enhance RecursivelyDeleteTriviallyDeadInstructions to make
PHIs dead if they are single-value.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60194 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index 1e1b386..cab7f03 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -190,6 +190,15 @@
while (!Insts.empty()) {
I = *Insts.begin();
Insts.erase(I);
+
+ // If this is a PHI node, we may be able to make it dead if we know all the
+ // input values are the same.
+ if (PHINode *PN = dyn_cast<PHINode>(I)) {
+ if (Value *PNV = PN->hasConstantValue())
+ PN->replaceAllUsesWith(PNV);
+ }
+
+ // Okay, if the instruction is dead, delete it.
if (!isInstructionTriviallyDead(I))
continue;