Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
const Constant *Idx) {
+ if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
+ return UndefValue::get(cast<PackedType>(Val->getType())->getElementType());
+
if (const ConstantPacked *CVal = dyn_cast<ConstantPacked>(Val)) {
if (const ConstantUInt *CIdx = dyn_cast<ConstantUInt>(Idx)) {
return const_cast<Constant*>(CVal->getOperand(CIdx->getValue()));
+ } else if (isa<UndefValue>(Idx)) {
+ // ee({w,x,y,z}, undef) -> w (an arbitrary value).
+ return const_cast<Constant*>(CVal->getOperand(0));
}
- }
+ }
return 0;
}