fdiv/frem of undef can produce undef, because the undef operand
can be a SNaN. We could be more aggressive and turn this into
unreachable, but that is less nice, and not really worth it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47313 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 5582f51..9957bc1 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -2590,9 +2590,13 @@
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 @@
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