//
if (isa<PHINode>(Succ->front())) {
std::set<BasicBlock*> BBPreds(pred_begin(BB), pred_end(BB));
- for (pred_iterator PI = pred_begin(Succ), PE = pred_end(Succ);\
+ for (pred_iterator PI = pred_begin(Succ), PE = pred_end(Succ);
PI != PE; ++PI)
if (std::find(BBPreds.begin(), BBPreds.end(), *PI) != BBPreds.end()) {
// Loop over all of the PHI nodes checking to see if there are
}
if (IsSafe) return true;
- // If the PHI nodes in BB are only used by instructions in Succ, we are ok.
- IsSafe = true;
- for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I) && IsSafe; ++I) {
+ // If the PHI nodes in BB are only used by instructions in Succ, we are ok if
+ // BB and Succ have no common predecessors.
+ for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E;
++UI)
- if (cast<Instruction>(*UI)->getParent() != Succ) {
- IsSafe = false;
- break;
- }
+ if (cast<Instruction>(*UI)->getParent() != Succ)
+ return false;
}
- return IsSafe;
+ // Scan the predecessor sets of BB and Succ, making sure there are no common
+ // predecessors. Common predecessors would cause us to build a phi node with
+ // differing incoming values, which is not legal.
+ std::set<BasicBlock*> BBPreds(pred_begin(BB), pred_end(BB));
+ for (pred_iterator PI = pred_begin(Succ), E = pred_end(Succ); PI != E; ++PI)
+ if (BBPreds.count(*PI))
+ return false;
+
+ return true;
}
/// TryToSimplifyUncondBranchFromEmptyBlock - BB contains an unconditional
//
if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
- DEBUG(std::cerr << "Killing Trivial BB: \n" << *BB);
+ DOUT << "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
static bool DominatesMergePoint(Value *V, BasicBlock *BB,
std::set<Instruction*> *AggressiveInsts) {
Instruction *I = dyn_cast<Instruction>(V);
- if (!I) return true; // Non-instructions all dominate instructions.
+ if (!I) {
+ // Non-instructions all dominate instructions, but not all constantexprs
+ // can be executed unconditionally.
+ if (ConstantExpr *C = dyn_cast<ConstantExpr>(V))
+ if (C->canTrap())
+ return false;
+ return true;
+ }
BasicBlock *PBB = I->getParent();
// We don't want to allow weird loops that might have the "if condition" in
case Instruction::Or:
case Instruction::Xor:
case Instruction::Shl:
- case Instruction::Shr:
- case Instruction::SetEQ:
- case Instruction::SetNE:
- case Instruction::SetLT:
- case Instruction::SetGT:
- case Instruction::SetLE:
- case Instruction::SetGE:
+ case Instruction::LShr:
+ case Instruction::AShr:
+ case Instruction::ICmp:
+ case Instruction::FCmp:
break; // These are all cheap and non-trapping instructions.
}
return true;
}
-// GatherConstantSetEQs - Given a potentially 'or'd together collection of seteq
-// instructions that compare a value against a constant, return the value being
-// compared, and stick the constant into the Values vector.
+// GatherConstantSetEQs - Given a potentially 'or'd together collection of
+// icmp_eq instructions that compare a value against a constant, return the
+// value being compared, and stick the constant into the Values vector.
static Value *GatherConstantSetEQs(Value *V, std::vector<ConstantInt*> &Values){
if (Instruction *Inst = dyn_cast<Instruction>(V))
- if (Inst->getOpcode() == Instruction::SetEQ) {
+ if (Inst->getOpcode() == Instruction::ICmp &&
+ cast<ICmpInst>(Inst)->getPredicate() == ICmpInst::ICMP_EQ) {
if (ConstantInt *C = dyn_cast<ConstantInt>(Inst->getOperand(1))) {
Values.push_back(C);
return Inst->getOperand(0);
// being compared, and stick the constant into the Values vector.
static Value *GatherConstantSetNEs(Value *V, std::vector<ConstantInt*> &Values){
if (Instruction *Inst = dyn_cast<Instruction>(V))
- if (Inst->getOpcode() == Instruction::SetNE) {
+ if (Inst->getOpcode() == Instruction::ICmp &&
+ cast<ICmpInst>(Inst)->getPredicate() == ICmpInst::ICMP_NE) {
if (ConstantInt *C = dyn_cast<ConstantInt>(Inst->getOperand(1))) {
Values.push_back(C);
return Inst->getOperand(0);
Values.push_back(C);
return Inst->getOperand(1);
}
- } else if (Inst->getOpcode() == Instruction::Cast) {
- // Cast of X to bool is really a comparison against zero.
