#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
#include "llvm/IntrinsicInst.h"
+#include "llvm/Metadata.h"
#include "llvm/Operator.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/DebugInfo.h"
#include "llvm/Analysis/DIBuilder.h"
#include "llvm/Analysis/Dominators.h"
-#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ProfileInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
-#include "llvm/SUpport/IRBuilder.h"
+#include "llvm/Support/IRBuilder.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Support/raw_ostream.h"
// Local constant propagation.
//
-// ConstantFoldTerminator - If a terminator instruction is predicated on a
-// constant value, convert it into an unconditional branch to the constant
-// destination.
-//
-bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
+/// ConstantFoldTerminator - If a terminator instruction is predicated on a
+/// constant value, convert it into an unconditional branch to the constant
+/// destination. This is a nontrivial operation because the successors of this
+/// basic block must have their PHI nodes updated.
+/// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
+/// conditions and indirectbr addresses this might make dead if
+/// DeleteDeadConditions is true.
+bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions) {
TerminatorInst *T = BB->getTerminator();
IRBuilder<> Builder(T);
// Replace the conditional branch with an unconditional one.
Builder.CreateBr(Dest1);
+ Value *Cond = BI->getCondition();
BI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Cond);
return true;
}
return false;
// If we are switching on a constant, we can convert the switch into a
// single branch instruction!
ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition());
- BasicBlock *TheOnlyDest = SI->getSuccessor(0); // The default dest
+ BasicBlock *TheOnlyDest = SI->getDefaultDest();
BasicBlock *DefaultDest = TheOnlyDest;
- assert(TheOnlyDest == SI->getDefaultDest() &&
- "Default destination is not successor #0?");
// Figure out which case it goes to.
- for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
+ for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
+ i != e; ++i) {
// Found case matching a constant operand?
- if (SI->getSuccessorValue(i) == CI) {
- TheOnlyDest = SI->getSuccessor(i);
+ if (i.getCaseValue() == CI) {
+ TheOnlyDest = i.getCaseSuccessor();
break;
}
// Check to see if this branch is going to the same place as the default
// dest. If so, eliminate it as an explicit compare.
- if (SI->getSuccessor(i) == DefaultDest) {
+ if (i.getCaseSuccessor() == DefaultDest) {
// Remove this entry.
DefaultDest->removePredecessor(SI->getParent());
SI->removeCase(i);
- --i; --e; // Don't skip an entry...
+ --i; --e;
continue;
}
// Otherwise, check to see if the switch only branches to one destination.
// We do this by reseting "TheOnlyDest" to null when we find two non-equal
// destinations.
- if (SI->getSuccessor(i) != TheOnlyDest) TheOnlyDest = 0;
+ if (i.getCaseSuccessor() != TheOnlyDest) TheOnlyDest = 0;
}
if (CI && !TheOnlyDest) {
}
// Delete the old switch.
- BB->getInstList().erase(SI);
+ Value *Cond = SI->getCondition();
+ SI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Cond);
return true;
}
- if (SI->getNumSuccessors() == 2) {
+ if (SI->getNumCases() == 1) {
// Otherwise, we can fold this switch into a conditional branch
// instruction if it has only one non-default destination.
+ SwitchInst::CaseIt FirstCase = SI->case_begin();
Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
- SI->getSuccessorValue(1), "cond");
+ FirstCase.getCaseValue(), "cond");
// Insert the new branch.
- Builder.CreateCondBr(Cond, SI->getSuccessor(1), SI->getSuccessor(0));
+ Builder.CreateCondBr(Cond, FirstCase.getCaseSuccessor(),
+ SI->getDefaultDest());
// Delete the old switch.
SI->eraseFromParent();
else
IBI->getDestination(i)->removePredecessor(IBI->getParent());
}
+ Value *Address = IBI->getAddress();
IBI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Address);
// If we didn't find our destination in the IBI successor list, then we
// have undefined behavior. Replace the unconditional branch with an
bool llvm::isInstructionTriviallyDead(Instruction *I) {
if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
+ // We don't want the landingpad instruction removed by anything this general.
