diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index 318992b55e4f9f..90b1c133461a40 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -2191,8 +2191,15 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) { // ((X - Y) - Op1) --> X - (Y + Op1) if (match(Op0, m_OneUse(m_Sub(m_Value(X), m_Value(Y))))) { - Value *Add = Builder.CreateAdd(Y, Op1); - return BinaryOperator::CreateSub(X, Add); + OverflowingBinaryOperator *LHSSub = cast(Op0); + bool HasNUW = I.hasNoUnsignedWrap() && LHSSub->hasNoUnsignedWrap(); + bool HasNSW = HasNUW && I.hasNoSignedWrap() && LHSSub->hasNoSignedWrap(); + Value *Add = Builder.CreateAdd(Y, Op1, "", /* HasNUW */ HasNUW, + /* HasNSW */ HasNSW); + BinaryOperator *Sub = BinaryOperator::CreateSub(X, Add); + Sub->setHasNoUnsignedWrap(HasNUW); + Sub->setHasNoSignedWrap(HasNSW); + return Sub; } // (~X) - (~Y) --> Y - X diff --git a/llvm/test/Transforms/InstCombine/sub-from-sub.ll b/llvm/test/Transforms/InstCombine/sub-from-sub.ll index 7976cdc970b9c5..7b9e2fe4e6cdf2 100644 --- a/llvm/test/Transforms/InstCombine/sub-from-sub.ll +++ b/llvm/test/Transforms/InstCombine/sub-from-sub.ll @@ -17,14 +17,82 @@ define i8 @t0(i8 %x, i8 %y, i8 %z) { ret i8 %r } -; No flags are propagated +; NSW/NUW flags are propagated define i8 @t1_flags(i8 %x, i8 %y, i8 %z) { ; CHECK-LABEL: @t1_flags( +; CHECK-NEXT: [[TMP1:%.*]] = add nuw nsw i8 [[Y:%.*]], [[Z:%.*]] +; CHECK-NEXT: [[R:%.*]] = sub nuw nsw i8 [[X:%.*]], [[TMP1]] +; CHECK-NEXT: ret i8 [[R]] +; + %o0 = sub nuw nsw i8 %x, %y + %r = sub nuw nsw i8 %o0, %z + ret i8 %r +} + +; NUW flags are propagated +define i8 @t1_flags_nuw_only(i8 %x, i8 %y, i8 %z) { +; CHECK-LABEL: @t1_flags_nuw_only( +; CHECK-NEXT: [[TMP1:%.*]] = add nuw i8 [[Y:%.*]], [[Z:%.*]] +; CHECK-NEXT: [[R:%.*]] = sub nuw i8 [[X:%.*]], [[TMP1]] +; CHECK-NEXT: ret i8 [[R]] +; + %o0 = sub nuw i8 %x, %y + %r = sub nuw i8 %o0, %z + ret i8 %r +} + +; Negative tests +define i8 @t1_flags_sub_nsw_sub(i8 %x, i8 %y, i8 %z) { +; CHECK-LABEL: @t1_flags_sub_nsw_sub( +; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[Y:%.*]], [[Z:%.*]] +; CHECK-NEXT: [[R:%.*]] = sub i8 [[X:%.*]], [[TMP1]] +; CHECK-NEXT: ret i8 [[R]] +; + %o0 = sub nsw i8 %x, %y + %r = sub i8 %o0, %z + ret i8 %r +} + +define i8 @t1_flags_nuw_first(i8 %x, i8 %y, i8 %z) { +; CHECK-LABEL: @t1_flags_nuw_first( +; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[Y:%.*]], [[Z:%.*]] +; CHECK-NEXT: [[R:%.*]] = sub i8 [[X:%.*]], [[TMP1]] +; CHECK-NEXT: ret i8 [[R]] +; + %o0 = sub nuw i8 %x, %y + %r = sub i8 %o0, %z + ret i8 %r +} + +define i8 @t1_flags_nuw_second(i8 %x, i8 %y, i8 %z) { +; CHECK-LABEL: @t1_flags_nuw_second( +; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[Y:%.*]], [[Z:%.*]] +; CHECK-NEXT: [[R:%.*]] = sub i8 [[X:%.*]], [[TMP1]] +; CHECK-NEXT: ret i8 [[R]] +; + %o0 = sub i8 %x, %y + %r = sub nuw i8 %o0, %z + ret i8 %r +} + +define i8 @t1_flags_nuw_nsw_first(i8 %x, i8 %y, i8 %z) { +; CHECK-LABEL: @t1_flags_nuw_nsw_first( ; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[Y:%.*]], [[Z:%.*]] ; CHECK-NEXT: [[R:%.*]] = sub i8 [[X:%.*]], [[TMP1]] ; CHECK-NEXT: ret i8 [[R]] ; %o0 = sub nuw nsw i8 %x, %y + %r = sub i8 %o0, %z + ret i8 %r +} + +define i8 @t1_flags_nuw_nsw_second(i8 %x, i8 %y, i8 %z) { +; CHECK-LABEL: @t1_flags_nuw_nsw_second( +; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[Y:%.*]], [[Z:%.*]] +; CHECK-NEXT: [[R:%.*]] = sub i8 [[X:%.*]], [[TMP1]] +; CHECK-NEXT: ret i8 [[R]] +; + %o0 = sub i8 %x, %y %r = sub nuw nsw i8 %o0, %z ret i8 %r }