Re: [PATCH] Fix PR66870 ppc64le, ppc64 split stack

[David Edelsohn <dje.gcc@gmail.com>]

On Fri, Jul 31, 2015 at 12:00 AM, Alan Modra <amodra@gmail.com> wrote:
> On Thu, Jul 30, 2015 at 03:30:12PM -0500, Lynn A. Boger wrote:
>>                 PR66870
>>                 * gcc/config/rs6000/rs6000.c:  Add check for no_split_stack
>>                 function attribute along with flag_split_stack check to
>>                 determine when to generate split stack prologue for
>>                 ppc64 and ppc64le.
>
> Looks good to me, except that the changelog entry should mention the
> modified functions, for example:
>
>         PR target/66870
>         * gcc/config/rs6000/rs6000.c (rs6000_emit_prologue): Check for
>         no_split_stack function attribute along with flag_split_stack.
>         (rs6000_expand_split_stack_prologue): Likewise.
>
> Also, formatting rules for gcc say to not split a line after an
> operator.
>
>> +  int using_split_stack = flag_split_stack &&
>> +   (lookup_attribute ("no_split_stack", DECL_ATTRIBUTES (cfun->decl))
>> +         == NULL);
>
> The "&&" belongs on the next line, with parentheses added so that emacs
> and indent will line up the continuation nicely.
>
>   int using_split_stack = (flag_split_stack
>                            && (lookup_attribute ("no_split_stack",
>                                                  DECL_ATTRIBUTES (cfun->decl))
>                                == NULL));
>
>
> David, the following is another piece of the PR66870 fixes.  This
> stops shrink-wrap from moving insns around in the first few blocks of
> a function, in a way that is incorrect given that r12 is live.
> Bootstrapped and regression tested powerpc64le-linux (and
> powerpc64-linux by Lynn).
>
>         PR target/66870
>         * config/rs6000/rs6000.c (machine_function): Add split_stack_argp_used.
>         (rs6000_emit_prologue): Set it.
>         (rs6000_set_up_by_prologue): Specify r12 when split_stack_argp_used.

Both patches with your suggested changes are okay.

Thanks, David