PGO: preserve branch-weight metadata when simplifying SwitchOnSelect.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164068 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 5a8d2e4..67cb8f5 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2213,7 +2213,9 @@
// Also makes sure not to introduce new successors by assuming that edges to
// non-successor TrueBBs and FalseBBs aren't reachable.
static bool SimplifyTerminatorOnSelect(TerminatorInst *OldTerm, Value *Cond,
- BasicBlock *TrueBB, BasicBlock *FalseBB){
+ BasicBlock *TrueBB, BasicBlock *FalseBB,
+ uint32_t TrueWeight,
+ uint32_t FalseWeight){
// Remove any superfluous successor edges from the CFG.
// First, figure out which successors to preserve.
// If TrueBB and FalseBB are equal, only try to preserve one copy of that
@@ -2242,10 +2244,15 @@
// We were only looking for one successor, and it was present.
// Create an unconditional branch to it.
Builder.CreateBr(TrueBB);
- else
+ else {
// We found both of the successors we were looking for.
// Create a conditional branch sharing the condition of the select.
- Builder.CreateCondBr(Cond, TrueBB, FalseBB);
+ BranchInst *NewBI = Builder.CreateCondBr(Cond, TrueBB, FalseBB);
+ if (TrueWeight != FalseWeight)
+ NewBI->setMetadata(LLVMContext::MD_prof,
+ MDBuilder(OldTerm->getContext()).
+ createBranchWeights(TrueWeight, FalseWeight));
+ }
} else if (KeepEdge1 && (KeepEdge2 || TrueBB == FalseBB)) {
// Neither of the selected blocks were successors, so this
// terminator must be unreachable.
@@ -2282,8 +2289,23 @@
BasicBlock *TrueBB = SI->findCaseValue(TrueVal).getCaseSuccessor();
BasicBlock *FalseBB = SI->findCaseValue(FalseVal).getCaseSuccessor();
+ // Get weight for TrueBB and FalseBB.
+ uint32_t TrueWeight = 0, FalseWeight = 0;
+ SmallVector<uint64_t, 8> Weights;
+ bool HasWeights = HasBranchWeights(SI);
+ if (HasWeights) {
+ GetBranchWeights(SI, Weights);
+ if (Weights.size() == 1 + SI->getNumCases()) {
+ TrueWeight = (uint32_t)Weights[SI->findCaseValue(TrueVal).
+ getSuccessorIndex()];
+ FalseWeight = (uint32_t)Weights[SI->findCaseValue(FalseVal).
+ getSuccessorIndex()];
+ }
+ }
+
// Perform the actual simplification.
- return SimplifyTerminatorOnSelect(SI, Condition, TrueBB, FalseBB);
+ return SimplifyTerminatorOnSelect(SI, Condition, TrueBB, FalseBB,
+ TrueWeight, FalseWeight);
}
// SimplifyIndirectBrOnSelect - Replaces
@@ -2303,7 +2325,8 @@
BasicBlock *FalseBB = FBA->getBasicBlock();
// Perform the actual simplification.
- return SimplifyTerminatorOnSelect(IBI, SI->getCondition(), TrueBB, FalseBB);
+ return SimplifyTerminatorOnSelect(IBI, SI->getCondition(), TrueBB, FalseBB,
+ 0, 0);
}
/// TryToSimplifyUncondBranchWithICmpInIt - This is called when we find an icmp