Re: [PATCH] Fix PR 110386: backprop vs ABSU_EXPR

[Richard Biener <richard.guenther@gmail.com>]

> Am 24.09.2023 um 17:24 schrieb Andrew Pinski <apinski@marvell.com>:
> 
> The issue here is that when backprop tries to go
> and strip sign ops, it skips over ABSU_EXPR but
> ABSU_EXPR not only does an ABS, it also changes the
> type to unsigned.
> Since strip_sign_op_1 is only supposed to strip off
> sign changing operands and not ones that change types,
> removing ABSU_EXPR here is correct. We don't handle
> nop conversions so this does cause any missed optimizations either.
> 
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

Ok

Richard 

>    PR tree-optimization/110386
> 
> gcc/ChangeLog:
> 
>    * gimple-ssa-backprop.cc (strip_sign_op_1): Remove ABSU_EXPR.
> 
> gcc/testsuite/ChangeLog:
> 
>    * gcc.c-torture/compile/pr110386-1.c: New test.
>    * gcc.c-torture/compile/pr110386-2.c: New test.
> ---
> gcc/gimple-ssa-backprop.cc                       |  1 -
> gcc/testsuite/gcc.c-torture/compile/pr110386-1.c |  9 +++++++++
> gcc/testsuite/gcc.c-torture/compile/pr110386-2.c | 11 +++++++++++
> 3 files changed, 20 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr110386-1.c
> create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr110386-2.c
> 
> diff --git a/gcc/gimple-ssa-backprop.cc b/gcc/gimple-ssa-backprop.cc
> index 65a65590017..dcb15ed4f61 100644
> --- a/gcc/gimple-ssa-backprop.cc
> +++ b/gcc/gimple-ssa-backprop.cc
> @@ -694,7 +694,6 @@ strip_sign_op_1 (tree rhs)
>     switch (gimple_assign_rhs_code (assign))
>       {
>       case ABS_EXPR:
> -      case ABSU_EXPR:
>       case NEGATE_EXPR:
>    return gimple_assign_rhs1 (assign);
> 
> diff --git a/gcc/testsuite/gcc.c-torture/compile/pr110386-1.c b/gcc/testsuite/gcc.c-torture/compile/pr110386-1.c
> new file mode 100644
> index 00000000000..4fcc977ad16
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/compile/pr110386-1.c
> @@ -0,0 +1,9 @@
> +
> +int f(int a)
> +{
> +        int c = c < 0 ? c : -c;
> +        c = -c;
> +        unsigned b =  c;
> +        unsigned t = b*a;
> +        return t*t;
> +}
> diff --git a/gcc/testsuite/gcc.c-torture/compile/pr110386-2.c b/gcc/testsuite/gcc.c-torture/compile/pr110386-2.c
> new file mode 100644
> index 00000000000..c60e1b6994b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/compile/pr110386-2.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
> +/* { dg-options "-mavx" } */
> +
> +#include <immintrin.h>
> +
> +__m128i do_stuff(__m128i XMM0) {
> +    __m128i ABS0 = _mm_abs_epi32(XMM0);
> +    __m128i MUL0 = _mm_mullo_epi32(ABS0, XMM0);
> +    __m128i MUL1 = _mm_mullo_epi32(MUL0, MUL0);
> +    return MUL1;
> +}
> -- 
> 2.31.1
>