[Mesa-dev] [PATCH 2/3] i965: Set dirty state for brw_draw_upload.c when num_instances changes.

[Kenneth Graunke]

On 10/31/2012 06:13 PM, Eric Anholt wrote:
> Kenneth Graunke <kenneth at whitecape.org> writes:
>
>> On 10/31/2012 02:26 PM, Eric Anholt wrote:
>>> Otherwise, if we had a set of prims passed in with a num_instances varying
>>> between them, we wouldn't upload enough (or too much!) from user vertex
>>> arrays.
>>> ---
>>>    src/mesa/drivers/dri/i965/brw_draw.c |    5 ++++-
>>>    1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/src/mesa/drivers/dri/i965/brw_draw.c b/src/mesa/drivers/dri/i965/brw_draw.c
>>> index 1cfba29..22d18f9 100644
>>> --- a/src/mesa/drivers/dri/i965/brw_draw.c
>>> +++ b/src/mesa/drivers/dri/i965/brw_draw.c
>>> @@ -474,7 +474,10 @@ static bool brw_try_draw_prims( struct gl_context *ctx,
>>>          intel_batchbuffer_require_space(intel, estimated_max_prim_size, false);
>>>          intel_batchbuffer_save_state(intel);
>>>
>>> -      brw->num_instances = prim->num_instances;
>>> +      if (brw->num_instances != prim->num_instances) {
>>> +         brw->num_instances = prim->num_instances;
>>> +         brw->state.dirty.brw |= BRW_NEW_VERTICES;
>>> +      }
>>>          if (intel->gen < 6)
>>>    	 brw_set_prim(brw, &prim[i]);
>>>          else
>>
>> I agree that BRW_NEW_VERTICES needs to be changed when num_instances
>> changes.  However, it's already unconditionally flagged above:
>>
>>      brw->vb.min_index = min_index;
>>      brw->vb.max_index = max_index;
>>      brw->state.dirty.brw |= BRW_NEW_VERTICES;
>>
>> So I don't think you'll be able to observe any problems.  That said, I
>> approve of this change anyway, because it's self-documentating and
>> guards against potential problems.
>
> That's outside the per-prim loop, though.

Oh dear.  Yes, brw_upload_state() is inside the loop, so it clears the 
BRW_NEW_VERTICES flag.  So your change is necessary.  My mistake.