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/Constants.h"
17 #include "llvm/GlobalAlias.h"
18 #include "llvm/GlobalVariable.h"
19 #include "llvm/DerivedTypes.h"
20 #include "llvm/Instructions.h"
21 #include "llvm/Intrinsics.h"
22 #include "llvm/IntrinsicInst.h"
23 #include "llvm/Metadata.h"
24 #include "llvm/Operator.h"
25 #include "llvm/ADT/DenseMap.h"
26 #include "llvm/ADT/SmallPtrSet.h"
27 #include "llvm/Analysis/DebugInfo.h"
28 #include "llvm/Analysis/DIBuilder.h"
29 #include "llvm/Analysis/Dominators.h"
30 #include "llvm/Analysis/InstructionSimplify.h"
31 #include "llvm/Analysis/MemoryBuiltins.h"
32 #include "llvm/Analysis/ProfileInfo.h"
33 #include "llvm/Analysis/ValueTracking.h"
34 #include "llvm/Target/TargetData.h"
35 #include "llvm/Support/CFG.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/GetElementPtrTypeIterator.h"
38 #include "llvm/Support/IRBuilder.h"
39 #include "llvm/Support/MathExtras.h"
40 #include "llvm/Support/ValueHandle.h"
41 #include "llvm/Support/raw_ostream.h"
44 //===----------------------------------------------------------------------===//
45 // Local constant propagation.
48 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
49 /// constant value, convert it into an unconditional branch to the constant
50 /// destination. This is a nontrivial operation because the successors of this
51 /// basic block must have their PHI nodes updated.
52 /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
53 /// conditions and indirectbr addresses this might make dead if
54 /// DeleteDeadConditions is true.
55 bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions) {
56 TerminatorInst *T = BB->getTerminator();
57 IRBuilder<> Builder(T);
59 // Branch - See if we are conditional jumping on constant
60 if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
61 if (BI->isUnconditional()) return false; // Can't optimize uncond branch
62 BasicBlock *Dest1 = BI->getSuccessor(0);
63 BasicBlock *Dest2 = BI->getSuccessor(1);
65 if (ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition())) {
66 // Are we branching on constant?
67 // YES. Change to unconditional branch...
68 BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2;
69 BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1;
71 //cerr << "Function: " << T->getParent()->getParent()
72 // << "\nRemoving branch from " << T->getParent()
73 // << "\n\nTo: " << OldDest << endl;
75 // Let the basic block know that we are letting go of it. Based on this,
76 // it will adjust it's PHI nodes.
77 OldDest->removePredecessor(BB);
79 // Replace the conditional branch with an unconditional one.
80 Builder.CreateBr(Destination);
81 BI->eraseFromParent();
85 if (Dest2 == Dest1) { // Conditional branch to same location?
86 // This branch matches something like this:
87 // br bool %cond, label %Dest, label %Dest
88 // and changes it into: br label %Dest
90 // Let the basic block know that we are letting go of one copy of it.
91 assert(BI->getParent() && "Terminator not inserted in block!");
92 Dest1->removePredecessor(BI->getParent());
94 // Replace the conditional branch with an unconditional one.
95 Builder.CreateBr(Dest1);
96 Value *Cond = BI->getCondition();
97 BI->eraseFromParent();
98 if (DeleteDeadConditions)
99 RecursivelyDeleteTriviallyDeadInstructions(Cond);
105 if (SwitchInst *SI = dyn_cast<SwitchInst>(T)) {
106 // If we are switching on a constant, we can convert the switch into a
107 // single branch instruction!
108 ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition());
109 BasicBlock *TheOnlyDest = SI->getDefaultDest();
110 BasicBlock *DefaultDest = TheOnlyDest;
112 // Figure out which case it goes to.
113 for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
115 // Found case matching a constant operand?
116 if (i.getCaseValue() == CI) {
117 TheOnlyDest = i.getCaseSuccessor();
121 // Check to see if this branch is going to the same place as the default
122 // dest. If so, eliminate it as an explicit compare.
