[cfe-dev] __attribute__ ((target("XXX"))) semantic in clang and gcc

[Dmitry Polukhin via cfe-dev]

FYI, I prepared patch for ifunc support in Clang
http://reviews.llvm.org/D15524 and LLVM http://reviews.llvm.org/D15525.
Please review if you are interested in.

On Wed, Dec 9, 2015 at 6:46 PM, David Blaikie <dblaikie at gmail.com> wrote:

>
>
> On Wed, Dec 9, 2015 at 12:34 AM, Dmitry Polukhin <
> dmitry.polukhin at gmail.com> wrote:
>
>> Thank you all for confirming that it is missing functionality in Clang.
>> Indeed proper ifunc support should be a good first step for multiversioning
>> support. Eric, are you working on ifunc support?
>>
>
> Nope, no one in the community is working on anything in this space at the
> moment.
>
> - Dave
>
>
>>
>> Multiversioning support will also needs name mangling enchantment to
>> encode target attributes.
>>
>> On Wed, Dec 9, 2015 at 12:42 AM, Eric Christopher via cfe-dev <
>> cfe-dev at lists.llvm.org> wrote:
>>
>>>
>>>
>>> On Tue, Dec 8, 2015 at 1:00 PM David Blaikie via cfe-dev <
>>> cfe-dev at lists.llvm.org> wrote:
>>>
>>>> On Tue, Dec 8, 2015 at 12:54 PM, Joerg Sonnenberger via cfe-dev <
>>>> cfe-dev at lists.llvm.org> wrote:
>>>>
>>>>> On Tue, Dec 08, 2015 at 12:41:57PM -0800, David Blaikie wrote:
>>>>> > On Tue, Dec 8, 2015 at 12:18 PM, Joerg Sonnenberger via cfe-dev <
>>>>> > cfe-dev at lists.llvm.org> wrote:
>>>>> >
>>>>> > > On Tue, Dec 08, 2015 at 09:38:58AM -0800, David Blaikie via
>>>>> cfe-dev wrote:
>>>>> > > > Implementing actual multiversioning (with the overloads, ifunc
>>>>> > > > relocations/stub generation, etc) is not implemented currently
>>>>> and while
>>>>> > > I
>>>>> > > > don't know of anyone who has plans to, it's certainly something
>>>>> that
>>>>> > > could
>>>>> > > > be done (ie: the project isn't philosophically opposed to the
>>>>> feature or
>>>>> > > > anything).
>>>>> > >
>>>>> > > We are not? IMO creating tools for magically matching the target to
>>>>> > > whatever the system currently runs on is not the job of the
>>>>> compiler.
>>>>> > >
>>>>> >
>>>>> > *shrug* Seems like a reasonable feature that GCC offers and people
>>>>> use.
>>>>> > What would be the problem with it?
>>>>>
>>>>> Do you want code emitted to magically call __cpuid() and match patterns
>>>>> or whatever on it?
>>>>
>>>>
>>>> That's what GCC does here, so far as I know.
>>>>
>>>>
>>>>> This kind of logic sounds to be exactly like the
>>>>> thing an application should be controlling.
>>>>>
>>>>
>>>> That's an option - if we surface the raw ifunc stuff, which I imagine
>>>> we would first before implementing the higher level function
>>>> multiversioning.
>>>>
>>>> But I'm not sure it adds a lot of value to have the application write
>>>> that code - but sure, could take a bit of a survey and see if function
>>>> multiversioning is used much/worth the compiler implementation complexity
>>>> over just implementing ifunc and letting the user figure it out from there.
>>>>
>>>>
>>> *shrug* FWIW this is why I haven't really implemented this side of
>>> things yet. I'm not convinced that the extra syntactic sugar around it is
>>> buying anyone anything, not even really convinced that the ifunc stuff in
>>> general is worth it, but not going to object if anyone else wants to
>>> implement it.
>>>
>>> -eric
>>>
>>>
>>>> - Dave
>>>>
>>>>
>>>>>
>>>>> Joerg
>>>>> _______________________________________________
>>>>> cfe-dev mailing list
>>>>> cfe-dev at lists.llvm.org
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>
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>>>
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>>
>
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