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PGO: preserve branch-weight metadata when simplifying Switch

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Hanlde the case when we split the default edge if the default target has "icmp"
and unconditinal branch.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164076 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Manman Ren
2012-09-17 23:07:43 +00:00
parent f23ddf54ea
commit b010277b59
2 changed files with 51 additions and 1 deletions
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15
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -2425,6 +2425,21 @@ static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI,
// the switch to the merge point on the compared value.
BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "switch.edge",
BB->getParent(), BB);
SmallVector<uint64_t, 8> Weights;
bool HasWeights = HasBranchWeights(SI);
if (HasWeights) {
GetBranchWeights(SI, Weights);
if (Weights.size() == 1 + SI->getNumCases()) {
// Split weight for default case to case for "Cst".
Weights[0] = (Weights[0]+1) >> 1;
Weights.push_back(Weights[0]);
SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());
SI->setMetadata(LLVMContext::MD_prof,
MDBuilder(SI->getContext()).
createBranchWeights(MDWeights));
}
}
SI->addCase(Cst, NewBB);
// NewBB branches to the phi block, add the uncond branch and the phi entry.