#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/IRBuilder.h"
+#include "llvm/Support/NoFolder.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <set>
BasicBlock *GetValueEqualityComparisonCases(TerminatorInst *TI,
std::vector<std::pair<ConstantInt*, BasicBlock*> > &Cases);
bool SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI,
- BasicBlock *Pred);
- bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI);
+ BasicBlock *Pred,
+ IRBuilder<> &Builder);
+ bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
+ IRBuilder<> &Builder);
- bool SimplifyReturn(ReturnInst *RI);
+ bool SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder);
+ bool SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder);
bool SimplifyUnwind(UnwindInst *UI, IRBuilder<> &Builder);
bool SimplifyUnreachable(UnreachableInst *UI);
- bool SimplifySwitch(SwitchInst *SI);
+ bool SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder);
bool SimplifyIndirectBr(IndirectBrInst *IBI);
bool SimplifyUncondBranch(BranchInst *BI, IRBuilder <> &Builder);
- bool SimplifyCondBranch(BranchInst *BI);
+ bool SimplifyCondBranch(BranchInst *BI, IRBuilder <>&Builder);
public:
explicit SimplifyCFGOpt(const TargetData *td) : TD(td) {}
// This is some kind of pointer constant. Turn it into a pointer-sized
// ConstantInt if possible.
- const IntegerType *PtrTy = TD->getIntPtrType(V->getContext());
+ IntegerType *PtrTy = TD->getIntPtrType(V->getContext());
// Null pointer means 0, see SelectionDAGBuilder::getValue(const Value*).
if (isa<ConstantPointerNull>(V))
/// form of jump threading.
bool SimplifyCFGOpt::
SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI,
- BasicBlock *Pred) {
+ BasicBlock *Pred,
+ IRBuilder<> &Builder) {
Value *PredVal = isValueEqualityComparison(Pred->getTerminator());
if (!PredVal) return false; // Not a value comparison in predecessor.
// uncond br.
assert(ThisCases.size() == 1 && "Branch can only have one case!");
// Insert the new branch.
- Instruction *NI = BranchInst::Create(ThisDef, TI);
+ Instruction *NI = Builder.CreateBr(ThisDef);
(void) NI;
// Remove PHI node entries for the dead edge.
CheckEdge = 0;
// Insert the new branch.
- Instruction *NI = BranchInst::Create(TheRealDest, TI);
+ Instruction *NI = Builder.CreateBr(TheRealDest);
(void) NI;
DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
/// equality comparison instruction (either a switch or a branch on "X == c").
/// See if any of the predecessors of the terminator block are value comparisons
/// on the same value. If so, and if safe to do so, fold them together.
-bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI) {
+bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
+ IRBuilder<> &Builder) {
BasicBlock *BB = TI->getParent();
Value *CV = isValueEqualityComparison(TI); // CondVal
assert(CV && "Not a comparison?");
for (unsigned i = 0, e = NewSuccessors.size(); i != e; ++i)
AddPredecessorToBlock(NewSuccessors[i], Pred, BB);
+ Builder.SetInsertPoint(PTI);
// Convert pointer to int before we switch.
if (CV->getType()->isPointerTy()) {
assert(TD && "Cannot switch on pointer without TargetData");
- CV = new PtrToIntInst(CV, TD->getIntPtrType(CV->getContext()),
- "magicptr", PTI);
- cast<PtrToIntInst>(CV)->setDebugLoc(PTI->getDebugLoc());
+ CV = Builder.CreatePtrToInt(CV, TD->getIntPtrType(CV->getContext()),
+ "magicptr");
}
// Now that the successors are updated, create the new Switch instruction.
- SwitchInst *NewSI = SwitchInst::Create(CV, PredDefault,
- PredCases.size(), PTI);
+ SwitchInst *NewSI = Builder.CreateSwitch(CV, PredDefault,
+ PredCases.size());
NewSI->setDebugLoc(PTI->getDebugLoc());
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
NewSI->addCase(PredCases[i].first, PredCases[i].second);
NT->takeName(I1);
}
+ IRBuilder<true, NoFolder> Builder(NT);
// Hoisting one of the terminators from our successor is a great thing.
