Fix a pretty serious misfeature of the inliner: if it inlines a function
with multiple return values it inserts a PHI to merge them all together.
However, if the return values are all the same, it ends up with a pointless
PHI and this pointless PHI happens to really block SRoA from happening in
at least a silly C++ example written by Doug, but probably others. This
fixes rdar://7339069.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85206 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/InlineFunction.cpp b/lib/Transforms/Utils/InlineFunction.cpp
index 619c939..20f5a4a 100644
--- a/lib/Transforms/Utils/InlineFunction.cpp
+++ b/lib/Transforms/Utils/InlineFunction.cpp
@@ -619,8 +619,17 @@
"Ret value not consistent in function!");
PHI->addIncoming(RI->getReturnValue(), RI->getParent());
}
+
+ // Now that we inserted the PHI, check to see if it has a single value
+ // (e.g. all the entries are the same or undef). If so, remove the PHI so
+ // it doesn't block other optimizations.
+ if (Value *V = PHI->hasConstantValue()) {
+ PHI->replaceAllUsesWith(V);
+ PHI->eraseFromParent();
+ }
}
+
// Add a branch to the merge points and remove return instructions.
for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
ReturnInst *RI = Returns[i];