
1918 // Insert a call to llvm.trap right before this. This turns the undefined
1919 // behavior into a hard fail instead of falling through into random code.
1920 if (UseLLVMTrap) {
1921 Function *TrapFn =
1922 Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
1923 CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
1924 CallTrap->setDebugLoc(I->getDebugLoc());
1925 }
1926 new UnreachableInst(I->getContext(), I);
1927
1928 // All instructions after this are dead.
1929 unsigned NumInstrsRemoved = 0;
1930 BasicBlock::iterator BBI = I->getIterator(), BBE = BB->end();
1931 while (BBI != BBE) {
1932 if (!BBI->use_empty())
1933 BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
1934 BB->getInstList().erase(BBI++);
1935 ++NumInstrsRemoved;
1936 }
1937 if (DDT)
1938 DDT->applyUpdates(Updates);
1939 return NumInstrsRemoved;
1940 }
1941
1942 /// changeToCall - Convert the specified invoke into a normal call.
changeToCall(InvokeInst * II,DeferredDominance * DDT=nullptr)1943 static void changeToCall(InvokeInst *II, DeferredDominance *DDT = nullptr) {
1944 SmallVector<Value*, 8> Args(II->arg_begin(), II->arg_end());
1945 SmallVector<OperandBundleDef, 1> OpBundles;
1946 II->getOperandBundlesAsDefs(OpBundles);
1947 CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, OpBundles,
1948 "", II);
1949 NewCall->takeName(II);
1950 NewCall->setCallingConv(II->getCallingConv());
1951 NewCall->setAttributes(II->getAttributes());
1952 NewCall->setDebugLoc(II->getDebugLoc());
1953 II->replaceAllUsesWith(NewCall);
1954
1955 // Follow the call by a branch to the normal destination.
1956 BasicBlock *NormalDestBB = II->getNormalDest();
1957 BranchInst::Create(NormalDestBB, II);
1958
1959 // Update PHI nodes in the unwind destination
1960 BasicBlock *BB = II->getParent();
1961 BasicBlock *UnwindDestBB = II->getUnwindDest();
1962 UnwindDestBB->removePredecessor(BB);
1963 II->eraseFromParent();
1964 if (DDT)
1965 DDT->deleteEdge(BB, UnwindDestBB);
1966 }
1967
changeToInvokeAndSplitBasicBlock(CallInst * CI,BasicBlock * UnwindEdge)1968 BasicBlock *llvm::changeToInvokeAndSplitBasicBlock(CallInst *CI,
1969 BasicBlock *UnwindEdge) {
1970 BasicBlock *BB = CI->getParent();
1971
1972 // Convert this function call into an invoke instruction. First, split the
1973 // basic block.
1974 BasicBlock *Split =
1975 BB->splitBasicBlock(CI->getIterator(), CI->getName() + ".noexc");
1976
1977 // Delete the unconditional branch inserted by splitBasicBlock
1978 BB->getInstList().pop_back();
1979
1980 // Create the new invoke instruction.
1981 SmallVector<Value *, 8> InvokeArgs(CI->arg_begin(), CI->arg_end());
1982 SmallVector<OperandBundleDef, 1> OpBundles;
1983
1984 CI->getOperandBundlesAsDefs(OpBundles);
1985
1986 // Note: we're round tripping operand bundles through memory here, and that
1987 // can potentially be avoided with a cleverer API design that we do not have
1988 // as of this time.
1989
1990 InvokeInst *II = InvokeInst::Create(CI->getCalledValue(), Split, UnwindEdge,
1991 InvokeArgs, OpBundles, CI->getName(), BB);
1992 II->setDebugLoc(CI->getDebugLoc());
1993 II->setCallingConv(CI->getCallingConv());
1994 II->setAttributes(CI->getAttributes());
1995
1996 // Make sure that anything using the call now uses the invoke! This also
1997 // updates the CallGraph if present, because it uses a WeakTrackingVH.
1998 CI->replaceAllUsesWith(II);
1999
2000 // Delete the original call
2001 Split->getInstList().pop_front();
2002 return Split;
2003 }
2004
markAliveBlocks(Function & F,SmallPtrSetImpl<BasicBlock * > & Reachable,DeferredDominance * DDT=nullptr)2005 static bool markAliveBlocks(Function &F,
2006 SmallPtrSetImpl<BasicBlock*> &Reachable,
2007 DeferredDominance *DDT = nullptr) {
2008 SmallVector<BasicBlock*, 128> Worklist;
2009 BasicBlock *BB = &F.front();
2010 Worklist.push_back(BB);
2011 Reachable.insert(BB);
2012 bool Changed = false;
2013 do {
2014 BB = Worklist.pop_back_val();
2015
2016 // Do a quick scan of the basic block, turning any obviously unreachable
2017 // instructions into LLVM unreachable insts. The instruction combining pass
2018 // canonicalizes unreachable insts into stores to null or undef.
2019 for (Instruction &I : *BB) {
2020 if (auto *CI = dyn_cast<CallInst>(&I)) {
2021 Value *Callee = CI->getCalledValue();
2022 // Handle intrinsic calls.
