Add a comment about a missed opportunity.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85635 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 859b875..8e1fb98 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1753,8 +1753,13 @@
/// nodes in this block. This doesn't try to be clever about PHI nodes
/// which differ only in the order of the incoming values, but instcombine
/// orders them so it usually won't matter.
+///
static bool EliminateDuplicatePHINodes(BasicBlock *BB) {
bool Changed = false;
+
+ // This implementation doesn't currently consider undef operands
+ // specially. Theroetically, two phis which are identical except for
+ // one having an undef where the other doesn't could be collapsed.
// Map from PHI hash values to PHI nodes. If multiple PHIs have
// the same hash value, the element is the first PHI in the