PGO: preserve branch-weight metadata when simplifying Switch
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
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 67cb8f5..1316b85 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2425,6 +2425,21 @@
// 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.