2023 if (Function *F = dyn_cast<Function>(Callee)) {
2024 auto IntrinsicID = F->getIntrinsicID();
2025 // Assumptions that are known to be false are equivalent to
2026 // unreachable. Also, if the condition is undefined, then we make the
2027 // choice most beneficial to the optimizer, and choose that to also be
2028 // unreachable.
2029 if (IntrinsicID == Intrinsic::assume) {
2030 if (match(CI->getArgOperand(0), m_CombineOr(m_Zero(), m_Undef()))) {
2031 // Don't insert a call to llvm.trap right before the unreachable.
2032 changeToUnreachable(CI, false, false, DDT);
2033 Changed = true;
2034 break;
2035 }
2036 } else if (IntrinsicID == Intrinsic::experimental_guard) {
2037 // A call to the guard intrinsic bails out of the current
2038 // compilation unit if the predicate passed to it is false. If the
2039 // predicate is a constant false, then we know the guard will bail
2040 // out of the current compile unconditionally, so all code following
2041 // it is dead.
2042 //
2043 // Note: unlike in llvm.assume, it is not "obviously profitable" for
2044 // guards to treat `undef` as `false` since a guard on `undef` can
2045 // still be useful for widening.
2046 if (match(CI->getArgOperand(0), m_Zero()))
2047 if (!isa<UnreachableInst>(CI->getNextNode())) {
2048 changeToUnreachable(CI->getNextNode(), /*UseLLVMTrap=*/false,
2049 false, DDT);
2050 Changed = true;
2051 break;
2052 }
2053 }
2054 } else if ((isa<ConstantPointerNull>(Callee) &&
2055 !NullPointerIsDefined(CI->getFunction())) ||
2056 isa<UndefValue>(Callee)) {
2057 changeToUnreachable(CI, /*UseLLVMTrap=*/false, false, DDT);
2058 Changed = true;
2059 break;
2060 }
2061 if (CI->doesNotReturn()) {
2062 // If we found a call to a no-return function, insert an unreachable
2063 // instruction after it. Make sure there isn't *already* one there
2064 // though.
2065 if (!isa<UnreachableInst>(CI->getNextNode())) {
2066 // Don't insert a call to llvm.trap right before the unreachable.
2067 changeToUnreachable(CI->getNextNode(), false, false, DDT);
2068 Changed = true;
2069 }
2070 break;
2071 }
2072 } else if (auto *SI = dyn_cast<StoreInst>(&I)) {
2073 // Store to undef and store to null are undefined and used to signal
2074 // that they should be changed to unreachable by passes that can't
2075 // modify the CFG.
2076
2077 // Don't touch volatile stores.
2078 if (SI->isVolatile()) continue;
2079
2080 Value *Ptr = SI->getOperand(1);
2081
2082 if (isa<UndefValue>(Ptr) ||
2083 (isa<ConstantPointerNull>(Ptr) &&
2084 !NullPointerIsDefined(SI->getFunction(),
2085 SI->getPointerAddressSpace()))) {
2086 changeToUnreachable(SI, true, false, DDT);
2087 Changed = true;
2088 break;
2089 }
2090 }
2091 }
2092
2093 TerminatorInst *Terminator = BB->getTerminator();
2094 if (auto *II = dyn_cast<InvokeInst>(Terminator)) {
2095 // Turn invokes that call 'nounwind' functions into ordinary calls.
2096 Value *Callee = II->getCalledValue();
2097 if ((isa<ConstantPointerNull>(Callee) &&
2098 !NullPointerIsDefined(BB->getParent())) ||
2099 isa<UndefValue>(Callee)) {
2100 changeToUnreachable(II, true, false, DDT);
2101 Changed = true;
2102 } else if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(&F)) {
2103 if (II->use_empty() && II->onlyReadsMemory()) {
2104 // jump to the normal destination branch.
2105 BasicBlock *NormalDestBB = II->getNormalDest();
2106 BasicBlock *UnwindDestBB = II->getUnwindDest();
2107 BranchInst::Create(NormalDestBB, II);
2108 UnwindDestBB->removePredecessor(II->getParent());
2109 II->eraseFromParent();
2110 if (DDT)
2111 DDT->deleteEdge(BB, UnwindDestBB);
2112 } else
2113 changeToCall(II, DDT);
2114 Changed = true;
2115 }
2116 } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(Terminator)) {
2117 // Remove catchpads which cannot be reached.
2118 struct CatchPadDenseMapInfo {
2119 static CatchPadInst *getEmptyKey() {
2120 return DenseMapInfo<CatchPadInst *>::getEmptyKey();
2121 }
2122
2123 static CatchPadInst *getTombstoneKey() {
2124 return DenseMapInfo<CatchPadInst *>::getTombstoneKey();
2125 }
2126
2127 static unsigned getHashValue(CatchPadInst *CatchPad) {
2128 return static_cast<unsigned>(hash_combine_range(
2129 CatchPad->value_op_begin(), CatchPad->value_op_end()));
2130 }
2131
2132 static bool isEqual(CatchPadInst *LHS, CatchPadInst *RHS) {
2133 if (LHS == getEmptyKey() || LHS == getTombstoneKey() ||
2134 RHS == getEmptyKey() || RHS == getTombstoneKey())
2135 return LHS == RHS;
2136 return LHS->isIdenticalTo(RHS);
2137 }
2138 };
2139
2140 // Set of unique CatchPads.
