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PGO: preserve branch-weight metadata when simplifying SwitchOnSelect.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164068 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Manman Ren 2012-09-17 22:28:55 +00:00
parent 97d552e5c7
commit b11cbe6b23
2 changed files with 54 additions and 6 deletions
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33
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -2213,7 +2213,9 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) {
// 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 @@ static bool SimplifyTerminatorOnSelect(TerminatorInst *OldTerm, Value *Cond,
// 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 @@ static bool SimplifySwitchOnSelect(SwitchInst *SI, SelectInst *Select) {
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 @@ static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) {
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

27
test/Transforms/SimplifyCFG/preserve-branchweights.ll
View File

@ -193,6 +193,29 @@ Z:
ret void
}
; Test basic folding to a conditional branch.
define void @test8(i64 %x, i64 %y) nounwind {
; CHECK: @test8
entry:
%lt = icmp slt i64 %x, %y
; CHECK: br i1 %lt, label %a, label %b, !prof !6
%qux = select i1 %lt, i32 0, i32 2
switch i32 %qux, label %bees [
i32 0, label %a
i32 1, label %b
i32 2, label %b
], !prof !7
a:
call void @helper(i32 0) nounwind
ret void
b:
call void @helper(i32 1) nounwind
ret void
bees:
call void @helper(i32 2) nounwind
ret void
}
!0 = metadata !{metadata !"branch_weights", i32 3, i32 5}
!1 = metadata !{metadata !"branch_weights", i32 1, i32 1}
!2 = metadata !{metadata !"branch_weights", i32 1, i32 2}
@ -200,6 +223,7 @@ Z:
!4 = metadata !{metadata !"branch_weights", i32 4, i32 3, i32 2, i32 1}
!5 = metadata !{metadata !"branch_weights", i32 7, i32 6, i32 5}
!6 = metadata !{metadata !"branch_weights", i32 1, i32 3}
!7 = metadata !{metadata !"branch_weights", i32 33, i32 9, i32 8, i32 7}
; CHECK: !0 = metadata !{metadata !"branch_weights", i32 5, i32 11}
; CHECK: !1 = metadata !{metadata !"branch_weights", i32 1, i32 5}
@ -207,4 +231,5 @@ Z:
; CHECK: !3 = metadata !{metadata !"branch_weights", i32 49, i32 12, i32 24, i32 35}
; CHECK: !4 = metadata !{metadata !"branch_weights", i32 11, i32 5}
; CHECK: !5 = metadata !{metadata !"branch_weights", i32 17, i32 15}
; CHECK-NOT: !6
; CHECK: !6 = metadata !{metadata !"branch_weights", i32 9, i32 7}
; CHECK-NOT: !7