On Wed, Feb 18, 2026 at 10:38 AM Richard Biener <[email protected]> wrote:
>
> When we search for a point in an inseration candidate block that has
> incoming live call clobbered regs we look for REG_DEAD notes of
> those and indication of FLAGS reg becoming live. But we consider
> insns like
>
> (insn 807 805 6 2 (parallel [
> (set (subreg:SI (reg:HI 509) 0)
> (lshiftrt:SI (reg:SI 514)
> (const_int 16 [0x10])))
> (clobber (reg:CC 17 flags))
> ])
> "/home/packages/tmp/onednn-3.9.1+ds/src/cpu/x64/brgemm/jit_brgemm_amx_uker.cpp":1891:25
> 1213 {*lshrsi3_1}
> (expr_list:REG_UNUSED (reg:CC 17 flags)
> (expr_list:REG_DEAD (reg:SI 514)
> (nil))))
>
> making the FLAGS_REG live despite the REG_UNUSED note or the setter
> being a CLOBBER. The following optimizes this by in turn honoring
> REG_UNUSED for FLAGS_REG, pruning it immediately again.
>
> This reduces required expensive iteration to other candidate BBs,
> reducing compile-time for the testcase in the PR from hours to 6s.
>
> Bootstrap and regtest running on x86_64-unknown-linux-gnu.
>
> OK for trunk?
>
> I have an optional followup simplifying the logic added in r16-3290
> as well, will post for consideration after testing succeeded.
>
> Thanks,
> Richard.
>
> PR target/123137
> * config/i386/i386-features.cc (ix86_emit_tls_call): Improve
> local FLAGS_REG liveness calculation.
OK.
Thanks,
Uros.
> ---
> gcc/config/i386/i386-features.cc | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/config/i386/i386-features.cc
> b/gcc/config/i386/i386-features.cc
> index d5435f009cb..a25f9c245d7 100644
> --- a/gcc/config/i386/i386-features.cc
> +++ b/gcc/config/i386/i386-features.cc
> @@ -4080,7 +4080,9 @@ ix86_emit_tls_call (rtx tls_set, x86_cse_kind kind,
> basic_block bb,
>
> rtx link;
> for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
> - if (REG_NOTE_KIND (link) == REG_DEAD
> + if ((REG_NOTE_KIND (link) == REG_DEAD
> + || (REG_NOTE_KIND (link) == REG_UNUSED
> + && REGNO (XEXP (link, 0)) == FLAGS_REG))
> && REG_P (XEXP (link, 0)))
> {
> /* Mark the live caller-saved register as dead. */
> --
> 2.51.0
