diff options
| -rw-r--r-- | llvm/lib/Transforms/Utils/SimplifyCFG.cpp | 22 | ||||
| -rw-r--r-- | llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll | 47 |
2 files changed, 60 insertions, 9 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp index fe7c609051e..beb98a36fad 100644 --- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp @@ -2860,9 +2860,29 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI, Value *PBIV = PN->getIncomingValue(PBBIdx); if (BIV != PBIV) { // Insert a select in PBI to pick the right value. - Value *NV = cast<SelectInst> + SelectInst *NV = cast<SelectInst> (Builder.CreateSelect(PBICond, PBIV, BIV, PBIV->getName() + ".mux")); PN->setIncomingValue(PBBIdx, NV); + // Although the select has the same condition as PBI, the original branch + // weights for PBI do not apply to the new select because the select's + // 'logical' edges are incoming edges of the phi that is eliminated, not + // the outgoing edges of PBI. + if (PredHasWeights && SuccHasWeights) { + uint64_t PredCommon = PBIOp ? PredFalseWeight : PredTrueWeight; + uint64_t PredOther = PBIOp ? PredTrueWeight : PredFalseWeight; + uint64_t SuccCommon = BIOp ? SuccFalseWeight : SuccTrueWeight; + uint64_t SuccOther = BIOp ? SuccTrueWeight : SuccFalseWeight; + // The weight to PredCommonDest should be PredCommon * SuccTotal. + // The weight to PredOtherDest should be PredOther * SuccCommon. + uint64_t NewWeights[2] = {PredCommon * (SuccCommon + SuccOther), + PredOther * SuccCommon}; + + FitWeights(NewWeights); + + NV->setMetadata(LLVMContext::MD_prof, + MDBuilder(BI->getContext()) + .createBranchWeights(NewWeights[0], NewWeights[1])); + } } } diff --git a/llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll b/llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll index ae32809395e..359f21a75ab 100644 --- a/llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll +++ b/llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll @@ -412,22 +412,48 @@ return: ret i32 %retval.0 } -; The 1st select should have branch weights equal to the 1st branch. -; The 2nd select should have freshly calculated branch weights. +; The selects should have freshly calculated branch weights. define i32 @SimplifyCondBranchToCondBranch(i1 %cmpa, i1 %cmpb) { ; CHECK-LABEL: @SimplifyCondBranchToCondBranch( ; CHECK-NEXT: block1: -; CHECK-NEXT: [[BRMERGE:%.*]] = or i1 %cmpb, %cmpa -; CHECK-NEXT: [[DOTMUX:%.*]] = select i1 %cmpb, i32 0, i32 2 -; CHECK-NEXT: [[OUTVAL:%.*]] = select i1 [[BRMERGE]], i32 [[DOTMUX]], i32 1, !prof !12 +; CHECK-NEXT: [[BRMERGE:%.*]] = or i1 %cmpa, %cmpb +; CHECK-NEXT: [[DOTMUX:%.*]] = select i1 %cmpa, i32 0, i32 2, !prof !12 +; CHECK-NEXT: [[OUTVAL:%.*]] = select i1 [[BRMERGE]], i32 [[DOTMUX]], i32 1, !prof !13 ; CHECK-NEXT: ret i32 [[OUTVAL]] ; block1: - br i1 %cmpb, label %block3, label %block2, !prof !0 + br i1 %cmpa, label %block3, label %block2, !prof !13 block2: - br i1 %cmpa, label %block3, label %exit, !prof !2 + br i1 %cmpb, label %block3, label %exit, !prof !14 + +block3: + %cowval = phi i32 [ 2, %block2 ], [ 0, %block1 ] + br label %exit + +exit: + %outval = phi i32 [ %cowval, %block3 ], [ 1, %block2 ] + ret i32 %outval +} + +; Swap the operands of the compares to verify that the weights update correctly. + +define i32 @SimplifyCondBranchToCondBranchSwap(i1 %cmpa, i1 %cmpb) { +; CHECK-LABEL: @SimplifyCondBranchToCondBranchSwap( +; CHECK-NEXT: block1: +; CHECK-NEXT: [[CMPA_NOT:%.*]] = xor i1 %cmpa, true +; CHECK-NEXT: [[CMPB_NOT:%.*]] = xor i1 %cmpb, true +; CHECK-NEXT: [[BRMERGE:%.*]] = or i1 [[CMPA_NOT]], [[CMPB_NOT]] +; CHECK-NEXT: [[DOTMUX:%.*]] = select i1 [[CMPA_NOT]], i32 0, i32 2, !prof !14 +; CHECK-NEXT: [[OUTVAL:%.*]] = select i1 [[BRMERGE]], i32 [[DOTMUX]], i32 1, !prof !15 +; CHECK-NEXT: ret i32 [[OUTVAL]] +; +block1: + br i1 %cmpa, label %block2, label %block3, !prof !13 + +block2: + br i1 %cmpb, label %exit, label %block3, !prof !14 block3: %cowval = phi i32 [ 2, %block2 ], [ 0, %block1 ] @@ -452,6 +478,8 @@ exit: !10 = !{!"branch_weights", i32 672646, i32 21604207} !11 = !{!"branch_weights", i32 6960, i32 21597248} !12 = !{!"these_are_not_the_branch_weights_you_are_looking_for", i32 3, i32 5} +!13 = !{!"branch_weights", i32 2, i32 3} +!14 = !{!"branch_weights", i32 4, i32 7} ; CHECK: !0 = !{!"branch_weights", i32 5, i32 11} ; CHECK: !1 = !{!"branch_weights", i32 1, i32 5} @@ -467,5 +495,8 @@ exit: ;; treat the weight as an unsigned integer. ; CHECK: !10 = !{!"branch_weights", i32 112017436, i32 -735157296} ; CHECK: !11 = !{!"branch_weights", i32 3, i32 5} -; CHECK: !12 = !{!"branch_weights", i32 14, i32 10} +; CHECK: !12 = !{!"branch_weights", i32 22, i32 12} +; CHECK: !13 = !{!"branch_weights", i32 34, i32 21} +; CHECK: !14 = !{!"branch_weights", i32 33, i32 14} +; CHECK: !15 = !{!"branch_weights", i32 47, i32 8} |
