1 //===-- Local.cpp - Functions to perform local transformations ------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This family of functions perform various local transformations to the
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Transforms/Utils/Local.h"
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/DenseSet.h"
18 #include "llvm/ADT/Hashing.h"
19 #include "llvm/ADT/STLExtras.h"
20 #include "llvm/ADT/SmallPtrSet.h"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/Analysis/InstructionSimplify.h"
23 #include "llvm/Analysis/LibCallSemantics.h"
24 #include "llvm/Analysis/MemoryBuiltins.h"
25 #include "llvm/Analysis/ValueTracking.h"
26 #include "llvm/IR/CFG.h"
27 #include "llvm/IR/Constants.h"
28 #include "llvm/IR/DIBuilder.h"
29 #include "llvm/IR/DataLayout.h"
30 #include "llvm/IR/DebugInfo.h"
31 #include "llvm/IR/DerivedTypes.h"
32 #include "llvm/IR/Dominators.h"
33 #include "llvm/IR/GetElementPtrTypeIterator.h"
34 #include "llvm/IR/GlobalAlias.h"
35 #include "llvm/IR/GlobalVariable.h"
36 #include "llvm/IR/IRBuilder.h"
37 #include "llvm/IR/Instructions.h"
38 #include "llvm/IR/IntrinsicInst.h"
39 #include "llvm/IR/Intrinsics.h"
40 #include "llvm/IR/MDBuilder.h"
41 #include "llvm/IR/Metadata.h"
42 #include "llvm/IR/Operator.h"
43 #include "llvm/IR/ValueHandle.h"
44 #include "llvm/Support/Debug.h"
45 #include "llvm/Support/MathExtras.h"
46 #include "llvm/Support/raw_ostream.h"
49 #define DEBUG_TYPE "local"
51 STATISTIC(NumRemoved, "Number of unreachable basic blocks removed");
53 //===----------------------------------------------------------------------===//
54 // Local constant propagation.
57 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
58 /// constant value, convert it into an unconditional branch to the constant
59 /// destination. This is a nontrivial operation because the successors of this
60 /// basic block must have their PHI nodes updated.
61 /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
62 /// conditions and indirectbr addresses this might make dead if
63 /// DeleteDeadConditions is true.
64 bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
65 const TargetLibraryInfo *TLI) {
66 TerminatorInst *T = BB->getTerminator();
67 IRBuilder<> Builder(T);
69 // Branch - See if we are conditional jumping on constant
70 if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
71 if (BI->isUnconditional()) return false; // Can't optimize uncond branch
72 BasicBlock *Dest1 = BI->getSuccessor(0);
73 BasicBlock *Dest2 = BI->getSuccessor(1);
75 if (ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition())) {
76 // Are we branching on constant?
77 // YES. Change to unconditional branch...
78 BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2;
79 BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1;
81 //cerr << "Function: " << T->getParent()->getParent()
82 // << "\nRemoving branch from " << T->getParent()
83 // << "\n\nTo: " << OldDest << endl;
85 // Let the basic block know that we are letting go of it. Based on this,
86 // it will adjust it's PHI nodes.
87 OldDest->removePredecessor(BB);
89 // Replace the conditional branch with an unconditional one.
90 Builder.CreateBr(Destination);
91 BI->eraseFromParent();
95 if (Dest2 == Dest1) { // Conditional branch to same location?
96 // This branch matches something like this:
97 // br bool %cond, label %Dest, label %Dest
98 // and changes it into: br label %Dest
100 // Let the basic block know that we are letting go of one copy of it.
101 assert(BI->getParent() && "Terminator not inserted in block!");
102 Dest1->removePredecessor(BI->getParent());
104 // Replace the conditional branch with an unconditional one.
105 Builder.CreateBr(Dest1);
106 Value *Cond = BI->getCondition();
107 BI->eraseFromParent();
108 if (DeleteDeadConditions)
109 RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
115 if (SwitchInst *SI = dyn_cast<SwitchInst>(T)) {
116 // If we are switching on a constant, we can convert the switch to an
117 // unconditional branch.
118 ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition());
119 BasicBlock *DefaultDest = SI->getDefaultDest();
120 BasicBlock *TheOnlyDest = DefaultDest;
122 // If the default is unreachable, ignore it when searching for TheOnlyDest.
123 if (isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg()) &&
124 SI->getNumCases() > 0) {
125 TheOnlyDest = SI->case_begin().getCaseSuccessor();
128 // Figure out which case it goes to.
129 for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
131 // Found case matching a constant operand?
132 if (i.getCaseValue() == CI) {
133 TheOnlyDest = i.getCaseSuccessor();
137 // Check to see if this branch is going to the same place as the default
138 // dest. If so, eliminate it as an explicit compare.
139 if (i.getCaseSuccessor() == DefaultDest) {
140 MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
141 unsigned NCases = SI->getNumCases();
142 // Fold the case metadata into the default if there will be any branches
143 // left, unless the metadata doesn't match the switch.
144 if (NCases > 1 && MD && MD->getNumOperands() == 2 + NCases) {
145 // Collect branch weights into a vector.
146 SmallVector<uint32_t, 8> Weights;
147 for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e;
150 mdconst::dyn_extract<ConstantInt>(MD->getOperand(MD_i));
152 Weights.push_back(CI->getValue().getZExtValue());
154 // Merge weight of this case to the default weight.
155 unsigned idx = i.getCaseIndex();
156 Weights[0] += Weights[idx+1];
157 // Remove weight for this case.
158 std::swap(Weights[idx+1], Weights.back());
160 SI->setMetadata(LLVMContext::MD_prof,
161 MDBuilder(BB->getContext()).
162 createBranchWeights(Weights));
164 // Remove this entry.
