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Use a simple comparison. Overflow on integer negation can only occur when the

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integer is "minint".


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60366 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2008-12-01 19:46:27 +00:00
parent 7b6113c6e2
commit c25c68305c
1 changed files with 2 additions and 13 deletions
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15
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -2934,20 +2934,9 @@ Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
if (Value *LHSNeg = dyn_castNegVal(Op0)) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(LHSNeg)) {
ConstantInt *RHSNeg = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
APInt RHSNegAPI(RHSNeg->getValue());
APInt NegOne = -APInt(RHSNeg->getBitWidth(), 1, true);
APInt TwoToExp(RHSNeg->getBitWidth(), 1 << (RHSNeg->getBitWidth() - 1));
if ((RHS->getValue().isNegative() &&
RHSNegAPI.slt(TwoToExp - 1)) ||
(RHS->getValue().isNonNegative() &&
RHSNegAPI.sgt(TwoToExp * NegOne))) {
if (RHS != RHSNeg) {
ConstantInt *CINeg = cast<ConstantInt>(ConstantExpr::getNeg(CI));
APInt CINegAPI(CINeg->getValue());
if ((CI->getValue().isNegative() && CINegAPI.slt(TwoToExp - 1)) ||
(CI->getValue().isNonNegative() && CINegAPI.sgt(TwoToExp*NegOne)))
if (CI != CINeg)
return BinaryOperator::CreateSDiv(LHSNeg,
ConstantExpr::getNeg(RHS));
}