On Sun, Oct 1, 2023 at 12:28 PM Andrew Pinski <pins...@gmail.com> wrote:
>
> From: Andrew Pinski <apin...@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.
>
> Committed to the GCC 13 branch after bootstrapped and
> tested on x86_64-linux-gnu with no regressions.
And to the GCC 12 and 11 branches too.
Thanks,
Andrew
>
> 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.
>
> (cherry picked from commit 2bbac12ea7bd8a3eef5382e1b13f6019df4ec03f)
> ---
> 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;
> +}
> --
> 2.39.3
>
