Hi Andrew,
That can't be right, on my system a test of asm vs asm volatile with -O3
and -flto=auto yields very different results, with only the latter being
correct. The patch fixed it and caused gcc to emit correct assembly
best regards,
Julian
On Wed, Jun 28, 2023 at 12:08 AM Andrew Pinski <pins...@gmail.com> wrote:
> On Tue, Jun 27, 2023 at 9:03 AM Julian Waters via Gcc <gcc@gcc.gnu.org>
> wrote:
> >
> > gcc's documentatation mentions that all basic asm blocks are always
> volatile,
> > yet the parser fails to account for this by only ever setting
> > volatile_p to true
> > if the volatile qualifier is found. This patch fixes this by adding a
> > special case check for extended_p before finish_asm_statement is called
>
> The patch which are you doing will not change the behavior of GCC as
> GCC already treats them as volatile later on.
> non-extended inline-asm has no outputs so the following code in the
> gimplifier will kick in and turn the gimple statement into volatile:
> gimple_asm_set_volatile (stmt, ASM_VOLATILE_P (expr) || noutputs ==
> 0);
>
> (note I am about to push a patch which changes the condition slightly
> to have `asm goto` as volatile).
>
> Thanks,
> Andrew
>
> >
> > From 3094be39e3e65a6a638f05fafd858b89fefde6b5 Mon Sep 17 00:00:00 2001
> > From: TheShermanTanker <tanksherma...@gmail.com>
> > Date: Tue, 27 Jun 2023 23:56:38 +0800
> > Subject: [PATCH] asm not using extended syntax should always be volatile
> >
> > ---
> > gcc/cp/parser.cc | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> > index a6341b9..ef3d06a 100644
> > --- a/gcc/cp/parser.cc
> > +++ b/gcc/cp/parser.cc
> > @@ -22355,6 +22355,9 @@ cp_parser_asm_definition (cp_parser* parser)
> > /* Create the ASM_EXPR. */
> > if (parser->in_function_body)
> > {
> > + if (!extended_p) {
> > + volatile_p = true;
> > + }
> > asm_stmt = finish_asm_stmt (asm_loc, volatile_p, string, outputs,
> > inputs, clobbers, labels, inline_p);
> > /* If the extended syntax was not used, mark the ASM_EXPR. */
> > --
> > 2.35.1.windows.2
>
