On Wed, Apr 30, 2025 at 7:37 PM Uros Bizjak <ubiz...@gmail.com> wrote:
>
> On Tue, Apr 29, 2025 at 11:40 PM H.J. Lu <hjl.to...@gmail.com> wrote:
> >
> > AREG, DREG, CREG and AD_REGS are kept in ix86_class_likely_spilled_p to
> > avoid the following regressions with
> >
> > $ make check RUNTESTFLAGS="--target_board='unix{-m32,}'"
> >
> > FAIL: gcc.dg/pr105911.c (internal compiler error: in
> > lra_split_hard_reg_for, at lra-assigns.cc:1863)
> > FAIL: gcc.dg/pr105911.c (test for excess errors)
> > FAIL: gcc.target/i386/avx512vl-stv-rotatedi-1.c scan-assembler-times
> > vpro[lr]q 29
> > FAIL: gcc.target/i386/bt-7.c scan-assembler-not and[lq][ \t]
> > FAIL: gcc.target/i386/naked-4.c scan-assembler-not %[re]bp
> > FAIL: gcc.target/i386/pr107548-1.c scan-assembler-not addl
> > FAIL: gcc.target/i386/pr107548-1.c scan-assembler-times \tv?movd\t 3
> > FAIL: gcc.target/i386/pr107548-1.c scan-assembler-times v?paddd 6
> > FAIL: gcc.target/i386/pr107548-2.c scan-assembler-not \taddq\t
> > FAIL: gcc.target/i386/pr107548-2.c scan-assembler-times v?paddq 2
> > FAIL: gcc.target/i386/pr119171-1.c (test for excess errors)
> > FAIL: gcc.target/i386/pr57189.c scan-assembler-not movaps
> > FAIL: gcc.target/i386/pr57189.c scan-assembler-not movaps
> > FAIL: gcc.target/i386/pr78904-1b.c scan-assembler [ \t]andb
> > FAIL: gcc.target/i386/pr78904-1b.c scan-assembler [ \t]orb
> > FAIL: gcc.target/i386/pr78904-7b.c scan-assembler-not movzbl
> > FAIL: gcc.target/i386/pr78904-7b.c scan-assembler [ \t]orb
> > FAIL: gcc.target/i386/pr91188-2c.c scan-assembler [ \t]andw
> >
> > Tested with glibc master branch at
> >
> > commit ccdb68e829a31e4cda8339ea0d2dc3e51fb81ba5
> > Author: Samuel Thibault <samuel.thiba...@ens-lyon.org>
> > Date: Sun Mar 2 15:16:45 2025 +0100
> >
> > htl: move pthread_once into libc
> >
> > and built Linux kernel 6.13.5 on x86-64.
> >
> > PR target/119083
> > * config/i386/i386.cc (ix86_class_likely_spilled_p): Remove CREG
> > and BREG.
>
> The commit message doesn't reflect what the patch does.
>
> OTOH, this is a very delicate part of the compiler. You are risking RA
> failures, the risk/benefit ratio is very high, so I wouldn't touch it
> without clear benefits. Do you have a concrete example where declaring
> BREG as spilled hurts?
>
I can find a testcase to show the improvement. But I am not sure if
it is what you were asking for. ix86_class_likely_spilled_p was
CLASS_LIKELY_SPILLED_P which was added by
commit f5316dfe88b8d1b8d3012c1f75349edf2ba1bdde
Author: Michael Meissner <meiss...@gcc.gnu.org>
Date: Thu Sep 8 17:59:18 1994 +0000
Add support for -mreg-alloc=<xxx>
This option is long gone and there is no test in GCC testsuite to show
that BX should be in ix86_class_likely_spilled_p. On x86-64, BX is just
another callee-saved register, not different from R12. On i386, BX is
used as the PIC register. But today RA may pick a different register if
PLT isn't involved. This patch gives RA a little bit more freedom.
--
H.J.
From 4fdcd7fc7e0dad6cb595e8807823cbfde49aab06 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.to...@gmail.com>
Date: Mon, 3 Mar 2025 12:42:31 +0800
Subject: [PATCH v2] x86: Remove BREG from ix86_class_likely_spilled_p
AREG, DREG, CREG and AD_REGS are kept in ix86_class_likely_spilled_p to
avoid the following regressions with
$ make check RUNTESTFLAGS="--target_board='unix{-m32,}'"
FAIL: gcc.dg/pr105911.c (internal compiler error: in lra_split_hard_reg_for, at lra-assigns.cc:1863)
FAIL: gcc.dg/pr105911.c (test for excess errors)
FAIL: gcc.target/i386/avx512vl-stv-rotatedi-1.c scan-assembler-times vpro[lr]q 29
FAIL: gcc.target/i386/bt-7.c scan-assembler-not and[lq][ \t]
FAIL: gcc.target/i386/naked-4.c scan-assembler-not %[re]bp
FAIL: gcc.target/i386/pr107548-1.c scan-assembler-not addl
FAIL: gcc.target/i386/pr107548-1.c scan-assembler-times \tv?movd\t 3
FAIL: gcc.target/i386/pr107548-1.c scan-assembler-times v?paddd 6
FAIL: gcc.target/i386/pr107548-2.c scan-assembler-not \taddq\t
FAIL: gcc.target/i386/pr107548-2.c scan-assembler-times v?paddq 2
FAIL: gcc.target/i386/pr119171-1.c (test for excess errors)
FAIL: gcc.target/i386/pr57189.c scan-assembler-not movaps
FAIL: gcc.target/i386/pr57189.c scan-assembler-not movaps
FAIL: gcc.target/i386/pr78904-1b.c scan-assembler [ \t]andb
FAIL: gcc.target/i386/pr78904-1b.c scan-assembler [ \t]orb
FAIL: gcc.target/i386/pr78904-7b.c scan-assembler-not movzbl
FAIL: gcc.target/i386/pr78904-7b.c scan-assembler [ \t]orb
FAIL: gcc.target/i386/pr91188-2c.c scan-assembler [ \t]andw
Tested with glibc master branch at
commit ccdb68e829a31e4cda8339ea0d2dc3e51fb81ba5
Author: Samuel Thibault <samuel.thiba...@ens-lyon.org>
Date: Sun Mar 2 15:16:45 2025 +0100
htl: move pthread_once into libc
and built Linux kernel 6.13.5 on x86-64.
PR target/119083
* config/i386/i386.cc (ix86_class_likely_spilled_p): Remove BREG.
Signed-off-by: H.J. Lu <hjl.to...@gmail.com>
---
gcc/config/i386/i386.cc | 1 -
1 file changed, 1 deletion(-)
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index c3c2a465b3c..c8df3af803b 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -20778,7 +20778,6 @@ ix86_class_likely_spilled_p (reg_class_t rclass)
case AREG:
case DREG:
case CREG:
- case BREG:
case AD_REGS:
case SIREG:
case DIREG:
--
2.49.0
