From 222d6192adeba434d64893de920bd72c36f7e8c8 Mon Sep 17 00:00:00 2001 From: Manman Ren Date: Tue, 18 Sep 2012 00:47:33 +0000 Subject: [PATCH] PGO: preserve branch-weight metadata when simplifying Switch to a sub, an icmp and a conditional branch; also when removing dead cases from a switch. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164084 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Utils/SimplifyCFG.cpp | 39 ++++++++++++++- .../SimplifyCFG/preserve-branchweights.ll | 48 ++++++++++++++++++- 2 files changed, 85 insertions(+), 2 deletions(-) diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 1316b859e8c..3365c2feed6 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -2853,9 +2853,28 @@ static bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder) { if (!Offset->isNullValue()) Sub = Builder.CreateAdd(Sub, Offset, Sub->getName()+".off"); Value *Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch"); - Builder.CreateCondBr( + BranchInst *NewBI = Builder.CreateCondBr( Cmp, SI->case_begin().getCaseSuccessor(), SI->getDefaultDest()); + // Update weight for the newly-created conditional branch. + SmallVector Weights; + bool HasWeights = HasBranchWeights(SI); + if (HasWeights) { + GetBranchWeights(SI, Weights); + if (Weights.size() == 1 + SI->getNumCases()) { + // Combine all weights for the cases to be the true weight of NewBI. + // We assume that the sum of all weights for a Terminator can fit into 32 + // bits. + uint32_t NewTrueWeight = 0; + for (unsigned I = 1, E = Weights.size(); I != E; ++I) + NewTrueWeight += (uint32_t)Weights[I]; + NewBI->setMetadata(LLVMContext::MD_prof, + MDBuilder(SI->getContext()). + createBranchWeights(NewTrueWeight, + (uint32_t)Weights[0])); + } + } + // Prune obsolete incoming values off the successor's PHI nodes. for (BasicBlock::iterator BBI = SI->case_begin().getCaseSuccessor()->begin(); isa(BBI); ++BBI) { @@ -2886,15 +2905,33 @@ static bool EliminateDeadSwitchCases(SwitchInst *SI) { } } + SmallVector Weights; + bool HasWeight = HasBranchWeights(SI); + if (HasWeight) { + GetBranchWeights(SI, Weights); + HasWeight = (Weights.size() == 1 + SI->getNumCases()); + } + // Remove dead cases from the switch. for (unsigned I = 0, E = DeadCases.size(); I != E; ++I) { SwitchInst::CaseIt Case = SI->findCaseValue(DeadCases[I]); assert(Case != SI->case_default() && "Case was not found. Probably mistake in DeadCases forming."); + if (HasWeight) { + std::swap(Weights[Case.getCaseIndex()+1], Weights.back()); + Weights.pop_back(); + } + // Prune unused values from PHI nodes. Case.getCaseSuccessor()->removePredecessor(SI->getParent()); SI->removeCase(Case); } + if (HasWeight) { + SmallVector MDWeights(Weights.begin(), Weights.end()); + SI->setMetadata(LLVMContext::MD_prof, + MDBuilder(SI->getParent()->getContext()). + createBranchWeights(MDWeights)); + } return !DeadCases.empty(); } diff --git a/test/Transforms/SimplifyCFG/preserve-branchweights.ll b/test/Transforms/SimplifyCFG/preserve-branchweights.ll index 4b78747cb7a..beef5270082 100644 --- a/test/Transforms/SimplifyCFG/preserve-branchweights.ll +++ b/test/Transforms/SimplifyCFG/preserve-branchweights.ll @@ -250,6 +250,49 @@ end: ret i1 %ret } +define void @test10(i32 %x) nounwind readnone ssp noredzone { +entry: + switch i32 %x, label %lor.rhs [ + i32 2, label %lor.end + i32 1, label %lor.end + i32 3, label %lor.end + ], !prof !7 + +lor.rhs: + call void @helper(i32 1) nounwind + ret void + +lor.end: + call void @helper(i32 0) nounwind + ret void + +; CHECK: test10 +; CHECK: %x.off = add i32 %x, -1 +; CHECK: %switch = icmp ult i32 %x.off, 3 +; CHECK: br i1 %switch, label %lor.end, label %lor.rhs, !prof !8 +} + +; Remove dead cases from the switch. +define void @test11(i32 %x) nounwind { + %i = shl i32 %x, 1 + switch i32 %i, label %a [ + i32 21, label %b + i32 24, label %c + ], !prof !8 +; CHECK: %cond = icmp eq i32 %i, 24 +; CHECK: br i1 %cond, label %c, label %a, !prof !9 + +a: + call void @helper(i32 0) nounwind + ret void +b: + call void @helper(i32 1) nounwind + ret void +c: + 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} @@ -258,6 +301,7 @@ end: !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} +!8 = metadata !{metadata !"branch_weights", i32 33, i32 9, i32 8} ; CHECK: !0 = metadata !{metadata !"branch_weights", i32 5, i32 11} ; CHECK: !1 = metadata !{metadata !"branch_weights", i32 1, i32 5} @@ -267,4 +311,6 @@ end: ; CHECK: !5 = metadata !{metadata !"branch_weights", i32 17, i32 15} ; CHECK: !6 = metadata !{metadata !"branch_weights", i32 9, i32 7} ; CHECK: !7 = metadata !{metadata !"branch_weights", i32 17, i32 9, i32 8, i32 7, i32 17} -; CHECK-NOT: !8 +; CHECK: !8 = metadata !{metadata !"branch_weights", i32 24, i32 33} +; CHECK: !9 = metadata !{metadata !"branch_weights", i32 8, i32 33} +; CHECK-NOT: !9