index 32a50b80cd52bcd3abfe3ecb5439a3a253cc26c1..2768041fb2b9d89b20773aaa17afe247a28c6437 100644 (file)
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Constants.h"
-#include "llvm/GlobalAlias.h"
-#include "llvm/GlobalVariable.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Instructions.h"
-#include "llvm/Intrinsics.h"
-#include "llvm/IntrinsicInst.h"
#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
-#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
-#include "llvm/Analysis/ProfileInfo.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/Target/TargetData.h"
+#include "llvm/DIBuilder.h"
+#include "llvm/DebugInfo.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/GlobalAlias.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/IR/Operator.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
+STATISTIC(NumRemoved, "Number of unreachable basic blocks removed");
+
//===----------------------------------------------------------------------===//
// 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,
+ const TargetLibraryInfo *TLI) {
TerminatorInst *T = BB->getTerminator();
+ IRBuilder<> Builder(T);
// Branch - See if we are conditional jumping on constant
if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
// Let the basic block know that we are letting go of it. Based on this,
// it will adjust it's PHI nodes.
- assert(BI->getParent() && "Terminator not inserted in block!");
- OldDest->removePredecessor(BI->getParent());
+ OldDest->removePredecessor(BB);
// Replace the conditional branch with an unconditional one.
- BranchInst::Create(Destination, BI);
+ Builder.CreateBr(Destination);
BI->eraseFromParent();
return true;
}
-
+
if (Dest2 == Dest1) { // Conditional branch to same location?
// This branch matches something like this:
// br bool %cond, label %Dest, label %Dest
Dest1->removePredecessor(BI->getParent());
// Replace the conditional branch with an unconditional one.
- BranchInst::Create(Dest1, BI);
+ Builder.CreateBr(Dest1);
+ Value *Cond = BI->getCondition();
BI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
return true;
}
return false;
}
-
+
if (SwitchInst *SI = dyn_cast<SwitchInst>(T)) {
// 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) {
+ MDNode* MD = SI->getMetadata(LLVMContext::MD_prof);
+ // MD should have 2 + NumCases operands.
+ if (MD && MD->getNumOperands() == 2 + SI->getNumCases()) {
+ // Collect branch weights into a vector.
+ SmallVector<uint32_t, 8> Weights;
+ for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e;
+ ++MD_i) {
+ ConstantInt* CI = dyn_cast<ConstantInt>(MD->getOperand(MD_i));
+ assert(CI);
+ Weights.push_back(CI->getValue().getZExtValue());
+ }
+ // Merge weight of this case to the default weight.
+ unsigned idx = i.getCaseIndex();
+ Weights[0] += Weights[idx+1];
+ // Remove weight for this case.
+ std::swap(Weights[idx+1], Weights.back());
+ Weights.pop_back();
+ SI->setMetadata(LLVMContext::MD_prof,
+ MDBuilder(BB->getContext()).
+ createBranchWeights(Weights));
+ }
// 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) {
// now.
if (TheOnlyDest) {
// Insert the new branch.
- BranchInst::Create(TheOnlyDest, SI);
+ Builder.CreateBr(TheOnlyDest);
BasicBlock *BB = SI->getParent();
// Remove entries from PHI nodes which we no longer branch to...
}
// Delete the old switch.
- BB->getInstList().erase(SI);
+ Value *Cond = SI->getCondition();
+ SI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
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.
- Value *Cond = new ICmpInst(SI, ICmpInst::ICMP_EQ, SI->getCondition(),
- SI->getSuccessorValue(1), "cond");
+ SwitchInst::CaseIt FirstCase = SI->case_begin();
+ Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
+ FirstCase.getCaseValue(), "cond");
+
// Insert the new branch.