// Unfortunately, the successors of the if/else blocks may have PHI nodes in
// them. If they do, all PHI entries for BB1/BB2 must agree for all PHI
// These values do not agree. Insert a select instruction before NT
// that determines the right value.
SelectInst *&SI = InsertedSelects[std::make_pair(BB1V, BB2V)];
- if (SI == 0) {
- SI = SelectInst::Create(BI->getCondition(), BB1V, BB2V,
- BB1V->getName()+"."+BB2V->getName(), NT);
- SI->setDebugLoc(BI->getDebugLoc());
- }
+ if (SI == 0)
+ SI = cast<SelectInst>
+ (Builder.CreateSelect(BI->getCondition(), BB1V, BB2V,
+ BB1V->getName()+"."+BB2V->getName()));
+
// Make the PHI node use the select for all incoming values for BB1/BB2
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingBlock(i) == BB1 || PN->getIncomingBlock(i) == BB2)
// Create a select whose true value is the speculatively executed value and
// false value is the previously determined FalseV.
+ IRBuilder<true, NoFolder> Builder(BI);
SelectInst *SI;
if (Invert)
- SI = SelectInst::Create(BrCond, FalseV, HInst,
- FalseV->getName() + "." + HInst->getName(), BI);
+ SI = cast<SelectInst>
+ (Builder.CreateSelect(BrCond, FalseV, HInst,
+ FalseV->getName() + "." + HInst->getName()));
else
- SI = SelectInst::Create(BrCond, HInst, FalseV,
- HInst->getName() + "." + FalseV->getName(), BI);
- SI->setDebugLoc(BI->getDebugLoc());
+ SI = cast<SelectInst>
+ (Builder.CreateSelect(BrCond, HInst, FalseV,
+ HInst->getName() + "." + FalseV->getName()));
// Make the PHI node use the select for all incoming values for "then" and
// "if" blocks.
BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue());
if (RealDest == BB) continue; // Skip self loops.
+ // Skip if the predecessor's terminator is an indirect branch.
+ if (isa<IndirectBrInst>(PredBB->getTerminator())) continue;
// The dest block might have PHI nodes, other predecessors and other
// difficult cases. Instead of being smart about this, just insert a new
BB->removePredecessor(PredBB);
PredBBTI->setSuccessor(i, EdgeBB);
}
-
+
// Recurse, simplifying any other constants.
return FoldCondBranchOnPHI(BI, TD) | true;
}
/// FoldTwoEntryPHINode - Given a BB that starts with the specified two-entry
/// PHI node, see if we can eliminate it.
-static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD,
- IRBuilder<> &Builder) {
+static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) {
// Ok, this is a two entry PHI node. Check to see if this is a simple "if
// statement", which has a very simple dominance structure. Basically, we
// are trying to find the condition that is being branched on, which
// If we can still promote the PHI nodes after this gauntlet of tests,
// do all of the PHI's now.
Instruction *InsertPt = DomBlock->getTerminator();
- Builder.SetInsertPoint(InsertPt);
+ IRBuilder<true, NoFolder> Builder(InsertPt);
// Move all 'aggressive' instructions, which are defined in the
// conditional parts of the if's up to the dominating block.
/// SimplifyCondBranchToTwoReturns - If we found a conditional branch that goes
/// to two returning blocks, try to merge them together into one return,
/// introducing a select if the return values disagree.