- assert(Inst->getType() == Type::BoolTy && "Can only handle bool values!");
- Values.push_back(ConstantInt::get(Inst->getOperand(0)->getType(), 0));
- return Inst->getOperand(0);
} else if (Inst->getOpcode() == Instruction::And) {
if (Value *LHS = GatherConstantSetNEs(Inst->getOperand(0), Values))
if (Value *RHS = GatherConstantSetNEs(Inst->getOperand(1), Values))
/// has no side effects, nuke it. If it uses any instructions that become dead
/// because the instruction is now gone, nuke them too.
static void ErasePossiblyDeadInstructionTree(Instruction *I) {
- if (isInstructionTriviallyDead(I)) {
- std::vector<Value*> Operands(I->op_begin(), I->op_end());
- I->getParent()->getInstList().erase(I);
- for (unsigned i = 0, e = Operands.size(); i != e; ++i)
- if (Instruction *OpI = dyn_cast<Instruction>(Operands[i]))
- ErasePossiblyDeadInstructionTree(OpI);
+ if (!isInstructionTriviallyDead(I)) return;
+
+ std::vector<Instruction*> InstrsToInspect;
+ InstrsToInspect.push_back(I);
+
+ while (!InstrsToInspect.empty()) {
+ I = InstrsToInspect.back();
+ InstrsToInspect.pop_back();
+
+ if (!isInstructionTriviallyDead(I)) continue;
+
+ // If I is in the work list multiple times, remove previous instances.
+ for (unsigned i = 0, e = InstrsToInspect.size(); i != e; ++i)
+ if (InstrsToInspect[i] == I) {
+ InstrsToInspect.erase(InstrsToInspect.begin()+i);
+ --i, --e;
+ }
+
+ // Add operands of dead instruction to worklist.
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
+ if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
+ InstrsToInspect.push_back(OpI);
+
+ // Remove dead instruction.
+ I->eraseFromParent();
}
}
}
if (BranchInst *BI = dyn_cast<BranchInst>(TI))
if (BI->isConditional() && BI->getCondition()->hasOneUse())
- if (SetCondInst *SCI = dyn_cast<SetCondInst>(BI->getCondition()))
- if ((SCI->getOpcode() == Instruction::SetEQ ||
- SCI->getOpcode() == Instruction::SetNE) &&
- isa<ConstantInt>(SCI->getOperand(1)))
- return SCI->getOperand(0);
+ if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition()))
+ if ((ICI->getPredicate() == ICmpInst::ICMP_EQ ||
+ ICI->getPredicate() == ICmpInst::ICMP_NE) &&
+ isa<ConstantInt>(ICI->getOperand(1)))
+ return ICI->getOperand(0);
return 0;
}
}
BranchInst *BI = cast<BranchInst>(TI);
- SetCondInst *SCI = cast<SetCondInst>(BI->getCondition());
- Cases.push_back(std::make_pair(cast<ConstantInt>(SCI->getOperand(1)),
- BI->getSuccessor(SCI->getOpcode() ==
- Instruction::SetNE)));
- return BI->getSuccessor(SCI->getOpcode() == Instruction::SetEQ);
+ ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
+ Cases.push_back(std::make_pair(cast<ConstantInt>(ICI->getOperand(1)),
+ BI->getSuccessor(ICI->getPredicate() ==
+ ICmpInst::ICMP_NE)));
+ return BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_EQ);
}
// Remove PHI node entries for the dead edge.
ThisCases[0].second->removePredecessor(TI->getParent());
- DEBUG(std::cerr << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
+ DOUT << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n";
TI->eraseFromParent(); // Nuke the old one.
// If condition is now dead, nuke it.
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
DeadCases.insert(PredCases[i].first);
- DEBUG(std::cerr << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI);
+ DOUT << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI;
for (unsigned i = SI->getNumCases()-1; i != 0; --i)
if (DeadCases.count(SI->getCaseValue(i))) {
SI->removeCase(i);
}
- DEBUG(std::cerr << "Leaving: " << *TI << "\n");
+ DOUT << "Leaving: " << *TI << "\n";
return true;
}
}
// Insert the new branch.