123 if (i.getCaseSuccessor() == DefaultDest) {
124 // Remove this entry.
125 DefaultDest->removePredecessor(SI->getParent());
131 // Otherwise, check to see if the switch only branches to one destination.
132 // We do this by reseting "TheOnlyDest" to null when we find two non-equal
134 if (i.getCaseSuccessor() != TheOnlyDest) TheOnlyDest = 0;
137 if (CI && !TheOnlyDest) {
138 // Branching on a constant, but not any of the cases, go to the default
140 TheOnlyDest = SI->getDefaultDest();
143 // If we found a single destination that we can fold the switch into, do so
146 // Insert the new branch.
147 Builder.CreateBr(TheOnlyDest);
148 BasicBlock *BB = SI->getParent();
150 // Remove entries from PHI nodes which we no longer branch to...
151 for (unsigned i = 0, e = SI->getNumSuccessors(); i != e; ++i) {
152 // Found case matching a constant operand?
153 BasicBlock *Succ = SI->getSuccessor(i);
154 if (Succ == TheOnlyDest)
155 TheOnlyDest = 0; // Don't modify the first branch to TheOnlyDest
157 Succ->removePredecessor(BB);
160 // Delete the old switch.
161 Value *Cond = SI->getCondition();
162 SI->eraseFromParent();
163 if (DeleteDeadConditions)
164 RecursivelyDeleteTriviallyDeadInstructions(Cond);
168 if (SI->getNumCases() == 1) {
169 // Otherwise, we can fold this switch into a conditional branch
170 // instruction if it has only one non-default destination.
171 SwitchInst::CaseIt FirstCase = SI->case_begin();
172 Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
173 FirstCase.getCaseValue(), "cond");
175 // Insert the new branch.
176 Builder.CreateCondBr(Cond, FirstCase.getCaseSuccessor(),
177 SI->getDefaultDest());
179 // Delete the old switch.
180 SI->eraseFromParent();
186 if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(T)) {
187 // indirectbr blockaddress(@F, @BB) -> br label @BB
188 if (BlockAddress *BA =
189 dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
190 BasicBlock *TheOnlyDest = BA->getBasicBlock();
191 // Insert the new branch.
192 Builder.CreateBr(TheOnlyDest);
194 for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
195 if (IBI->getDestination(i) == TheOnlyDest)
198 IBI->getDestination(i)->removePredecessor(IBI->getParent());
200 Value *Address = IBI->getAddress();
201 IBI->eraseFromParent();
202 if (DeleteDeadConditions)
203 RecursivelyDeleteTriviallyDeadInstructions(Address);
205 // If we didn't find our destination in the IBI successor list, then we
206 // have undefined behavior. Replace the unconditional branch with an
207 // 'unreachable' instruction.
209 BB->getTerminator()->eraseFromParent();
210 new UnreachableInst(BB->getContext(), BB);
221 //===----------------------------------------------------------------------===//
222 // Local dead code elimination.
225 /// isInstructionTriviallyDead - Return true if the result produced by the
226 /// instruction is not used, and the instruction has no side effects.
228 bool llvm::isInstructionTriviallyDead(Instruction *I) {
229 if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
231 // We don't want the landingpad instruction removed by anything this general.
232 if (isa<LandingPadInst>(I))
235 // We don't want debug info removed by anything this general, unless
236 // debug info is empty.
237 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
238 if (DDI->getAddress())
242 if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
248 if (!I->mayHaveSideEffects()) return true;
250 // Special case intrinsics that "may have side effects" but can be deleted
252 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
253 // Safe to delete llvm.stacksave if dead.
254 if (II->getIntrinsicID() == Intrinsic::stacksave)
257 // Lifetime intrinsics are dead when their right-hand is undef.
258 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
259 II->getIntrinsicID() == Intrinsic::lifetime_end)
260 return isa<UndefValue>(II->getArgOperand(1));
263 if (extractMallocCall(I)) return true;
265 if (CallInst *CI = isFreeCall(I))
266 if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
267 return C->isNullValue() || isa<UndefValue>(C);
272 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
273 /// trivially dead instruction, delete it. If that makes any of its operands
274 /// trivially dead, delete them too, recursively. Return true if any
275 /// instructions were deleted.
