[Nouveau] Fermi+ shader header docs

[Ilia Mirkin]

Hi,

As I'm looking to add some support to nouveau for features like atomic
counters and images, I'm running into some confusion about what the
first word of the shader header means. Here is the definition as we
have it today:

https://github.com/envytools/envytools/blob/master/rnndb/graph/gf100_shaders.xml

VS/HS/DS/GS:
<reg32 offset="0" name="0">
  <bitfield high="7" low="0" name="MAGIC">
    <value value="0x61" name="VP_MAGIC"/>
  </bitfield>
  <bitfield high="12" low="10" name="KIND" type="GF100_SHADER_KIND"/>
  <bitfield pos="16" name="GMEM_ENABLE"/>
  <bitfield pos="17" name="UNK17"/><!-- default 1 -->
  <bitfield pos="26" name="LMEM_ENABLE"/>
  <bitfield pos="27" name="FP64_ENABLE"/>
</reg32>

FS:
<reg32 offset="0" name="0">
  <bitfield high="7" low="0" name="MAGIC">
    <value value="0x62" name="FP_MAGIC"/>
  </bitfield>
  <bitfield high="12" low="10" name="KIND" type="GF100_SHADER_KIND"/>
  <bitfield pos="14" name="MULTIPLE_COLOR_OUTPUTS" type="boolean"/>
  <bitfield pos="15" name="USES_KIL" type="boolean"/>
  <bitfield pos="16" name="GMEM_ENABLE"/>
  <bitfield pos="17" name="UNK17"/><!-- default 1 -->
  <bitfield pos="26" name="LMEM_ENABLE"/>
  <bitfield pos="27" name="FP64_ENABLE"/>
</reg32>

However I know that these are somewhat wrong. I've seen shaders that
use gmem accesses (i.e. mov r0, [r0]) that just have the LMEM enable
bit set (and they use no lmem). And I've seen additional bits set, esp
relating to images, but I haven't spent enough time looking at all the
variations to make sense of it yet. For example, I think that Fermi
and Kepler+ have different meanings for some of the bits.

I was hoping you could just release the docs for the shader headers,
or at least the first word of the shader header.

I know that it can take some time to get it all approved, but if you
think this is *not* information you can release, please let me know
soon so that I don't lose a month waiting.

Thanks,

  -ilia