165 DefaultDest->removePredecessor(SI->getParent());
171 // Otherwise, check to see if the switch only branches to one destination.
172 // We do this by reseting "TheOnlyDest" to null when we find two non-equal
174 if (i.getCaseSuccessor() != TheOnlyDest) TheOnlyDest = nullptr;
177 if (CI && !TheOnlyDest) {
178 // Branching on a constant, but not any of the cases, go to the default
180 TheOnlyDest = SI->getDefaultDest();
183 // If we found a single destination that we can fold the switch into, do so
186 // Insert the new branch.
187 Builder.CreateBr(TheOnlyDest);
188 BasicBlock *BB = SI->getParent();
190 // Remove entries from PHI nodes which we no longer branch to...
191 for (BasicBlock *Succ : SI->successors()) {
192 // Found case matching a constant operand?
193 if (Succ == TheOnlyDest)
194 TheOnlyDest = nullptr; // Don't modify the first branch to TheOnlyDest
196 Succ->removePredecessor(BB);
199 // Delete the old switch.
200 Value *Cond = SI->getCondition();
201 SI->eraseFromParent();
202 if (DeleteDeadConditions)
203 RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
207 if (SI->getNumCases() == 1) {
208 // Otherwise, we can fold this switch into a conditional branch
209 // instruction if it has only one non-default destination.
210 SwitchInst::CaseIt FirstCase = SI->case_begin();
211 Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
212 FirstCase.getCaseValue(), "cond");
214 // Insert the new branch.
215 BranchInst *NewBr = Builder.CreateCondBr(Cond,
216 FirstCase.getCaseSuccessor(),
217 SI->getDefaultDest());
218 MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
219 if (MD && MD->getNumOperands() == 3) {
220 ConstantInt *SICase =
221 mdconst::dyn_extract<ConstantInt>(MD->getOperand(2));
223 mdconst::dyn_extract<ConstantInt>(MD->getOperand(1));
224 assert(SICase && SIDef);
225 // The TrueWeight should be the weight for the single case of SI.
226 NewBr->setMetadata(LLVMContext::MD_prof,
227 MDBuilder(BB->getContext()).
228 createBranchWeights(SICase->getValue().getZExtValue(),
229 SIDef->getValue().getZExtValue()));
232 // Update make.implicit metadata to the newly-created conditional branch.
233 MDNode *MakeImplicitMD = SI->getMetadata(LLVMContext::MD_make_implicit);
235 NewBr->setMetadata(LLVMContext::MD_make_implicit, MakeImplicitMD);
237 // Delete the old switch.
238 SI->eraseFromParent();
244 if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(T)) {
245 // indirectbr blockaddress(@F, @BB) -> br label @BB
246 if (BlockAddress *BA =
247 dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
248 BasicBlock *TheOnlyDest = BA->getBasicBlock();
249 // Insert the new branch.
250 Builder.CreateBr(TheOnlyDest);
252 for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
253 if (IBI->getDestination(i) == TheOnlyDest)
254 TheOnlyDest = nullptr;
256 IBI->getDestination(i)->removePredecessor(IBI->getParent());
258 Value *Address = IBI->getAddress();
259 IBI->eraseFromParent();
260 if (DeleteDeadConditions)
261 RecursivelyDeleteTriviallyDeadInstructions(Address, TLI);
263 // If we didn't find our destination in the IBI successor list, then we
264 // have undefined behavior. Replace the unconditional branch with an
265 // 'unreachable' instruction.
267 BB->getTerminator()->eraseFromParent();
268 new UnreachableInst(BB->getContext(), BB);
279 //===----------------------------------------------------------------------===//
280 // Local dead code elimination.
283 /// isInstructionTriviallyDead - Return true if the result produced by the
284 /// instruction is not used, and the instruction has no side effects.
286 bool llvm::isInstructionTriviallyDead(Instruction *I,
287 const TargetLibraryInfo *TLI) {
288 if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
290 // We don't want the landingpad-like instructions removed by anything this
295 // We don't want debug info removed by anything this general, unless
296 // debug info is empty.
297 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
298 if (DDI->getAddress())
302 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
308 if (!I->mayHaveSideEffects()) return true;
310 // Special case intrinsics that "may have side effects" but can be deleted
312 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
313 // Safe to delete llvm.stacksave if dead.
314 if (II->getIntrinsicID() == Intrinsic::stacksave)
317 // Lifetime intrinsics are dead when their right-hand is undef.
318 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
319 II->getIntrinsicID() == Intrinsic::lifetime_end)
320 return isa<UndefValue>(II->getArgOperand(1));
322 // Assumptions are dead if their condition is trivially true.
323 if (II->getIntrinsicID() == Intrinsic::assume) {
324 if (ConstantInt *Cond = dyn_cast<ConstantInt>(II->getArgOperand(0)))
325 return !Cond->isZero();
331 if (isAllocLikeFn(I, TLI)) return true;
333 if (CallInst *CI = isFreeCall(I, TLI))
334 if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
335 return C->isNullValue() || isa<UndefValue>(C);
340 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
341 /// trivially dead instruction, delete it. If that makes any of its operands
342 /// trivially dead, delete them too, recursively. Return true if any
343 /// instructions were deleted.