276 bool llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V) {
277 Instruction *I = dyn_cast<Instruction>(V);
278 if (!I || !I->use_empty() || !isInstructionTriviallyDead(I))
281 SmallVector<Instruction*, 16> DeadInsts;
282 DeadInsts.push_back(I);
285 I = DeadInsts.pop_back_val();
287 // Null out all of the instruction's operands to see if any operand becomes
289 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
290 Value *OpV = I->getOperand(i);
293 if (!OpV->use_empty()) continue;
295 // If the operand is an instruction that became dead as we nulled out the
296 // operand, and if it is 'trivially' dead, delete it in a future loop
298 if (Instruction *OpI = dyn_cast<Instruction>(OpV))
299 if (isInstructionTriviallyDead(OpI))
300 DeadInsts.push_back(OpI);
303 I->eraseFromParent();
304 } while (!DeadInsts.empty());
309 /// areAllUsesEqual - Check whether the uses of a value are all the same.
310 /// This is similar to Instruction::hasOneUse() except this will also return
311 /// true when there are no uses or multiple uses that all refer to the same
313 static bool areAllUsesEqual(Instruction *I) {
314 Value::use_iterator UI = I->use_begin();
315 Value::use_iterator UE = I->use_end();
320 for (++UI; UI != UE; ++UI) {
327 /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
328 /// dead PHI node, due to being a def-use chain of single-use nodes that
329 /// either forms a cycle or is terminated by a trivially dead instruction,
330 /// delete it. If that makes any of its operands trivially dead, delete them
331 /// too, recursively. Return true if a change was made.
332 bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN) {
333 SmallPtrSet<Instruction*, 4> Visited;
334 for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects();
335 I = cast<Instruction>(*I->use_begin())) {
337 return RecursivelyDeleteTriviallyDeadInstructions(I);
339 // If we find an instruction more than once, we're on a cycle that
340 // won't prove fruitful.
341 if (!Visited.insert(I)) {
342 // Break the cycle and delete the instruction and its operands.
343 I->replaceAllUsesWith(UndefValue::get(I->getType()));
344 (void)RecursivelyDeleteTriviallyDeadInstructions(I);
351 /// SimplifyInstructionsInBlock - Scan the specified basic block and try to
352 /// simplify any instructions in it and recursively delete dead instructions.
354 /// This returns true if it changed the code, note that it can delete
355 /// instructions in other blocks as well in this block.
356 bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD) {
357 bool MadeChange = false;
358 for (BasicBlock::iterator BI = BB->begin(), E = --BB->end(); BI != E; ) {
359 assert(!BI->isTerminator());
360 Instruction *Inst = BI++;
363 if (recursivelySimplifyInstruction(Inst, TD)) {
370 MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst);
377 //===----------------------------------------------------------------------===//
378 // Control Flow Graph Restructuring.
382 /// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
383 /// method is called when we're about to delete Pred as a predecessor of BB. If
384 /// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
386 /// Unlike the removePredecessor method, this attempts to simplify uses of PHI
387 /// nodes that collapse into identity values. For example, if we have:
388 /// x = phi(1, 0, 0, 0)
391 /// .. and delete the predecessor corresponding to the '1', this will attempt to
392 /// recursively fold the and to 0.
393 void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
395 // This only adjusts blocks with PHI nodes.
396 if (!isa<PHINode>(BB->begin()))
399 // Remove the entries for Pred from the PHI nodes in BB, but do not simplify
400 // them down. This will leave us with single entry phi nodes and other phis
401 // that can be removed.
402 BB->removePredecessor(Pred, true);
404 WeakVH PhiIt = &BB->front();
405 while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) {
406 PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt));
407 Value *OldPhiIt = PhiIt;
409 if (!recursivelySimplifyInstruction(PN, TD))
412 // If recursive simplification ended up deleting the next PHI node we would
413 // iterate to, then our iterator is invalid, restart scanning from the top
415 if (PhiIt != OldPhiIt) PhiIt = &BB->front();
420 /// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its
421 /// predecessor is known to have one successor (DestBB!). Eliminate the edge
422 /// between them, moving the instructions in the predecessor into DestBB and
423 /// deleting the predecessor block.
