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fdiv/frem of undef can produce undef, because the undef operand

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can be a SNaN.  We could be more aggressive and turn this into 
unreachable, but that is less nice, and not really worth it.

llvm-svn: 47313
This commit is contained in:
Chris Lattner 2008-02-19 06:12:18 +00:00
parent 851ebb75de
commit 6bb889cf84
1 changed files with 11 additions and 4 deletions
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15
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -2590,9 +2590,13 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
Instruction *InstCombiner::commonDivTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// undef / X -> 0
if (isa<UndefValue>(Op0))
// undef / X -> 0 for integer.
// undef / X -> undef for FP (the undef could be a snan).
if (isa<UndefValue>(Op0)) {
if (Op0->getType()->isFPOrFPVector())
return ReplaceInstUsesWith(I, Op0);
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
// X / undef -> undef
if (isa<UndefValue>(Op1))
@ -2821,13 +2825,16 @@ static Constant *GetFactor(Value *V) {
Instruction *InstCombiner::commonRemTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// 0 % X == 0, we don't need to preserve faults!
// 0 % X == 0 for integer, we don't need to preserve faults!
if (Constant *LHS = dyn_cast<Constant>(Op0))
if (LHS->isNullValue())
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (isa<UndefValue>(Op0)) // undef % X -> 0
if (isa<UndefValue>(Op0)) { // undef % X -> 0
if (I.getType()->isFPOrFPVector())
return ReplaceInstUsesWith(I, Op0); // X % undef -> undef (could be SNaN)
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1); // X % undef -> undef