diff options
| -rw-r--r-- | llvm/lib/Transforms/Utils/Local.cpp | 6 | ||||
| -rw-r--r-- | llvm/test/Transforms/SimplifyCFG/branch-fold.ll | 34 |
2 files changed, 40 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp index 123881e..1a3d543 100644 --- a/llvm/lib/Transforms/Utils/Local.cpp +++ b/llvm/lib/Transforms/Utils/Local.cpp @@ -1159,6 +1159,12 @@ bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB, bool BBPhisMergeable = BBKillable || CanRedirectPredsOfEmptyBBToSucc( BB, Succ, BBPreds, CommonPred); + // If the function has the "no-jump-tables" attribute, merging phis + // can make size worse at -Oz. + auto *MF = BB->getParent(); + if (MF->hasMinSize() && MF->hasFnAttribute("no-jump-tables")) + BBPhisMergeable = false; + if ((!BBKillable && !BBPhisMergeable) || introduceTooManyPhiEntries(BB, Succ)) return false; diff --git a/llvm/test/Transforms/SimplifyCFG/branch-fold.ll b/llvm/test/Transforms/SimplifyCFG/branch-fold.ll index 8e7b91e..2f4c5d9 100644 --- a/llvm/test/Transforms/SimplifyCFG/branch-fold.ll +++ b/llvm/test/Transforms/SimplifyCFG/branch-fold.ll @@ -145,8 +145,42 @@ Succ: ret i8 %phi2 } +define i8 @common_pred_no_jt(i8 noundef %arg, i1 %c1, i1 %c2) #0 { +; CHECK-LABEL: @common_pred_no_jt( +; CHECK-NEXT: Pred: +; CHECK-NEXT: call void @dummy() +; CHECK-NEXT: br i1 [[C1:%.*]], label [[COMMONPRED:%.*]], label [[SUCC:%.*]] +; CHECK: CommonPred: +; CHECK-NEXT: call void @dummy() +; CHECK-NEXT: br i1 [[C2:%.*]], label [[SUCC1:%.*]], label [[SUCC]] +; CHECK: BB: +; CHECK-NEXT: [[PHI1:%.*]] = phi i8 [ 0, [[PRED:%.*]] ], [ 1, [[COMMONPRED]] ] +; CHECK-NEXT: br label [[SUCC1]] +; CHECK: Succ: +; CHECK-NEXT: [[PHI2:%.*]] = phi i8 [ [[PHI1]], [[SUCC]] ], [ 4, [[COMMONPRED]] ] +; CHECK-NEXT: ret i8 [[PHI2]] +; +Pred: +call void @dummy() + br i1 %c1, label %CommonPred, label %BB + +CommonPred: +call void @dummy() + br i1 %c2, label %Succ, label %BB + +BB: + %phi1 = phi i8 [ 0, %Pred ], [1, %CommonPred] + br label %Succ + +Succ: + %phi2 = phi i8 [ %phi1, %BB ], [ 4, %CommonPred ] + ret i8 %phi2 +} declare void @dummy() +attributes #0 = { minsize "no-jump-tables"="true" } + + !0 = !{!"branch_weights", i32 3, i32 7} !1 = !{!"branch_weights", i32 11, i32 4} ;. |