+ if (isa<LandingPadInst>(I))
+ return false;
+
// We don't want debug info removed by anything this general, unless
// debug info is empty.
if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
- if (DDI->getAddress())
+ if (DDI->getAddress())
return false;
return true;
- }
+ }
if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
if (DVI->getValue())
return false;
// Special case intrinsics that "may have side effects" but can be deleted
// when dead.
- if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
// Safe to delete llvm.stacksave if dead.
if (II->getIntrinsicID() == Intrinsic::stacksave)
return true;
+
+ // Lifetime intrinsics are dead when their right-hand is undef.
+ if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
+ II->getIntrinsicID() == Intrinsic::lifetime_end)
+ return isa<UndefValue>(II->getArgOperand(1));
+ }
+
+ if (extractMallocCall(I)) return true;
+
+ if (CallInst *CI = isFreeCall(I))
+ if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
+ return C->isNullValue() || isa<UndefValue>(C);
+
return false;
}
/// instructions in other blocks as well in this block.
bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD) {
bool MadeChange = false;
- for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
+
+#ifndef NDEBUG
+ // In debug builds, ensure that the terminator of the block is never replaced
+ // or deleted by these simplifications. The idea of simplification is that it
+ // cannot introduce new instructions, and there is no way to replace the
+ // terminator of a block without introducing a new instruction.
+ AssertingVH<Instruction> TerminatorVH(--BB->end());
+#endif
+
+ for (BasicBlock::iterator BI = BB->begin(), E = --BB->end(); BI != E; ) {
+ assert(!BI->isTerminator());
Instruction *Inst = BI++;
-
- if (Value *V = SimplifyInstruction(Inst, TD)) {
- WeakVH BIHandle(BI);
- ReplaceAndSimplifyAllUses(Inst, V, TD);
+
+ WeakVH BIHandle(BI);
+ if (recursivelySimplifyInstruction(Inst, TD)) {
MadeChange = true;
if (BIHandle != BI)
BI = BB->begin();
continue;
}
- if (Inst->isTerminator())
- break;
-
- WeakVH BIHandle(BI);
MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst);
if (BIHandle != BI)
BI = BB->begin();
WeakVH PhiIt = &BB->front();
while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) {
PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt));
+ Value *OldPhiIt = PhiIt;
- Value *PNV = SimplifyInstruction(PN, TD);
- if (PNV == 0) continue;
+ if (!recursivelySimplifyInstruction(PN, TD))
+ continue;
- // If we're able to simplify the phi to a single value, substitute the new
- // value into all of its uses.
- assert(PNV != PN && "SimplifyInstruction broken!");
-
- Value *OldPhiIt = PhiIt;
- ReplaceAndSimplifyAllUses(PN, PNV, TD);
-
// If recursive simplification ended up deleting the next PHI node we would
// iterate to, then our iterator is invalid, restart scanning from the top
// of the block.
BasicBlock *PredBB = DestBB->getSinglePredecessor();
assert(PredBB && "Block doesn't have a single predecessor!");
- // Splice all the instructions from PredBB to DestBB.
- PredBB->getTerminator()->eraseFromParent();
- DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
-
// Zap anything that took the address of DestBB. Not doing this will give the
// address an invalid value.
if (DestBB->hasAddressTaken()) {
// Anything that branched to PredBB now branches to DestBB.
PredBB->replaceAllUsesWith(DestBB);
+ // Splice all the instructions from PredBB to DestBB.