- BranchInst::Create(SI->getSuccessor(1), SI->getSuccessor(0), Cond, SI);
+ BranchInst *NewBr = Builder.CreateCondBr(Cond,
+ FirstCase.getCaseSuccessor(),
+ SI->getDefaultDest());
+ MDNode* MD = SI->getMetadata(LLVMContext::MD_prof);
+ if (MD && MD->getNumOperands() == 3) {
+ ConstantInt *SICase = dyn_cast<ConstantInt>(MD->getOperand(2));
+ ConstantInt *SIDef = dyn_cast<ConstantInt>(MD->getOperand(1));
+ assert(SICase && SIDef);
+ // The TrueWeight should be the weight for the single case of SI.
+ NewBr->setMetadata(LLVMContext::MD_prof,
+ MDBuilder(BB->getContext()).
+ createBranchWeights(SICase->getValue().getZExtValue(),
+ SIDef->getValue().getZExtValue()));
+ }
// Delete the old switch.
SI->eraseFromParent();
dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
BasicBlock *TheOnlyDest = BA->getBasicBlock();
// Insert the new branch.
- BranchInst::Create(TheOnlyDest, IBI);
-
+ Builder.CreateBr(TheOnlyDest);
+
for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
if (IBI->getDestination(i) == TheOnlyDest)
TheOnlyDest = 0;
else
IBI->getDestination(i)->removePredecessor(IBI->getParent());
}
+ Value *Address = IBI->getAddress();
IBI->eraseFromParent();
-
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Address, TLI);
+
// If we didn't find our destination in the IBI successor list, then we
// have undefined behavior. Replace the unconditional branch with an
// 'unreachable' instruction.
BB->getTerminator()->eraseFromParent();
new UnreachableInst(BB->getContext(), BB);
}
-
+
return true;
}
}
-
+
return false;
}
/// isInstructionTriviallyDead - Return true if the result produced by the
/// instruction is not used, and the instruction has no side effects.
///
-bool llvm::isInstructionTriviallyDead(Instruction *I) {
+bool llvm::isInstructionTriviallyDead(Instruction *I,
+ const TargetLibraryInfo *TLI) {
if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
- // We don't want debug info removed by anything this general.
- if (isa<DbgInfoIntrinsic>(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())
+ return false;
+ return true;
+ }
+ if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
+ if (DVI->getValue())
+ return false;
+ return true;
+ }
if (!I->mayHaveSideEffects()) return true;
// 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 (isAllocLikeFn(I, TLI)) return true;
+
+ if (CallInst *CI = isFreeCall(I, TLI))
+ if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
+ return C->isNullValue() || isa<UndefValue>(C);
+
return false;
}
/// trivially dead instruction, delete it. If that makes any of its operands
/// trivially dead, delete them too, recursively. Return true if any
/// instructions were deleted.
-bool llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V) {
+bool
+llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V,
+ const TargetLibraryInfo *TLI) {
Instruction *I = dyn_cast<Instruction>(V);
- if (!I || !I->use_empty() || !isInstructionTriviallyDead(I))
+ if (!I || !I->use_empty() || !isInstructionTriviallyDead(I, TLI))
return false;
-
+
SmallVector<Instruction*, 16> DeadInsts;
DeadInsts.push_back(I);
-
+
do {
I = DeadInsts.pop_back_val();
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
Value *OpV = I->getOperand(i);
I->setOperand(i, 0);
-
+
if (!OpV->use_empty()) continue;
-
+
// If the operand is an instruction that became dead as we nulled out the
// operand, and if it is 'trivially' dead, delete it in a future loop
// iteration.
if (Instruction *OpI = dyn_cast<Instruction>(OpV))
- if (isInstructionTriviallyDead(OpI))
+ if (isInstructionTriviallyDead(OpI, TLI))
DeadInsts.push_back(OpI);
}
-
+
I->eraseFromParent();
} while (!DeadInsts.empty());
/// either forms a cycle or is terminated by a trivially dead instruction,
/// delete it. If that makes any of its operands trivially dead, delete them
/// too, recursively. Return true if a change was made.
-bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN) {
+bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN,
+ const TargetLibraryInfo *TLI) {
SmallPtrSet<Instruction*, 4> Visited;
for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects();
I = cast<Instruction>(*I->use_begin())) {
if (I->use_empty())
- return RecursivelyDeleteTriviallyDeadInstructions(I);
+ return RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
// If we find an instruction more than once, we're on a cycle that
// won't prove fruitful.
if (!Visited.insert(I)) {
// Break the cycle and delete the instruction and its operands.