2141 SmallDenseMap<CatchPadInst *, detail::DenseSetEmpty, 4,
2142 CatchPadDenseMapInfo, detail::DenseSetPair<CatchPadInst *>>
2143 HandlerSet;
2144 detail::DenseSetEmpty Empty;
2145 for (CatchSwitchInst::handler_iterator I = CatchSwitch->handler_begin(),
2146 E = CatchSwitch->handler_end();
2147 I != E; ++I) {
2148 BasicBlock *HandlerBB = *I;
2149 auto *CatchPad = cast<CatchPadInst>(HandlerBB->getFirstNonPHI());
2150 if (!HandlerSet.insert({CatchPad, Empty}).second) {
2151 CatchSwitch->removeHandler(I);
2152 --I;
2153 --E;
2154 Changed = true;
2155 }
2156 }
2157 }
2158
2159 Changed |= ConstantFoldTerminator(BB, true, nullptr, DDT);
2160 for (BasicBlock *Successor : successors(BB))
2161 if (Reachable.insert(Successor).second)
2162 Worklist.push_back(Successor);
2163 } while (!Worklist.empty());
2164 return Changed;
2165 }
2166
removeUnwindEdge(BasicBlock * BB,DeferredDominance * DDT)2167 void llvm::removeUnwindEdge(BasicBlock *BB, DeferredDominance *DDT) {
2168 TerminatorInst *TI = BB->getTerminator();
2169
2170 if (auto *II = dyn_cast<InvokeInst>(TI)) {
2171 changeToCall(II, DDT);
2172 return;
2173 }
2174
2175 TerminatorInst *NewTI;
2176 BasicBlock *UnwindDest;
2177
2178 if (auto *CRI = dyn_cast<CleanupReturnInst>(TI)) {
2179 NewTI = CleanupReturnInst::Create(CRI->getCleanupPad(), nullptr, CRI);
2180 UnwindDest = CRI->getUnwindDest();
2181 } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(TI)) {
2182 auto *NewCatchSwitch = CatchSwitchInst::Create(
2183 CatchSwitch->getParentPad(), nullptr, CatchSwitch->getNumHandlers(),
2184 CatchSwitch->getName(), CatchSwitch);
2185 for (BasicBlock *PadBB : CatchSwitch->handlers())
2186 NewCatchSwitch->addHandler(PadBB);
2187
2188 NewTI = NewCatchSwitch;
2189 UnwindDest = CatchSwitch->getUnwindDest();
2190 } else {
2191 llvm_unreachable("Could not find unwind successor");
2192 }
2193
2194 NewTI->takeName(TI);
2195 NewTI->setDebugLoc(TI->getDebugLoc());
2196 UnwindDest->removePredecessor(BB);
2197 TI->replaceAllUsesWith(NewTI);
2198 TI->eraseFromParent();
2199 if (DDT)
2200 DDT->deleteEdge(BB, UnwindDest);
2201 }
2202
2203 /// removeUnreachableBlocks - Remove blocks that are not reachable, even
2204 /// if they are in a dead cycle. Return true if a change was made, false
2205 /// otherwise. If `LVI` is passed, this function preserves LazyValueInfo
2206 /// after modifying the CFG.
removeUnreachableBlocks(Function & F,LazyValueInfo * LVI,DeferredDominance * DDT)2207 bool llvm::removeUnreachableBlocks(Function &F, LazyValueInfo *LVI,
2208 DeferredDominance *DDT) {
2209 SmallPtrSet<BasicBlock*, 16> Reachable;
2210 bool Changed = markAliveBlocks(F, Reachable, DDT);
2211
2212 // If there are unreachable blocks in the CFG...
2213 if (Reachable.size() == F.size())
2214 return Changed;
2215
2216 assert(Reachable.size() < F.size());
2217 NumRemoved += F.size()-Reachable.size();
2218
2219 // Loop over all of the basic blocks that are not reachable, dropping all of
2220 // their internal references. Update DDT and LVI if available.