Instruction *NI = new BranchInst(TheRealDest, TI);
- DEBUG(std::cerr << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
+ DOUT << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n";
Instruction *Cond = 0;
if (BranchInst *BI = dyn_cast<BranchInst>(TI))
Cond = dyn_cast<Instruction>(BI->getCondition());
BasicBlock *BB2 = BI->getSuccessor(1); // The false destination
Instruction *I1 = BB1->begin(), *I2 = BB2->begin();
- if (I1->getOpcode() != I2->getOpcode() || !I1->isIdenticalTo(I2) ||
- isa<PHINode>(I1))
+ if (I1->getOpcode() != I2->getOpcode() || isa<PHINode>(I1) ||
+ isa<InvokeInst>(I1) || !I1->isIdenticalTo(I2))
return false;
// If we get here, we can hoist at least one instruction.
/// across this block.
static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) {
BranchInst *BI = cast<BranchInst>(BB->getTerminator());
- Value *Cond = BI->getCondition();
-
unsigned Size = 0;
// If this basic block contains anything other than a PHI (which controls the
// Okay, this is a simple enough basic block. See if any phi values are
// constants.
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
- if (ConstantBool *CB = dyn_cast<ConstantBool>(PN->getIncomingValue(i))) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ ConstantInt *CB;
+ if ((CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i))) &&
+ CB->getType() == Type::Int1Ty) {
// Okay, we now know that all edges from PredBB should be revectored to
// branch to RealDest.
BasicBlock *PredBB = PN->getIncomingBlock(i);
- BasicBlock *RealDest = BI->getSuccessor(!CB->getValue());
+ BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue());
if (RealDest == BB) continue; // Skip self loops.
// Check for trivial simplification.
if (Constant *C = ConstantFoldInstruction(N)) {
- std::cerr << "FOLDED: " << *N;
TranslateMap[BBI] = C;
delete N; // Constant folded away, don't need actual inst
} else {
// Recurse, simplifying any other constants.
return FoldCondBranchOnPHI(BI) | true;
}
+ }
return false;
}
Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse);
if (!IfCond) return false;
- DEBUG(std::cerr << "FOUND IF CONDITION! " << *IfCond << " T: "
- << IfTrue->getName() << " F: " << IfFalse->getName() << "\n");
+ // Okay, we found that we can merge this two-entry phi node into a select.
+ // Doing so would require us to fold *all* two entry phi nodes in this block.
+ // At some point this becomes non-profitable (particularly if the target
+ // doesn't support cmov's). Only do this transformation if there are two or
+ // fewer PHI nodes in this block.
+ unsigned NumPhis = 0;
+ for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++NumPhis, ++I)
+ if (NumPhis > 2)
+ return false;
+
+ DOUT << "FOUND IF CONDITION! " << *IfCond << " T: "
+ << IfTrue->getName() << " F: " << IfFalse->getName() << "\n";
// Loop over the PHI's seeing if we can promote them all to select
// instructions. While we are at it, keep track of the instructions
/// applications that sort ConstantInt's to ensure uniqueness.
struct ConstantIntOrdering {
bool operator()(const ConstantInt *LHS, const ConstantInt *RHS) const {
- return LHS->getRawValue() < RHS->getRawValue();
+ return LHS->getZExtValue() < RHS->getZExtValue();
}
};
}
// Remove basic blocks that have no predecessors... which are unreachable.
if (pred_begin(BB) == pred_end(BB) ||
*pred_begin(BB) == BB && ++pred_begin(BB) == pred_end(BB)) {
- DEBUG(std::cerr << "Removing BB: \n" << *BB);
+ DOUT << "Removing BB: \n" << *BB;
// Loop through all of our successors and make sure they know that one
// of their predecessors is going away.
if (!UncondBranchPreds.empty()) {
while (!UncondBranchPreds.empty()) {
BasicBlock *Pred = UncondBranchPreds.back();
- DEBUG(std::cerr << "FOLDING: " << *BB
- << "INTO UNCOND BRANCH PRED: " << *Pred);
+ DOUT << "FOLDING: " << *BB
+ << "INTO UNCOND BRANCH PRED: " << *Pred;
UncondBranchPreds.pop_back();
Instruction *UncondBranch = Pred->getTerminator();
// Clone the return and add it to the end of the predecessor.
if (FVPN->getParent() == FalseSucc)
FalseValue = FVPN->getIncomingValueForBlock(BI->getParent());
- TrueSucc->removePredecessor(BI->getParent());
- FalseSucc->removePredecessor(BI->getParent());
-
- // Insert a new select instruction.
