Re: kern/58539: AVX-512 support incomplete/broken

["Taylor R Campbell via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR toolchain/58539; it has been noted by GNATS.

From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
To: Thomas Klausner <wiz%NetBSD.org@localhost>
Cc: PHO <pho%cielonegro.org@localhost>,
	gnats-bugs%NetBSD.org@localhost, netbsd-bugs%NetBSD.org@localhost
Subject: Re: kern/58539: AVX-512 support incomplete/broken
Date: Wed, 24 Dec 2025 19:45:50 +0000

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 If you boot a kernel from the tip of netbsd-9, netbsd-10, netbsd-11,
 or HEAD on an affected machine:
 
 1. Is this still reproducible, when you re-enable the upstream AVX512
    logic?
 
 2. Can you share the output of `cpuctl identify 0'?
 
 3. Can you try running the attached program and tell me what it prints?
 
 	$ make avx512ftest DBG=-g\ -O2\ -Wall\ -Werror\ -mavx512f
 	$ ./avx512ftest
 
 I don't seem to have machines with AVX512 handy, and qemu doesn't seem
 to emulate it.
 
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 Content-Type: text/plain; charset="ISO-8859-1"; name="avx512ftest"
 Content-Transfer-Encoding: quoted-printable
 Content-Disposition: attachment; filename="avx512ftest.c"
 
 #include <immintrin.h>
 #include <stdio.h>
 
 int
 main(void)
 {
 	volatile int z =3D 0x5a5a5a5a;
 	__m512i x =3D _mm512_set1_epi32(z);
 	__m512i y =3D _mm512_set_epi32(z + 0, z + 1, z + 2, z + 3,
 	    z + 4, z + 5, z + 6, z + 7,
 	    z + 8, z + 9, z + 10, z + 11,
 	    z + 12, z + 13, z + 14, z + 15);
 	__m512i xy =3D x ^ y;
 	char buf[64];
 	unsigned i;
 
 	_mm512_store_epi64(buf, xy);
 	for (i =3D 0; i < sizeof(buf); i++)
 		printf("%02hhx\n", buf[i]);
 	fflush(stdout);
 	return ferror(stdout);
 }
 
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