-static bool SimplifyCondBranchToTwoReturns(BranchInst *BI) {
+static bool SimplifyCondBranchToTwoReturns(BranchInst *BI,
+ IRBuilder<> &Builder) {
assert(BI->isConditional() && "Must be a conditional branch");
BasicBlock *TrueSucc = BI->getSuccessor(0);
BasicBlock *FalseSucc = BI->getSuccessor(1);
if (!FalseSucc->getFirstNonPHIOrDbg()->isTerminator())
return false;
+ Builder.SetInsertPoint(BI);
// Okay, we found a branch that is going to two return nodes. If
// there is no return value for this function, just change the
// branch into a return.
if (FalseRet->getNumOperands() == 0) {
TrueSucc->removePredecessor(BI->getParent());
FalseSucc->removePredecessor(BI->getParent());
- ReturnInst::Create(BI->getContext(), 0, BI);
+ Builder.CreateRetVoid();
EraseTerminatorInstAndDCECond(BI);
return true;
}
} else if (isa<UndefValue>(TrueValue)) {
TrueValue = FalseValue;
} else {
- TrueValue = SelectInst::Create(BrCond, TrueValue,
- FalseValue, "retval", BI);
+ TrueValue = Builder.CreateSelect(BrCond, TrueValue,
+ FalseValue, "retval");
}
}
- Value *RI = !TrueValue ?
- ReturnInst::Create(BI->getContext(), BI) :
- ReturnInst::Create(BI->getContext(), TrueValue, BI);
+ Value *RI = !TrueValue ?
+ Builder.CreateRetVoid() : Builder.CreateRet(TrueValue);
+
(void) RI;
DEBUG(dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
/// the predecessor and use logical operations to pick the right destination.
bool llvm::FoldBranchToCommonDest(BranchInst *BI) {
BasicBlock *BB = BI->getParent();
+
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (Cond == 0 || (!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
Cond->getParent() != BB || !Cond->hasOneUse())
}
DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB);
-
+ IRBuilder<> Builder(PBI);
+
// If we need to invert the condition in the pred block to match, do so now.
if (InvertPredCond) {
Value *NewCond = PBI->getCondition();
CmpInst *CI = cast<CmpInst>(NewCond);
CI->setPredicate(CI->getInversePredicate());
} else {
- NewCond = BinaryOperator::CreateNot(NewCond,
- PBI->getCondition()->getName()+".not", PBI);
+ NewCond = Builder.CreateNot(NewCond,
+ PBI->getCondition()->getName()+".not");
}
PBI->setCondition(NewCond);
New->takeName(Cond);
Cond->setName(New->getName()+".old");
- Instruction *NewCond = BinaryOperator::Create(Opc, PBI->getCondition(),
- New, "or.cond", PBI);
- NewCond->setDebugLoc(PBI->getDebugLoc());
+ Instruction *NewCond =
+ cast<Instruction>(Builder.CreateBinOp(Opc, PBI->getCondition(),
+ New, "or.cond"));
PBI->setCondition(NewCond);
if (PBI->getSuccessor(0) == BB) {
AddPredecessorToBlock(TrueDest, PredBlock, BB);
}
DEBUG(dbgs() << *PBI->getParent()->getParent());
-
+
// BI may have other predecessors. Because of this, we leave
// it alone, but modify PBI.
// Make sure we get to CommonDest on True&True directions.
Value *PBICond = PBI->getCondition();
+ IRBuilder<true, NoFolder> Builder(PBI);
if (PBIOp)
- PBICond = BinaryOperator::CreateNot(PBICond,
- PBICond->getName()+".not",
- PBI);
+ PBICond = Builder.CreateNot(PBICond, PBICond->getName()+".not");
+
Value *BICond = BI->getCondition();
if (BIOp)
- BICond = BinaryOperator::CreateNot(BICond,
- BICond->getName()+".not",
- PBI);
+ BICond = Builder.CreateNot(BICond, BICond->getName()+".not");
+
// Merge the conditions.
- Value *Cond = BinaryOperator::CreateOr(PBICond, BICond, "brmerge", PBI);
+ Value *Cond = Builder.CreateOr(PBICond, BICond, "brmerge");
// Modify PBI to branch on the new condition to the new dests.
PBI->setCondition(Cond);
Value *PBIV = PN->getIncomingValue(PBBIdx);
if (BIV != PBIV) {
// Insert a select in PBI to pick the right value.
- Value *NV = SelectInst::Create(PBICond, PBIV, BIV,
- PBIV->getName()+".mux", PBI);
+ Value *NV = cast<SelectInst>
+ (Builder.CreateSelect(PBICond, PBIV, BIV, PBIV->getName()+".mux"));
PN->setIncomingValue(PBBIdx, NV);
}
}
/// SimplifyBranchOnICmpChain - The specified branch is a conditional branch.
/// Check to see if it is branching on an or/and chain of icmp instructions, and
/// fold it into a switch instruction if so.
-static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD) {
+static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD,
+ IRBuilder<> &Builder) {
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (Cond == 0) return false;
BasicBlock *NewBB = BB->splitBasicBlock(BI, "switch.early.test");
// Remove the uncond branch added to the old block.
TerminatorInst *OldTI = BB->getTerminator();
-
+ Builder.SetInsertPoint(OldTI);
+
if (TrueWhenEqual)
- BranchInst::Create(EdgeBB, NewBB, ExtraCase, OldTI);
+ Builder.CreateCondBr(ExtraCase, EdgeBB, NewBB);
else
- BranchInst::Create(NewBB, EdgeBB, ExtraCase, OldTI);
+ Builder.CreateCondBr(ExtraCase, NewBB, EdgeBB);
OldTI->eraseFromParent();
<< "\nEXTRABB = " << *BB);
BB = NewBB;
}
-
+
+ Builder.SetInsertPoint(BI);
// Convert pointer to int before we switch.
if (CompVal->getType()->isPointerTy()) {
assert(TD && "Cannot switch on pointer without TargetData");
- CompVal = new PtrToIntInst(CompVal,
- TD->getIntPtrType(CompVal->getContext()),
- "magicptr", BI);
- cast<PtrToIntInst>(CompVal)->setDebugLoc(BI->getDebugLoc());
+ CompVal = Builder.CreatePtrToInt(CompVal,
+ TD->getIntPtrType(CompVal->getContext()),
+ "magicptr");
}
// Create the new switch instruction now.
- SwitchInst *New = SwitchInst::Create(CompVal, DefaultBB, Values.size(), BI);
- New->setDebugLoc(BI->getDebugLoc());
+ SwitchInst *New = Builder.CreateSwitch(CompVal, DefaultBB, Values.size());
// Add all of the 'cases' to the switch instruction.
for (unsigned i = 0, e = Values.size(); i != e; ++i)
return true;
}
-bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI) {
+bool SimplifyCFGOpt::SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder) {
+ // If this is a trivial landing pad that just continues unwinding the caught
+ // exception then zap the landing pad, turning its invokes into calls.
+ BasicBlock *BB = RI->getParent();
+ LandingPadInst *LPInst = dyn_cast<LandingPadInst>(BB->getFirstNonPHI());
+ if (RI->getValue() != LPInst)
+ // Not a landing pad, or the resume is not unwinding the exception that
+ // caused control to branch here.
+ return false;
+
+ // Check that there are no other instructions except for debug intrinsics.
+ BasicBlock::iterator I = LPInst, E = RI;
+ while (++I != E)
+ if (!isa<DbgInfoIntrinsic>(I))
+ return false;
+
+ // Turn all invokes that unwind here into calls and delete the basic block.
+ for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) {
+ InvokeInst *II = cast<InvokeInst>((*PI++)->getTerminator());
+ SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
+ // Insert a call instruction before the invoke.
+ CallInst *Call = CallInst::Create(II->getCalledValue(), Args, "", II);
+ Call->takeName(II);
+ Call->setCallingConv(II->getCallingConv());
+ Call->setAttributes(II->getAttributes());
+ Call->setDebugLoc(II->getDebugLoc());
+
+ // Anything that used the value produced by the invoke instruction now uses
+ // the value produced by the call instruction. Note that we do this even
+ // for void functions and calls with no uses so that the callgraph edge is
+ // updated.
+ II->replaceAllUsesWith(Call);
+ BB->removePredecessor(II->getParent());
+
+ // Insert a branch to the normal destination right before the invoke.
