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Re: [PATCH] x86-64: Compile branred.c with -mprefer-vector-width=128 [BZ #24603]
On 6/17/19 3:37 PM, Joseph Myers wrote:
> On Mon, 17 Jun 2019, H.J. Lu wrote:
>
>> On Mon, Jun 17, 2019 at 12:12 PM Florian Weimer <fweimer@redhat.com> wrote:
>>>
>>> * Jeff Law:
>>>
>>>> ISTM that 8, 9, 10 would use the new flag. 11 would issue an error
>>>> which would trigger a reinvestigation roughly a year from now.
>>>
>>> Do you suggest to put in a #warning for GCC 11, so that people can
>>> configure with --disable-werror and still build with GCC 11?
>>>
>>> Given that GCC 11 will probably add other warnings that break the build,
>>> this proposal isn't entirely unreasonable (even though I generally
>>> dislike such time bombs).
>>>
>>
>> Since there is no issue in source, this requires an artificial warning
>> purely based on GCC version. We can place GCC version check in
>> configure script with explicit -mprefer-vector-width=128 support.
>>
>> --enable-mprefer-vector-width:
>>
>> 1. Default. For GCC 8, 9, 10, use -mprefer-vector-width=128.
>> For GCC 11 and above, issue a configure error.
>
> I don't think anything causing the build to break with newer GCC versions
> is appropriate.
Fair enough -- hence a bit of a step away from the decision process in
my prior message on this subject. I threw it out as a way to address
the issue Florian raised, but I strongly believe it's up to the glibc
team to decide how they want to go forward.
jeff