425 void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, Pass *P) {
426 // If BB has single-entry PHI nodes, fold them.
427 while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
428 Value *NewVal = PN->getIncomingValue(0);
429 // Replace self referencing PHI with undef, it must be dead.
430 if (NewVal == PN) NewVal = UndefValue::get(PN->getType());
431 PN->replaceAllUsesWith(NewVal);
432 PN->eraseFromParent();
435 BasicBlock *PredBB = DestBB->getSinglePredecessor();
436 assert(PredBB && "Block doesn't have a single predecessor!");
438 // Zap anything that took the address of DestBB. Not doing this will give the
439 // address an invalid value.
440 if (DestBB->hasAddressTaken()) {
441 BlockAddress *BA = BlockAddress::get(DestBB);
442 Constant *Replacement =
443 ConstantInt::get(llvm::Type::getInt32Ty(BA->getContext()), 1);
444 BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
446 BA->destroyConstant();
449 // Anything that branched to PredBB now branches to DestBB.
450 PredBB->replaceAllUsesWith(DestBB);
452 // Splice all the instructions from PredBB to DestBB.
453 PredBB->getTerminator()->eraseFromParent();
454 DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
457 DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>();
459 BasicBlock *PredBBIDom = DT->getNode(PredBB)->getIDom()->getBlock();
460 DT->changeImmediateDominator(DestBB, PredBBIDom);
461 DT->eraseNode(PredBB);
463 ProfileInfo *PI = P->getAnalysisIfAvailable<ProfileInfo>();
465 PI->replaceAllUses(PredBB, DestBB);
466 PI->removeEdge(ProfileInfo::getEdge(PredBB, DestBB));
470 PredBB->eraseFromParent();
473 /// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
474 /// almost-empty BB ending in an unconditional branch to Succ, into succ.
476 /// Assumption: Succ is the single successor for BB.
478 static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
479 assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
481 DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
482 << Succ->getName() << "\n");
483 // Shortcut, if there is only a single predecessor it must be BB and merging
485 if (Succ->getSinglePredecessor()) return true;
487 // Make a list of the predecessors of BB
488 SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
490 // Look at all the phi nodes in Succ, to see if they present a conflict when
491 // merging these blocks
492 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
493 PHINode *PN = cast<PHINode>(I);
495 // If the incoming value from BB is again a PHINode in
496 // BB which has the same incoming value for *PI as PN does, we can
497 // merge the phi nodes and then the blocks can still be merged
498 PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
499 if (BBPN && BBPN->getParent() == BB) {
500 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
501 BasicBlock *IBB = PN->getIncomingBlock(PI);
502 if (BBPreds.count(IBB) &&
503 BBPN->getIncomingValueForBlock(IBB) != PN->getIncomingValue(PI)) {
504 DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
505 << Succ->getName() << " is conflicting with "
506 << BBPN->getName() << " with regard to common predecessor "
507 << IBB->getName() << "\n");
512 Value* Val = PN->getIncomingValueForBlock(BB);
513 for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
514 // See if the incoming value for the common predecessor is equal to the
515 // one for BB, in which case this phi node will not prevent the merging
517 BasicBlock *IBB = PN->getIncomingBlock(PI);
518 if (BBPreds.count(IBB) && Val != PN->getIncomingValue(PI)) {
519 DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
520 << Succ->getName() << " is conflicting with regard to common "
521 << "predecessor " << IBB->getName() << "\n");
531 /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
532 /// unconditional branch, and contains no instructions other than PHI nodes,
533 /// potential side-effect free intrinsics and the branch. If possible,
534 /// eliminate BB by rewriting all the predecessors to branch to the successor
535 /// block and return true. If we can't transform, return false.
536 bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) {
537 assert(BB != &BB->getParent()->getEntryBlock() &&
538 "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
540 // We can't eliminate infinite loops.
