From: Tulio Magno Quites Machado Filho <tuliom@ascii.art.br>
To: Florian Weimer <fweimer@redhat.com>,
"Lucas A. M. Magalhaes" <lamm@linux.ibm.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH 2/3] powerpc64le: Check HWCAP bits against compiler build flags
Date: Wed, 12 May 2021 11:52:23 -0300 [thread overview]
Message-ID: <871racxavs.fsf@linux.ibm.com> (raw)
In-Reply-To: <87im3owe4q.fsf@oldenburg.str.redhat.com>
Florian Weimer via Libc-alpha <libc-alpha@sourceware.org> writes:
> I tried to allude in the commit message that this is expected. Maybe I
> should drop the POWER10 check?
I don't think this is necessary.
Even if you removed the P10 check, I don't think the P9 check is guaranteed to
work because when _ARCH_PWR9 is set, the compiler is allowed to use P9
instructions in this function before the test is executed.
I think this patch is trying to improve the error message to the user.
With that said, it doesn't hurt to copy your explanation as a source code
comment, i.e.:
/* This approach does not work for the POWER10 because the bootstrap
relocation already uses PCREL instructions, so the detection code does
not actually run. */
>> +#ifdef __MMA__
>> + if ((GLRO (dl_hwcap2) & PPC_FEATURE2_MMA) == 0)
>> + _dl_fatal_printf ("\
>> +Fatal glibc error: CPU lacks MMA support (POWER10 or later required)\n");
>> +#endif
>> +}
I'm not sure it's a good idea to require MMA.
__MMA__ is enabled with -mcpu=power10. However, I'm not aware of any compilers
able to auto-mma code. In other words, we have to use it explicitly right now.
Which means we shouldn't have MMA instructions in glibc at the moment.
--
Tulio Magno
next prev parent reply other threads:[~2021-05-12 15:09 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-06 12:30 [PATCH 0/3] Checking HWCAP bits against compiler flags Florian Weimer
2021-05-06 12:30 ` [PATCH 1/3] elf: Add hook for checking HWCAP bits after auxiliary vector parsing Florian Weimer
2021-05-12 7:43 ` Stefan Liebler
2021-05-06 12:30 ` [PATCH 2/3] powerpc64le: Check HWCAP bits against compiler build flags Florian Weimer
2021-05-11 21:12 ` Lucas A. M. Magalhaes
2021-05-12 8:27 ` Florian Weimer
2021-05-12 14:50 ` Lucas A. M. Magalhaes
2021-05-12 14:52 ` Tulio Magno Quites Machado Filho [this message]
2021-05-12 17:27 ` Florian Weimer
2021-05-12 19:24 ` Tulio Magno Quites Machado Filho
2021-05-18 16:59 ` Florian Weimer
2021-05-18 17:26 ` Tulio Magno Quites Machado Filho
2021-05-18 17:41 ` Florian Weimer
2021-05-06 12:30 ` [PATCH 3/3] s390x: Check HWCAP bits against compiler flags Florian Weimer
2021-05-12 7:43 ` Stefan Liebler
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