I->replaceAllUsesWith(UndefValue::get(I->getType()));
- (void)RecursivelyDeleteTriviallyDeadInstructions(I);
+ (void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
return true;
}
}
///
/// This returns true if it changed the code, note that it can delete
/// instructions in other blocks as well in this block.
-bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD) {
+bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const DataLayout *TD,
+ const TargetLibraryInfo *TLI) {
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, TLI)) {
MadeChange = true;
if (BIHandle != BI)
BI = BB->begin();
continue;
}
-
- MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst);
+
+ MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst, TLI);
+ if (BIHandle != BI)
+ BI = BB->begin();
}
return MadeChange;
}
@@ -343,30 +443,24 @@ bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD) {
/// .. and delete the predecessor corresponding to the '1', this will attempt to
/// recursively fold the and to 0.
void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
- TargetData *TD) {
+ DataLayout *TD) {
// This only adjusts blocks with PHI nodes.
if (!isa<PHINode>(BB->begin()))
return;
-
+
// Remove the entries for Pred from the PHI nodes in BB, but do not simplify
// them down. This will leave us with single entry phi nodes and other phis
// that can be removed.
BB->removePredecessor(Pred, true);
-
+
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.
PN->replaceAllUsesWith(NewVal);
PN->eraseFromParent();
}
-
+
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.
BA->getType()));
BA->destroyConstant();
}
-
+
// 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) {
DT->changeImmediateDominator(DestBB, PredBBIDom);
DT->eraseNode(PredBB);
}
- ProfileInfo *PI = P->getAnalysisIfAvailable<ProfileInfo>();
- if (PI) {
- PI->replaceAllUses(PredBB, DestBB);
- PI->removeEdge(ProfileInfo::getEdge(PredBB, DestBB));
- }
}
// Nuke BB.
PredBB->eraseFromParent();
}
+/// CanMergeValues - Return true if we can choose one of these values to use
+/// in place of the other. Note that we will always choose the non-undef
+/// value to keep.
+static bool CanMergeValues(Value *First, Value *Second) {
+ return First == Second || isa<UndefValue>(First) || isa<UndefValue>(Second);
+}
+
/// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
-/// almost-empty BB ending in an unconditional branch to Succ, into succ.
+/// almost-empty BB ending in an unconditional branch to Succ, into Succ.
///
/// Assumption: Succ is the single successor for BB.
///
static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
- DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
+ DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
<< Succ->getName() << "\n");
// Shortcut, if there is only a single predecessor it must be BB and merging
// is always safe
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) {
@@ -469,28 +551,30 @@ static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
// 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)) {
- DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
- << Succ->getName() << " is conflicting with "
+ for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
+ BasicBlock *IBB = PN->getIncomingBlock(PI);
+ if (BBPreds.count(IBB) &&
+ !CanMergeValues(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)) {
- DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
+ BasicBlock *IBB = PN->getIncomingBlock(PI);
+ if (BBPreds.count(IBB) &&
+ !CanMergeValues(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;
}
}
@@ -500,11 +584,144 @@ static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
return true;
}
+typedef SmallVector<BasicBlock *, 16> PredBlockVector;
+typedef DenseMap<BasicBlock *, Value *> IncomingValueMap;
+
+/// \brief Determines the value to use as the phi node input for a block.
+///
+/// Select between \p OldVal any value that we know flows from \p BB
+/// to a particular phi on the basis of which one (if either) is not
+/// undef. Update IncomingValues based on the selected value.
+///
+/// \param OldVal The value we are considering selecting.
+/// \param BB The block that the value flows in from.
+/// \param IncomingValues A map from block-to-value for other phi inputs
+/// that we have examined.
+///
+/// \returns the selected value.
