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-rw-r--r--llvm/lib/Transforms/Scalar/JumpThreading.cpp71
1 files changed, 46 insertions, 25 deletions
diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 2b4e3ff00dd..bd8c0e8e699 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -124,9 +124,11 @@ namespace {
bool ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,
PredValueInfo &Result,
- ConstantPreference Preference);
+ ConstantPreference Preference,
+ Instruction *CxtI = nullptr);
bool ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
- ConstantPreference Preference);
+ ConstantPreference Preference,
+ Instruction *CxtI = nullptr);
bool ProcessBranchOnPHI(PHINode *PN);
bool ProcessBranchOnXOR(BinaryOperator *BO);
@@ -340,7 +342,8 @@ static Constant *getKnownConstant(Value *Val, ConstantPreference Preference) {
///
bool JumpThreading::
ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
- ConstantPreference Preference) {
+ ConstantPreference Preference,
+ Instruction *CxtI) {
// This method walks up use-def chains recursively. Because of this, we could
// get into an infinite loop going around loops in the use-def chain. To
// prevent this, keep track of what (value, block) pairs we've already visited
@@ -382,7 +385,7 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
BasicBlock *P = *PI;
// If the value is known by LazyValueInfo to be a constant in a
// predecessor, use that information to try to thread this block.
- Constant *PredCst = LVI->getConstantOnEdge(V, P, BB);
+ Constant *PredCst = LVI->getConstantOnEdge(V, P, BB, CxtI);
if (Constant *KC = getKnownConstant(PredCst, Preference))
Result.push_back(std::make_pair(KC, P));
}
@@ -398,7 +401,8 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
Result.push_back(std::make_pair(KC, PN->getIncomingBlock(i)));
} else {
Constant *CI = LVI->getConstantOnEdge(InVal,
- PN->getIncomingBlock(i), BB);
+ PN->getIncomingBlock(i),
+ BB, CxtI);
if (Constant *KC = getKnownConstant(CI, Preference))
Result.push_back(std::make_pair(KC, PN->getIncomingBlock(i)));
}
@@ -417,9 +421,9 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
if (I->getOpcode() == Instruction::Or ||
I->getOpcode() == Instruction::And) {
ComputeValueKnownInPredecessors(I->getOperand(0), BB, LHSVals,
- WantInteger);
+ WantInteger, CxtI);
ComputeValueKnownInPredecessors(I->getOperand(1), BB, RHSVals,
- WantInteger);
+ WantInteger, CxtI);
if (LHSVals.empty() && RHSVals.empty())
return false;
@@ -460,7 +464,7 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
isa<ConstantInt>(I->getOperand(1)) &&
cast<ConstantInt>(I->getOperand(1))->isOne()) {
ComputeValueKnownInPredecessors(I->getOperand(0), BB, Result,
- WantInteger);
+ WantInteger, CxtI);
if (Result.empty())
return false;
@@ -478,7 +482,7 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
PredValueInfoTy LHSVals;
ComputeValueKnownInPredecessors(BO->getOperand(0), BB, LHSVals,
- WantInteger);
+ WantInteger, CxtI);
// Try to use constant folding to simplify the binary operator.
for (unsigned i = 0, e = LHSVals.size(); i != e; ++i) {
@@ -512,7 +516,8 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
LazyValueInfo::Tristate
ResT = LVI->getPredicateOnEdge(Cmp->getPredicate(), LHS,
- cast<Constant>(RHS), PredBB, BB);
+ cast<Constant>(RHS), PredBB, BB,
+ CxtI ? CxtI : Cmp);
if (ResT == LazyValueInfo::Unknown)
continue;
Res = ConstantInt::get(Type::getInt1Ty(LHS->getContext()), ResT);
@@ -525,7 +530,6 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
return !Result.empty();
}
-
// If comparing a live-in value against a constant, see if we know the
// live-in value on any predecessors.
if (isa<Constant>(Cmp->getOperand(1)) && Cmp->getType()->isIntegerTy()) {
@@ -539,7 +543,7 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
// predecessor, use that information to try to thread this block.
LazyValueInfo::Tristate Res =
LVI->getPredicateOnEdge(Cmp->getPredicate(), Cmp->getOperand(0),
- RHSCst, P, BB);
+ RHSCst, P, BB, CxtI ? CxtI : Cmp);
if (Res == LazyValueInfo::Unknown)
continue;
@@ -555,7 +559,7 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
if (Constant *CmpConst = dyn_cast<Constant>(Cmp->getOperand(1))) {
PredValueInfoTy LHSVals;
ComputeValueKnownInPredecessors(I->getOperand(0), BB, LHSVals,
- WantInteger);
+ WantInteger, CxtI);
for (unsigned i = 0, e = LHSVals.size(); i != e; ++i) {
Constant *V = LHSVals[i].first;
@@ -578,7 +582,7 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
PredValueInfoTy Conds;
if ((TrueVal || FalseVal) &&
ComputeValueKnownInPredecessors(SI->getCondition(), BB, Conds,
- WantInteger)) {
+ WantInteger, CxtI)) {
for (unsigned i = 0, e = Conds.size(); i != e; ++i) {
Constant *Cond = Conds[i].first;
@@ -605,7 +609,7 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
}
// If all else fails, see if LVI can figure out a constant value for us.
