On 04/15/2015 04:28 PM, Kenneth Graunke wrote: > On Wednesday, April 15, 2015 02:47:01 PM Ian Romanick wrote: >> On 04/15/2015 12:41 PM, Kristian Høgsberg wrote: >>> The ir_tex opcode turns into a sample or sample_c message, which will try to >>> compute derivatives to determine the lod. This produces garbage for >>> non-fragment shaders where the sample coordinates don't correspond to >>> subspans. >>> >>> We fix this by rewriting the opcode from ir_tex to ir_txl and setting the >>> lod to 0. >> >> This seems logical, but... why the heck hasn't this been a problem >> before? Is this some weirdness of just BSW? Should we perhaps only do >> this on BSW? > > In the vec4 backend, we've always made ir_tex use the SAMPLE_LOD message > with lod set to 0.0 - so Gen4-7.5 have always done this workaround. > > When Kristian added SIMD8 VS support (Oct 2014, Gen8+), we started using > SAMPLE (by virtue of not changing the FS behavior). We honestly have no
Yes, that's the part the slipped my mind. In that case, FWIW, Reviewed-by: Ian Romanick <ian.d.roman...@intel.com> > idea why it appears to work on Broadwell - it sure seems like it ought > to be broken there. Maybe we've just been lucky. > > There's also a message header bit for "Force LOD to Zero", which the > docs say is mandatory if you're going to use the "SAMPLE" message in > SIMD4x2 stages (i.e. not fragment). We've wondered whether headerless > messages in non-fragment stages magically get that right. That could > make the issue less noticable... > > Using SAMPLE_LOD is easier than setting the message header bit, and > seems just as effective. I think we should do it on Broadwell too. > > Thanks for fixing this, Kristian! > > Cc: "10.5" <mesa-sta...@lists.freedesktop.org> > Reviewed-by: Kenneth Graunke <kenn...@whitecape.org> > >> >>> https://bugs.freedesktop.org/show_bug.cgi?id=89457 >> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89457 >> >> That allows the bin/bugzilla_mesa.sh script to find it for generating >> release notes. >> >>> Signed-off-by: Kristian Høgsberg <k...@bitplanet.net> >>> --- >>> src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 9 +++++++++ >>> 1 file changed, 9 insertions(+) >>> >>> diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp >>> b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp >>> index 0049b2d..4e99366 100644 >>> --- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp >>> +++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp >>> @@ -1839,6 +1839,15 @@ fs_visitor::emit_texture_gen7(ir_texture_opcode op, >>> fs_reg dst, >>> offset_value.file != BAD_FILE && offset_value.file != IMM; >>> bool coordinate_done = false; >>> >>> + /* The sampler can only meaningfully compute LOD for fragment shader >>> + * messages. For all other stages, we change the opcode to ir_txl and >>> + * hardcode the LOD to 0. >>> + */ >>> + if (stage != MESA_SHADER_FRAGMENT && op == ir_tex) { >>> + op = ir_txl; >>> + lod = fs_reg(0.0f); >>> + } >>> + >>> /* Set up the LOD info */ >>> switch (op) { >>> case ir_tex: >>> >> >> _______________________________________________ >> mesa-dev mailing list >> mesa-dev@lists.freedesktop.org >> http://lists.freedesktop.org/mailman/listinfo/mesa-dev >>
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