345 llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V,
346 const TargetLibraryInfo *TLI) {
347 Instruction *I = dyn_cast<Instruction>(V);
348 if (!I || !I->use_empty() || !isInstructionTriviallyDead(I, TLI))
351 SmallVector<Instruction*, 16> DeadInsts;
352 DeadInsts.push_back(I);
355 I = DeadInsts.pop_back_val();
357 // Null out all of the instruction's operands to see if any operand becomes
359 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
360 Value *OpV = I->getOperand(i);
361 I->setOperand(i, nullptr);
363 if (!OpV->use_empty()) continue;
365 // If the operand is an instruction that became dead as we nulled out the
366 // operand, and if it is 'trivially' dead, delete it in a future loop
368 if (Instruction *OpI = dyn_cast<Instruction>(OpV))
369 if (isInstructionTriviallyDead(OpI, TLI))
370 DeadInsts.push_back(OpI);
373 I->eraseFromParent();
374 } while (!DeadInsts.empty());
379 /// areAllUsesEqual - Check whether the uses of a value are all the same.
380 /// This is similar to Instruction::hasOneUse() except this will also return
381 /// true when there are no uses or multiple uses that all refer to the same
383 static bool areAllUsesEqual(Instruction *I) {
384 Value::user_iterator UI = I->user_begin();
385 Value::user_iterator UE = I->user_end();
390 for (++UI; UI != UE; ++UI) {
397 /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
398 /// dead PHI node, due to being a def-use chain of single-use nodes that
399 /// either forms a cycle or is terminated by a trivially dead instruction,
400 /// delete it. If that makes any of its operands trivially dead, delete them
401 /// too, recursively. Return true if a change was made.
402 bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN,
403 const TargetLibraryInfo *TLI) {
404 SmallPtrSet<Instruction*, 4> Visited;
405 for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects();
406 I = cast<Instruction>(*I->user_begin())) {
408 return RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
410 // If we find an instruction more than once, we're on a cycle that
411 // won't prove fruitful.
412 if (!Visited.insert(I).second) {
413 // Break the cycle and delete the instruction and its operands.
414 I->replaceAllUsesWith(UndefValue::get(I->getType()));
415 (void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
422 /// SimplifyInstructionsInBlock - Scan the specified basic block and try to
423 /// simplify any instructions in it and recursively delete dead instructions.
425 /// This returns true if it changed the code, note that it can delete
426 /// instructions in other blocks as well in this block.
427 bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB,
428 const TargetLibraryInfo *TLI) {
429 bool MadeChange = false;
432 // In debug builds, ensure that the terminator of the block is never replaced
433 // or deleted by these simplifications. The idea of simplification is that it
434 // cannot introduce new instructions, and there is no way to replace the
435 // terminator of a block without introducing a new instruction.
436 AssertingVH<Instruction> TerminatorVH(--BB->end());
439 for (BasicBlock::iterator BI = BB->begin(), E = --BB->end(); BI != E; ) {
440 assert(!BI->isTerminator());
441 Instruction *Inst = BI++;
444 if (recursivelySimplifyInstruction(Inst, TLI)) {
451 MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst, TLI);
458 //===----------------------------------------------------------------------===//
459 // Control Flow Graph Restructuring.
463 /// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
464 /// method is called when we're about to delete Pred as a predecessor of BB. If
465 /// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
467 /// Unlike the removePredecessor method, this attempts to simplify uses of PHI
468 /// nodes that collapse into identity values. For example, if we have:
469 /// x = phi(1, 0, 0, 0)
472 /// .. and delete the predecessor corresponding to the '1', this will attempt to
473 /// recursively fold the and to 0.
474 void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred) {
475 // This only adjusts blocks with PHI nodes.
476 if (!isa<PHINode>(BB->begin()))
479 // Remove the entries for Pred from the PHI nodes in BB, but do not simplify
480 // them down. This will leave us with single entry phi nodes and other phis
481 // that can be removed.
482 BB->removePredecessor(Pred, true);
484 WeakVH PhiIt = &BB->front();
485 while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) {
486 PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt));
487 Value *OldPhiIt = PhiIt;
489 if (!recursivelySimplifyInstruction(PN))
492 // If recursive simplification ended up deleting the next PHI node we would
493 // iterate to, then our iterator is invalid, restart scanning from the top
495 if (PhiIt != OldPhiIt) PhiIt = &BB->front();
500 /// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its
501 /// predecessor is known to have one successor (DestBB!). Eliminate the edge
502 /// between them, moving the instructions in the predecessor into DestBB and
503 /// deleting the predecessor block.
505 void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, DominatorTree *DT) {
506 // If BB has single-entry PHI nodes, fold them.
507 while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
508 Value *NewVal = PN->getIncomingValue(0);
509 // Replace self referencing PHI with undef, it must be dead.
510 if (NewVal == PN) NewVal = UndefValue::get(PN->getType());
511 PN->replaceAllUsesWith(NewVal);
512 PN->eraseFromParent();
515 BasicBlock *PredBB = DestBB->getSinglePredecessor();
516 assert(PredBB && "Block doesn't have a single predecessor!");
518 // Zap anything that took the address of DestBB. Not doing this will give the
519 // address an invalid value.
520 if (DestBB->hasAddressTaken()) {
521 BlockAddress *BA = BlockAddress::get(DestBB);
522 Constant *Replacement =
523 ConstantInt::get(llvm::Type::getInt32Ty(BA->getContext()), 1);
524 BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
526 BA->destroyConstant();
529 // Anything that branched to PredBB now branches to DestBB.
530 PredBB->replaceAllUsesWith(DestBB);
532 // Splice all the instructions from PredBB to DestBB.
533 PredBB->getTerminator()->eraseFromParent();
534 DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
536 // If the PredBB is the entry block of the function, move DestBB up to
537 // become the entry block after we erase PredBB.
