diff options
| -rw-r--r-- | lib/Transforms/Utils/Local.cpp | 16 | ||||
| -rw-r--r-- | lib/Transforms/Utils/SimplifyCFG.cpp | 19 | ||||
| -rw-r--r-- | test/Transforms/SimplifyCFG/preserve-branchweights.ll | 50 |
3 files changed, 82 insertions, 3 deletions
diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp index dc6b506..2d89516 100644 --- a/lib/Transforms/Utils/Local.cpp +++ b/lib/Transforms/Utils/Local.cpp @@ -200,8 +200,20 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions, "cond"); // Insert the new branch. - Builder.CreateCondBr(Cond, FirstCase.getCaseSuccessor(), - SI->getDefaultDest()); + BranchInst *NewBr = Builder.CreateCondBr(Cond, + FirstCase.getCaseSuccessor(), + SI->getDefaultDest()); + MDNode* MD = SI->getMetadata(LLVMContext::MD_prof); + if (MD && MD->getNumOperands() == 3) { + ConstantInt *SICase = dyn_cast<ConstantInt>(MD->getOperand(2)); + ConstantInt *SIDef = dyn_cast<ConstantInt>(MD->getOperand(1)); + assert(SICase && SIDef); + // The TrueWeight should be the weight for the single case of SI. + NewBr->setMetadata(LLVMContext::MD_prof, + MDBuilder(BB->getContext()). + createBranchWeights(SICase->getValue().getZExtValue(), + SIDef->getValue().getZExtValue())); + } // Delete the old switch. SI->eraseFromParent(); diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 551df00..a9d74cd 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -667,13 +667,32 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator() << "Through successor TI: " << *TI); + // Collect branch weights into a vector. + SmallVector<uint32_t, 8> Weights; + MDNode* MD = SI->getMetadata(LLVMContext::MD_prof); + bool HasWeight = MD && (MD->getNumOperands() == 2 + SI->getNumCases()); + if (HasWeight) + for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e; + ++MD_i) { + ConstantInt* CI = dyn_cast<ConstantInt>(MD->getOperand(MD_i)); + assert(CI); + Weights.push_back(CI->getValue().getZExtValue()); + } for (SwitchInst::CaseIt i = SI->case_end(), e = SI->case_begin(); i != e;) { --i; if (DeadCases.count(i.getCaseValue())) { + if (HasWeight) { + std::swap(Weights[i.getCaseIndex()+1], Weights.back()); + Weights.pop_back(); + } i.getCaseSuccessor()->removePredecessor(TI->getParent()); SI->removeCase(i); } } + if (HasWeight) + SI->setMetadata(LLVMContext::MD_prof, + MDBuilder(SI->getParent()->getContext()). + createBranchWeights(Weights)); DEBUG(dbgs() << "Leaving: " << *TI << "\n"); return true; diff --git a/test/Transforms/SimplifyCFG/preserve-branchweights.ll b/test/Transforms/SimplifyCFG/preserve-branchweights.ll index 71b2780..93bbcfb 100644 --- a/test/Transforms/SimplifyCFG/preserve-branchweights.ll +++ b/test/Transforms/SimplifyCFG/preserve-branchweights.ll @@ -109,12 +109,60 @@ sw.epilog: ret void } +;; test6 - Some cases of the second switch are pruned during optimization. +;; Then the second switch will be converted to a branch, finally, the first +;; switch and the branch will be merged into a single switch. +define void @test6(i32 %M, i32 %N) nounwind uwtable { +entry: + switch i32 %N, label %sw2 [ + i32 1, label %sw2 + i32 2, label %sw.bb + i32 3, label %sw.bb1 + ], !prof !4 +; CHECK: test6 +; CHECK: switch i32 %N, label %sw.epilog +; CHECK: i32 3, label %sw.bb1 +; CHECK: i32 2, label %sw.bb +; CHECK: i32 4, label %sw.bb5 +; CHECK: ], !prof !3 + +sw.bb: + call void @helper(i32 0) + br label %sw.epilog + +sw.bb1: + call void @helper(i32 1) + br label %sw.epilog + +sw2: +;; Here "case 2" is invalidated since the default case of the first switch +;; does not include "case 2". + switch i32 %N, label %sw.epilog [ + i32 2, label %sw.bb4 + i32 4, label %sw.bb5 + ], !prof !5 + +sw.bb4: + call void @helper(i32 2) + br label %sw.epilog + +sw.bb5: + call void @helper(i32 3) + br label %sw.epilog + +sw.epilog: + 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} !3 = metadata !{metadata !"branch_weights", i32 4, i32 3, i32 2, i32 1} +!4 = metadata !{metadata !"branch_weights", i32 4, i32 3, i32 2, i32 1} +!5 = metadata !{metadata !"branch_weights", i32 7, i32 6, i32 5} ; CHECK: !0 = metadata !{metadata !"branch_weights", i32 5, i32 11} ; CHECK: !1 = metadata !{metadata !"branch_weights", i32 1, i32 5} ; CHECK: !2 = metadata !{metadata !"branch_weights", i32 7, i32 1, i32 2} -; CHECK-NOT: !3 +; CHECK: !3 = metadata !{metadata !"branch_weights", i32 49, i32 12, i32 24, i32 35} +; CHECK-NOT: !4 |