This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH] power: Fix VSCR position on ucontext
- From: "Gabriel F. T. Gomes" <gabriel at inconstante dot eti dot br>
- To: Tulio Magno Quites Machado Filho <tuliom at ascii dot art dot br>
- Cc: Rogerio Alves <rcardoso at linux dot ibm dot com>, Florian Weimer <fweimer at redhat dot com>, <libc-alpha at sourceware dot org>
- Date: Mon, 10 Dec 2018 16:08:19 -0200
- Subject: Re: [PATCH] power: Fix VSCR position on ucontext
- References: <8a619ad1-b7f2-04f8-f9a7-0a19cbf98f4c@linux.ibm.com> <87lg5va6a6.fsf@oldenburg.str.redhat.com> <20181116111825.43b60283@tereshkova.br.ibm.com> <5e1d1cab-7c91-90f8-82d2-fd38f8676f30@linux.ibm.com> <20181207162959.5e5d8933@tereshkova> <87wooh8gfg.fsf@linux.ibm.com>
On Mon, 10 Dec 2018, Tulio Magno Quites Machado Filho wrote:
>"Gabriel F. T. Gomes" <gabriel@inconstante.eti.br> writes:
>
>> [ text/plain ]
>> On Fri, 07 Dec 2018, Rogerio Alves wrote:
>>
>>>+/* This test is supported only on POWER 5 or higher. */
>>>+#define PPC_CPU_SUPPORTED (PPC_FEATURE_POWER5 | PPC_FEATURE_POWER5_PLUS | \
>>>+ PPC_FEATURE_ARCH_2_05 | PPC_FEATURE_ARCH_2_06 | \
>>>+ PPC_FEATURE2_ARCH_2_07)
>>
>> Is this actually needed? Glibc has code to fill all the bits for older
>> architectures in sysdeps/powerpc/hwcapinfo.c [1]. So, as far as I can
>> see, you only need to test for AT_HWCAP & PPC_FEATURE_POWER5.
>
>Yes, it's indeed required to check all these bits when using getauxval().
>
>> [1] https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/powerpc/hwcapinfo.c;h=a09b18309324423d0cdf04e88367899a4396bab7;hb=HEAD#l47
>
>This code is preparing the data for __builtin_cpu_supports().
>So, when using this built-in, it wouldn't be necessary to check for all those
>AT_HWCAP bits.
Oh, I see. Thanks for the explanation. :)