+ BranchInst::Create(II->getNormalDest(), II);
+
+ // Finally, delete the invoke instruction!
+ II->eraseFromParent();
+ }
+
+ // The landingpad is now unreachable. Zap it.
+ BB->eraseFromParent();
+ return true;
+}
+
+bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) {
BasicBlock *BB = RI->getParent();
if (!BB->getFirstNonPHIOrDbg()->isTerminator()) return false;
// Check to see if the non-BB successor is also a return block.
if (isa<ReturnInst>(BI->getSuccessor(0)->getTerminator()) &&
isa<ReturnInst>(BI->getSuccessor(1)->getTerminator()) &&
- SimplifyCondBranchToTwoReturns(BI))
+ SimplifyCondBranchToTwoReturns(BI, Builder))
return true;
}
return false;
SmallVector<Value*,8> Args(II->op_begin(), II->op_end()-3);
Builder.SetInsertPoint(BI);
CallInst *CI = Builder.CreateCall(II->getCalledValue(),
- Args.begin(), Args.end(),
- II->getName());
+ Args, II->getName());
CI->setCallingConv(II->getCallingConv());
CI->setAttributes(II->getAttributes());
// If the invoke produced a value, the Call now does instead.
while (UI != BB->begin()) {
BasicBlock::iterator BBI = UI;
--BBI;
- // Do not delete instructions that can have side effects, like calls
- // (which may never return) and volatile loads and stores.
+ // Do not delete instructions that can have side effects which might cause
+ // the unreachable to not be reachable; specifically, calls and volatile
+ // operations may have this effect.
if (isa<CallInst>(BBI) && !isa<DbgInfoIntrinsic>(BBI)) break;
-
- if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
- if (SI->isVolatile())
- break;
-
- if (LoadInst *LI = dyn_cast<LoadInst>(BBI))
- if (LI->isVolatile())
+
+ if (BBI->mayHaveSideEffects()) {
+ if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
+ if (SI->isVolatile())
+ break;
+ } else if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
+ if (LI->isVolatile())
+ break;
+ } else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(BBI)) {
+ if (RMWI->isVolatile())
+ break;
+ } else if (AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(BBI)) {
+ if (CXI->isVolatile())
+ break;
+ } else if (!isa<FenceInst>(BBI) && !isa<VAArgInst>(BBI) &&
+ !isa<LandingPadInst>(BBI)) {
break;
-
+ }
+ // Note that deleting LandingPad's here is in fact okay, although it
+ // involves a bit of subtle reasoning. If this inst is a LandingPad,
+ // all the predecessors of this block will be the unwind edges of Invokes,
+ // and we can therefore guarantee this block will be erased.
+ }
+
// Delete this instruction (any uses are guaranteed to be dead)
if (!BBI->use_empty())
BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB));
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
TerminatorInst *TI = Preds[i]->getTerminator();
-
+ IRBuilder<> Builder(TI);
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isUnconditional()) {
if (BI->getSuccessor(0) == BB) {
}
} else {
if (BI->getSuccessor(0) == BB) {
- BranchInst::Create(BI->getSuccessor(1), BI);
+ Builder.CreateBr(BI->getSuccessor(1));
EraseTerminatorInstAndDCECond(BI);
} else if (BI->getSuccessor(1) == BB) {
- BranchInst::Create(BI->getSuccessor(0), BI);
+ Builder.CreateBr(BI->getSuccessor(0));
EraseTerminatorInstAndDCECond(BI);
Changed = true;
}
if (II->getUnwindDest() == BB) {
// Convert the invoke to a call instruction. This would be a good
// place to note that the call does not throw though.
- BranchInst *BI = BranchInst::Create(II->getNormalDest(), II);
+ BranchInst *BI = Builder.CreateBr(II->getNormalDest());
II->removeFromParent(); // Take out of symbol table
// Insert the call now...
