Re: [gentoo-dev] [RFC] New USE_EXPAND: LLVM_TARGETS

[Michał Górny]

On Mon, 26 Sep 2016 00:42:11 +0300
Mart Raudsepp <leio@g.o> wrote:

> Ühel kenal päeval, P, 25.09.2016 kell 23:08, kirjutas Michał Górny:
> > I'd like to introduce a new USE_EXPAND for LLVM & clang. It'd be
> > named
> > LLVM_TARGETS, and it's going to replace the current solution based on
> > USE=multitarget & VIDEO_CARDS=radeon.
> >
> > - VIDEO_CARDS=radeon enabled additional R600 target,
>
> No. It enables AMDGPU target these days, which is for the modern stuff
> and very much needed by them.
> r600 stuff was in the llvm 3.3-3.6 era, which was used by old
> experimental mesa[r600-llvm-compiler] as an alternative shader compiler
> for r600 instead of builtin mesa stuff. This work has been ditched long
> ago afaik.
> Instead now VIDEO_CARDS=radeon is required on llvm for radeonsi and
> later AMD GPUs for _ANY_ shader compiler support at all, plus other
> things (from it adding AMDGPU to llvm targets in current ebuild).

Yes, yes, I am old :-P. You are right, it's AMDGPU these days.

> > The new system will be applied to 3.9.0 and 9999 ebuilds. VIDEO_CARDS
> > flag will be removed completely because of no revdeps.
>
> People with radeonsi graphics set VIDEO_CARDS=radeon already, I'm a bit
> reserved about having to force them to set some LLVM_TARGETS=radeon or
> LLVM_TARGETS=amdgpu on top of that to satisfy some USE depends on
> mesa[video_cards_radeon].

How about nvidia users who seem to require NVPTX for libclc these days?
Do they set VIDEO_CARDS='nvidia nv nouveau ...'? The problem is that
this abuse of VIDEO_CARDS is never going to be 100% clear to users.

I guess we can enable GPU targets in desktop profiles by default to
save most of our users from the issues.

-- 
Best regards,
Michał Górny
<http://dev.gentoo.org/~mgorny/>