Similar to const buffers. The driver must not emit any tes-related state if tes
is disabled, since the hw slots are all shared by VS, therefore it would
overwrite them (the mesa state tracker might not do this, but it would be
perfectly legal to do so).
Nevertheless I think the dirty state tracking logic in the driver is
fundamentally flawed when tes is disabled/enabled, since it looks to me like
the VS (and TES) state would not get reemitted to the correct slots (if it's
not dirty anyway). Unless I'm missing something...
Theoretically, the overwrite problem could be solved by using non-overlapping
resource slots for TES and VS (since we're not even close to using half the
resource slots), but it wouldn't work for constant buffers nor samplers, and
for VS would still need to propagate changes to both LS and VS, so probably
not a useful idea.
Unfortunately there's zero coverage of this with piglit, since all tessellation
shader tests are just shader_runner tests, which are unsuitable for testing
any kind of state dependency tracking issues (so I can't even quickly hack
something up to proove it and fix it...).
TCS otoh is just fine - like GS it has its own hw slots.

Tested-by: Konstantin Kharlamov <hi-angel@yandex.ru>
Reviewed-by: Dave Airlie <airlied@redhat.com>