541 BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0);
542 if (BB == Succ) return false;
544 // Check to see if merging these blocks would cause conflicts for any of the
545 // phi nodes in BB or Succ. If not, we can safely merge.
546 if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
548 // Check for cases where Succ has multiple predecessors and a PHI node in BB
549 // has uses which will not disappear when the PHI nodes are merged. It is
550 // possible to handle such cases, but difficult: it requires checking whether
551 // BB dominates Succ, which is non-trivial to calculate in the case where
552 // Succ has multiple predecessors. Also, it requires checking whether
553 // constructing the necessary self-referential PHI node doesn't intoduce any
554 // conflicts; this isn't too difficult, but the previous code for doing this
557 // Note that if this check finds a live use, BB dominates Succ, so BB is
558 // something like a loop pre-header (or rarely, a part of an irreducible CFG);
559 // folding the branch isn't profitable in that case anyway.
560 if (!Succ->getSinglePredecessor()) {
561 BasicBlock::iterator BBI = BB->begin();
562 while (isa<PHINode>(*BBI)) {
563 for (Value::use_iterator UI = BBI->use_begin(), E = BBI->use_end();
565 if (PHINode* PN = dyn_cast<PHINode>(*UI)) {
566 if (PN->getIncomingBlock(UI) != BB)
576 DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
578 if (isa<PHINode>(Succ->begin())) {
579 // If there is more than one pred of succ, and there are PHI nodes in
580 // the successor, then we need to add incoming edges for the PHI nodes
582 const SmallVector<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
584 // Loop over all of the PHI nodes in the successor of BB.
585 for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
586 PHINode *PN = cast<PHINode>(I);
587 Value *OldVal = PN->removeIncomingValue(BB, false);
588 assert(OldVal && "No entry in PHI for Pred BB!");
590 // If this incoming value is one of the PHI nodes in BB, the new entries
591 // in the PHI node are the entries from the old PHI.
592 if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
593 PHINode *OldValPN = cast<PHINode>(OldVal);
594 for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i)
595 // Note that, since we are merging phi nodes and BB and Succ might
596 // have common predecessors, we could end up with a phi node with
597 // identical incoming branches. This will be cleaned up later (and
598 // will trigger asserts if we try to clean it up now, without also
599 // simplifying the corresponding conditional branch).
600 PN->addIncoming(OldValPN->getIncomingValue(i),
601 OldValPN->getIncomingBlock(i));
603 // Add an incoming value for each of the new incoming values.
604 for (unsigned i = 0, e = BBPreds.size(); i != e; ++i)
605 PN->addIncoming(OldVal, BBPreds[i]);
610 if (Succ->getSinglePredecessor()) {
611 // BB is the only predecessor of Succ, so Succ will end up with exactly
612 // the same predecessors BB had.
614 // Copy over any phi, debug or lifetime instruction.
615 BB->getTerminator()->eraseFromParent();
616 Succ->getInstList().splice(Succ->getFirstNonPHI(), BB->getInstList());
618 while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
619 // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
620 assert(PN->use_empty() && "There shouldn't be any uses here!");
621 PN->eraseFromParent();
625 // Everything that jumped to BB now goes to Succ.
626 BB->replaceAllUsesWith(Succ);
627 if (!Succ->hasName()) Succ->takeName(BB);
628 BB->eraseFromParent(); // Delete the old basic block.
632 /// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
633 /// nodes in this block. This doesn't try to be clever about PHI nodes
634 /// which differ only in the order of the incoming values, but instcombine
635 /// orders them so it usually won't matter.
637 bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) {
638 bool Changed = false;
640 // This implementation doesn't currently consider undef operands
641 // specially. Theoretically, two phis which are identical except for
642 // one having an undef where the other doesn't could be collapsed.
644 // Map from PHI hash values to PHI nodes. If multiple PHIs have
645 // the same hash value, the element is the first PHI in the
646 // linked list in CollisionMap.
647 DenseMap<uintptr_t, PHINode *> HashMap;
649 // Maintain linked lists of PHI nodes with common hash values.