+static Value *selectIncomingValueForBlock(Value *OldVal, BasicBlock *BB,
+ IncomingValueMap &IncomingValues) {
+ if (!isa<UndefValue>(OldVal)) {
+ assert((!IncomingValues.count(BB) ||
+ IncomingValues.find(BB)->second == OldVal) &&
+ "Expected OldVal to match incoming value from BB!");
+
+ IncomingValues.insert(std::make_pair(BB, OldVal));
+ return OldVal;
+ }
+
+ IncomingValueMap::const_iterator It = IncomingValues.find(BB);
+ if (It != IncomingValues.end()) return It->second;
+
+ return OldVal;
+}
+
+/// \brief Create a map from block to value for the operands of a
+/// given phi.
+///
+/// Create a map from block to value for each non-undef value flowing
+/// into \p PN.
+///
+/// \param PN The phi we are collecting the map for.
+/// \param IncomingValues [out] The map from block to value for this phi.
+static void gatherIncomingValuesToPhi(PHINode *PN,
+ IncomingValueMap &IncomingValues) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ BasicBlock *BB = PN->getIncomingBlock(i);
+ Value *V = PN->getIncomingValue(i);
+
+ if (!isa<UndefValue>(V))
+ IncomingValues.insert(std::make_pair(BB, V));
+ }
+}
+
+/// \brief Replace the incoming undef values to a phi with the values
+/// from a block-to-value map.
+///
+/// \param PN The phi we are replacing the undefs in.
+/// \param IncomingValues A map from block to value.
+static void replaceUndefValuesInPhi(PHINode *PN,
+ const IncomingValueMap &IncomingValues) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ Value *V = PN->getIncomingValue(i);
+
+ if (!isa<UndefValue>(V)) continue;
+
+ BasicBlock *BB = PN->getIncomingBlock(i);
+ IncomingValueMap::const_iterator It = IncomingValues.find(BB);
+ if (It == IncomingValues.end()) continue;
+
+ PN->setIncomingValue(i, It->second);
+ }
+}
+
+/// \brief Replace a value flowing from a block to a phi with
+/// potentially multiple instances of that value flowing from the
+/// block's predecessors to the phi.
+///
+/// \param BB The block with the value flowing into the phi.
+/// \param BBPreds The predecessors of BB.
+/// \param PN The phi that we are updating.
+static void redirectValuesFromPredecessorsToPhi(BasicBlock *BB,
+ const PredBlockVector &BBPreds,
+ PHINode *PN) {
+ Value *OldVal = PN->removeIncomingValue(BB, false);
+ assert(OldVal && "No entry in PHI for Pred BB!");
+
+ IncomingValueMap IncomingValues;
+
+ // We are merging two blocks - BB, and the block containing PN - and
+ // as a result we need to redirect edges from the predecessors of BB
+ // to go to the block containing PN, and update PN
+ // accordingly. Since we allow merging blocks in the case where the
+ // predecessor and successor blocks both share some predecessors,
+ // and where some of those common predecessors might have undef
+ // values flowing into PN, we want to rewrite those values to be
+ // consistent with the non-undef values.
+
+ gatherIncomingValuesToPhi(PN, IncomingValues);
+
+ // If this incoming value is one of the PHI nodes in BB, the new entries
+ // in the PHI node are the entries from the old PHI.
+ if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
+ PHINode *OldValPN = cast<PHINode>(OldVal);
+ for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i) {
+ // Note that, since we are merging phi nodes and BB and Succ might
+ // have common predecessors, we could end up with a phi node with
+ // identical incoming branches. This will be cleaned up later (and
+ // will trigger asserts if we try to clean it up now, without also
+ // simplifying the corresponding conditional branch).
+ BasicBlock *PredBB = OldValPN->getIncomingBlock(i);
+ Value *PredVal = OldValPN->getIncomingValue(i);
+ Value *Selected = selectIncomingValueForBlock(PredVal, PredBB,
+ IncomingValues);
+
+ // And add a new incoming value for this predecessor for the
+ // newly retargeted branch.