SmallVector<Value*, 8> Args(II->op_begin(), II->op_end()-3);
- CallInst *CI = CallInst::Create(II->getCalledValue(),
- Args.begin(), Args.end(),
- II->getName(), BI);
+ Builder.SetInsertPoint(BI);
+ CallInst *CI = Builder.CreateCall(II->getCalledValue(),
+ Args, II->getName());
CI->setCallingConv(II->getCallingConv());
CI->setAttributes(II->getAttributes());
// If the invoke produced a value, the call does now instead.
/// TurnSwitchRangeIntoICmp - Turns a switch with that contains only a
/// integer range comparison into a sub, an icmp and a branch.
-static bool TurnSwitchRangeIntoICmp(SwitchInst *SI) {
+static bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder) {
assert(SI->getNumCases() > 2 && "Degenerate switch?");
// Make sure all cases point to the same destination and gather the values.
Value *Sub = SI->getCondition();
if (!Offset->isNullValue())
- Sub = BinaryOperator::CreateAdd(Sub, Offset, Sub->getName()+".off", SI);
- Value *Cmp = new ICmpInst(SI, ICmpInst::ICMP_ULT, Sub, NumCases, "switch");
- BranchInst::Create(SI->getSuccessor(1), SI->getDefaultDest(), Cmp, SI);
+ Sub = Builder.CreateAdd(Sub, Offset, Sub->getName()+".off");
+ Value *Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch");
+ Builder.CreateCondBr(Cmp, SI->getSuccessor(1), SI->getDefaultDest());
// Prune obsolete incoming values off the successor's PHI nodes.
for (BasicBlock::iterator BBI = SI->getSuccessor(1)->begin();
return !DeadCases.empty();
}
-bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI) {
+/// FindPHIForConditionForwarding - If BB would be eligible for simplification
+/// by TryToSimplifyUncondBranchFromEmptyBlock (i.e. it is empty and terminated
+/// by an unconditional branch), look at the phi node for BB in the successor
+/// block and see if the incoming value is equal to CaseValue. If so, return
+/// the phi node, and set PhiIndex to BB's index in the phi node.
+static PHINode *FindPHIForConditionForwarding(ConstantInt *CaseValue,
+ BasicBlock *BB,
+ int *PhiIndex) {
+ if (BB->getFirstNonPHIOrDbg() != BB->getTerminator())
+ return NULL; // BB must be empty to be a candidate for simplification.
+ if (!BB->getSinglePredecessor())
+ return NULL; // BB must be dominated by the switch.
+
+ BranchInst *Branch = dyn_cast<BranchInst>(BB->getTerminator());
+ if (!Branch || !Branch->isUnconditional())
+ return NULL; // Terminator must be unconditional branch.
+
+ BasicBlock *Succ = Branch->getSuccessor(0);
+
+ BasicBlock::iterator I = Succ->begin();
+ while (PHINode *PHI = dyn_cast<PHINode>(I++)) {
+ int Idx = PHI->getBasicBlockIndex(BB);
+ assert(Idx >= 0 && "PHI has no entry for predecessor?");
+
+ Value *InValue = PHI->getIncomingValue(Idx);
+ if (InValue != CaseValue) continue;
+
+ *PhiIndex = Idx;
+ return PHI;
+ }
+
+ return NULL;
+}
+
+/// ForwardSwitchConditionToPHI - Try to forward the condition of a switch
+/// instruction to a phi node dominated by the switch, if that would mean that
+/// some of the destination blocks of the switch can be folded away.
+/// Returns true if a change is made.
+static bool ForwardSwitchConditionToPHI(SwitchInst *SI) {
+ typedef DenseMap<PHINode*, SmallVector<int,4> > ForwardingNodesMap;
+ ForwardingNodesMap ForwardingNodes;
+
+ for (unsigned I = 1; I < SI->getNumCases(); ++I) { // 0 is the default case.
