diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp index 06014335653..dc6b506a3ba 100644 --- a/lib/Transforms/Utils/Local.cpp +++ b/lib/Transforms/Utils/Local.cpp @@ -23,6 +23,7 @@ #include "llvm/Instructions.h" #include "llvm/IntrinsicInst.h" #include "llvm/Intrinsics.h" +#include "llvm/MDBuilder.h" #include "llvm/Metadata.h" #include "llvm/Operator.h" #include "llvm/ADT/DenseMap.h" @@ -122,6 +123,27 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions, // Check to see if this branch is going to the same place as the default // dest. If so, eliminate it as an explicit compare. if (i.getCaseSuccessor() == DefaultDest) { + MDNode* MD = SI->getMetadata(LLVMContext::MD_prof); + // MD should have 2 + NumCases operands. + if (MD && MD->getNumOperands() == 2 + SI->getNumCases()) { + // Collect branch weights into a vector. + SmallVector Weights; + for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e; + ++MD_i) { + ConstantInt* CI = dyn_cast(MD->getOperand(MD_i)); + assert(CI); + Weights.push_back(CI->getValue().getZExtValue()); + } + // Merge weight of this case to the default weight. + unsigned idx = i.getCaseIndex(); + Weights[0] += Weights[idx+1]; + // Remove weight for this case. + std::swap(Weights[idx+1], Weights.back()); + Weights.pop_back(); + SI->setMetadata(LLVMContext::MD_prof, + MDBuilder(BB->getContext()). + createBranchWeights(Weights)); + } // Remove this entry. DefaultDest->removePredecessor(SI->getParent()); SI->removeCase(i); diff --git a/test/Transforms/SimplifyCFG/preserve-branchweights.ll b/test/Transforms/SimplifyCFG/preserve-branchweights.ll index c7917857ee6..71b27809ff8 100644 --- a/test/Transforms/SimplifyCFG/preserve-branchweights.ll +++ b/test/Transforms/SimplifyCFG/preserve-branchweights.ll @@ -79,10 +79,42 @@ Z: ret void } +;; test5 - The case where it jumps to the default target will be removed. +define void @test5(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 !3 +; CHECK: test5 +; CHECK: switch i32 %N, label %sw2 [ +; CHECK: i32 3, label %sw.bb1 +; CHECK: i32 2, label %sw.bb +; CHECK: ], !prof !2 + +sw.bb: + call void @helper(i32 0) + br label %sw.epilog + +sw.bb1: + call void @helper(i32 1) + br label %sw.epilog + +sw2: + call void @helper(i32 2) + 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} ; CHECK: !0 = metadata !{metadata !"branch_weights", i32 5, i32 11} ; CHECK: !1 = metadata !{metadata !"branch_weights", i32 1, i32 5} -; CHECK-NOT: !2 +; CHECK: !2 = metadata !{metadata !"branch_weights", i32 7, i32 1, i32 2} +; CHECK-NOT: !3