Re: [PATCH] i386: Relax inline requirement for functions with different target attrs

[Uros Bizjak <ubizjak@gmail.com>]

On Mon, Jun 26, 2023 at 4:36 AM Hongyu Wang <hongyu.wang@intel.com> wrote:
>
> Hi,
>
> For function with different target attributes, current logic rejects to
> inline the callee when any arch or tune is mismatched. Relax the
> condition to honor just prefer_vecotr_width_type and other flags that
> may cause safety issue so caller can get more optimization opportunity.

I don't think this is desirable. If we inline something with different
ISAs, we get some strange mix of ISAs when the function is inlined.
OTOH - we already inline with mismatched tune flags if the function is
marked with always_inline.

Uros.

> Bootstrapped/regtested on x86_64-pc-linux-gnu{-m32,}
>
> Ok for trunk?
>
> gcc/ChangeLog:
>
>         * config/i386/i386.cc (ix86_can_inline_p): Do not check arch or
>         tune directly, just check prefer_vector_width_type and make sure
>         not to inline if they mismatch.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/i386/inline-target-attr.c: New test.
> ---
>  gcc/config/i386/i386.cc                       | 11 +++++----
>  .../gcc.target/i386/inline-target-attr.c      | 24 +++++++++++++++++++
>  2 files changed, 30 insertions(+), 5 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/i386/inline-target-attr.c
>
> diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
> index 0761965344b..1d86384ac06 100644
> --- a/gcc/config/i386/i386.cc
> +++ b/gcc/config/i386/i386.cc
> @@ -605,11 +605,12 @@ ix86_can_inline_p (tree caller, tree callee)
>                != (callee_opts->x_target_flags & ~always_inline_safe_mask))
>      ret = false;
>
> -  /* See if arch, tune, etc. are the same.  */
> -  else if (caller_opts->arch != callee_opts->arch)
> -    ret = false;
> -
> -  else if (!always_inline && caller_opts->tune != callee_opts->tune)
> +  /* Do not inline when specified perfer-vector-width mismatched between
> +     callee and caller.  */
> +  else if ((callee_opts->x_prefer_vector_width_type != PVW_NONE
> +          && caller_opts->x_prefer_vector_width_type != PVW_NONE)
> +          && callee_opts->x_prefer_vector_width_type
> +             != caller_opts->x_prefer_vector_width_type)
>      ret = false;
>
>    else if (caller_opts->x_ix86_fpmath != callee_opts->x_ix86_fpmath
> diff --git a/gcc/testsuite/gcc.target/i386/inline-target-attr.c b/gcc/testsuite/gcc.target/i386/inline-target-attr.c
> new file mode 100644
> index 00000000000..995502165f0
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/inline-target-attr.c
> @@ -0,0 +1,24 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler-not "call\[ \t\]callee" } } */
> +
> +__attribute__((target("arch=skylake")))
> +int callee (int n)
> +{
> +  int sum = 0;
> +  for (int i = 0; i < n; i++)
> +    {
> +      if (i % 2 == 0)
> +       sum +=i;
> +      else
> +       sum += (i - 1);
> +    }
> +  return sum + n;
> +}
> +
> +__attribute__((target("arch=icelake-server")))
> +int caller (int n)
> +{
> +  return callee (n) + n;
> +}
> +
> --
> 2.31.1
>