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PGO: preserve branch-weight metadata when merging two switches where

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the default target of the first switch is not the basic block the second switch
is in (PredDefault != BB).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163916 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Manman Ren 2012-09-14 17:29:56 +00:00
parent d039b383e7
commit a8a2b99aec
2 changed files with 60 additions and 5 deletions
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17
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -898,18 +898,21 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
Weights[0] *= SuccWeights[0];
}
} else {
// FIXME: preserve branch weight metadata, similarly to the 'then'
// above. For now, drop it.
PredHasWeights = false;
SuccHasWeights = false;
// If this is not the default destination from PSI, only the edges
// in SI that occur in PSI with a destination of BB will be
// activated.
std::set<ConstantInt*, ConstantIntOrdering> PTIHandled;
std::map<ConstantInt*, uint64_t> WeightsForHandled;
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
if (PredCases[i].Dest == BB) {
PTIHandled.insert(PredCases[i].Value);
if (PredHasWeights || SuccHasWeights) {
WeightsForHandled[PredCases[i].Value] = Weights[i+1];
std::swap(Weights[i+1], Weights.back());
Weights.pop_back();
}
std::swap(PredCases[i], PredCases.back());
PredCases.pop_back();
--i; --e;
@ -920,6 +923,8 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
for (unsigned i = 0, e = BBCases.size(); i != e; ++i)
if (PTIHandled.count(BBCases[i].Value)) {
// If this is one we are capable of getting...
if (PredHasWeights || SuccHasWeights)
Weights.push_back(WeightsForHandled[BBCases[i].Value]);
PredCases.push_back(BBCases[i]);
NewSuccessors.push_back(BBCases[i].Dest);
PTIHandled.erase(BBCases[i].Value);// This constant is taken care of
@ -930,6 +935,8 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
for (std::set<ConstantInt*, ConstantIntOrdering>::iterator I =
PTIHandled.begin(),
E = PTIHandled.end(); I != E; ++I) {
if (PredHasWeights || SuccHasWeights)
Weights.push_back(WeightsForHandled[*I]);
PredCases.push_back(ValueEqualityComparisonCase(*I, BBDefault));
NewSuccessors.push_back(BBDefault);
}

48
test/Transforms/SimplifyCFG/preserve-branchweights-switch-create.ll
View File

@ -84,9 +84,57 @@ sw.epilog:
ret void
}
;; test3 - Merge two switches where PredDefault != BB.
define void @test3(i32 %M, i32 %N) nounwind uwtable {
entry:
%cmp = icmp sgt i32 %M, 2
br i1 %cmp, label %sw1, label %sw2
sw1:
switch i32 %N, label %sw.bb [
i32 2, label %sw2
i32 3, label %sw2
i32 1, label %sw.bb1
], !prof !4
; CHECK: test3
; CHECK: switch i32 %N, label %sw.bb
; CHECK: i32 1, label %sw.bb1
; CHECK: i32 3, label %sw.bb4
; CHECK: i32 2, label %sw.epilog
; CHECK: ], !prof !3
sw.bb:
call void @func2(i32 %N) nounwind
br label %sw.epilog
sw.bb1:
call void @func4(i32 %N) nounwind
br label %sw.epilog
sw2:
switch i32 %N, label %sw.epilog [
i32 3, label %sw.bb4
i32 4, label %sw.bb5
], !prof !5
sw.bb4:
call void @func6(i32 %N) nounwind
br label %sw.epilog
sw.bb5:
call void @func8(i32 %N) nounwind
br label %sw.epilog
sw.epilog:
ret void
}
!0 = metadata !{metadata !"branch_weights", i32 64, i32 4}
!1 = metadata !{metadata !"branch_weights", i32 4, i32 64}
; CHECK: !0 = metadata !{metadata !"branch_weights", i32 256, i32 4352, i32 16}
!2 = metadata !{metadata !"branch_weights", i32 4, i32 4, i32 8}
!3 = metadata !{metadata !"branch_weights", i32 8, i32 8, i32 4}
; CHECK: !1 = metadata !{metadata !"branch_weights", i32 32, i32 48, i32 96, i32 16}
!4 = metadata !{metadata !"branch_weights", i32 7, i32 6, i32 4, i32 3}
!5 = metadata !{metadata !"branch_weights", i32 17, i32 13, i32 9}
; CHECK: !3 = metadata !{metadata !"branch_weights", i32 7, i32 3, i32 4, i32 6}