Re: [PATCH] i386: fix ix86_hardreg_mov_ok with lra_in_progress

[Hongtao Liu <crazylht@gmail.com>]

On Mon, May 6, 2024 at 3:40 PM Kong, Lingling <lingling.kong@intel.com> wrote:
>
> Hi,
> Originally eliminate_regs_in_insn will transform
> (parallel [
>   (set (reg:QI 130)
>     (plus:QI (subreg:QI (reg:DI 19 frame) 0)
>       (const_int 96)))
>   (clobber (reg:CC 17 flag))]) {*addqi_1}
> to
> (set (reg:QI 130)
>   (subreg:QI (reg:DI 19 frame) 0)) {*movqi_internal}
> when verify_changes.
>
> But with No Flags add, it transforms
> (set (reg:QI 5 di)
>   (plus:QI (subreg:QI (reg:DI 19 frame) 0)
>    (const_int 96))) {*addqi_1_nf}
> to
> (set (reg:QI 5 di)
>  (subreg:QI (reg:DI 19 frame) 0)) {*addqi_1_nf}.
> there is no extra clobbers at the end, and its dest reg just is a hardreg. For ix86_hardreg_mov_ok, it returns false. So it fails to update insn and causes the ICE when transform to movqi_internal.
>
> But actually it is ok and safe for ix86_hardreg_mov_ok when lra_in_progress.
>
> And tested the spec2017, the performance was not affected.
> Bootstrapped and regtested on x86_64-pc-linux-gnu. OK for trunk?
Ok.
>
> gcc/ChangeLog:
>
>         * config/i386/i386.cc (ix86_hardreg_mov_ok): Relax
>         hard reg mov restriction when lra in progress.
> ---
>  gcc/config/i386/i386.cc | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc index 4d6b2b98761..ca4348a18bf 100644
> --- a/gcc/config/i386/i386.cc
> +++ b/gcc/config/i386/i386.cc
> @@ -20357,7 +20357,8 @@ ix86_hardreg_mov_ok (rtx dst, rtx src)
>            ? standard_sse_constant_p (src, GET_MODE (dst))
>            : x86_64_immediate_operand (src, GET_MODE (dst)))
>        && ix86_class_likely_spilled_p (REGNO_REG_CLASS (REGNO (dst)))
> -      && !reload_completed)
> +      && !reload_completed
> +      && !lra_in_progress)
>      return false;
>    return true;
>  }
> --
> 2.31.1
>


-- 
BR,
Hongtao