Index: llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp =================================================================== --- llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp +++ llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp @@ -781,6 +781,14 @@ return Builder.CreateBinaryIntrinsic( Intrinsic::uadd_sat, BO->getOperand(0), BO->getOperand(1)); } + // With an overflowing add + if (match(Cmp0, m_c_Add(m_Value(X), m_Value(Y))) && + (X == Cmp1 || Y == Cmp1) && + match(FVal, m_c_Add(m_Specific(X), m_Specific(Y)))) { + // ((X + Y) u< X) ? -1 : (X + Y) --> uadd.sat(X, Y) + // ((X + Y) u< Y) ? -1 : (X + Y) --> uadd.sat(X, Y) + return Builder.CreateBinaryIntrinsic(Intrinsic::uadd_sat, X, Y); + } return nullptr; } Index: llvm/test/Transforms/InstCombine/saturating-add-sub.ll =================================================================== --- llvm/test/Transforms/InstCombine/saturating-add-sub.ll +++ llvm/test/Transforms/InstCombine/saturating-add-sub.ll @@ -1486,10 +1486,8 @@ define i32 @uadd_sat_canon(i32 %x, i32 %y) { ; CHECK-LABEL: @uadd_sat_canon( -; CHECK-NEXT: [[A:%.*]] = add i32 [[X:%.*]], [[Y:%.*]] -; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[A]], [[X]] -; CHECK-NEXT: [[R:%.*]] = select i1 [[C]], i32 -1, i32 [[A]] -; CHECK-NEXT: ret i32 [[R]] +; CHECK-NEXT: [[TMP1:%.*]] = call i32 @llvm.uadd.sat.i32(i32 [[X:%.*]], i32 [[Y:%.*]]) +; CHECK-NEXT: ret i32 [[TMP1]] ; %a = add i32 %x, %y %c = icmp ult i32 %a, %x @@ -1499,10 +1497,8 @@ define i32 @uadd_sat_canon_y(i32 %x, i32 %y) { ; CHECK-LABEL: @uadd_sat_canon_y( -; CHECK-NEXT: [[A:%.*]] = add i32 [[X:%.*]], [[Y:%.*]] -; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[A]], [[Y]] -; CHECK-NEXT: [[R:%.*]] = select i1 [[C]], i32 -1, i32 [[A]] -; CHECK-NEXT: ret i32 [[R]] +; CHECK-NEXT: [[TMP1:%.*]] = call i32 @llvm.uadd.sat.i32(i32 [[X:%.*]], i32 [[Y:%.*]]) +; CHECK-NEXT: ret i32 [[TMP1]] ; %a = add i32 %x, %y %c = icmp ult i32 %a, %y