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pass TD into a SimplifyCmpInst call. Add another case that 

uses LVI info when -enable-jump-threading-lvi is passed.

llvm-svn: 86886
This commit is contained in:
Chris Lattner 2009-11-11 22:31:38 +00:00
parent 02b155427e
commit 67146695b6
1 changed files with 24 additions and 3 deletions
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27
llvm/lib/Transforms/Scalar/JumpThreading.cpp
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@ -361,7 +361,7 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
Value *LHS = PN->getIncomingValue(i);
Value *RHS = Cmp->getOperand(1)->DoPHITranslation(BB, PredBB);
Value *Res = SimplifyCmpInst(Cmp->getPredicate(), LHS, RHS);
Value *Res = SimplifyCmpInst(Cmp->getPredicate(), LHS, RHS, TD);
if (Res == 0) continue;
if (isa<UndefValue>(Res))
@ -373,8 +373,29 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
return !Result.empty();
}
// TODO: We could also recurse to see if we can determine constants another
// way.
// If comparing a live-in value against a constant, see if we know the
// live-in value on any predecessors.
if (LVI && isa<Constant>(Cmp->getOperand(1)) &&
(!isa<Instruction>(Cmp->getOperand(0)) ||
cast<Instruction>(Cmp->getOperand(0))->getParent() != BB)) {
Constant *RHSCst = cast<Constant>(Cmp->getOperand(1));
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++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->getConstant(Cmp->getOperand(0), *PI);
if (PredCst == 0)
continue;
// Constant fold the compare.
Value *Res = SimplifyCmpInst(Cmp->getPredicate(), PredCst, RHSCst, TD);
if (isa<ConstantInt>(Res) || isa<UndefValue>(Res))
Result.push_back(std::make_pair(dyn_cast<ConstantInt>(Res), *PI));
}
return !Result.empty();
}
}
return false;
}