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Re: [PATCH] Define HAS_CPUID/HAS_I586/HAS_I686 from -march=
- From: "Carlos O'Donell" <carlos at redhat dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: OndÅej BÃlka <neleai at seznam dot cz>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 18 Aug 2015 11:56:20 -0400
- Subject: Re: [PATCH] Define HAS_CPUID/HAS_I586/HAS_I686 from -march=
- Authentication-results: sourceware.org; auth=none
- References: <20150817231005 dot GA24205 at intel dot com> <20150818052442 dot GA26531 at domone> <CAMe9rOrqkqVJVrs9qy83u-vZTjOBk4Shd-H2zsBJTzc+sHa3Aw at mail dot gmail dot com> <55D35419 dot 5050109 at redhat dot com> <CAMe9rOo9r-X5o1uNj9azjY5+a7WUh4ikYR8_cJyc_NXs_7xhvQ at mail dot gmail dot com>
On 08/18/2015 11:52 AM, H.J. Lu wrote:
> On Tue, Aug 18, 2015 at 8:49 AM, Carlos O'Donell <firstname.lastname@example.org> wrote:
>> On 08/18/2015 09:34 AM, H.J. Lu wrote:
>>> On Mon, Aug 17, 2015 at 10:24 PM, OndÅej BÃlka <email@example.com> wrote:
>>>> On Mon, Aug 17, 2015 at 04:10:05PM -0700, H.J. Lu wrote:
>>>>> cpuid, i586 and i686 instructions are available if the processor
>>>>> specified by -march= supports them. We can use this information
>>>>> to determine whether those instructions can be used safely.
>>>>> OK for master?
>>>> Patch itself looks ok. It fixes theoretical problem that if there would
>>>> be new processor without cpuid it would cause problem.
>>>> But could you explain rationale? Here you replaced one like with
>>>> equivalent longer macro and HAS_I586 is never used. Do you plan followup
>>>> patches that use that?
>>> I will use HAS_I586 and HAS_I686 in multi-arch for i486 and i586
>>> I am working on.
>> Does this include folding i486 up a directory and doing away with the
>> i386 support? Since we need the i486 instructions to implement NPTL.
> I will investigate it and it will take a while.