Re: [PATCH] [x86] Fix unrecognizable insn due to illegal immediate_operand (const_int 255) of QImode.

[Hongtao Liu <crazylht@gmail.com>]

On Mon, Nov 28, 2022 at 9:06 PM liuhongt <hongtao.liu@intel.com> wrote:
>
> For __builtin_ia32_vec_set_v16qi (a, -1, 2) with
> !flag_signed_char. it's transformed to
> __builtin_ia32_vec_set_v16qi (_4, 255, 2) in the gimple,
> and expanded to (const_int 255) in the rtl. But for immediate_operand,
> it expects (const_int 255) to be signed extended to
> (const_int -1). The mismatch caused an unrecognizable insn error.
>
> expand_expr_real_1 generates (const_int 255) without considering the target mode.
> I guess it's on purpose, so I'll leave that alone and only change the expander
> in the backend. After applying convert_modes to (const_int 255),
> it's transformed to (const_int -1) which fix the issue.
>
> Bootstrapped and regtested x86_64-pc-linux-gnu{-m32,}.
> Ok for trunk(and backport to GCC-10/11/12 release branches)?
Drop this patch since it's not a complete solution, there're also
other QI builtins which is not handled.
>
> gcc/ChangeLog:
>
>         PR target/107863
>         * config/i386/i386-expand.cc (ix86_expand_vec_set_builtin):
>         Convert op1 to target mode whenever mode mismatch.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/i386/pr107863.c: New test.
> ---
>  gcc/config/i386/i386-expand.cc           | 2 +-
>  gcc/testsuite/gcc.target/i386/pr107863.c | 8 ++++++++
>  2 files changed, 9 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr107863.c
>
> diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
> index 0373c3614a4..c639ee3a9f7 100644
> --- a/gcc/config/i386/i386-expand.cc
> +++ b/gcc/config/i386/i386-expand.cc
> @@ -12475,7 +12475,7 @@ ix86_expand_vec_set_builtin (tree exp)
>    op1 = expand_expr (arg1, NULL_RTX, mode1, EXPAND_NORMAL);
>    elt = get_element_number (TREE_TYPE (arg0), arg2);
>
> -  if (GET_MODE (op1) != mode1 && GET_MODE (op1) != VOIDmode)
> +  if (GET_MODE (op1) != mode1)
>      op1 = convert_modes (mode1, GET_MODE (op1), op1, true);
>
>    op0 = force_reg (tmode, op0);
> diff --git a/gcc/testsuite/gcc.target/i386/pr107863.c b/gcc/testsuite/gcc.target/i386/pr107863.c
> new file mode 100644
> index 00000000000..99fd85d9765
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr107863.c
> @@ -0,0 +1,8 @@
> +/* { dg-do compile } */
> +/* { dg-options "-mavx2 -O" } */
> +
> +typedef char v16qi __attribute__((vector_size(16)));
> +
> +v16qi foo(v16qi a){
> +  return __builtin_ia32_vec_set_v16qi (a, -1, 2);
> +}
> --
> 2.27.0
>


-- 
BR,
Hongtao