On Jan 14, 2016 9:30 PM, "Jordan Justen" <<a href="mailto:jordan.l.justen@intel.com">jordan.l.justen@intel.com</a>> wrote: > > On 2016-01-14 20:43:17, Jason Ekstrand wrote: > > --- > > src/mesa/drivers/dri/i965/brw_fs_generator.cpp | 16 ++++++++++++++++ > > 1 file changed, 16 insertions(+) > > > > diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp > > index eebb485..70ca7cd 100644 > > --- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp > > +++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp > > @@ -914,6 +914,22 @@ fs_generator::generate_tex(fs_inst *inst, struct brw_reg dst, struct brw_reg src > > /* Set the offset bits in DWord 2. */ > > brw_MOV(p, get_element_ud(header_reg, 2), > > brw_imm_ud(inst->offset)); > > + } else if (stage != MESA_SHADER_VERTEX && > > + stage != MESA_SHADER_FRAGMENT) { > > + /* In the vertex and fragment stages, the hardware is nice to us > > + * and leaves g0.2 zerod out for us so we can use it for headers. > > + * However, in compute, geometry, and tessellation stages, the > > + * hardware is not so nice. In particular, for compute shaders on > > + * BDW, the hardware places some debug bits in 23:15. As it > > + * happens, bit 15 is the alpha channel mask. This means that if > > + * you use a texturing instruction with a header in a compute > > + * shader, you may randomly get the alpha channel randomly > > + * disabled. Since channel masks affect the return length of the > > + * sampler message, this can lead the GPU to expect a different > > + * mlen to the one you specified in the shader (probably 4 or 8) > > + * and this, in turn, hangs your GPU. > > + */ > > This explanation is great, but my personal opinion is that it is > better for the commit message than the comment. For a comment, what > about something more terse, like: That's fair. I sometimes get a bit long-winded and ranty in my comments. > /* The vertex and fragment stages have g0.2 set to 0, so > * header0.2 is 0 when g0 is copied. Other stages may not, so we > * must set it to 0 to avoid setting undesirable bits in the > * message. > */ I'll just copy+paste that in. > For the series: Reviewed-by: Jordan Justen <<a href="mailto:jordan.l.justen@intel.com">jordan.l.justen@intel.com</a>> Thanks! > > + brw_MOV(p, get_element_ud(header_reg, 2), brw_imm_ud(0)); > > } > > > > brw_adjust_sampler_state_pointer(p, header_reg, sampler_index); > > -- > > 2.5.0.400.gff86faf > > > > _______________________________________________ > > mesa-dev mailing list > > <a href="mailto:mesa-dev@lists.freedesktop.org">mesa-dev@lists.freedesktop.org</a> > > <a href="http://lists.freedesktop.org/mailman/listinfo/mesa-dev">http://lists.freedesktop.org/mailman/listinfo/mesa-dev</a>