2221 std::vector <DominatorTree::UpdateType> Updates;
2222 for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ++I) {
2223 auto *BB = &*I;
2224 if (Reachable.count(BB))
2225 continue;
2226 for (BasicBlock *Successor : successors(BB)) {
2227 if (Reachable.count(Successor))
2228 Successor->removePredecessor(BB);
2229 if (DDT)
2230 Updates.push_back({DominatorTree::Delete, BB, Successor});
2231 }
2232 if (LVI)
2233 LVI->eraseBlock(BB);
2234 BB->dropAllReferences();
2235 }
2236
2237 for (Function::iterator I = ++F.begin(); I != F.end();) {
2238 auto *BB = &*I;
2239 if (Reachable.count(BB)) {
2240 ++I;
2241 continue;
2242 }
2243 if (DDT) {
2244 DDT->deleteBB(BB); // deferred deletion of BB.
2245 ++I;
2246 } else {
2247 I = F.getBasicBlockList().erase(I);
2248 }
2249 }
2250
2251 if (DDT)
2252 DDT->applyUpdates(Updates);
2253 return true;
2254 }
2255
combineMetadata(Instruction * K,const Instruction * J,ArrayRef<unsigned> KnownIDs)2256 void llvm::combineMetadata(Instruction *K, const Instruction *J,
2257 ArrayRef<unsigned> KnownIDs) {
2258 SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata;
2259 K->dropUnknownNonDebugMetadata(KnownIDs);
2260 K->getAllMetadataOtherThanDebugLoc(Metadata);
2261 for (const auto &MD : Metadata) {
2262 unsigned Kind = MD.first;
2263 MDNode *JMD = J->getMetadata(Kind);
2264 MDNode *KMD = MD.second;
2265
2266 switch (Kind) {
2267 default:
2268 K->setMetadata(Kind, nullptr); // Remove unknown metadata
2269 break;
2270 case LLVMContext::MD_dbg:
2271 llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg");
2272 case LLVMContext::MD_tbaa:
2273 K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD));
2274 break;
2275 case LLVMContext::MD_alias_scope:
2276 K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD));
2277 break;
2278 case LLVMContext::MD_noalias:
2279 case LLVMContext::MD_mem_parallel_loop_access:
2280 K->setMetadata(Kind, MDNode::intersect(JMD, KMD));
2281 break;
2282 case LLVMContext::MD_range:
2283 K->setMetadata(Kind, MDNode::getMostGenericRange(JMD, KMD));
2284 break;
2285 case LLVMContext::MD_fpmath:
2286 K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD));
2287 break;
2288 case LLVMContext::MD_invariant_load:
2289 // Only set the !invariant.load if it is present in both instructions.
2290 K->setMetadata(Kind, JMD);
2291 break;
2292 case LLVMContext::MD_nonnull:
2293 // Only set the !nonnull if it is present in both instructions.
2294 K->setMetadata(Kind, JMD);
2295 break;
2296 case LLVMContext::MD_invariant_group:
2297 // Preserve !invariant.group in K.
2298 break;
2299 case LLVMContext::MD_align:
2300 K->setMetadata(Kind,
2301 MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD));
2302 break;
2303 case LLVMContext::MD_dereferenceable:
2304 case LLVMContext::MD_dereferenceable_or_null:
2305 K->setMetadata(Kind,
2306 MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD));
2307 break;
2308 }
2309 }
2310 // Set !invariant.group from J if J has it. If both instructions have it
2311 // then we will just pick it from J - even when they are different.
2312 // Also make sure that K is load or store - f.e. combining bitcast with load
2313 // could produce bitcast with invariant.group metadata, which is invalid.
2314 // FIXME: we should try to preserve both invariant.group md if they are
2315 // different, but right now instruction can only have one invariant.group.
2316 if (auto *JMD = J->getMetadata(LLVMContext::MD_invariant_group))
2317 if (isa<LoadInst>(K) || isa<StoreInst>(K))
2318 K->setMetadata(LLVMContext::MD_invariant_group, JMD);
2319 }
2320
combineMetadataForCSE(Instruction * K,const Instruction * J)2321 void llvm::combineMetadataForCSE(Instruction *K, const Instruction *J) {
2322 unsigned KnownIDs[] = {
2323 LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope,
2324 LLVMContext::MD_noalias, LLVMContext::MD_range,
2325 LLVMContext::MD_invariant_load, LLVMContext::MD_nonnull,
2326 LLVMContext::MD_invariant_group, LLVMContext::MD_align,
2327 LLVMContext::MD_dereferenceable,
2328 LLVMContext::MD_dereferenceable_or_null};
2329 combineMetadata(K, J, KnownIDs);
2330 }
2331
2332 template <typename RootType, typename DominatesFn>
replaceDominatedUsesWith(Value * From,Value * To,const RootType & Root,const DominatesFn & Dominates)2333 static unsigned replaceDominatedUsesWith(Value *From, Value *To,
2334 const RootType &Root,
2335 const DominatesFn &Dominates) {
2336 assert(From->getType() == To->getType());
2337
2338 unsigned Count = 0;
2339 for (Value::use_iterator UI = From->use_begin(), UE = From->use_end();
