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fix a potential overflow issue Eli pointed out.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94336 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-01-23 23:31:46 +00:00
parent 44540740ae
commit f7d0d163c5
1 changed files with 3 additions and 3 deletions
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6
lib/Transforms/InstCombine/InstCombineShifts.cpp
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@ -394,16 +394,16 @@ Instruction *InstCombiner::visitLShr(BinaryOperator &I) {
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1))
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op0)) {
unsigned BitWidth = Op0->getType()->getScalarSizeInBits();
// ctlz.i32(x)>>5 --> zext(x == 0)
// cttz.i32(x)>>5 --> zext(x == 0)
// ctpop.i32(x)>>5 --> zext(x == -1)
if ((II->getIntrinsicID() == Intrinsic::ctlz ||
II->getIntrinsicID() == Intrinsic::cttz ||
II->getIntrinsicID() == Intrinsic::ctpop) &&
(1ULL << Op1C->getZExtValue()) ==
Op0->getType()->getScalarSizeInBits()) {
isPowerOf2_32(BitWidth) && Log2_32(BitWidth) == Op1C->getZExtValue()){
bool isCtPop = II->getIntrinsicID() == Intrinsic::ctpop;
Constant *RHS = ConstantInt::getSigned(Op0->getType(), isCtPop ? -1 : 0);
Constant *RHS = ConstantInt::getSigned(Op0->getType(), isCtPop ? -1:0);
Value *Cmp = Builder->CreateICmpEQ(II->getOperand(1), RHS);
return new ZExtInst(Cmp, II->getType());
}