+ PN->addIncoming(Selected, PredBB);
+ }
+ } else {
+ for (unsigned i = 0, e = BBPreds.size(); i != e; ++i) {
+ // Update existing incoming values in PN for this
+ // predecessor of BB.
+ BasicBlock *PredBB = BBPreds[i];
+ Value *Selected = selectIncomingValueForBlock(OldVal, PredBB,
+ IncomingValues);
+
+ // And add a new incoming value for this predecessor for the
+ // newly retargeted branch.
+ PN->addIncoming(Selected, PredBB);
+ }
+ }
+
+ replaceUndefValuesInPhi(PN, IncomingValues);
+}
+
/// 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!");
// We can't eliminate infinite loops.
BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0);
if (BB == Succ) return false;
-
+
// Check to see if merging these blocks would cause conflicts for any of the
// phi nodes in BB or Succ. If not, we can safely merge.
if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
// possible to handle such cases, but difficult: it requires checking whether
// BB dominates Succ, which is non-trivial to calculate in the case where
// Succ has multiple predecessors. Also, it requires checking whether
- // constructing the necessary self-referential PHI node doesn't intoduce any
+ // constructing the necessary self-referential PHI node doesn't introduce any
// conflicts; this isn't too difficult, but the previous code for doing this
// was incorrect.
//
}
DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
-
+
if (isa<PHINode>(Succ->begin())) {
// If there is more than one pred of succ, and there are PHI nodes in
// the successor, then we need to add incoming edges for the PHI nodes
//
- const SmallVector<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
-
+ const PredBlockVector BBPreds(pred_begin(BB), pred_end(BB));
+
// Loop over all of the PHI nodes in the successor of BB.
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
- Value *OldVal = PN->removeIncomingValue(BB, false);
- assert(OldVal && "No entry in PHI for Pred BB!");
-
- // If this incoming value is one of the PHI nodes in BB, the new entries
- // in the PHI node are the entries from the old PHI.
- if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
- PHINode *OldValPN = cast<PHINode>(OldVal);
- for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i)
- // Note that, since we are merging phi nodes and BB and Succ might
- // have common predecessors, we could end up with a phi node with
- // identical incoming branches. This will be cleaned up later (and
- // will trigger asserts if we try to clean it up now, without also
- // simplifying the corresponding conditional branch).
- PN->addIncoming(OldValPN->getIncomingValue(i),
- OldValPN->getIncomingBlock(i));
- } else {
- // Add an incoming value for each of the new incoming values.
- for (unsigned i = 0, e = BBPreds.size(); i != e; ++i)
- PN->addIncoming(OldVal, BBPreds[i]);
- }
+
+ redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN);
}
}
-
- 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();
}
}
-
+
// Everything that jumped to BB now goes to Succ.
BB->replaceAllUsesWith(Succ);
if (!Succ->hasName()) Succ->takeName(BB);
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.
CollisionMap[PN] = Old;
break;
}
- // Procede to the next PHI in the list.
+ // Proceed to the next PHI in the list.
OtherPN = I->second;
}
}
/// 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 DataLayout *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();
// We can only increase the alignment of the global if it has no alignment
/// and it is more than the alignment of the ultimate object, see if we can
/// increase the alignment of the ultimate object, making this check succeed.
unsigned llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
- const TargetData *TD) {
+ const DataLayout *DL) {
assert(V->getType()->isPointerTy() &&
"getOrEnforceKnownAlignment expects a pointer!");
- unsigned BitWidth = TD ? TD->getPointerSizeInBits() : 64;
- APInt Mask = APInt::getAllOnesValue(BitWidth);
+ unsigned BitWidth = DL ? DL->getPointerTypeSizeInBits(V->getType()) : 64;
+
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
- ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD);
+ ComputeMaskedBits(V, KnownZero, KnownOne, DL);
unsigned TrailZ = KnownZero.countTrailingOnes();
-
- // Avoid trouble with rediculously large TrailZ values, such as
+
+ // Avoid trouble with ridiculously large TrailZ values, such as
// those computed from a null pointer.
TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
-
+
unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
-
+
// LLVM doesn't support alignments larger than this currently.