- Value *NewRetVal;
- Value *BrCond = BI->getCondition();
- if (TrueValue != FalseValue)
- NewRetVal = new SelectInst(BrCond, TrueValue,
- FalseValue, "retval", BI);
- else
- NewRetVal = TrueValue;
-
- new ReturnInst(NewRetVal, BI);
- BI->getParent()->getInstList().erase(BI);
- if (BrCond->use_empty())
+ // In order for this transformation to be safe, we must be able to
+ // unconditionally execute both operands to the return. This is
+ // normally the case, but we could have a potentially-trapping
+ // constant expression that prevents this transformation from being
+ // safe.
+ if ((!isa<ConstantExpr>(TrueValue) ||
+ !cast<ConstantExpr>(TrueValue)->canTrap()) &&
+ (!isa<ConstantExpr>(TrueValue) ||
+ !cast<ConstantExpr>(TrueValue)->canTrap())) {
+ TrueSucc->removePredecessor(BI->getParent());
+ FalseSucc->removePredecessor(BI->getParent());
+
+ // Insert a new select instruction.
+ Value *NewRetVal;
+ Value *BrCond = BI->getCondition();
+ if (TrueValue != FalseValue)
+ NewRetVal = new SelectInst(BrCond, TrueValue,
+ FalseValue, "retval", BI);
+ else
+ NewRetVal = TrueValue;
+
+ DOUT << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
+ << "\n " << *BI << "Select = " << *NewRetVal
+ << "TRUEBLOCK: " << *TrueSucc << "FALSEBLOCK: "<< *FalseSucc;
+
+ new ReturnInst(NewRetVal, BI);
+ BI->eraseFromParent();
if (Instruction *BrCondI = dyn_cast<Instruction>(BrCond))
- BrCondI->getParent()->getInstList().erase(BrCondI);
- return true;
+ if (isInstructionTriviallyDead(BrCondI))
+ BrCondI->eraseFromParent();
+ return true;
+ }
}
}
}
}
- } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->begin())) {
+ } else if (isa<UnwindInst>(BB->begin())) {
// Check to see if the first instruction in this block is just an unwind.
// If so, replace any invoke instructions which use this as an exception
// destination with call instructions, and any unconditional branch
return 1;
} else { // Conditional branch
- if (Value *CompVal = isValueEqualityComparison(BI)) {
+ if (isValueEqualityComparison(BI)) {
// 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.
// predecessor and use logical operations to pick the right destination.
BasicBlock *TrueDest = BI->getSuccessor(0);
BasicBlock *FalseDest = BI->getSuccessor(1);
- if (BinaryOperator *Cond = dyn_cast<BinaryOperator>(BI->getCondition()))
- if (Cond->getParent() == BB && &BB->front() == Cond &&
+ if (Instruction *Cond = dyn_cast<Instruction>(BI->getCondition()))
+ if ((isa<CmpInst>(Cond) || isa<BinaryOperator>(Cond)) &&
+ Cond->getParent() == BB && &BB->front() == Cond &&
Cond->getNext() == BI && Cond->hasOneUse() &&
TrueDest != BB && FalseDest != BB)
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI!=E; ++PI)
PBI->setSuccessor(1, OldTrue);
}
- if (PBI->getSuccessor(0) == TrueDest ||
- PBI->getSuccessor(1) == FalseDest) {
+ if ((PBI->getSuccessor(0) == TrueDest && FalseDest != BB) ||
+ (PBI->getSuccessor(1) == FalseDest && TrueDest != BB)) {
// Clone Cond into the predecessor basic block, and or/and the
// two conditions together.
Instruction *New = Cond->clone();
if (PBI != BI && PBI->isConditional()) {
// If this block ends with a branch instruction, and if there is a
- // predecessor that ends on a branch of the same condition, make this
- // conditional branch redundant.
+ // predecessor that ends on a branch of the same condition, make
+ // this conditional branch redundant.
if (PBI->getCondition() == BI->getCondition() &&
PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
// Okay, the outcome of this conditional branch is statically
if (BB->getSinglePredecessor()) {
// Turn this into a branch on constant.
bool CondIsTrue = PBI->getSuccessor(0) == BB;
- BI->setCondition(ConstantBool::get(CondIsTrue));
+ BI->setCondition(ConstantInt::get(Type::Int1Ty, CondIsTrue));
return SimplifyCFG(BB); // Nuke the branch on constant.