+ ConstantInt *CaseValue = SI->getCaseValue(I);
+ BasicBlock *CaseDest = SI->getSuccessor(I);
+
+ int PhiIndex;
+ PHINode *PHI = FindPHIForConditionForwarding(CaseValue, CaseDest,
+ &PhiIndex);
+ if (!PHI) continue;
+
+ ForwardingNodes[PHI].push_back(PhiIndex);
+ }
+
+ bool Changed = false;
+
+ for (ForwardingNodesMap::iterator I = ForwardingNodes.begin(),
+ E = ForwardingNodes.end(); I != E; ++I) {
+ PHINode *Phi = I->first;
+ SmallVector<int,4> &Indexes = I->second;
+
+ if (Indexes.size() < 2) continue;
+
+ for (size_t I = 0, E = Indexes.size(); I != E; ++I)
+ Phi->setIncomingValue(Indexes[I], SI->getCondition());
+ Changed = true;
+ }
+
+ return Changed;
+}
+
+bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) {
// If this switch is too complex to want to look at, ignore it.
if (!isValueEqualityComparison(SI))
return false;
// If we only have one predecessor, and if it is a branch on this value,
// see if that predecessor totally determines the outcome of this switch.
if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
- if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred))
+ if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder))
return SimplifyCFG(BB) | true;
Value *Cond = SI->getCondition();
while (isa<DbgInfoIntrinsic>(BBI))
++BBI;
if (SI == &*BBI)
- if (FoldValueComparisonIntoPredecessors(SI))
+ if (FoldValueComparisonIntoPredecessors(SI, Builder))
return SimplifyCFG(BB) | true;
// Try to transform the switch into an icmp and a branch.
- if (TurnSwitchRangeIntoICmp(SI))
+ if (TurnSwitchRangeIntoICmp(SI, Builder))
return SimplifyCFG(BB) | true;
// Remove unreachable cases.
if (EliminateDeadSwitchCases(SI))
return SimplifyCFG(BB) | true;
+ if (ForwardSwitchConditionToPHI(SI))
+ return SimplifyCFG(BB) | true;
+
return false;
}
BasicBlock *BB = BI->getParent();
// If the Terminator is the only non-phi instruction, simplify the block.
- BasicBlock::iterator I = BB->getFirstNonPHIOrDbg();
+ BasicBlock::iterator I = BB->getFirstNonPHIOrDbgOrLifetime();
if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() &&
TryToSimplifyUncondBranchFromEmptyBlock(BB))
return true;
}
-bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI) {
+bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
BasicBlock *BB = BI->getParent();
// Conditional branch
// see if that predecessor totally determines the outcome of this
// switch.
if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
- if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred))
+ if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred, Builder))
return SimplifyCFG(BB) | true;
// This block must be empty, except for the setcond inst, if it exists.
while (isa<DbgInfoIntrinsic>(I))
++I;
if (&*I == BI) {
- if (FoldValueComparisonIntoPredecessors(BI))
+ if (FoldValueComparisonIntoPredecessors(BI, Builder))
return SimplifyCFG(BB) | true;
} else if (&*I == cast<Instruction>(BI->getCondition())){
++I;
// Ignore dbg intrinsics.
while (isa<DbgInfoIntrinsic>(I))
++I;
- if (&*I == BI && FoldValueComparisonIntoPredecessors(BI))
+ if (&*I == BI && FoldValueComparisonIntoPredecessors(BI, Builder))
return SimplifyCFG(BB) | true;
}
}
// Try to turn "br (X == 0 | X == 1), T, F" into a switch instruction.
- if (SimplifyBranchOnICmpChain(BI, TD))
+ if (SimplifyBranchOnICmpChain(BI, TD, Builder))
return true;
// We have a conditional branch to two blocks that are only reachable
return false;
}
+/// Check if passing a value to an instruction will cause undefined behavior.
+static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I) {
+ Constant *C = dyn_cast<Constant>(V);
+ if (!C)
+ return false;
+
+ if (!I->hasOneUse()) // Only look at single-use instructions, for compile time
+ return false;
+
+ if (C->isNullValue()) {
+ Instruction *Use = I->use_back();
+
+ // Now make sure that there are no instructions in between that can alter
+ // control flow (eg. calls)
+ for (BasicBlock::iterator i = ++BasicBlock::iterator(I); &*i != Use; ++i)
+ if (i == I->getParent()->end() || i->mayHaveSideEffects())
+ return false;
+
+ // Look through GEPs. A load from a GEP derived from NULL is still undefined
+ if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Use))
+ if (GEP->getPointerOperand() == I)
+ return passingValueIsAlwaysUndefined(V, GEP);
+
+ // Look through bitcasts.