Align = std::min(Align, +Value::MaximumAlignment);
-
+
if (PrefAlign > Align)
- Align = enforceKnownAlignment(V, Align, PrefAlign);
-
+ Align = enforceKnownAlignment(V, Align, PrefAlign, DL);
+
// We don't need to make any adjustment.
return Align;
}
+///===---------------------------------------------------------------------===//
+/// Dbg Intrinsic utilities
+///
+
+/// See if there is a dbg.value intrinsic for DIVar before I.
+static bool LdStHasDebugValue(DIVariable &DIVar, Instruction *I) {
+ // Since we can't guarantee that the original dbg.declare instrinsic
+ // is removed by LowerDbgDeclare(), we need to make sure that we are
+ // not inserting the same dbg.value intrinsic over and over.
+ llvm::BasicBlock::InstListType::iterator PrevI(I);
+ if (PrevI != I->getParent()->getInstList().begin()) {
+ --PrevI;
+ if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(PrevI))
+ if (DVI->getValue() == I->getOperand(0) &&
+ DVI->getOffset() == 0 &&
+ DVI->getVariable() == DIVar)
+ return true;
+ }
+ return false;
+}
+
+/// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
+/// that has an associated llvm.dbg.decl intrinsic.
+bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
+ StoreInst *SI, DIBuilder &Builder) {
+ DIVariable DIVar(DDI->getVariable());
+ assert((!DIVar || DIVar.isVariable()) &&
+ "Variable in DbgDeclareInst should be either null or a DIVariable.");
+ if (!DIVar)
+ return false;
+
+ if (LdStHasDebugValue(DIVar, SI))
+ return true;
+
+ Instruction *DbgVal = NULL;
+ // If an argument is zero extended then use argument directly. The ZExt
+ // may be zapped by an optimization pass in future.
+ Argument *ExtendedArg = NULL;
+ if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
+ ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0));
+ if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
+ ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0));
+ if (ExtendedArg)
+ DbgVal = Builder.insertDbgValueIntrinsic(ExtendedArg, 0, DIVar, SI);
+ else
+ DbgVal = Builder.insertDbgValueIntrinsic(SI->getOperand(0), 0, DIVar, SI);
+
+ // Propagate any debug metadata from the store onto the dbg.value.
+ DebugLoc SIDL = SI->getDebugLoc();
+ if (!SIDL.isUnknown())
+ DbgVal->setDebugLoc(SIDL);
+ // Otherwise propagate debug metadata from dbg.declare.
+ else
+ DbgVal->setDebugLoc(DDI->getDebugLoc());
+ return true;
+}
+
+/// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
+/// that has an associated llvm.dbg.decl intrinsic.
+bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
+ LoadInst *LI, DIBuilder &Builder) {
+ DIVariable DIVar(DDI->getVariable());
+ assert((!DIVar || DIVar.isVariable()) &&
+ "Variable in DbgDeclareInst should be either null or a DIVariable.");
+ if (!DIVar)
+ return false;
+
+ if (LdStHasDebugValue(DIVar, LI))
+ return true;
+
+ Instruction *DbgVal =
+ Builder.insertDbgValueIntrinsic(LI->getOperand(0), 0,
+ DIVar, LI);
+
+ // Propagate any debug metadata from the store onto the dbg.value.
+ DebugLoc LIDL = LI->getDebugLoc();
+ if (!LIDL.isUnknown())
+ DbgVal->setDebugLoc(LIDL);
+ // Otherwise propagate debug metadata from dbg.declare.
+ else
+ DbgVal->setDebugLoc(DDI->getDebugLoc());
+ return true;
+}
+
+/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
+/// of llvm.dbg.value intrinsics.