2340 UI != UE;) {
2341 Use &U = *UI++;
2342 if (!Dominates(Root, U))
2343 continue;
2344 U.set(To);
2345 LLVM_DEBUG(dbgs() << "Replace dominated use of '" << From->getName()
2346 << "' as " << *To << " in " << *U << "\n");
2347 ++Count;
2348 }
2349 return Count;
2350 }
2351
replaceNonLocalUsesWith(Instruction * From,Value * To)2352 unsigned llvm::replaceNonLocalUsesWith(Instruction *From, Value *To) {
2353 assert(From->getType() == To->getType());
2354 auto *BB = From->getParent();
2355 unsigned Count = 0;
2356
2357 for (Value::use_iterator UI = From->use_begin(), UE = From->use_end();
2358 UI != UE;) {
2359 Use &U = *UI++;
2360 auto *I = cast<Instruction>(U.getUser());
2361 if (I->getParent() == BB)
2362 continue;
2363 U.set(To);
2364 ++Count;
2365 }
2366 return Count;
2367 }
2368
replaceDominatedUsesWith(Value * From,Value * To,DominatorTree & DT,const BasicBlockEdge & Root)2369 unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To,
2370 DominatorTree &DT,
2371 const BasicBlockEdge &Root) {
2372 auto Dominates = [&DT](const BasicBlockEdge &Root, const Use &U) {
2373 return DT.dominates(Root, U);
2374 };
2375 return ::replaceDominatedUsesWith(From, To, Root, Dominates);
2376 }
2377
replaceDominatedUsesWith(Value * From,Value * To,DominatorTree & DT,const BasicBlock * BB)2378 unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To,
2379 DominatorTree &DT,
2380 const BasicBlock *BB) {
2381 auto ProperlyDominates = [&DT](const BasicBlock *BB, const Use &U) {
2382 auto *I = cast<Instruction>(U.getUser())->getParent();
2383 return DT.properlyDominates(BB, I);
2384 };
2385 return ::replaceDominatedUsesWith(From, To, BB, ProperlyDominates);
2386 }
2387
callsGCLeafFunction(ImmutableCallSite CS,const TargetLibraryInfo & TLI)2388 bool llvm::callsGCLeafFunction(ImmutableCallSite CS,
2389 const TargetLibraryInfo &TLI) {
2390 // Check if the function is specifically marked as a gc leaf function.
2391 if (CS.hasFnAttr("gc-leaf-function"))
2392 return true;
2393 if (const Function *F = CS.getCalledFunction()) {
2394 if (F->hasFnAttribute("gc-leaf-function"))
2395 return true;
2396
2397 if (auto IID = F->getIntrinsicID())
2398 // Most LLVM intrinsics do not take safepoints.
2399 return IID != Intrinsic::experimental_gc_statepoint &&
2400 IID != Intrinsic::experimental_deoptimize;
2401 }
2402
2403 // Lib calls can be materialized by some passes, and won't be
2404 // marked as 'gc-leaf-function.' All available Libcalls are
2405 // GC-leaf.
2406 LibFunc LF;
2407 if (TLI.getLibFunc(CS, LF)) {
2408 return TLI.has(LF);
2409 }
2410
2411 return false;
2412 }
2413
copyNonnullMetadata(const LoadInst & OldLI,MDNode * N,LoadInst & NewLI)2414 void llvm::copyNonnullMetadata(const LoadInst &OldLI, MDNode *N,
2415 LoadInst &NewLI) {
2416 auto *NewTy = NewLI.getType();
2417
2418 // This only directly applies if the new type is also a pointer.
2419 if (NewTy->isPointerTy()) {
2420 NewLI.setMetadata(LLVMContext::MD_nonnull, N);
2421 return;
2422 }
2423
2424 // The only other translation we can do is to integral loads with !range
2425 // metadata.
2426 if (!NewTy->isIntegerTy())
2427 return;
2428
2429 MDBuilder MDB(NewLI.getContext());
2430 const Value *Ptr = OldLI.getPointerOperand();
2431 auto *ITy = cast<IntegerType>(NewTy);
2432 auto *NullInt = ConstantExpr::getPtrToInt(
2433 ConstantPointerNull::get(cast<PointerType>(Ptr->getType())), ITy);
2434 auto *NonNullInt = ConstantExpr::getAdd(NullInt, ConstantInt::get(ITy, 1));
2435 NewLI.setMetadata(LLVMContext::MD_range,
2436 MDB.createRange(NonNullInt, NullInt));
2437 }
2438
copyRangeMetadata(const DataLayout & DL,const LoadInst & OldLI,MDNode * N,LoadInst & NewLI)2439 void llvm::copyRangeMetadata(const DataLayout &DL, const LoadInst &OldLI,
2440 MDNode *N, LoadInst &NewLI) {
2441 auto *NewTy = NewLI.getType();
2442
2443 // Give up unless it is converted to a pointer where there is a single very
2444 // valuable mapping we can do reliably.
2445 // FIXME: It would be nice to propagate this in more ways, but the type
2446 // conversions make it hard.
2447 if (!NewTy->isPointerTy())
2448 return;
2449
2450 unsigned BitWidth = DL.getIndexTypeSizeInBits(NewTy);
2451 if (!getConstantRangeFromMetadata(*N).contains(APInt(BitWidth, 0))) {
2452 MDNode *NN = MDNode::get(OldLI.getContext(), None);
2453 NewLI.setMetadata(LLVMContext::MD_nonnull, NN);
2454 }
2455 }
2456
2457 namespace {
2458
2459 /// A potential constituent of a bitreverse or bswap expression. See
2460 /// collectBitParts for a fuller explanation.