+ PredBB->getTerminator()->eraseFromParent();
+ DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
+
if (P) {
DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>();
if (DT) {
if (Succ->getSinglePredecessor()) return true;
// Make a list of the predecessors of BB
- typedef SmallPtrSet<BasicBlock*, 16> BlockSet;
- BlockSet BBPreds(pred_begin(BB), pred_end(BB));
-
- // Use that list to make another list of common predecessors of BB and Succ
- BlockSet CommonPreds;
- for (pred_iterator PI = pred_begin(Succ), PE = pred_end(Succ);
- PI != PE; ++PI) {
- BasicBlock *P = *PI;
- if (BBPreds.count(P))
- CommonPreds.insert(P);
- }
+ SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
- // Shortcut, if there are no common predecessors, merging is always safe
- if (CommonPreds.empty())
- return true;
-
// Look at all the phi nodes in Succ, to see if they present a conflict when
// merging these blocks
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
// merge the phi nodes and then the blocks can still be merged
PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
if (BBPN && BBPN->getParent() == BB) {
- for (BlockSet::iterator PI = CommonPreds.begin(), PE = CommonPreds.end();
- PI != PE; PI++) {
- if (BBPN->getIncomingValueForBlock(*PI)
- != PN->getIncomingValueForBlock(*PI)) {
+ for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
+ BasicBlock *IBB = PN->getIncomingBlock(PI);
+ if (BBPreds.count(IBB) &&
+ BBPN->getIncomingValueForBlock(IBB) != PN->getIncomingValue(PI)) {
DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
<< Succ->getName() << " is conflicting with "
<< BBPN->getName() << " with regard to common predecessor "
- << (*PI)->getName() << "\n");
+ << IBB->getName() << "\n");
return false;
}
}
} else {
Value* Val = PN->getIncomingValueForBlock(BB);
- for (BlockSet::iterator PI = CommonPreds.begin(), PE = CommonPreds.end();
- PI != PE; PI++) {
+ for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
// See if the incoming value for the common predecessor is equal to the
// one for BB, in which case this phi node will not prevent the merging
// of the block.
- if (Val != PN->getIncomingValueForBlock(*PI)) {
+ BasicBlock *IBB = PN->getIncomingBlock(PI);
+ if (BBPreds.count(IBB) && Val != PN->getIncomingValue(PI)) {
DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
<< Succ->getName() << " is conflicting with regard to common "
- << "predecessor " << (*PI)->getName() << "\n");
+ << "predecessor " << IBB->getName() << "\n");
return false;
}
}
/// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
/// unconditional branch, and contains no instructions other than PHI nodes,
-/// potential debug intrinsics and the branch. If possible, eliminate BB by
-/// rewriting all the predecessors to branch to the successor block and return
-/// true. If we can't transform, return false.
+/// potential side-effect free intrinsics and the branch. If possible,
+/// eliminate BB by rewriting all the predecessors to branch to the successor
+/// block and return true. If we can't transform, return false.
bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) {
assert(BB != &BB->getParent()->getEntryBlock() &&
"TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
}
}
- while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
- if (Succ->getSinglePredecessor()) {
- // BB is the only predecessor of Succ, so Succ will end up with exactly
- // the same predecessors BB had.
- Succ->getInstList().splice(Succ->begin(),
- BB->getInstList(), BB->begin());
- } else {
+ if (Succ->getSinglePredecessor()) {
+ // BB is the only predecessor of Succ, so Succ will end up with exactly
+ // the same predecessors BB had.
+
+ // Copy over any phi, debug or lifetime instruction.
+ BB->getTerminator()->eraseFromParent();
+ Succ->getInstList().splice(Succ->getFirstNonPHI(), BB->getInstList());
+ } else {
+ while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
// We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
assert(PN->use_empty() && "There shouldn't be any uses here!");
PN->eraseFromParent();
bool Changed = false;
// This implementation doesn't currently consider undef operands
- // specially. Theroetically, two phis which are identical except for
+ // specially. Theoretically, two phis which are identical except for
// one having an undef where the other doesn't could be collapsed.
// Map from PHI hash values to PHI nodes. If multiple PHIs have
// them, which helps expose duplicates, but we have to check all the
// operands to be safe in case instcombine hasn't run.
uintptr_t Hash = 0;
+ // This hash algorithm is quite weak as hash functions go, but it seems
+ // to do a good enough job for this particular purpose, and is very quick.
for (User::op_iterator I = PN->op_begin(), E = PN->op_end(); I != E; ++I) {
- // This hash algorithm is quite weak as hash functions go, but it seems
- // to do a good enough job for this particular purpose, and is very quick.
