On Wed, 3 Jul 2024, Jakub Jelinek wrote:
> On Wed, Jul 03, 2024 at 02:24:19PM +0200, Jakub Jelinek wrote:
> > > >From 40023cac83562a1451aba550533d042fec1c144e Mon Sep 17 00:00:00 2001
> > > From: Richard Biener <rguent...@suse.de>
> > > Date: Tue, 11 Jun 2024 13:11:08 +0200
> > > Subject: [PATCH] middle-end/115426 - wrong gimplification of "rm" asm
> > > output
> > > operand
> > > To: gcc-patches@gcc.gnu.org
> > >
> > > When the operand is gimplified to an extract of a register or a
> > > register we have to disallow memory as we otherwise fail to
> > > gimplify it properly. Instead of
> > >
> > > __asm__("" : "=rm" __imag <r>);
> > >
> > > we want
> > >
> > > __asm__("" : "=rm" D.2772);
> > > _1 = REALPART_EXPR <r>;
> > > r = COMPLEX_EXPR <_1, D.2772>;
> > >
> > > otherwise SSA rewrite will fail and generate wrong code with 'r'
> > > left bare in the asm output.
> > >
> > > PR middle-end/115426
> > > * gimplify.cc (gimplify_asm_expr): Handle "rm" output
> > > constraint gimplified to a register (operation).
> > >
> > > * gcc.dg/pr115426.c: New testcase.
> >
> > LGTM, thanks.
>
> Actually, wonder if that assert won't trigger on something invalid like
> "=i" (__imag__ r)
> which previously got rejected only during expansion.
This case works - the path only triggers when allows_mem so I think it
should be safe.
> So maybe instead of the assert just do your new handling just for allows_reg
> && allows_mem and leave the rest as before.
But "=mi" would be a valid constraint (even if a literal immediate
would be never OK there)?
But yeah, && allows_reg would make it obviously safe. I'll adjust
and re-fire the testing.
Richard.
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