2461 struct BitPart {
BitPart__anone7f9a6bc0a11::BitPart2462 BitPart(Value *P, unsigned BW) : Provider(P) {
2463 Provenance.resize(BW);
2464 }
2465
2466 /// The Value that this is a bitreverse/bswap of.
2467 Value *Provider;
2468
2469 /// The "provenance" of each bit. Provenance[A] = B means that bit A
2470 /// in Provider becomes bit B in the result of this expression.
2471 SmallVector<int8_t, 32> Provenance; // int8_t means max size is i128.
2472
2473 enum { Unset = -1 };
2474 };
2475
2476 } // end anonymous namespace
2477
2478 /// Analyze the specified subexpression and see if it is capable of providing
2479 /// pieces of a bswap or bitreverse. The subexpression provides a potential
2480 /// piece of a bswap or bitreverse if it can be proven that each non-zero bit in
2481 /// the output of the expression came from a corresponding bit in some other
2482 /// value. This function is recursive, and the end result is a mapping of
2483 /// bitnumber to bitnumber. It is the caller's responsibility to validate that
2484 /// the bitnumber to bitnumber mapping is correct for a bswap or bitreverse.
2485 ///
2486 /// For example, if the current subexpression if "(shl i32 %X, 24)" then we know
2487 /// that the expression deposits the low byte of %X into the high byte of the
2488 /// result and that all other bits are zero. This expression is accepted and a
2489 /// BitPart is returned with Provider set to %X and Provenance[24-31] set to
2490 /// [0-7].
2491 ///
2492 /// To avoid revisiting values, the BitPart results are memoized into the
2493 /// provided map. To avoid unnecessary copying of BitParts, BitParts are
2494 /// constructed in-place in the \c BPS map. Because of this \c BPS needs to
2495 /// store BitParts objects, not pointers. As we need the concept of a nullptr
2496 /// BitParts (Value has been analyzed and the analysis failed), we an Optional
2497 /// type instead to provide the same functionality.
2498 ///
2499 /// Because we pass around references into \c BPS, we must use a container that
2500 /// does not invalidate internal references (std::map instead of DenseMap).
2501 static const Optional<BitPart> &
collectBitParts(Value * V,bool MatchBSwaps,bool MatchBitReversals,std::map<Value *,Optional<BitPart>> & BPS)2502 collectBitParts(Value *V, bool MatchBSwaps, bool MatchBitReversals,
2503 std::map<Value *, Optional<BitPart>> &BPS) {
2504 auto I = BPS.find(V);
2505 if (I != BPS.end())
2506 return I->second;
2507
2508 auto &Result = BPS[V] = None;
2509 auto BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
2510
2511 if (Instruction *I = dyn_cast<Instruction>(V)) {
2512 // If this is an or instruction, it may be an inner node of the bswap.
2513 if (I->getOpcode() == Instruction::Or) {
2514 auto &A = collectBitParts(I->getOperand(0), MatchBSwaps,
2515 MatchBitReversals, BPS);
2516 auto &B = collectBitParts(I->getOperand(1), MatchBSwaps,
2517 MatchBitReversals, BPS);
2518 if (!A || !B)
2519 return Result;
2520
2521 // Try and merge the two together.
2522 if (!A->Provider || A->Provider != B->Provider)
2523 return Result;
2524
2525 Result = BitPart(A->Provider, BitWidth);
2526 for (unsigned i = 0; i < A->Provenance.size(); ++i) {
2527 if (A->Provenance[i] != BitPart::Unset &&
2528 B->Provenance[i] != BitPart::Unset &&
2529 A->Provenance[i] != B->Provenance[i])
2530 return Result = None;
2531
2532 if (A->Provenance[i] == BitPart::Unset)
2533 Result->Provenance[i] = B->Provenance[i];
2534 else
2535 Result->Provenance[i] = A->Provenance[i];
2536 }
2537
2538 return Result;
2539 }
2540
2541 // If this is a logical shift by a constant, recurse then shift the result.
2542 if (I->isLogicalShift() && isa<ConstantInt>(I->getOperand(1))) {
2543 unsigned BitShift =
2544 cast<ConstantInt>(I->getOperand(1))->getLimitedValue(~0U);
2545 // Ensure the shift amount is defined.
2546 if (BitShift > BitWidth)
2547 return Result;
2548
2549 auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
2550 MatchBitReversals, BPS);
2551 if (!Res)
2552 return Result;
2553 Result = Res;
2554
2555 // Perform the "shift" on BitProvenance.
2556 auto &P = Result->Provenance;
2557 if (I->getOpcode() == Instruction::Shl) {
2558 P.erase(std::prev(P.end(), BitShift), P.end());
2559 P.insert(P.begin(), BitShift, BitPart::Unset);
2560 } else {
2561 P.erase(P.begin(), std::next(P.begin(), BitShift));
2562 P.insert(P.end(), BitShift, BitPart::Unset);
2563 }
2564
2565 return Result;
2566 }
2567
2568 // If this is a logical 'and' with a mask that clears bits, recurse then
2569 // unset the appropriate bits.
