On Fri, Mar 31, 2023 at 7:11 AM liuhongt <hongtao....@intel.com> wrote:
>
> RA sometimes will use lowest the cost of the mode with all different
> regclasses
> w/o check if it's hard_regno_mode_ok.
> It's impossible to put modes whose size > 8 into MASK_REGS, ajdust the cost to
> avoid potential performance issue.
I was going to ask to open a PR in order to fix RA instead of the
proposed workaround, but the patch just prevents a theoretical issue
and follows the established practice with other regclasses. Perhaps
these workarounds are not needed with the current RA, but this is a
tangential issue which should be fixed for all regclasses.
> Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> Ok for trunk?
OK.
Thanks,
Uros.
>
> gcc/ChangeLog:
>
> * config/i386/i386.cc (inline_memory_move_cost): Return 100
> for MASK_REGS when MODE_SIZE > 8.
> ---
> gcc/config/i386/i386.cc | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
> index 2cc8e9548a9..2581b800a06 100644
> --- a/gcc/config/i386/i386.cc
> +++ b/gcc/config/i386/i386.cc
> @@ -19847,9 +19847,12 @@ inline_memory_move_cost (machine_mode mode, enum
> reg_class regclass, int in)
> index = 1;
> break;
> /* DImode loads and stores assumed to cost the same as SImode. */
> - default:
> + case 4:
> + case 8:
> index = 2;
> break;
> + default:
> + return 100;
> }
>
> if (in == 2)
> --
> 2.39.1.388.g2fc9e9ca3c
>