}
- // Otherwise, if there are multiple predecessors, insert a PHI that
- // merges in the constant and simplify the block result.
+ // Otherwise, if there are multiple predecessors, insert a PHI
+ // that merges in the constant and simplify the block result.
if (BlockIsSimpleEnoughToThreadThrough(BB)) {
- PHINode *NewPN = new PHINode(Type::BoolTy,
- BI->getCondition()->getName()+".pr",
- BB->begin());
+ PHINode *NewPN = new PHINode(Type::Int1Ty,
+ BI->getCondition()->getName()+".pr",
+ BB->begin());
for (PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
if ((PBI = dyn_cast<BranchInst>((*PI)->getTerminator())) &&
PBI != BI && PBI->isConditional() &&
PBI->getCondition() == BI->getCondition() &&
PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
bool CondIsTrue = PBI->getSuccessor(0) == BB;
- NewPN->addIncoming(ConstantBool::get(CondIsTrue), *PI);
+ NewPN->addIncoming(ConstantInt::get(Type::Int1Ty,
+ CondIsTrue), *PI);
} else {
NewPN->addIncoming(BI->getCondition(), *PI);
}
PBIOp = BIOp = -1;
}
+ // Check to make sure that the other destination of this branch
+ // isn't BB itself. If so, this is an infinite loop that will
+ // keep getting unwound.
+ if (PBIOp != -1 && PBI->getSuccessor(PBIOp) == BB)
+ PBIOp = BIOp = -1;
+
+ // Do not perform this transformation if it would require
+ // insertion of a large number of select instructions. For targets
+ // without predication/cmovs, this is a big pessimization.
+ if (PBIOp != -1) {
+ BasicBlock *CommonDest = PBI->getSuccessor(PBIOp);
+
+ unsigned NumPhis = 0;
+ for (BasicBlock::iterator II = CommonDest->begin();
+ isa<PHINode>(II); ++II, ++NumPhis) {
+ if (NumPhis > 2) {
+ // Disable this xform.
+ PBIOp = -1;
+ break;
+ }
+ }
+ }
+
// Finally, if everything is ok, fold the branches to logical ops.
if (PBIOp != -1) {
BasicBlock *CommonDest = PBI->getSuccessor(PBIOp);
BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1);
- DEBUG(std::cerr << "FOLDING BRs:" << *PBI->getParent()
- << "AND: " << *BI->getParent());
+ // If OtherDest *is* BB, then this is a basic block with just
+ // a conditional branch in it, where one edge (OtherDesg) goes
+ // back to the block. We know that the program doesn't get
+ // stuck in the infinite loop, so the condition must be such
+ // that OtherDest isn't branched through. Forward to CommonDest,
+ // and avoid an infinite loop at optimizer time.
+ if (OtherDest == BB)
+ OtherDest = CommonDest;
+
+ DOUT << "FOLDING BRs:" << *PBI->getParent()
+ << "AND: " << *BI->getParent();
// BI may have other predecessors. Because of this, we leave
// it alone, but modify PBI.
}
}
- DEBUG(std::cerr << "INTO: " << *PBI->getParent());
+ DOUT << "INTO: " << *PBI->getParent();
// This basic block is probably dead. We know it has at least
// one fewer predecessor.
}
if (OnlySucc) {
- DEBUG(std::cerr << "Merging: " << *BB << "into: " << *OnlyPred);
- TerminatorInst *Term = OnlyPred->getTerminator();
+ DOUT << "Merging: " << *BB << "into: " << *OnlyPred;
// Resolve any PHI nodes at the start of the block. They are all
// guaranteed to have exactly one entry if they exist, unless there are
Value *CompVal = 0;
std::vector<ConstantInt*> Values;
bool TrueWhenEqual = GatherValueComparisons(Cond, CompVal, Values);
- if (CompVal && CompVal->getType()->isInteger()) {
+ if (CompVal && CompVal->getType()->isIntegral()) {
// There might be duplicate constants in the list, which the switch
// instruction can't handle, remove them now.
std::sort(Values.begin(), Values.end(), ConstantIntOrdering());
projects / oota-llvm.git / blobdiff