2570 if (I->getOpcode() == Instruction::And &&
2571 isa<ConstantInt>(I->getOperand(1))) {
2572 APInt Bit(I->getType()->getPrimitiveSizeInBits(), 1);
2573 const APInt &AndMask = cast<ConstantInt>(I->getOperand(1))->getValue();
2574
2575 // Check that the mask allows a multiple of 8 bits for a bswap, for an
2576 // early exit.
2577 unsigned NumMaskedBits = AndMask.countPopulation();
2578 if (!MatchBitReversals && NumMaskedBits % 8 != 0)
2579 return Result;
2580
2581 auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
2582 MatchBitReversals, BPS);
2583 if (!Res)
2584 return Result;
2585 Result = Res;
2586
2587 for (unsigned i = 0; i < BitWidth; ++i, Bit <<= 1)
2588 // If the AndMask is zero for this bit, clear the bit.
2589 if ((AndMask & Bit) == 0)
2590 Result->Provenance[i] = BitPart::Unset;
2591 return Result;
2592 }
2593
2594 // If this is a zext instruction zero extend the result.
2595 if (I->getOpcode() == Instruction::ZExt) {
2596 auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
2597 MatchBitReversals, BPS);
2598 if (!Res)
2599 return Result;
2600
2601 Result = BitPart(Res->Provider, BitWidth);
2602 auto NarrowBitWidth =
2603 cast<IntegerType>(cast<ZExtInst>(I)->getSrcTy())->getBitWidth();
2604 for (unsigned i = 0; i < NarrowBitWidth; ++i)
2605 Result->Provenance[i] = Res->Provenance[i];
2606 for (unsigned i = NarrowBitWidth; i < BitWidth; ++i)
2607 Result->Provenance[i] = BitPart::Unset;
2608 return Result;
2609 }
2610 }
2611
2612 // Okay, we got to something that isn't a shift, 'or' or 'and'. This must be
2613 // the input value to the bswap/bitreverse.
2614 Result = BitPart(V, BitWidth);
2615 for (unsigned i = 0; i < BitWidth; ++i)
2616 Result->Provenance[i] = i;
2617 return Result;
2618 }
2619
bitTransformIsCorrectForBSwap(unsigned From,unsigned To,unsigned BitWidth)2620 static bool bitTransformIsCorrectForBSwap(unsigned From, unsigned To,
2621 unsigned BitWidth) {
2622 if (From % 8 != To % 8)
2623 return false;
2624 // Convert from bit indices to byte indices and check for a byte reversal.
2625 From >>= 3;
2626 To >>= 3;
2627 BitWidth >>= 3;
2628 return From == BitWidth - To - 1;
2629 }
2630
bitTransformIsCorrectForBitReverse(unsigned From,unsigned To,unsigned BitWidth)2631 static bool bitTransformIsCorrectForBitReverse(unsigned From, unsigned To,
2632 unsigned BitWidth) {
2633 return From == BitWidth - To - 1;
2634 }
2635
recognizeBSwapOrBitReverseIdiom(Instruction * I,bool MatchBSwaps,bool MatchBitReversals,SmallVectorImpl<Instruction * > & InsertedInsts)2636 bool llvm::recognizeBSwapOrBitReverseIdiom(
2637 Instruction *I, bool MatchBSwaps, bool MatchBitReversals,
2638 SmallVectorImpl<Instruction *> &InsertedInsts) {
2639 if (Operator::getOpcode(I) != Instruction::Or)
2640 return false;
2641 if (!MatchBSwaps && !MatchBitReversals)
2642 return false;
2643 IntegerType *ITy = dyn_cast<IntegerType>(I->getType());
2644 if (!ITy || ITy->getBitWidth() > 128)
2645 return false; // Can't do vectors or integers > 128 bits.
2646 unsigned BW = ITy->getBitWidth();
2647
2648 unsigned DemandedBW = BW;
2649 IntegerType *DemandedTy = ITy;
2650 if (I->hasOneUse()) {
2651 if (TruncInst *Trunc = dyn_cast<TruncInst>(I->user_back())) {
2652 DemandedTy = cast<IntegerType>(Trunc->getType());
2653 DemandedBW = DemandedTy->getBitWidth();
2654 }
2655 }
2656
2657 // Try to find all the pieces corresponding to the bswap.
2658 std::map<Value *, Optional<BitPart>> BPS;
2659 auto Res = collectBitParts(I, MatchBSwaps, MatchBitReversals, BPS);
2660 if (!Res)
2661 return false;
2662 auto &BitProvenance = Res->Provenance;
2663
2664 // Now, is the bit permutation correct for a bswap or a bitreverse? We can
2665 // only byteswap values with an even number of bytes.
