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Message-ID: <4e42947a1c9577da0d86b3fe266b2ffeb49cc743.camel@t-online.de>
Subject: Re: autoinc / postinc not used
From: Oleg Endo <oleg.endo@t-online.de>
To: stefan@franke.ms, gcc-help@gcc.gnu.org
Date: Wed, 17 Jan 2024 08:52:20 +0900
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Hi,


On Tue, 2024-01-16 at 21:02 +0100, stefan@franke.ms wrote:
> Hi all,
>=20
> =20
>=20
> I work a lot with the good old m68k target where post-increment is suppor=
ted, and I was surprised that there almost no post-increments are used in t=
he generated code.
>=20
> This simple code:
>=20
> =20
>=20
> void memclr (int length, long * ptr) {
>=20
>   for(;length--;){
>=20
>     *ptr++=3D 0;
>=20
>   }
>=20
> }=20
>=20
> =20
>=20
> does not use post-increments on AVR or SH. See also https://godbolt.org/z=
/fTvdv65rr
>=20
>=20

This issue has been around for a very long time.  I guess auto-inc is not
important enough on modern architectures to be of a major concern.

On SH{1,2,3,4} post-inc is only available for mem stores, not for mem loads=
.
SH2A adds support for stores with post-inc.  You have to specify "-mb -m2a"
for that, as the default target of sh-elf is SH1 (-m1).  But yeah, it's als=
o
not utilized in this case.

Cheers,
Oleg