Re: [PATCH] forwprop: Remove incorrect assertion [PR102897]

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

On Tue, Oct 26, 2021 at 5:40 AM Kewen.Lin <linkw@linux.ibm.com> wrote:
>
> Hi,
>
> As PR102897 shows, there is one incorrect assertion in function
> simplify_permutation, which is based on the wrong assumption that
> all cases with op2_type == tgt_type are handled previously, the
> proposed fix is to remove this wrong assertion.
>
> Bootstrapped and regtested on x86_64-redhat-linux,
> aarch64-linux-gnu and powerpc64{,le}-linux-gnu.

I think you need to enable optimization in the new testcase, gcc.dg/ only
runs -O0 by default which wouldn't trigger forwprop?  Please verify the
testcase ICEs before the fix.

Otherwise OK.

Thanks,
Richard,

> BR,
> Kewen
> -----
> gcc/ChangeLog:
>
>         PR tree-optimization/102897
>         * tree-ssa-forwprop.c (simplify_permutation): Remove a wrong assertion.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.dg/pr102897.c: New test.
> ---
>  gcc/testsuite/gcc.dg/pr102897.c | 16 ++++++++++++++++
>  gcc/tree-ssa-forwprop.c         |  2 --
>  2 files changed, 16 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/pr102897.c
>
> diff --git a/gcc/testsuite/gcc.dg/pr102897.c b/gcc/testsuite/gcc.dg/pr102897.c
> new file mode 100644
> index 00000000000..d96b0e48ccc
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr102897.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* Specify C99 to avoid the warning/error on compound literals.  */
> +/* { dg-options "-std=c99" } */
> +
> +/* Verify that there is no ICE.  */
> +
> +typedef __attribute__((vector_size(8))) signed char int8x8_t;
> +typedef __attribute__((vector_size(8))) unsigned char uint8x8_t;
> +
> +int8x8_t fn1 (int8x8_t val20, char tmp)
> +{
> +  uint8x8_t __trans_tmp_3;
> +  __trans_tmp_3 = (uint8x8_t){tmp};
> +  int8x8_t __a = (int8x8_t) __trans_tmp_3;
> +  return __builtin_shuffle (__a, val20, (uint8x8_t){0});
> +}
> diff --git a/gcc/tree-ssa-forwprop.c b/gcc/tree-ssa-forwprop.c
> index 5b30d4c1a76..a830bab78ba 100644
> --- a/gcc/tree-ssa-forwprop.c
> +++ b/gcc/tree-ssa-forwprop.c
> @@ -2267,8 +2267,6 @@ simplify_permutation (gimple_stmt_iterator *gsi)
>           if (!VECTOR_TYPE_P (tgt_type))
>             return 0;
>           tree op2_type = TREE_TYPE (op2);
> -         /* Should have folded this before.  */
> -         gcc_assert (op2_type != tgt_type);
>
>           /* Figure out the shrunk factor.  */
>           poly_uint64 tgt_units = TYPE_VECTOR_SUBPARTS (tgt_type);
> --
> 2.27.0