538 if (PredBB == &DestBB->getParent()->getEntryBlock())
539 DestBB->moveAfter(PredBB);
542 BasicBlock *PredBBIDom = DT->getNode(PredBB)->getIDom()->getBlock();
543 DT->changeImmediateDominator(DestBB, PredBBIDom);
544 DT->eraseNode(PredBB);
547 PredBB->eraseFromParent();
550 /// CanMergeValues - Return true if we can choose one of these values to use
551 /// in place of the other. Note that we will always choose the non-undef
553 static bool CanMergeValues(Value *First, Value *Second) {
554 return First == Second || isa<UndefValue>(First) || isa<UndefValue>(Second);
557 /// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
558 /// almost-empty BB ending in an unconditional branch to Succ, into Succ.
560 /// Assumption: Succ is the single successor for BB.
562 static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
563 assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
565 DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
566 << Succ->getName() << "\n");
567 // Shortcut, if there is only a single predecessor it must be BB and merging
569 if (Succ->getSinglePredecessor()) return true;
571 // Make a list of the predecessors of BB
572 SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
574 // Look at all the phi nodes in Succ, to see if they present a conflict when
575 // merging these blocks
576 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
577 PHINode *PN = cast<PHINode>(I);
579 // If the incoming value from BB is again a PHINode in
580 // BB which has the same incoming value for *PI as PN does, we can
581 // merge the phi nodes and then the blocks can still be merged
582 PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
583 if (BBPN && BBPN->getParent() == BB) {
584 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
585 BasicBlock *IBB = PN->getIncomingBlock(PI);
586 if (BBPreds.count(IBB) &&
587 !CanMergeValues(BBPN->getIncomingValueForBlock(IBB),
588 PN->getIncomingValue(PI))) {
589 DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
590 << Succ->getName() << " is conflicting with "
591 << BBPN->getName() << " with regard to common predecessor "
592 << IBB->getName() << "\n");
597 Value* Val = PN->getIncomingValueForBlock(BB);
598 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
599 // See if the incoming value for the common predecessor is equal to the
600 // one for BB, in which case this phi node will not prevent the merging
602 BasicBlock *IBB = PN->getIncomingBlock(PI);
603 if (BBPreds.count(IBB) &&
604 !CanMergeValues(Val, PN->getIncomingValue(PI))) {
605 DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
606 << Succ->getName() << " is conflicting with regard to common "
607 << "predecessor " << IBB->getName() << "\n");
617 typedef SmallVector<BasicBlock *, 16> PredBlockVector;
618 typedef DenseMap<BasicBlock *, Value *> IncomingValueMap;
620 /// \brief Determines the value to use as the phi node input for a block.
622 /// Select between \p OldVal any value that we know flows from \p BB
623 /// to a particular phi on the basis of which one (if either) is not
624 /// undef. Update IncomingValues based on the selected value.
626 /// \param OldVal The value we are considering selecting.
627 /// \param BB The block that the value flows in from.
628 /// \param IncomingValues A map from block-to-value for other phi inputs
629 /// that we have examined.
631 /// \returns the selected value.
632 static Value *selectIncomingValueForBlock(Value *OldVal, BasicBlock *BB,
633 IncomingValueMap &IncomingValues) {
634 if (!isa<UndefValue>(OldVal)) {
635 assert((!IncomingValues.count(BB) ||
636 IncomingValues.find(BB)->second == OldVal) &&
637 "Expected OldVal to match incoming value from BB!");
639 IncomingValues.insert(std::make_pair(BB, OldVal));
643 IncomingValueMap::const_iterator It = IncomingValues.find(BB);
644 if (It != IncomingValues.end()) return It->second;
649 /// \brief Create a map from block to value for the operands of a
652 /// Create a map from block to value for each non-undef value flowing
655 /// \param PN The phi we are collecting the map for.
656 /// \param IncomingValues [out] The map from block to value for this phi.
657 static void gatherIncomingValuesToPhi(PHINode *PN,
658 IncomingValueMap &IncomingValues) {
659 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
660 BasicBlock *BB = PN->getIncomingBlock(i);
661 Value *V = PN->getIncomingValue(i);
663 if (!isa<UndefValue>(V))
664 IncomingValues.insert(std::make_pair(BB, V));
668 /// \brief Replace the incoming undef values to a phi with the values
669 /// from a block-to-value map.
671 /// \param PN The phi we are replacing the undefs in.
672 /// \param IncomingValues A map from block to value.
673 static void replaceUndefValuesInPhi(PHINode *PN,
674 const IncomingValueMap &IncomingValues) {
675 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
676 Value *V = PN->getIncomingValue(i);
678 if (!isa<UndefValue>(V)) continue;
680 BasicBlock *BB = PN->getIncomingBlock(i);
681 IncomingValueMap::const_iterator It = IncomingValues.find(BB);
682 if (It == IncomingValues.end()) continue;
684 PN->setIncomingValue(i, It->second);
688 /// \brief Replace a value flowing from a block to a phi with
689 /// potentially multiple instances of that value flowing from the
690 /// block's predecessors to the phi.
692 /// \param BB The block with the value flowing into the phi.
693 /// \param BBPreds The predecessors of BB.
694 /// \param PN The phi that we are updating.
695 static void redirectValuesFromPredecessorsToPhi(BasicBlock *BB,
696 const PredBlockVector &BBPreds,
698 Value *OldVal = PN->removeIncomingValue(BB, false);
699 assert(OldVal && "No entry in PHI for Pred BB!");
701 IncomingValueMap IncomingValues;
703 // We are merging two blocks - BB, and the block containing PN - and
704 // as a result we need to redirect edges from the predecessors of BB
705 // to go to the block containing PN, and update PN
706 // accordingly. Since we allow merging blocks in the case where the
707 // predecessor and successor blocks both share some predecessors,
708 // and where some of those common predecessors might have undef
709 // values flowing into PN, we want to rewrite those values to be
710 // consistent with the non-undef values.