+ if (BitCastInst *BC = dyn_cast<BitCastInst>(Use))
+ return passingValueIsAlwaysUndefined(V, BC);
+
+ // Load from null is undefined.
+ if (LoadInst *LI = dyn_cast<LoadInst>(Use))
+ return LI->getPointerAddressSpace() == 0;
+
+ // Store to null is undefined.
+ if (StoreInst *SI = dyn_cast<StoreInst>(Use))
+ return SI->getPointerAddressSpace() == 0 && SI->getPointerOperand() == I;
+ }
+ return false;
+}
+
+/// If BB has an incoming value that will always trigger undefined behavior
+/// (eg. null pointer derefence), remove the branch leading here.
+static bool removeUndefIntroducingPredecessor(BasicBlock *BB) {
+ for (BasicBlock::iterator i = BB->begin();
+ PHINode *PHI = dyn_cast<PHINode>(i); ++i)
+ for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i)
+ if (passingValueIsAlwaysUndefined(PHI->getIncomingValue(i), PHI)) {
+ TerminatorInst *T = PHI->getIncomingBlock(i)->getTerminator();
+ IRBuilder<> Builder(T);
+ if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
+ BB->removePredecessor(PHI->getIncomingBlock(i));
+ // Turn uncoditional branches into unreachables and remove the dead
+ // destination from conditional branches.
+ if (BI->isUnconditional())
+ Builder.CreateUnreachable();
+ else
+ Builder.CreateBr(BI->getSuccessor(0) == BB ? BI->getSuccessor(1) :
+ BI->getSuccessor(0));
+ BI->eraseFromParent();
+ return true;
+ }
+ // TODO: SwitchInst.
+ }
+
+ return false;
+}
+
bool SimplifyCFGOpt::run(BasicBlock *BB) {
bool Changed = false;
// Check to see if we can constant propagate this terminator instruction
// away...
- Changed |= ConstantFoldTerminator(BB);
+ Changed |= ConstantFoldTerminator(BB, true);
// Check for and eliminate duplicate PHI nodes in this block.
Changed |= EliminateDuplicatePHINodes(BB);
+ // Check for and remove branches that will always cause undefined behavior.
+ Changed |= removeUndefIntroducingPredecessor(BB);
+
// Merge basic blocks into their predecessor if there is only one distinct
// pred, and if there is only one distinct successor of the predecessor, and
// if there are no PHI nodes.
// eliminate it, do so now.
if (PHINode *PN = dyn_cast<PHINode>(BB->begin()))
if (PN->getNumIncomingValues() == 2)
- Changed |= FoldTwoEntryPHINode(PN, TD, Builder);
+ Changed |= FoldTwoEntryPHINode(PN, TD);
+ Builder.SetInsertPoint(BB->getTerminator());
if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
if (BI->isUnconditional()) {
if (SimplifyUncondBranch(BI, Builder)) return true;
} else {
- if (SimplifyCondBranch(BI)) return true;
+ if (SimplifyCondBranch(BI, Builder)) return true;
}
+ } else if (ResumeInst *RI = dyn_cast<ResumeInst>(BB->getTerminator())) {
+ if (SimplifyResume(RI, Builder)) return true;
} else if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
- if (SimplifyReturn(RI)) return true;
+ if (SimplifyReturn(RI, Builder)) return true;
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
- if (SimplifySwitch(SI)) return true;
+ if (SimplifySwitch(SI, Builder)) return true;
} else if (UnreachableInst *UI =
dyn_cast<UnreachableInst>(BB->getTerminator())) {
if (SimplifyUnreachable(UI)) return true;
projects / oota-llvm.git / blobdiff