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From: "tnfchris at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/113257] -march=native or -mcpu=native are ineffective,
 but -march=native -mcpu=native works on arm64 M2 Ultra
Date: Thu, 22 Feb 2024 18:35:24 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113257

--- Comment #5 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
(In reply to Sam James from comment #3)
> (In reply to Richard Earnshaw from comment #2)
> I'm missing why the combination then works though?

So we've made several changes here over time.

-mcpu=3Dnative does attempt to find the core id to know what it is, but sin=
ce
GCC-12 we also enable extensions that don't have a requirement on an
architecture.

So for instance on an SVE capable core we would enable it, but we of course
can't enable a tuning model.

But between GCC 13 and GCC 14 many things have changes.  It looks like GCC-=
14
works as expected:

> ./install/bin/gcc -xc -S -o - - -march=3Dnative < /dev/null
        .arch
armv8-a+flagm+dotprod+rdma+lse+crc+aes+sha3+fp16fml+rcpc+i8mm+bf16+sb+ssbs+=
pauth
        .file   "<stdin>"
        .text
        .ident  "GCC: (GNU) 14.0.1 20240129 (experimental)"=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20
                                     .section=20=20=20=20=20=20=20
.note.GNU-stack,"",@progbits

> ./install/bin/gcc -xc -S -o - - -mcpu=3Dnative < /dev/null
        .arch
armv8-a+flagm+dotprod+rdma+lse+crc+aes+sha3+fp16fml+rcpc+i8mm+bf16+sb+ssbs+=
pauth
        .file   "<stdin>"
        .text
        .ident  "GCC: (GNU) 14.0.1 20240129 (experimental)"=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20
                                     .section=20=20=20=20=20=20=20
.note.GNU-stack,"",@progbits

> ./install/bin/gcc -xc -S -o - - -mcpu=3Dnative -march=3Dnative < /dev/null
        .arch
armv8-a+flagm+dotprod+rdma+lse+crc+aes+sha3+fp16fml+rcpc+i8mm+bf16+sb+ssbs+=
pauth
        .file   "<stdin>"
        .text
        .ident  "GCC: (GNU) 14.0.1 20240129 (experimental)"=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20
                                     .section=20=20=20=20=20=20=20
.note.GNU-stack,"",@progbits

So first question is, can you confirm it does for GCC-14 for you too?

In the meantime I'll try GCC-13=