712 gatherIncomingValuesToPhi(PN, IncomingValues);
714 // If this incoming value is one of the PHI nodes in BB, the new entries
715 // in the PHI node are the entries from the old PHI.
716 if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
717 PHINode *OldValPN = cast<PHINode>(OldVal);
718 for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i) {
719 // Note that, since we are merging phi nodes and BB and Succ might
720 // have common predecessors, we could end up with a phi node with
721 // identical incoming branches. This will be cleaned up later (and
722 // will trigger asserts if we try to clean it up now, without also
723 // simplifying the corresponding conditional branch).
724 BasicBlock *PredBB = OldValPN->getIncomingBlock(i);
725 Value *PredVal = OldValPN->getIncomingValue(i);
726 Value *Selected = selectIncomingValueForBlock(PredVal, PredBB,
729 // And add a new incoming value for this predecessor for the
730 // newly retargeted branch.
731 PN->addIncoming(Selected, PredBB);
734 for (unsigned i = 0, e = BBPreds.size(); i != e; ++i) {
735 // Update existing incoming values in PN for this
736 // predecessor of BB.
737 BasicBlock *PredBB = BBPreds[i];
738 Value *Selected = selectIncomingValueForBlock(OldVal, PredBB,
741 // And add a new incoming value for this predecessor for the
742 // newly retargeted branch.
743 PN->addIncoming(Selected, PredBB);
747 replaceUndefValuesInPhi(PN, IncomingValues);
750 /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
751 /// unconditional branch, and contains no instructions other than PHI nodes,
752 /// potential side-effect free intrinsics and the branch. If possible,
753 /// eliminate BB by rewriting all the predecessors to branch to the successor
754 /// block and return true. If we can't transform, return false.
755 bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) {
756 assert(BB != &BB->getParent()->getEntryBlock() &&
757 "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
759 // We can't eliminate infinite loops.
760 BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0);
761 if (BB == Succ) return false;
763 // Check to see if merging these blocks would cause conflicts for any of the
764 // phi nodes in BB or Succ. If not, we can safely merge.
765 if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
767 // Check for cases where Succ has multiple predecessors and a PHI node in BB
768 // has uses which will not disappear when the PHI nodes are merged. It is
769 // possible to handle such cases, but difficult: it requires checking whether
770 // BB dominates Succ, which is non-trivial to calculate in the case where
771 // Succ has multiple predecessors. Also, it requires checking whether
772 // constructing the necessary self-referential PHI node doesn't introduce any
773 // conflicts; this isn't too difficult, but the previous code for doing this
776 // Note that if this check finds a live use, BB dominates Succ, so BB is
777 // something like a loop pre-header (or rarely, a part of an irreducible CFG);
778 // folding the branch isn't profitable in that case anyway.
779 if (!Succ->getSinglePredecessor()) {
780 BasicBlock::iterator BBI = BB->begin();
781 while (isa<PHINode>(*BBI)) {
782 for (Use &U : BBI->uses()) {
783 if (PHINode* PN = dyn_cast<PHINode>(U.getUser())) {
784 if (PN->getIncomingBlock(U) != BB)
794 DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
796 if (isa<PHINode>(Succ->begin())) {
797 // If there is more than one pred of succ, and there are PHI nodes in
798 // the successor, then we need to add incoming edges for the PHI nodes
800 const PredBlockVector BBPreds(pred_begin(BB), pred_end(BB));
802 // Loop over all of the PHI nodes in the successor of BB.
803 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
804 PHINode *PN = cast<PHINode>(I);
806 redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN);
810 if (Succ->getSinglePredecessor()) {
811 // BB is the only predecessor of Succ, so Succ will end up with exactly
812 // the same predecessors BB had.
814 // Copy over any phi, debug or lifetime instruction.
815 BB->getTerminator()->eraseFromParent();
816 Succ->getInstList().splice(Succ->getFirstNonPHI(), BB->getInstList());
818 while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
819 // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
820 assert(PN->use_empty() && "There shouldn't be any uses here!");
821 PN->eraseFromParent();
825 // Everything that jumped to BB now goes to Succ.
826 BB->replaceAllUsesWith(Succ);
827 if (!Succ->hasName()) Succ->takeName(BB);
828 BB->eraseFromParent(); // Delete the old basic block.
832 /// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
833 /// nodes in this block. This doesn't try to be clever about PHI nodes
834 /// which differ only in the order of the incoming values, but instcombine
835 /// orders them so it usually won't matter.
837 bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) {
838 // This implementation doesn't currently consider undef operands
839 // specially. Theoretically, two phis which are identical except for
840 // one having an undef where the other doesn't could be collapsed.
842 struct PHIDenseMapInfo {
843 static PHINode *getEmptyKey() {
844 return DenseMapInfo<PHINode *>::getEmptyKey();
846 static PHINode *getTombstoneKey() {
847 return DenseMapInfo<PHINode *>::getTombstoneKey();
849 static unsigned getHashValue(PHINode *PN) {
850 // Compute a hash value on the operands. Instcombine will likely have
851 // sorted them, which helps expose duplicates, but we have to check all
852 // the operands to be safe in case instcombine hasn't run.