- Constant *CI = LVI->getConstant(V, BB);
+ Constant *CI = LVI->getConstant(V, BB, CxtI);
if (Constant *KC = getKnownConstant(CI, Preference)) {
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
Result.push_back(std::make_pair(KC, *PI));
@@ -745,7 +749,7 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
// All the rest of our checks depend on the condition being an instruction.
if (!CondInst) {
// FIXME: Unify this with code below.
- if (ProcessThreadableEdges(Condition, BB, Preference))
+ if (ProcessThreadableEdges(Condition, BB, Preference, Terminator))
return true;
return false;
}
@@ -767,13 +771,14 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
// FIXME: We could handle mixed true/false by duplicating code.
LazyValueInfo::Tristate Baseline =
LVI->getPredicateOnEdge(CondCmp->getPredicate(), CondCmp->getOperand(0),
- CondConst, *PI, BB);
+ CondConst, *PI, BB, CondCmp);
if (Baseline != LazyValueInfo::Unknown) {
// Check that all remaining incoming values match the first one.
while (++PI != PE) {
LazyValueInfo::Tristate Ret =
LVI->getPredicateOnEdge(CondCmp->getPredicate(),
- CondCmp->getOperand(0), CondConst, *PI, BB);
+ CondCmp->getOperand(0), CondConst, *PI, BB,
+ CondCmp);
if (Ret != Baseline) break;
}
@@ -788,6 +793,21 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
}
}
+ } else if (CondBr && CondConst && CondBr->isConditional()) {
+ // There might be an invairant in the same block with the conditional
+ // that can determine the predicate.
+
+ LazyValueInfo::Tristate Ret =
+ LVI->getPredicateAt(CondCmp->getPredicate(), CondCmp->getOperand(0),
+ CondConst, CondCmp);
+ if (Ret != LazyValueInfo::Unknown) {
+ unsigned ToRemove = Ret == LazyValueInfo::True ? 1 : 0;
+ unsigned ToKeep = Ret == LazyValueInfo::True ? 0 : 1;
+ CondBr->getSuccessor(ToRemove)->removePredecessor(BB, true);
+ BranchInst::Create(CondBr->getSuccessor(ToKeep), CondBr);
+ CondBr->eraseFromParent();
+ return true;
+ }
}
if (CondBr && CondConst && TryToUnfoldSelect(CondCmp, BB))
@@ -815,7 +835,7 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
// a PHI node in the current block. If we can prove that any predecessors
// compute a predictable value based on a PHI node, thread those predecessors.
//
- if (ProcessThreadableEdges(CondInst, BB, Preference))
+ if (ProcessThreadableEdges(CondInst, BB, Preference, Terminator))
return true;
// If this is an otherwise-unfoldable branch on a phi node in the current
@@ -1083,14 +1103,15 @@ FindMostPopularDest(BasicBlock *BB,
}
bool JumpThreading::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
- ConstantPreference Preference) {
+ ConstantPreference Preference,
+ Instruction *CxtI) {
// If threading this would thread across a loop header, don't even try to
// thread the edge.
if (LoopHeaders.count(BB))
return false;
PredValueInfoTy PredValues;
- if (!ComputeValueKnownInPredecessors(Cond, BB, PredValues, Preference))
+ if (!ComputeValueKnownInPredecessors(Cond, BB, PredValues, Preference, CxtI))
return false;
assert(!PredValues.empty() &&
@@ -1255,10 +1276,10 @@ bool JumpThreading::ProcessBranchOnXOR(BinaryOperator *BO) {
PredValueInfoTy XorOpValues;
bool isLHS = true;
if (!ComputeValueKnownInPredecessors(BO->getOperand(0), BB, XorOpValues,
- WantInteger)) {
+ WantInteger, BO)) {
assert(XorOpValues.empty());
if (!ComputeValueKnownInPredecessors(BO->getOperand(1), BB, XorOpValues,
- WantInteger))
+ WantInteger, BO))
return false;
isLHS = false;
}
@@ -1674,10 +1695,10 @@ bool JumpThreading::TryToUnfoldSelect(CmpInst *CondCmp, BasicBlock *BB) {
// cases will be threaded in any case.
LazyValueInfo::Tristate LHSFolds =
LVI->getPredicateOnEdge(CondCmp->getPredicate(), SI->getOperand(1),
- CondRHS, Pred, BB);
+ CondRHS, Pred, BB, CondCmp);
LazyValueInfo::Tristate RHSFolds =
LVI->getPredicateOnEdge(CondCmp->getPredicate(), SI->getOperand(2),
- CondRHS, Pred, BB);
+ CondRHS, Pred, BB, CondCmp);
if ((LHSFolds != LazyValueInfo::Unknown ||
RHSFolds != LazyValueInfo::Unknown) &&
LHSFolds != RHSFolds) {
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