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Diffstat (limited to 'llvm/lib/Transforms/Utils/SimplifyCFG.cpp')
| -rw-r--r-- | llvm/lib/Transforms/Utils/SimplifyCFG.cpp | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp index a58568d..f2f1519 100644 --- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp @@ -2372,6 +2372,20 @@ bool SimplifyCFGOpt::SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB, } assert(EndBB == BI->getSuccessor(!Invert) && "No edge from to end block"); + // If the branch is non-unpredictable, and is predicted to *not* branch to + // the `then` block, then avoid speculating it. + if (!BI->getMetadata(LLVMContext::MD_unpredictable)) { + uint64_t TWeight, FWeight; + if (BI->extractProfMetadata(TWeight, FWeight) && (TWeight + FWeight) != 0) { + uint64_t EndWeight = Invert ? TWeight : FWeight; + BranchProbability BIEndProb = + BranchProbability::getBranchProbability(EndWeight, TWeight + FWeight); + BranchProbability Likely = TTI.getPredictableBranchThreshold(); + if (BIEndProb >= Likely) + return false; + } + } + // Keep a count of how many times instructions are used within ThenBB when // they are candidates for sinking into ThenBB. Specifically: // - They are defined in BB, and |