+bool llvm::LowerDbgDeclare(Function &F) {
+ DIBuilder DIB(*F.getParent());
+ SmallVector<DbgDeclareInst *, 4> Dbgs;
+ for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
+ for (BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ++BI) {
+ if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(BI))
+ Dbgs.push_back(DDI);
+ }
+ if (Dbgs.empty())
+ return false;
+
+ for (SmallVectorImpl<DbgDeclareInst *>::iterator I = Dbgs.begin(),
+ E = Dbgs.end(); I != E; ++I) {
+ DbgDeclareInst *DDI = *I;
+ AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress());
+ // If this is an alloca for a scalar variable, insert a dbg.value
+ // at each load and store to the alloca and erase the dbg.declare.
+ if (AI && !AI->isArrayAllocation()) {
+
+ // We only remove the dbg.declare intrinsic if all uses are
+ // converted to dbg.value intrinsics.
+ bool RemoveDDI = true;
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
+ UI != E; ++UI)
+ if (StoreInst *SI = dyn_cast<StoreInst>(*UI))
+ ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
+ else if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
+ ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
+ else
+ RemoveDDI = false;
+ if (RemoveDDI)
+ DDI->eraseFromParent();
+ }
+ }
+ 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;
+}
+
+bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
+ DIBuilder &Builder) {
+ DbgDeclareInst *DDI = FindAllocaDbgDeclare(AI);
+ if (!DDI)
+ return false;
+ DIVariable DIVar(DDI->getVariable());
+ assert((!DIVar || DIVar.isVariable()) &&
+ "Variable in DbgDeclareInst should be either null or a DIVariable.");
+ if (!DIVar)
+ return false;
+
+ // Create a copy of the original DIDescriptor for user variable, appending
+ // "deref" operation to a list of address elements, as new llvm.dbg.declare
+ // will take a value storing address of the memory for variable, not
+ // alloca itself.
+ Type *Int64Ty = Type::getInt64Ty(AI->getContext());
+ SmallVector<Value*, 4> NewDIVarAddress;
+ if (DIVar.hasComplexAddress()) {
+ for (unsigned i = 0, n = DIVar.getNumAddrElements(); i < n; ++i) {
+ NewDIVarAddress.push_back(
+ ConstantInt::get(Int64Ty, DIVar.getAddrElement(i)));
+ }
+ }
+ NewDIVarAddress.push_back(ConstantInt::get(Int64Ty, DIBuilder::OpDeref));
+ DIVariable NewDIVar = Builder.createComplexVariable(
+ DIVar.getTag(), DIVar.getContext(), DIVar.getName(),
+ DIVar.getFile(), DIVar.getLineNumber(), DIVar.getType(),
+ NewDIVarAddress, DIVar.getArgNumber());
+
+ // Insert llvm.dbg.declare in the same basic block as the original alloca,
+ // and remove old llvm.dbg.declare.
+ BasicBlock *BB = AI->getParent();
+ Builder.insertDeclare(NewAllocaAddress, NewDIVar, BB);
+ DDI->eraseFromParent();
+ return true;
+}
+
+/// changeToUnreachable - Insert an unreachable instruction before the specified
+/// instruction, making it and the rest of the code in the block dead.
+static void changeToUnreachable(Instruction *I, bool UseLLVMTrap) {
+ BasicBlock *BB = I->getParent();
+ // Loop over all of the successors, removing BB's entry from any PHI
+ // nodes.
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
+ (*SI)->removePredecessor(BB);
+
+ // Insert a call to llvm.trap right before this. This turns the undefined
+ // behavior into a hard fail instead of falling through into random code.
+ if (UseLLVMTrap) {
+ Function *TrapFn =
+ Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
+ CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
+ CallTrap->setDebugLoc(I->getDebugLoc());
+ }
+ new UnreachableInst(I->getContext(), I);
+
+ // All instructions after this are dead.
+ BasicBlock::iterator BBI = I, BBE = BB->end();
+ while (BBI != BBE) {
+ if (!BBI->use_empty())
+ BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
+ BB->getInstList().erase(BBI++);
+ }
+}
+
+/// changeToCall - Convert the specified invoke into a normal call.
