<div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small"> </div><div class="gmail_extra"> <div class="gmail_quote">On Wed, Feb 7, 2018 at 12:24 PM, Francisco Jerez <<a href="mailto:currojerez@riseup.net" target="_blank">currojerez@riseup.net</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="HOEnZb"><div class="h5">Anuj Phogat <<a href="mailto:anuj.phogat@gmail.com">anuj.phogat@gmail.com</a>> writes: > On Wed, Feb 7, 2018 at 11:55 AM, Francisco Jerez <<a href="mailto:currojerez@riseup.net">currojerez@riseup.net</a>> > wrote: > >> Anuj Phogat <<a href="mailto:anuj.phogat@gmail.com">anuj.phogat@gmail.com</a>> writes: >> >> > On Wed, Feb 7, 2018 at 11:14 AM, Kenneth Graunke <<a href="mailto:kenneth@whitecape.org">kenneth@whitecape.org</a>> >> > 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 <<a href="mailto:anuj.phogat@gmail.com">anuj.phogat@gmail.com</a>> >> >> > Cc: <a href="mailto:mesa-stable@lists.freedesktop.org">mesa-stable@lists.freedesktop.org</a> >> >> > --- >> >> > 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? >> > It also fixes a fulsim error other than reducing register pressure. </div></div>On what platform? </blockquote><div><div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small;display:inline">I noticed this on Icelake. But, I'm sure it exists on CNL as well.</div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> > I'll look in to how to stop allocating dst register for memory fences > and send out a v2. Thanks for the suggestion. > In that case I think it would be nice to avoid duplicating the logic used to decide whether to enable the commit bit or not. You can allocate the register conditionally in the visitor (providing a null register on HSW-SKL), and have brw_memory_fence() enable the commit bit if and only if dst is not null, that way we have the guarantee that the back-end and front-end are kept in sync. <div class="gmail_default" style="font-family:verdana,sans-serif;font-size:small;display:inline">sounds good to me.</div> </blockquote><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> > > >> >> > >> >> Cc'ing Curro. >> >> >> </blockquote></div> </div></div>