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eliminate some uses of canLosslesslyBitCastTo, this actually makes the code stronger, by nuking 

relational pointer comparisons with casts.

llvm-svn: 32947
This commit is contained in:
Chris Lattner 2007-01-06 01:45:59 +00:00
parent 3fe98ae10a
commit 64d87b0215
1 changed files with 14 additions and 15 deletions
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29
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -5133,25 +5133,22 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
return NI;
// Test to see if the operands of the icmp are casted versions of other
// values. If the cast can be stripped off both arguments, we do so now.
if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
Value *CastOp0 = CI->getOperand(0);
if (CI->isLosslessCast() && I.isEquality() &&
(isa<Constant>(Op1) || isa<CastInst>(Op1))) {
// values. If the ptr->ptr cast can be stripped off both arguments, we do so
// now.
if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
if (isa<PointerType>(Op0->getType()) &&
(isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
// We keep moving the cast from the left operand over to the right
// operand, where it can often be eliminated completely.
Op0 = CastOp0;
Op0 = CI->getOperand(0);
// If operand #1 is a cast instruction, see if we can eliminate it as
// well.
if (CastInst *CI2 = dyn_cast<CastInst>(Op1)) {
Value *CI2Op0 = CI2->getOperand(0);
if (CI2Op0->getType()->canLosslesslyBitCastTo(Op0->getType()))
Op1 = CI2Op0;
}
// If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
// so eliminate it as well.
if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
Op1 = CI2->getOperand(0);
// If Op1 is a constant, we can fold the cast into the constant.
if (Op1->getType() != Op0->getType())
if (Op0->getType() != Op1->getType())
if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
} else {
@ -5160,7 +5157,9 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
}
return new ICmpInst(I.getPredicate(), Op0, Op1);
}
}
if (isa<CastInst>(Op0)) {
// Handle the special case of: icmp (cast bool to X), <cst>
// This comes up when you have code like
// int X = A < B;