Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp =================================================================== --- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -3997,15 +3997,15 @@ if (OR == OverflowResult::NeverOverflows) return SetResult(Builder.CreateNUWSub(LHS, RHS), Builder.getFalse(), true); - - if (OR == OverflowResult::AlwaysOverflows) - return SetResult(Builder.CreateSub(LHS, RHS), Builder.getTrue(), true); } else { OR = computeOverflowForSignedSub(LHS, RHS, &OrigI); if (OR == OverflowResult::NeverOverflows) return SetResult(Builder.CreateNSWSub(LHS, RHS), Builder.getFalse(), true); } + + if (OR == OverflowResult::AlwaysOverflows) + return SetResult(Builder.CreateSub(LHS, RHS), Builder.getTrue(), true); break; } Index: llvm/test/Transforms/InstCombine/with_overflow.ll =================================================================== --- llvm/test/Transforms/InstCombine/with_overflow.ll +++ llvm/test/Transforms/InstCombine/with_overflow.ll @@ -582,8 +582,9 @@ ; CHECK-LABEL: @ssub_always_overflow( ; CHECK-NEXT: [[C:%.*]] = icmp sgt i8 [[X:%.*]], 29 ; CHECK-NEXT: [[Y:%.*]] = select i1 [[C]], i8 [[X]], i8 29 -; CHECK-NEXT: [[A:%.*]] = call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 -100, i8 [[Y]]) -; CHECK-NEXT: ret { i8, i1 } [[A]] +; CHECK-NEXT: [[A:%.*]] = sub nuw i8 -100, [[Y]] +; CHECK-NEXT: [[TMP1:%.*]] = insertvalue { i8, i1 } { i8 undef, i1 true }, i8 [[A]], 0 +; CHECK-NEXT: ret { i8, i1 } [[TMP1]] ; %c = icmp sgt i8 %x, 29 %y = select i1 %c, i8 %x, i8 29