From c581acbbba3cb1af6a08e17314b26344333f9267 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Tue, 27 Oct 2009 05:39:41 +0000 Subject: 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 --- lib/Transforms/Utils/InlineFunction.cpp | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'lib/Transforms/Utils/InlineFunction.cpp') diff --git a/lib/Transforms/Utils/InlineFunction.cpp b/lib/Transforms/Utils/InlineFunction.cpp index 619c939064..20f5a4a942 100644 --- a/lib/Transforms/Utils/InlineFunction.cpp +++ b/lib/Transforms/Utils/InlineFunction.cpp @@ -619,8 +619,17 @@ bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD, "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]; -- cgit v1.2.3-18-g5258