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Date: Tue, 11 Jul 2023 14:00:03 +0000 (UTC)
From: Michael Matz <matz@suse.de>
To: Jan Hubicka <hubicka@ucw.cz>
cc: Richard Biener <richard.guenther@gmail.com>, 
    Alexander Monakov <amonakov@ispras.ru>, gcc-patches@gcc.gnu.org
Subject: Re: [x86-64] RFC: Add nosse abi attribute
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Hello,

On Tue, 11 Jul 2023, Jan Hubicka wrote:

> > > > When a function doesn't contain calls to
> > > > unknown functions we can be a bit more lenient: we can make it so that
> > > > GCC simply doesn't touch xmm8-15 at all, then no save/restore is
> > > > necessary.
> 
> One may also take into account that first 8 registers are cheaper to
> encode than the later 8, so perhaps we may want to choose range that
> contains both.

There is actually none in the low range that's usable.  xmm0/1 are used 
for return values and xmm2-7 are used for argument passing.  Arguments are 
by default callee clobbered, and we do not want to change this (or limit 
the number of register arguments for the alternate ABI).


Ciao,
Michael.