[llvm] a547b4e - Revert "[InstCombine] Fold `((X - Y) - Z)` to `X - (Y + Z)` (PR49858)"

[Roman Lebedev via llvm-commits]

Reproducer please?

On Wed, Apr 7, 2021 at 8:46 AM Petr Hosek via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
>
>
> Author: Petr Hosek
> Date: 2021-04-06T22:30:28-07:00
> New Revision: a547b4e26b311e417cd51100e379693f51a3f448
>
> URL: https://github.com/llvm/llvm-project/commit/a547b4e26b311e417cd51100e379693f51a3f448
> DIFF: https://github.com/llvm/llvm-project/commit/a547b4e26b311e417cd51100e379693f51a3f448.diff
>
> LOG: Revert "[InstCombine] Fold `((X - Y) - Z)` to `X - (Y + Z)` (PR49858)"
>
> This reverts commit 31d219d2997fed1b7dc97e0adf170d5aaf65883e which
> causes an infinite loop when compiling the XRay runtime.
>
> Added:
>
>
> Modified:
>     llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
>     llvm/test/Transforms/InstCombine/abs-1.ll
>     llvm/test/Transforms/InstCombine/sub-from-sub.ll
>
> Removed:
>
>
>
> ################################################################################
> diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
> index 4ced5994ffa6..bacb8689892a 100644
> --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
> +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
> @@ -1801,12 +1801,6 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
>      return BinaryOperator::CreateSub(XZ, YW);
>    }
>
> -  // ((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);
> -  }
> -
>    auto m_AddRdx = [](Value *&Vec) {
>      return m_OneUse(m_Intrinsic<Intrinsic::vector_reduce_add>(m_Value(Vec)));
>    };
>
> diff  --git a/llvm/test/Transforms/InstCombine/abs-1.ll b/llvm/test/Transforms/InstCombine/abs-1.ll
> index ea77dfb5fef4..7452798ead77 100644
> --- a/llvm/test/Transforms/InstCombine/abs-1.ll
> +++ b/llvm/test/Transforms/InstCombine/abs-1.ll
> @@ -305,9 +305,9 @@ define i32 @nabs_canonical_8(i32 %a) {
>  define i32 @nabs_canonical_9(i32 %a, i32 %b) {
>  ; CHECK-LABEL: @nabs_canonical_9(
>  ; CHECK-NEXT:    [[T1:%.*]] = sub i32 [[A:%.*]], [[B:%.*]]
> +; CHECK-NEXT:    [[T2:%.*]] = sub i32 [[B]], [[A]]
>  ; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @llvm.abs.i32(i32 [[T1]], i1 false)
> -; CHECK-NEXT:    [[TMP2:%.*]] = add i32 [[TMP1]], [[A]]
> -; CHECK-NEXT:    [[ADD:%.*]] = sub i32 [[B]], [[TMP2]]
> +; CHECK-NEXT:    [[ADD:%.*]] = sub i32 [[T2]], [[TMP1]]
>  ; CHECK-NEXT:    ret i32 [[ADD]]
>  ;
>    %t1 = sub i32 %a, %b
>
> diff  --git a/llvm/test/Transforms/InstCombine/sub-from-sub.ll b/llvm/test/Transforms/InstCombine/sub-from-sub.ll
> index aaa8b1db32de..202dbd1072a4 100644
> --- a/llvm/test/Transforms/InstCombine/sub-from-sub.ll
> +++ b/llvm/test/Transforms/InstCombine/sub-from-sub.ll
> @@ -8,8 +8,8 @@ declare void @use8(i8)
>  ; Basic test
>  define i8 @t0(i8 %x, i8 %y, i8 %z) {
>  ; CHECK-LABEL: @t0(
> -; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[Y:%.*]], [[Z:%.*]]
> -; CHECK-NEXT:    [[R:%.*]] = sub i8 [[X:%.*]], [[TMP1]]
> +; CHECK-NEXT:    [[I0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
> +; CHECK-NEXT:    [[R:%.*]] = sub i8 [[I0]], [[Z:%.*]]
>  ; CHECK-NEXT:    ret i8 [[R]]
>  ;
>    %i0 = sub i8 %x, %y
> @@ -20,8 +20,8 @@ define i8 @t0(i8 %x, i8 %y, i8 %z) {
>  ; No flags are propagated
>  define i8 @t1_flags(i8 %x, i8 %y, i8 %z) {
>  ; CHECK-LABEL: @t1_flags(
> -; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[Y:%.*]], [[Z:%.*]]
> -; CHECK-NEXT:    [[R:%.*]] = sub i8 [[X:%.*]], [[TMP1]]
> +; CHECK-NEXT:    [[O0:%.*]] = sub nuw nsw i8 [[X:%.*]], [[Y:%.*]]
> +; CHECK-NEXT:    [[R:%.*]] = sub nuw nsw i8 [[O0]], [[Z:%.*]]
>  ; CHECK-NEXT:    ret i8 [[R]]
>  ;
>    %o0 = sub nuw nsw i8 %x, %y
> @@ -47,8 +47,8 @@ define i8 @n2(i8 %x, i8 %y, i8 %z) {
>
>  define i8 @t3_c0(i8 %y, i8 %z) {
>  ; CHECK-LABEL: @t3_c0(
> -; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[Y:%.*]], [[Z:%.*]]
> -; CHECK-NEXT:    [[R:%.*]] = sub i8 42, [[TMP1]]
> +; CHECK-NEXT:    [[I0:%.*]] = sub i8 42, [[Y:%.*]]
> +; CHECK-NEXT:    [[R:%.*]] = sub i8 [[I0]], [[Z:%.*]]
>  ; CHECK-NEXT:    ret i8 [[R]]
>  ;
>    %i0 = sub i8 42, %y
>
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits