Clarify a comment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52212 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 3b181c8..a1a3333 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -10613,7 +10613,6 @@
}
Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
-
// If vector val is undef, replace extract with scalar undef.
if (isa<UndefValue>(EI.getOperand(0)))
return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
@@ -10623,8 +10622,9 @@
return ReplaceInstUsesWith(EI, Constant::getNullValue(EI.getType()));
if (ConstantVector *C = dyn_cast<ConstantVector>(EI.getOperand(0))) {
- // If vector val is constant with uniform operands, replace EI
- // with that operand
+ // If vector val is constant with all elements the same, replace EI with
+ // that element. When the elements are not identical, we cannot replace yet
+ // (we do that below, but only when the index is constant).
Constant *op0 = C->getOperand(0);
for (unsigned i = 1; i < C->getNumOperands(); ++i)
if (C->getOperand(i) != op0) {