Re: [PATCH 2/2] [x86] Adjust rtx_cost for MEM to enable more simplication

[Uros Bizjak <ubizjak@gmail.com>]

On Tue, May 21, 2024 at 7:13 AM liuhongt <hongtao.liu@intel.com> wrote:
>
> For CONST_VECTOR_DUPLICATE_P in constant_pool, it is just broadcast or
> variants in ix86_vector_duplicate_simode_const.
> Adjust the cost to COSTS_N_INSNS (2) + speed which should be a little
> bit larger than broadcast.
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> Ok for trunk?
>
> gcc/ChangeLog:
>         PR target/114428
>         * config/i386/i386.cc (ix86_rtx_costs): Adjust cost for
>         CONST_VECTOR_DUPLICATE_P in constant_pool.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/i386/pr114428.c: New test.

LGTM.

Thanks,
Uros.

> ---
>  gcc/config/i386/i386-expand.cc           |  2 +-
>  gcc/config/i386/i386-protos.h            |  1 +
>  gcc/config/i386/i386.cc                  | 13 +++++++++++++
>  gcc/testsuite/gcc.target/i386/pr114428.c | 18 ++++++++++++++++++
>  4 files changed, 33 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr114428.c
>
> diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
> index 4e16aedc5c1..d96c365e144 100644
> --- a/gcc/config/i386/i386-expand.cc
> +++ b/gcc/config/i386/i386-expand.cc
> @@ -588,7 +588,7 @@ ix86_expand_move (machine_mode mode, rtx operands[])
>
>  /* OP is a memref of CONST_VECTOR, return scalar constant mem
>     if CONST_VECTOR is a vec_duplicate, else return NULL.  */
> -static rtx
> +rtx
>  ix86_broadcast_from_constant (machine_mode mode, rtx op)
>  {
>    int nunits = GET_MODE_NUNITS (mode);
> diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h
> index dbc861fb1ea..90712769200 100644
> --- a/gcc/config/i386/i386-protos.h
> +++ b/gcc/config/i386/i386-protos.h
> @@ -107,6 +107,7 @@ extern void ix86_expand_clear (rtx);
>  extern void ix86_expand_move (machine_mode, rtx[]);
>  extern void ix86_expand_vector_move (machine_mode, rtx[]);
>  extern void ix86_expand_vector_move_misalign (machine_mode, rtx[]);
> +extern rtx ix86_broadcast_from_constant (machine_mode, rtx);
>  extern rtx ix86_fixup_binary_operands (enum rtx_code, machine_mode,
>                                        rtx[], bool = false);
>  extern void ix86_fixup_binary_operands_no_copy (enum rtx_code, machine_mode,
> diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
> index b4838b7939e..fdd9343e47a 100644
> --- a/gcc/config/i386/i386.cc
> +++ b/gcc/config/i386/i386.cc
> @@ -22197,6 +22197,19 @@ ix86_rtx_costs (rtx x, machine_mode mode, int outer_code_i, int opno,
>        return true;
>
>      case MEM:
> +      /* CONST_VECTOR_DUPLICATE_P in constant_pool is just broadcast.
> +        or variants in ix86_vector_duplicate_simode_const.  */
> +
> +      if (GET_MODE_SIZE (mode) >= 16
> +         && VECTOR_MODE_P (mode)
> +         && SYMBOL_REF_P (XEXP (x, 0))
> +         && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0))
> +         && ix86_broadcast_from_constant (mode, x))
> +       {
> +         *total = COSTS_N_INSNS (2) + speed;
> +         return true;
> +       }
> +
>        /* An insn that accesses memory is slightly more expensive
>           than one that does not.  */
>        if (speed)
> diff --git a/gcc/testsuite/gcc.target/i386/pr114428.c b/gcc/testsuite/gcc.target/i386/pr114428.c
> new file mode 100644
> index 00000000000..bbbc5a080f6
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr114428.c
> @@ -0,0 +1,18 @@
> +/* { dg-do compile } */
> +/* { dg-options "-march=x86-64-v3 -mno-avx512f -O2" } */
> +/* { dg-final { scan-assembler-not "vpsra[dw]" } } */
> +
> +void
> +foo2 (char* __restrict a, short* b)
> +{
> +  for (int i = 0; i != 32; i++)
> +    a[i] = b[i] >> (short)8;
> +}
> +
> +void
> +foo3 (char* __restrict a, short* b)
> +{
> +  for (int i = 0; i != 16; i++)
> +    a[i] = b[i] >> (short)8;
> +}
> +
> --
> 2.31.1
>