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Fix a pretty serious misfeature of the inliner: if it inlines a function

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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
This commit is contained in:
Chris Lattner
2009-10-27 05:39:41 +00:00
parent 744f19aa15
commit c581acbbba
2 changed files with 41 additions and 1 deletions
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9
lib/Transforms/Utils/InlineFunction.cpp
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@ -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];