853 return static_cast<unsigned>(hash_combine(
854 hash_combine_range(PN->value_op_begin(), PN->value_op_end()),
855 hash_combine_range(PN->block_begin(), PN->block_end())));
857 static bool isEqual(PHINode *LHS, PHINode *RHS) {
858 if (LHS == getEmptyKey() || LHS == getTombstoneKey() ||
859 RHS == getEmptyKey() || RHS == getTombstoneKey())
861 return LHS->isIdenticalTo(RHS);
865 // Set of unique PHINodes.
866 DenseSet<PHINode *, PHIDenseMapInfo> PHISet;
869 bool Changed = false;
870 for (auto I = BB->begin(); PHINode *PN = dyn_cast<PHINode>(I++);) {
871 auto Inserted = PHISet.insert(PN);
872 if (!Inserted.second) {
873 // A duplicate. Replace this PHI with its duplicate.
874 PN->replaceAllUsesWith(*Inserted.first);
875 PN->eraseFromParent();
883 /// enforceKnownAlignment - If the specified pointer points to an object that
884 /// we control, modify the object's alignment to PrefAlign. This isn't
885 /// often possible though. If alignment is important, a more reliable approach
886 /// is to simply align all global variables and allocation instructions to
887 /// their preferred alignment from the beginning.
889 static unsigned enforceKnownAlignment(Value *V, unsigned Align,
891 const DataLayout &DL) {
892 V = V->stripPointerCasts();
894 if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
895 // If the preferred alignment is greater than the natural stack alignment
896 // then don't round up. This avoids dynamic stack realignment.
897 if (DL.exceedsNaturalStackAlignment(PrefAlign))
899 // If there is a requested alignment and if this is an alloca, round up.
900 if (AI->getAlignment() >= PrefAlign)
901 return AI->getAlignment();
902 AI->setAlignment(PrefAlign);
906 if (auto *GO = dyn_cast<GlobalObject>(V)) {
907 // If there is a large requested alignment and we can, bump up the alignment
908 // of the global. If the memory we set aside for the global may not be the
909 // memory used by the final program then it is impossible for us to reliably
910 // enforce the preferred alignment.
911 if (!GO->isStrongDefinitionForLinker())
914 if (GO->getAlignment() >= PrefAlign)
915 return GO->getAlignment();
916 // We can only increase the alignment of the global if it has no alignment
917 // specified or if it is not assigned a section. If it is assigned a
918 // section, the global could be densely packed with other objects in the
919 // section, increasing the alignment could cause padding issues.
920 if (!GO->hasSection() || GO->getAlignment() == 0)
921 GO->setAlignment(PrefAlign);
922 return GO->getAlignment();
928 /// getOrEnforceKnownAlignment - If the specified pointer has an alignment that
929 /// we can determine, return it, otherwise return 0. If PrefAlign is specified,
930 /// and it is more than the alignment of the ultimate object, see if we can
931 /// increase the alignment of the ultimate object, making this check succeed.
932 unsigned llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
933 const DataLayout &DL,
934 const Instruction *CxtI,
936 const DominatorTree *DT) {
937 assert(V->getType()->isPointerTy() &&
938 "getOrEnforceKnownAlignment expects a pointer!");
939 unsigned BitWidth = DL.getPointerTypeSizeInBits(V->getType());
941 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
942 computeKnownBits(V, KnownZero, KnownOne, DL, 0, AC, CxtI, DT);
943 unsigned TrailZ = KnownZero.countTrailingOnes();
945 // Avoid trouble with ridiculously large TrailZ values, such as
946 // those computed from a null pointer.
947 TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
949 unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
951 // LLVM doesn't support alignments larger than this currently.
952 Align = std::min(Align, +Value::MaximumAlignment);
954 if (PrefAlign > Align)
955 Align = enforceKnownAlignment(V, Align, PrefAlign, DL);
957 // We don't need to make any adjustment.
961 ///===---------------------------------------------------------------------===//
962 /// Dbg Intrinsic utilities
965 /// See if there is a dbg.value intrinsic for DIVar before I.
966 static bool LdStHasDebugValue(const DILocalVariable *DIVar, Instruction *I) {
967 // Since we can't guarantee that the original dbg.declare instrinsic
968 // is removed by LowerDbgDeclare(), we need to make sure that we are
969 // not inserting the same dbg.value intrinsic over and over.
970 llvm::BasicBlock::InstListType::iterator PrevI(I);
971 if (PrevI != I->getParent()->getInstList().begin()) {
973 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(PrevI))
974 if (DVI->getValue() == I->getOperand(0) &&
975 DVI->getOffset() == 0 &&
976 DVI->getVariable() == DIVar)
982 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
983 /// that has an associated llvm.dbg.decl intrinsic.
984 bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
985 StoreInst *SI, DIBuilder &Builder) {
986 auto *DIVar = DDI->getVariable();
987 auto *DIExpr = DDI->getExpression();
988 assert(DIVar && "Missing variable");
990 if (LdStHasDebugValue(DIVar, SI))
993 // If an argument is zero extended then use argument directly. The ZExt
994 // may be zapped by an optimization pass in future.
995 Argument *ExtendedArg = nullptr;
996 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
997 ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0));
998 if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
999 ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0));
1001 Builder.insertDbgValueIntrinsic(ExtendedArg, 0, DIVar, DIExpr,
1002 DDI->getDebugLoc(), SI);
1004 Builder.insertDbgValueIntrinsic(SI->getOperand(0), 0, DIVar, DIExpr,
1005 DDI->getDebugLoc(), SI);
1009 /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
1010 /// that has an associated llvm.dbg.decl intrinsic.