2666 bool OKForBSwap = DemandedBW % 16 == 0, OKForBitReverse = true;
2667 for (unsigned i = 0; i < DemandedBW; ++i) {
2668 OKForBSwap &=
2669 bitTransformIsCorrectForBSwap(BitProvenance[i], i, DemandedBW);
2670 OKForBitReverse &=
2671 bitTransformIsCorrectForBitReverse(BitProvenance[i], i, DemandedBW);
2672 }
2673
2674 Intrinsic::ID Intrin;
2675 if (OKForBSwap && MatchBSwaps)
2676 Intrin = Intrinsic::bswap;
2677 else if (OKForBitReverse && MatchBitReversals)
2678 Intrin = Intrinsic::bitreverse;
2679 else
2680 return false;
2681
2682 if (ITy != DemandedTy) {
2683 Function *F = Intrinsic::getDeclaration(I->getModule(), Intrin, DemandedTy);
2684 Value *Provider = Res->Provider;
2685 IntegerType *ProviderTy = cast<IntegerType>(Provider->getType());
2686 // We may need to truncate the provider.
2687 if (DemandedTy != ProviderTy) {
2688 auto *Trunc = CastInst::Create(Instruction::Trunc, Provider, DemandedTy,
2689 "trunc", I);
2690 InsertedInsts.push_back(Trunc);
2691 Provider = Trunc;
2692 }
2693 auto *CI = CallInst::Create(F, Provider, "rev", I);
2694 InsertedInsts.push_back(CI);
2695 auto *ExtInst = CastInst::Create(Instruction::ZExt, CI, ITy, "zext", I);
2696 InsertedInsts.push_back(ExtInst);
2697 return true;
2698 }
2699
2700 Function *F = Intrinsic::getDeclaration(I->getModule(), Intrin, ITy);
2701 InsertedInsts.push_back(CallInst::Create(F, Res->Provider, "rev", I));
2702 return true;
2703 }
2704
2705 // CodeGen has special handling for some string functions that may replace
2706 // them with target-specific intrinsics. Since that'd skip our interceptors
2707 // in ASan/MSan/TSan/DFSan, and thus make us miss some memory accesses,
2708 // we mark affected calls as NoBuiltin, which will disable optimization
2709 // in CodeGen.
maybeMarkSanitizerLibraryCallNoBuiltin(CallInst * CI,const TargetLibraryInfo * TLI)2710 void llvm::maybeMarkSanitizerLibraryCallNoBuiltin(
2711 CallInst *CI, const TargetLibraryInfo *TLI) {
2712 Function *F = CI->getCalledFunction();
2713 LibFunc Func;
2714 if (F && !F->hasLocalLinkage() && F->hasName() &&
2715 TLI->getLibFunc(F->getName(), Func) && TLI->hasOptimizedCodeGen(Func) &&
2716 !F->doesNotAccessMemory())
2717 CI->addAttribute(AttributeList::FunctionIndex, Attribute::NoBuiltin);
2718 }
2719
canReplaceOperandWithVariable(const Instruction * I,unsigned OpIdx)2720 bool llvm::canReplaceOperandWithVariable(const Instruction *I, unsigned OpIdx) {
2721 // We can't have a PHI with a metadata type.
2722 if (I->getOperand(OpIdx)->getType()->isMetadataTy())
2723 return false;
2724
2725 // Early exit.
2726 if (!isa<Constant>(I->getOperand(OpIdx)))
2727 return true;
2728
2729 switch (I->getOpcode()) {
2730 default:
2731 return true;
2732 case Instruction::Call:
2733 case Instruction::Invoke:
2734 // Can't handle inline asm. Skip it.
2735 if (isa<InlineAsm>(ImmutableCallSite(I).getCalledValue()))
2736 return false;
2737 // Many arithmetic intrinsics have no issue taking a
2738 // variable, however it's hard to distingish these from
2739 // specials such as @llvm.frameaddress that require a constant.
2740 if (isa<IntrinsicInst>(I))
2741 return false;
2742
2743 // Constant bundle operands may need to retain their constant-ness for
2744 // correctness.
2745 if (ImmutableCallSite(I).isBundleOperand(OpIdx))
2746 return false;
2747 return true;
2748 case Instruction::ShuffleVector:
2749 // Shufflevector masks are constant.
2750 return OpIdx != 2;
2751 case Instruction::Switch:
2752 case Instruction::ExtractValue:
2753 // All operands apart from the first are constant.
2754 return OpIdx == 0;
2755 case Instruction::InsertValue:
2756 // All operands apart from the first and the second are constant.
2757 return OpIdx < 2;
2758 case Instruction::Alloca:
2759 // Static allocas (constant size in the entry block) are handled by
2760 // prologue/epilogue insertion so they're free anyway. We definitely don't
2761 // want to make them non-constant.
2762 return !cast<AllocaInst>(I)->isStaticAlloca();
2763 case Instruction::GetElementPtr:
2764 if (OpIdx == 0)
2765 return true;
2766 gep_type_iterator It = gep_type_begin(I);
2767 for (auto E = std::next(It, OpIdx); It != E; ++It)
2768 if (It.isStruct())
2769 return false;
2770 return true;
2771 }
2772 }
2773