PING [GCC 10] [PATCH] IRA: Don't make a global register eliminable

["H.J. Lu" <hjl.tools@gmail.com>]

On Fri, Sep 18, 2020 at 10:21 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Thu, Sep 17, 2020 at 3:52 PM Jeff Law <law@redhat.com> wrote:
> >
> >
> > On 9/16/20 8:46 AM, Richard Sandiford wrote:
> >
> > "H.J. Lu" <hjl.tools@gmail.com> writes:
> >
> > On Tue, Sep 15, 2020 at 7:44 AM Richard Sandiford
> > <richard.sandiford@arm.com> wrote:
> >
> > Thanks for looking at this.
> >
> > "H.J. Lu" <hjl.tools@gmail.com> writes:
> >
> > commit 1bcb4c4faa4bd6b1c917c75b100d618faf9e628c
> > Author: Richard Sandiford <richard.sandiford@arm.com>
> > Date:   Wed Oct 2 07:37:10 2019 +0000
> >
> >     [LRA] Don't make eliminable registers live (PR91957)
> >
> > didn't make eliminable registers live which breaks
> >
> > register void *cur_pro asm("reg");
> >
> > where "reg" is an eliminable register.  Make fixed eliminable registers
> > live to fix it.
> >
> > I don't think fixedness itself is the issue here: it's usual for at
> > least some registers involved in eliminations to be fixed registers.
> >
> > I think what makes this case different is instead that cur_pro/ebp
> > is a global register.  But IMO things have already gone wrong if we
> > think that a global register is eliminable.
> >
> > So I wonder if instead we should check global_regs at the beginning of:
> >
> >       for (i = 0; i < fp_reg_count; i++)
> >         if (!TEST_HARD_REG_BIT (crtl->asm_clobbers,
> >                                 HARD_FRAME_POINTER_REGNUM + i))
> >           {
> >             SET_HARD_REG_BIT (eliminable_regset,
> >                               HARD_FRAME_POINTER_REGNUM + i);
> >             if (frame_pointer_needed)
> >               SET_HARD_REG_BIT (ira_no_alloc_regs,
> >                                 HARD_FRAME_POINTER_REGNUM + i);
> >           }
> >         else if (frame_pointer_needed)
> >           error ("%s cannot be used in %<asm%> here",
> >                  reg_names[HARD_FRAME_POINTER_REGNUM + i]);
> >         else
> >           df_set_regs_ever_live (HARD_FRAME_POINTER_REGNUM + i, true);
> >
> > (ira_setup_eliminable_regset), and handle the global_regs[] case in
> > the same way as the else case, i.e. short-circuiting both of the ifs.
> >
> > Like this?
> >
> > Sorry for the delay.  I was testing this in parallel.
> >
> > Bootstrapped & regression-tested on x86_64-linux-gnu.
> >
> > Thanks,
> > Richard
> >
> >
> > 0001-ira-Fix-elimination-for-global-hard-FPs-PR91957.patch
> >
> > From af4499845d26fe65573b21197a79fd22fd38694e Mon Sep 17 00:00:00 2001
> > From: "H.J. Lu" <hjl.tools@gmail.com>
> > Date: Tue, 15 Sep 2020 06:23:26 -0700
> > Subject: [PATCH] ira: Fix elimination for global hard FPs [PR91957]
> > MIME-Version: 1.0
> > Content-Type: text/plain; charset=UTF-8
> > Content-Transfer-Encoding: 8bit
> >
> > If the hard frame pointer is being used as a global register,
> > we should skip the usual handling for eliminations.  As the
> > comment says, the register cannot in that case be eliminated
> > (or eliminated to) and is already marked live where appropriate.
> >
> > Doing this removes the duplicate error for gcc.target/i386/pr82673.c.
> > The “cannot be used in 'asm' here” message is meant to be for asm
> > statements rather than register asms, and the function that the
> > error is reported against doesn't use asm.
> >
> > gcc/
> > 2020-09-16  Richard Sandiford  <richard.sandiford@arm.com>
> >
> > PR middle-end/91957
> > * ira.c (ira_setup_eliminable_regset): Skip the special elimination
> > handling of the hard frame pointer if the hard frame pointer is fixed.
> >
> > gcc/testsuite/
> > 2020-09-16  H.J. Lu  <hjl.tools@gmail.com>
> >    Richard Sandiford  <richard.sandiford@arm.com>
> >
> > PR middle-end/91957
> > * g++.target/i386/pr97054.C: New test.
> > * gcc.target/i386/pr82673.c: Remove redundant extra message.
> >
> > OK
>
> OK for GCC 10 branch?
>
> Thanks.

PING:

https://gcc.gnu.org/pipermail/gcc-patches/2020-September/554268.html

-- 
H.J.