Anuj Phogat <anuj.pho...@gmail.com> writes: > On Wed, Feb 7, 2018 at 11:14 AM, Kenneth Graunke <kenn...@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.pho...@gmail.com> >> > Cc: mesa-sta...@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. > >
You can also just drop the patch, unless you want to change the front-end in addition to stop allocating a destination for memory fences on HSW-SKL in order to save a small amount of register pressure? > >> Cc'ing Curro. >>
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