+static void changeToCall(InvokeInst *II) {
+ SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
+ CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, "", II);
+ NewCall->takeName(II);
+ NewCall->setCallingConv(II->getCallingConv());
+ NewCall->setAttributes(II->getAttributes());
+ NewCall->setDebugLoc(II->getDebugLoc());
+ II->replaceAllUsesWith(NewCall);
+
+ // Follow the call by a branch to the normal destination.
+ BranchInst::Create(II->getNormalDest(), II);
+
+ // Update PHI nodes in the unwind destination
+ II->getUnwindDest()->removePredecessor(II->getParent());
+ II->eraseFromParent();
+}
+
+static bool markAliveBlocks(BasicBlock *BB,
+ SmallPtrSet<BasicBlock*, 128> &Reachable) {
+
+ SmallVector<BasicBlock*, 128> Worklist;
+ Worklist.push_back(BB);
+ Reachable.insert(BB);
+ bool Changed = false;
+ do {
+ BB = Worklist.pop_back_val();
+
+ // Do a quick scan of the basic block, turning any obviously unreachable
+ // instructions into LLVM unreachable insts. The instruction combining pass
+ // canonicalizes unreachable insts into stores to null or undef.
+ for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
+ if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
+ if (CI->doesNotReturn()) {
+ // If we found a call to a no-return function, insert an unreachable
+ // instruction after it. Make sure there isn't *already* one there
+ // though.
+ ++BBI;
+ if (!isa<UnreachableInst>(BBI)) {
+ // Don't insert a call to llvm.trap right before the unreachable.
+ changeToUnreachable(BBI, false);
+ Changed = true;
+ }
+ break;
+ }
+ }
+
+ // Store to undef and store to null are undefined and used to signal that
+ // they should be changed to unreachable by passes that can't modify the
+ // CFG.
+ if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
+ // Don't touch volatile stores.
+ if (SI->isVolatile()) continue;
+
+ Value *Ptr = SI->getOperand(1);
+
+ if (isa<UndefValue>(Ptr) ||
+ (isa<ConstantPointerNull>(Ptr) &&
+ SI->getPointerAddressSpace() == 0)) {
+ changeToUnreachable(SI, true);
+ Changed = true;
+ break;
+ }
+ }
+ }
+
+ // Turn invokes that call 'nounwind' functions into ordinary calls.
+ if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
+ Value *Callee = II->getCalledValue();
+ if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
+ changeToUnreachable(II, true);
+ Changed = true;
+ } else if (II->doesNotThrow()) {
+ if (II->use_empty() && II->onlyReadsMemory()) {
+ // jump to the normal destination branch.
+ BranchInst::Create(II->getNormalDest(), II);
+ II->getUnwindDest()->removePredecessor(II->getParent());
+ II->eraseFromParent();
+ } else
+ changeToCall(II);
+ Changed = true;
+ }
+ }
+
+ Changed |= ConstantFoldTerminator(BB, true);
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
+ if (Reachable.insert(*SI))
+ Worklist.push_back(*SI);
+ } while (!Worklist.empty());
+ return Changed;
+}
+
+/// removeUnreachableBlocksFromFn - Remove blocks that are not reachable, even
+/// if they are in a dead cycle. Return true if a change was made, false
+/// otherwise.
+bool llvm::removeUnreachableBlocks(Function &F) {
+ SmallPtrSet<BasicBlock*, 128> Reachable;
+ bool Changed = markAliveBlocks(F.begin(), Reachable);
+
+ // If there are unreachable blocks in the CFG...
+ if (Reachable.size() == F.size())
+ return Changed;
+
+ assert(Reachable.size() < F.size());
+ NumRemoved += F.size()-Reachable.size();
+
+ // Loop over all of the basic blocks that are not reachable, dropping all of
+ // their internal references...
+ for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) {
+ if (Reachable.count(BB))
+ continue;
+
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
+ if (Reachable.count(*SI))
+ (*SI)->removePredecessor(BB);
+ BB->dropAllReferences();
+ }
+
+ for (Function::iterator I = ++F.begin(); I != F.end();)
+ if (!Reachable.count(I))
+ I = F.getBasicBlockList().erase(I);
+ else
+ ++I;
+
+ return true;
+}