[Mesa-dev] [PATCH 2/2] intel/compiler: Use null destination register for memory fence messages

[Anuj Phogat]

On Wed, Feb 7, 2018 at 11:14 AM, Kenneth Graunke <kenneth at whitecape.org>
wrote:

> On Tuesday, February 6, 2018 5:09:10 PM PST Anuj Phogat wrote:
> > From Message Descriptor section in gfxspecs:
> >  "Memory fence messages without Commit Enable set do not return
> >   anything to the thread (response length is 0 and destination
> >   register is null)."
> >
> > It fixes a piglit GPU hang in simulation environment.
> > Piglit test: arb_shader_image_load_store-shader-mem-barrier
> >
> > Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
> > Cc: mesa-stable at lists.freedesktop.org
> > ---
> >  src/intel/compiler/brw_eu_emit.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/intel/compiler/brw_eu_emit.c
> b/src/intel/compiler/brw_eu_emit.c
> > index 1fb9aab51c..c66b813af8 100644
> > --- a/src/intel/compiler/brw_eu_emit.c
> > +++ b/src/intel/compiler/brw_eu_emit.c
> > @@ -3290,7 +3290,13 @@ brw_memory_fence(struct brw_codegen *p,
> >      */
> >     insn = next_insn(p, BRW_OPCODE_SEND);
> >     dst = retype(dst, BRW_REGISTER_TYPE_UW);
> > -   brw_set_dest(p, insn, dst);
> > +
> > +  /* From Message Descriptor section in gfxspecs:
> > +        "Memory fence messages without Commit Enable set do not return
> > +         anything to the thread (response length is 0 and destination
> > +         register is null).
> > +   */
> > +   brw_set_dest(p, insn, retype(vec1(brw_null_reg()),
> BRW_REGISTER_TYPE_UW));
> >     brw_set_src0(p, insn, dst);
> >     brw_set_memory_fence_message(p, insn, GEN7_SFID_DATAPORT_DATA_CACHE,
> >                                  commit_enable);
> >
>
> This seems wrong - it looks like you're doing this for messages with
> commit enable set, which do return things...
>
> ​Right. I've to check for commit_enable to use null or non-null destination
here. I'll send out a v2.
​


> Cc'ing Curro.
>
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