Changing "target" parameter via attribute

[Iain Buclaw]

On 27 May 2013 09:21, Manu <turkeyman at gmail.com> wrote:
> Actually, I think the C counterpart is actually
> __attribute__((__target__("targetstring"))), with bonus underscores ;)
>
>
> On 27 May 2013 18:15, Manu <turkeyman at gmail.com> wrote:
>>
>> So we talked about this at DConf.
>>
>> Working on std.simd, I need to be able to change the target parameter on a
>> per-function basis.
>> GCC supports this via: __attribute__((target("sse2"))) for instance.
>>
>> I need the ability to set this from D, but the trick is, I need to be able
>> to set the target string according to a template arg.
>>
>> Eg:
>>   enum Targets { SSE2, SSE3 };
>>   enum targets[] = [ "sse2", "sse3" ];
>>
>>   @attribute("target", targets[T]) // <- attribute needs to refer to the
>> template arg T
>>   void func(Targets T)();
>>
>>

I'll turn on rudimentary support, as the backend takes care of pretty
much all the work.  But I think this should work as UDAs work off CTFE
with string manipulation.


>>   {
>>     // this way, it is possibly to produce dynamic selection of code paths
>> optimised for different CPU features (a task which is usually very tedious
>> in C/C++)
>>     func!(Targets.SSE2)();
>>   }
>>
>

As a small experiment, I could turn on versioning for these
functions...  However is only available for x86 targets.

eg:

void foo() @target("sse")    // mangled 'foo.sse'
{
}

void foo() @target("mmx")   // mangled 'foo.mmx'
{
}



Regards
--
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';