Changing "target" parameter via attribute

[Manu]

On 27 May 2013 19:01, Iain Buclaw <ibuclaw at ubuntu.com> wrote:

> 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'
> {
> }
>

I'm confused, are you suggesting to handle these particular values
explicitly in gdc?
I was giving examples of the code I want to write (and work). I can handle
this in std.simd.
I don't think there's any reason to handle arch-specific cases like that in
gdc.

Or rather, was the point you were trying to make here the possible support
of a @target() attribute (which affects the mangling), rather than
@attribute("target")?
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