650 DenseMap<PHINode *, PHINode *> CollisionMap;
653 for (BasicBlock::iterator I = BB->begin();
654 PHINode *PN = dyn_cast<PHINode>(I++); ) {
655 // Compute a hash value on the operands. Instcombine will likely have sorted
656 // them, which helps expose duplicates, but we have to check all the
657 // operands to be safe in case instcombine hasn't run.
659 // This hash algorithm is quite weak as hash functions go, but it seems
660 // to do a good enough job for this particular purpose, and is very quick.
661 for (User::op_iterator I = PN->op_begin(), E = PN->op_end(); I != E; ++I) {
662 Hash ^= reinterpret_cast<uintptr_t>(static_cast<Value *>(*I));
663 Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
665 for (PHINode::block_iterator I = PN->block_begin(), E = PN->block_end();
667 Hash ^= reinterpret_cast<uintptr_t>(static_cast<BasicBlock *>(*I));
668 Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
670 // Avoid colliding with the DenseMap sentinels ~0 and ~0-1.
672 // If we've never seen this hash value before, it's a unique PHI.
673 std::pair<DenseMap<uintptr_t, PHINode *>::iterator, bool> Pair =
674 HashMap.insert(std::make_pair(Hash, PN));
675 if (Pair.second) continue;
676 // Otherwise it's either a duplicate or a hash collision.
677 for (PHINode *OtherPN = Pair.first->second; ; ) {
678 if (OtherPN->isIdenticalTo(PN)) {
679 // A duplicate. Replace this PHI with its duplicate.
680 PN->replaceAllUsesWith(OtherPN);
681 PN->eraseFromParent();
685 // A non-duplicate hash collision.
686 DenseMap<PHINode *, PHINode *>::iterator I = CollisionMap.find(OtherPN);
687 if (I == CollisionMap.end()) {
688 // Set this PHI to be the head of the linked list of colliding PHIs.
689 PHINode *Old = Pair.first->second;
690 Pair.first->second = PN;
691 CollisionMap[PN] = Old;
694 // Procede to the next PHI in the list.
702 /// enforceKnownAlignment - If the specified pointer points to an object that
703 /// we control, modify the object's alignment to PrefAlign. This isn't
704 /// often possible though. If alignment is important, a more reliable approach
705 /// is to simply align all global variables and allocation instructions to
706 /// their preferred alignment from the beginning.
708 static unsigned enforceKnownAlignment(Value *V, unsigned Align,
709 unsigned PrefAlign, const TargetData *TD) {
710 V = V->stripPointerCasts();
712 if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
713 // If the preferred alignment is greater than the natural stack alignment
714 // then don't round up. This avoids dynamic stack realignment.
715 if (TD && TD->exceedsNaturalStackAlignment(PrefAlign))
717 // If there is a requested alignment and if this is an alloca, round up.
718 if (AI->getAlignment() >= PrefAlign)
719 return AI->getAlignment();
720 AI->setAlignment(PrefAlign);
724 if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
725 // If there is a large requested alignment and we can, bump up the alignment
727 if (GV->isDeclaration()) return Align;
728 // If the memory we set aside for the global may not be the memory used by
729 // the final program then it is impossible for us to reliably enforce the
730 // preferred alignment.
731 if (GV->isWeakForLinker()) return Align;
733 if (GV->getAlignment() >= PrefAlign)
734 return GV->getAlignment();
735 // We can only increase the alignment of the global if it has no alignment
736 // specified or if it is not assigned a section. If it is assigned a
737 // section, the global could be densely packed with other objects in the
738 // section, increasing the alignment could cause padding issues.
739 if (!GV->hasSection() || GV->getAlignment() == 0)
740 GV->setAlignment(PrefAlign);
741 return GV->getAlignment();
747 /// getOrEnforceKnownAlignment - If the specified pointer has an alignment that
748 /// we can determine, return it, otherwise return 0. If PrefAlign is specified,
749 /// and it is more than the alignment of the ultimate object, see if we can
750 /// increase the alignment of the ultimate object, making this check succeed.