1011 bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
1012 LoadInst *LI, DIBuilder &Builder) {
1013 auto *DIVar = DDI->getVariable();
1014 auto *DIExpr = DDI->getExpression();
1015 assert(DIVar && "Missing variable");
1017 if (LdStHasDebugValue(DIVar, LI))
1020 Builder.insertDbgValueIntrinsic(LI->getOperand(0), 0, DIVar, DIExpr,
1021 DDI->getDebugLoc(), LI);
1025 /// Determine whether this alloca is either a VLA or an array.
1026 static bool isArray(AllocaInst *AI) {
1027 return AI->isArrayAllocation() ||
1028 AI->getType()->getElementType()->isArrayTy();
1031 /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
1032 /// of llvm.dbg.value intrinsics.
1033 bool llvm::LowerDbgDeclare(Function &F) {
1034 DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false);
1035 SmallVector<DbgDeclareInst *, 4> Dbgs;
1037 for (BasicBlock::iterator BI : FI)
1038 if (auto DDI = dyn_cast<DbgDeclareInst>(BI))
1039 Dbgs.push_back(DDI);
1044 for (auto &I : Dbgs) {
1045 DbgDeclareInst *DDI = I;
1046 AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress());
1047 // If this is an alloca for a scalar variable, insert a dbg.value
1048 // at each load and store to the alloca and erase the dbg.declare.
1049 // The dbg.values allow tracking a variable even if it is not
1050 // stored on the stack, while the dbg.declare can only describe
1051 // the stack slot (and at a lexical-scope granularity). Later
1052 // passes will attempt to elide the stack slot.
1053 if (AI && !isArray(AI)) {
1054 for (User *U : AI->users())
1055 if (StoreInst *SI = dyn_cast<StoreInst>(U))
1056 ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
1057 else if (LoadInst *LI = dyn_cast<LoadInst>(U))
1058 ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
1059 else if (CallInst *CI = dyn_cast<CallInst>(U)) {
1060 // This is a call by-value or some other instruction that
1061 // takes a pointer to the variable. Insert a *value*
1062 // intrinsic that describes the alloca.
1063 DIB.insertDbgValueIntrinsic(AI, 0, DDI->getVariable(),
1064 DDI->getExpression(), DDI->getDebugLoc(),
1067 DDI->eraseFromParent();
1073 /// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic describing the
1074 /// alloca 'V', if any.
1075 DbgDeclareInst *llvm::FindAllocaDbgDeclare(Value *V) {
1076 if (auto *L = LocalAsMetadata::getIfExists(V))
1077 if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
1078 for (User *U : MDV->users())
1079 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
1085 bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
1086 DIBuilder &Builder, bool Deref) {
1087 DbgDeclareInst *DDI = FindAllocaDbgDeclare(AI);
1090 DebugLoc Loc = DDI->getDebugLoc();
1091 auto *DIVar = DDI->getVariable();
1092 auto *DIExpr = DDI->getExpression();
1093 assert(DIVar && "Missing variable");
1096 // Create a copy of the original DIDescriptor for user variable, prepending
1097 // "deref" operation to a list of address elements, as new llvm.dbg.declare
1098 // will take a value storing address of the memory for variable, not
1100 SmallVector<uint64_t, 4> NewDIExpr;
1101 NewDIExpr.push_back(dwarf::DW_OP_deref);
1103 NewDIExpr.append(DIExpr->elements_begin(), DIExpr->elements_end());
1104 DIExpr = Builder.createExpression(NewDIExpr);
1107 // Insert llvm.dbg.declare in the same basic block as the original alloca,
1108 // and remove old llvm.dbg.declare.
1109 BasicBlock *BB = AI->getParent();
1110 Builder.insertDeclare(NewAllocaAddress, DIVar, DIExpr, Loc, BB);
1111 DDI->eraseFromParent();
1115 /// changeToUnreachable - Insert an unreachable instruction before the specified
1116 /// instruction, making it and the rest of the code in the block dead.
1117 static void changeToUnreachable(Instruction *I, bool UseLLVMTrap) {
1118 BasicBlock *BB = I->getParent();
1119 // Loop over all of the successors, removing BB's entry from any PHI
1121 for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
1122 (*SI)->removePredecessor(BB);
1124 // Insert a call to llvm.trap right before this. This turns the undefined
1125 // behavior into a hard fail instead of falling through into random code.
1128 Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
1129 CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
1130 CallTrap->setDebugLoc(I->getDebugLoc());
1132 new UnreachableInst(I->getContext(), I);
1134 // All instructions after this are dead.
1135 BasicBlock::iterator BBI = I, BBE = BB->end();
1136 while (BBI != BBE) {
1137 if (!BBI->use_empty())
1138 BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
1139 BB->getInstList().erase(BBI++);
1143 /// changeToCall - Convert the specified invoke into a normal call.
1144 static void changeToCall(InvokeInst *II) {
1145 SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
1146 CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, "", II);
1147 NewCall->takeName(II);
1148 NewCall->setCallingConv(II->getCallingConv());
1149 NewCall->setAttributes(II->getAttributes());
1150 NewCall->setDebugLoc(II->getDebugLoc());
1151 II->replaceAllUsesWith(NewCall);
1153 // Follow the call by a branch to the normal destination.
1154 BranchInst::Create(II->getNormalDest(), II);
1156 // Update PHI nodes in the unwind destination
1157 II->getUnwindDest()->removePredecessor(II->getParent());
1158 II->eraseFromParent();
1161 static bool markAliveBlocks(Function &F,
1162 SmallPtrSetImpl<BasicBlock*> &Reachable) {
1164 SmallVector<BasicBlock*, 128> Worklist;
1165 BasicBlock *BB = F.begin();
1166 Worklist.push_back(BB);
1167 Reachable.insert(BB);
1168 bool Changed = false;
1170 BB = Worklist.pop_back_val();
1172 // Do a quick scan of the basic block, turning any obviously unreachable
1173 // instructions into LLVM unreachable insts. The instruction combining pass
1174 // canonicalizes unreachable insts into stores to null or undef.
