[Piglit] [Mesa-dev] [PATCH] Add (un)packHalf tests which don't fail on GCN

[Matt Turner]

On Thu, Feb 4, 2016 at 10:50 AM, Marek Olšák <maraeo at gmail.com> wrote:
> From: Marek Olšák <marek.olsak at amd.com>
>
> This is a subset of the generated tests which are known to fail
> on everything except CPU emulation (AFAIK).
> ---

This is really awful. Committing a generated test, but with unknown
bits chopped out is gross.

If it were me, I'd want to understand why my hardware behaved
differently -- not just hack up *different* tests and claim victory.

FWIW, the generated tests pass on all Intel hardware exposing
ARB_shading_language_packing. Gen7+ has native half-float support, and
Gen6 uses the lowering code in lower_packing_builtins.cpp to turn the
built-ins into a pile of instructions.

If you can identify how AMD hardware behaves differently and can prove
that the generator needs to be relaxed or something, that's cool. But
as is, I hate this patch.

I can't find anything in the AMD docs (I looked at GCN3) about
half-precision support, so I can't check my theory that AMD hardware
rounds towards zero instead of to-nearest/even like Intel.