751 unsigned llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
752 const TargetData *TD) {
753 assert(V->getType()->isPointerTy() &&
754 "getOrEnforceKnownAlignment expects a pointer!");
755 unsigned BitWidth = TD ? TD->getPointerSizeInBits() : 64;
756 APInt Mask = APInt::getAllOnesValue(BitWidth);
757 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
758 ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD);
759 unsigned TrailZ = KnownZero.countTrailingOnes();
761 // Avoid trouble with rediculously large TrailZ values, such as
762 // those computed from a null pointer.
763 TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
765 unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
767 // LLVM doesn't support alignments larger than this currently.
768 Align = std::min(Align, +Value::MaximumAlignment);
770 if (PrefAlign > Align)
771 Align = enforceKnownAlignment(V, Align, PrefAlign, TD);
773 // We don't need to make any adjustment.
777 ///===---------------------------------------------------------------------===//
778 /// Dbg Intrinsic utilities
781 /// Inserts a llvm.dbg.value instrinsic before the stores to an alloca'd value
782 /// that has an associated llvm.dbg.decl intrinsic.
783 bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
784 StoreInst *SI, DIBuilder &Builder) {
785 DIVariable DIVar(DDI->getVariable());
789 Instruction *DbgVal = NULL;
790 // If an argument is zero extended then use argument directly. The ZExt
791 // may be zapped by an optimization pass in future.
792 Argument *ExtendedArg = NULL;
793 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
794 ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0));
795 if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
796 ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0));
798 DbgVal = Builder.insertDbgValueIntrinsic(ExtendedArg, 0, DIVar, SI);
800 DbgVal = Builder.insertDbgValueIntrinsic(SI->getOperand(0), 0, DIVar, SI);
802 // Propagate any debug metadata from the store onto the dbg.value.
803 DebugLoc SIDL = SI->getDebugLoc();
804 if (!SIDL.isUnknown())
805 DbgVal->setDebugLoc(SIDL);
806 // Otherwise propagate debug metadata from dbg.declare.
808 DbgVal->setDebugLoc(DDI->getDebugLoc());
812 /// Inserts a llvm.dbg.value instrinsic before the stores to an alloca'd value
813 /// that has an associated llvm.dbg.decl intrinsic.
814 bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
815 LoadInst *LI, DIBuilder &Builder) {
816 DIVariable DIVar(DDI->getVariable());
820 Instruction *DbgVal =
821 Builder.insertDbgValueIntrinsic(LI->getOperand(0), 0,
824 // Propagate any debug metadata from the store onto the dbg.value.
825 DebugLoc LIDL = LI->getDebugLoc();
826 if (!LIDL.isUnknown())
827 DbgVal->setDebugLoc(LIDL);
828 // Otherwise propagate debug metadata from dbg.declare.
830 DbgVal->setDebugLoc(DDI->getDebugLoc());
834 /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
835 /// of llvm.dbg.value intrinsics.
836 bool llvm::LowerDbgDeclare(Function &F) {
837 DIBuilder DIB(*F.getParent());
838 SmallVector<DbgDeclareInst *, 4> Dbgs;
839 for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
840 for (BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ++BI) {
841 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(BI))
847 for (SmallVector<DbgDeclareInst *, 4>::iterator I = Dbgs.begin(),
848 E = Dbgs.end(); I != E; ++I) {
849 DbgDeclareInst *DDI = *I;
850 if (AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress())) {
851 bool RemoveDDI = true;
852 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
854 if (StoreInst *SI = dyn_cast<StoreInst>(*UI))
855 ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
856 else if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
857 ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
861 DDI->eraseFromParent();
867 /// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic describing the
868 /// alloca 'V', if any.
869 DbgDeclareInst *llvm::FindAllocaDbgDeclare(Value *V) {
870 if (MDNode *DebugNode = MDNode::getIfExists(V->getContext(), V))
871 for (Value::use_iterator UI = DebugNode->use_begin(),
872 E = DebugNode->use_end(); UI != E; ++UI)
873 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI))