Re: [x86-64] RFC: Add nosse abi attribute

[Richard Biener <richard.guenther@gmail.com>]

On Tue, Jul 11, 2023 at 10:53 AM Jan Hubicka <hubicka@ucw.cz> wrote:
>
> > > > FWIW, this particular patch was regstrapped on x86-64-linux
> > > > with trunk from a week ago (and sniff-tested on current trunk).
> > >
> > > This looks really cool.
> >
> > The biggest benefit might be from IPA with LTO where we'd carefully place those
> > attributes at WPA time (at that time tieing our hands for later).
>
> Within single partition IRA already propagates the knowledge about
> callee-clobbered registers.
>
> Across partition we already automatically enable regparm with -m32
> see ix86_function_regparm and tests for target->local and
> can_change_attribute
>
> Enabling SSE at the same spot should be easy.

It's probably slightly different since we want to enable it for a "leaf"
sub-callgraph (or where edges to extern have the appropriate ABI
by means of attributes) irrespective of whether the functions are exported
(we're adding to the callee save set, which is ABI compatible
with the default ABI).  But yes, that place would be appropriate.

Richard.

>
> Honza