Hash ^= reinterpret_cast<uintptr_t>(static_cast<Value *>(*I));
Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
}
+ for (PHINode::block_iterator I = PN->block_begin(), E = PN->block_end();
+ I != E; ++I) {
+ Hash ^= reinterpret_cast<uintptr_t>(static_cast<BasicBlock *>(*I));
+ Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
+ }
// Avoid colliding with the DenseMap sentinels ~0 and ~0-1.
Hash >>= 1;
// If we've never seen this hash value before, it's a unique PHI.
/// their preferred alignment from the beginning.
///
static unsigned enforceKnownAlignment(Value *V, unsigned Align,
- unsigned PrefAlign) {
-
- User *U = dyn_cast<User>(V);
- if (!U) return Align;
-
- switch (Operator::getOpcode(U)) {
- default: break;
- case Instruction::BitCast:
- return enforceKnownAlignment(U->getOperand(0), Align, PrefAlign);
- case Instruction::GetElementPtr: {
- // If all indexes are zero, it is just the alignment of the base pointer.
- bool AllZeroOperands = true;
- for (User::op_iterator i = U->op_begin() + 1, e = U->op_end(); i != e; ++i)
- if (!isa<Constant>(*i) ||
- !cast<Constant>(*i)->isNullValue()) {
- AllZeroOperands = false;
- break;
- }
-
- if (AllZeroOperands) {
- // Treat this like a bitcast.
- return enforceKnownAlignment(U->getOperand(0), Align, PrefAlign);
- }
- return Align;
- }
- case Instruction::Alloca: {
- AllocaInst *AI = cast<AllocaInst>(V);
+ unsigned PrefAlign, const TargetData *TD) {
+ V = V->stripPointerCasts();
+
+ if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
+ // If the preferred alignment is greater than the natural stack alignment
+ // then don't round up. This avoids dynamic stack realignment.
+ if (TD && TD->exceedsNaturalStackAlignment(PrefAlign))
+ return Align;
// If there is a requested alignment and if this is an alloca, round up.
if (AI->getAlignment() >= PrefAlign)
return AI->getAlignment();
AI->setAlignment(PrefAlign);
return PrefAlign;
}
- }
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
// If there is a large requested alignment and we can, bump up the alignment
// of the global.
if (GV->isDeclaration()) return Align;
+ // If the memory we set aside for the global may not be the memory used by
+ // the final program then it is impossible for us to reliably enforce the
+ // preferred alignment.
+ if (GV->isWeakForLinker()) return Align;
if (GV->getAlignment() >= PrefAlign)
return GV->getAlignment();
assert(V->getType()->isPointerTy() &&
"getOrEnforceKnownAlignment expects a pointer!");
unsigned BitWidth = TD ? TD->getPointerSizeInBits() : 64;
- APInt Mask = APInt::getAllOnesValue(BitWidth);
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
- ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD);
+ ComputeMaskedBits(V, KnownZero, KnownOne, TD);
unsigned TrailZ = KnownZero.countTrailingOnes();
// Avoid trouble with rediculously large TrailZ values, such as
Align = std::min(Align, +Value::MaximumAlignment);
if (PrefAlign > Align)
- Align = enforceKnownAlignment(V, Align, PrefAlign);
+ Align = enforceKnownAlignment(V, Align, PrefAlign, TD);
// We don't need to make any adjustment.
return Align;
}
return true;
}
+
+/// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic describing the
+/// alloca 'V', if any.
+DbgDeclareInst *llvm::FindAllocaDbgDeclare(Value *V) {
+ if (MDNode *DebugNode = MDNode::getIfExists(V->getContext(), V))
+ for (Value::use_iterator UI = DebugNode->use_begin(),
+ E = DebugNode->use_end(); UI != E; ++UI)
+ if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI))
+ return DDI;
+
+ return 0;
+}
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