1175 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
1176 // Assumptions that are known to be false are equivalent to unreachable.
1177 // Also, if the condition is undefined, then we make the choice most
1178 // beneficial to the optimizer, and choose that to also be unreachable.
1179 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
1180 if (II->getIntrinsicID() == Intrinsic::assume) {
1181 bool MakeUnreachable = false;
1182 if (isa<UndefValue>(II->getArgOperand(0)))
1183 MakeUnreachable = true;
1184 else if (ConstantInt *Cond =
1185 dyn_cast<ConstantInt>(II->getArgOperand(0)))
1186 MakeUnreachable = Cond->isZero();
1188 if (MakeUnreachable) {
1189 // Don't insert a call to llvm.trap right before the unreachable.
1190 changeToUnreachable(BBI, false);
1196 if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
1197 if (CI->doesNotReturn()) {
1198 // If we found a call to a no-return function, insert an unreachable
1199 // instruction after it. Make sure there isn't *already* one there
1202 if (!isa<UnreachableInst>(BBI)) {
1203 // Don't insert a call to llvm.trap right before the unreachable.
1204 changeToUnreachable(BBI, false);
1211 // Store to undef and store to null are undefined and used to signal that
1212 // they should be changed to unreachable by passes that can't modify the
1214 if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
1215 // Don't touch volatile stores.
1216 if (SI->isVolatile()) continue;
1218 Value *Ptr = SI->getOperand(1);
1220 if (isa<UndefValue>(Ptr) ||
1221 (isa<ConstantPointerNull>(Ptr) &&
1222 SI->getPointerAddressSpace() == 0)) {
1223 changeToUnreachable(SI, true);
1230 // Turn invokes that call 'nounwind' functions into ordinary calls.
1231 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
1232 Value *Callee = II->getCalledValue();
1233 if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
1234 changeToUnreachable(II, true);
1236 } else if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(&F)) {
1237 if (II->use_empty() && II->onlyReadsMemory()) {
1238 // jump to the normal destination branch.
1239 BranchInst::Create(II->getNormalDest(), II);
1240 II->getUnwindDest()->removePredecessor(II->getParent());
1241 II->eraseFromParent();
1248 Changed |= ConstantFoldTerminator(BB, true);
1249 for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
1250 if (Reachable.insert(*SI).second)
1251 Worklist.push_back(*SI);
1252 } while (!Worklist.empty());
1256 /// removeUnreachableBlocksFromFn - Remove blocks that are not reachable, even
1257 /// if they are in a dead cycle. Return true if a change was made, false
1259 bool llvm::removeUnreachableBlocks(Function &F) {
1260 SmallPtrSet<BasicBlock*, 128> Reachable;
1261 bool Changed = markAliveBlocks(F, Reachable);
1263 // If there are unreachable blocks in the CFG...
1264 if (Reachable.size() == F.size())
1267 assert(Reachable.size() < F.size());
1268 NumRemoved += F.size()-Reachable.size();
1270 // Loop over all of the basic blocks that are not reachable, dropping all of
1271 // their internal references...
1272 for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) {
1273 if (Reachable.count(BB))
1276 for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
1277 if (Reachable.count(*SI))
1278 (*SI)->removePredecessor(BB);
1279 BB->dropAllReferences();
1282 for (Function::iterator I = ++F.begin(); I != F.end();)
1283 if (!Reachable.count(I))
1284 I = F.getBasicBlockList().erase(I);
1291 void llvm::combineMetadata(Instruction *K, const Instruction *J, ArrayRef<unsigned> KnownIDs) {
1292 SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata;
1293 K->dropUnknownNonDebugMetadata(KnownIDs);
1294 K->getAllMetadataOtherThanDebugLoc(Metadata);
1295 for (unsigned i = 0, n = Metadata.size(); i < n; ++i) {
1296 unsigned Kind = Metadata[i].first;
1297 MDNode *JMD = J->getMetadata(Kind);
1298 MDNode *KMD = Metadata[i].second;
1302 K->setMetadata(Kind, nullptr); // Remove unknown metadata
1304 case LLVMContext::MD_dbg:
1305 llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg");
1306 case LLVMContext::MD_tbaa:
1307 K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD));
1309 case LLVMContext::MD_alias_scope:
1310 K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD));
1312 case LLVMContext::MD_noalias:
1313 K->setMetadata(Kind, MDNode::intersect(JMD, KMD));
1315 case LLVMContext::MD_range:
1316 K->setMetadata(Kind, MDNode::getMostGenericRange(JMD, KMD));
1318 case LLVMContext::MD_fpmath:
1319 K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD));
1321 case LLVMContext::MD_invariant_load:
1322 // Only set the !invariant.load if it is present in both instructions.
1323 K->setMetadata(Kind, JMD);
1325 case LLVMContext::MD_nonnull:
1326 // Only set the !nonnull if it is present in both instructions.
1327 K->setMetadata(Kind, JMD);
1333 unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To,
1335 const BasicBlockEdge &Root) {
1336 assert(From->getType() == To->getType());
1339 for (Value::use_iterator UI = From->use_begin(), UE = From->use_end();
1342 if (DT.dominates(Root, U)) {
1344 DEBUG(dbgs() << "Replace dominated use of '"
1345 << From->getName() << "' as "
1346 << *To << " in " << *U << "\n");