On 24 May 2013 12:23, Ian Romanick <i...@freedesktop.org> wrote:
> On 05/23/2013 03:46 PM, Kenneth Graunke wrote:
>
>> According to the documentation: "The Cut Index is compared to the
>> fetched (and possibly-sign-extended) vertex index, and if these values
>>
>
> Which documentation is this? The only types that are valid for index
> buffers are unsigned, so what does "possibly-sign-extended" even mean?
>
>
This is from the Haswell bspec. I have never understood what they mean by
"possibly-sign-extended" either.
>
> are equal, the current primitive topology is terminated. Note that,
>> for index buffers <32bpp, it is possible to set the Cut Index to a
>> (large) value that will never match a sign-extended vertex index."
>>
>> This suggests that we should not set the value to 0xFFFFFFFF for
>> unsigned byte or short index buffers, but rather 0xFF or 0xFFFF.
>>
>
> For GL_PRIMITIVE_RESTART_FIXED_**INDEX (ES and desktop 4.something),
> where the setting of the restart value is out of application control, this
> is absolutely correct. The OpenGL 4.3 spec says:
>
> "Primitive restart can also be enabled or disabled with a target
> of PRIMITIVE_RESTART_FIXED_INDEX. In this case, the primitive
> restart index is equal to 2^N - 1, where N is 8, 16 or 32 if the
> type is UNSIGNED_BYTE, UNSIGNED_SHORT, or UNSIGNED_INT,
> respectively, and the index value specified by
> PrimitiveRestartIndex is ignored."
>
> For GL_PRIMITIVE_RESTART, I'm not so sure. I couldn't find anything
> conclusive any of the specs. The only thing I found was a hint in the
> NV_primitive_restart extension spec:
>
> * What should the default primitive restart index be?
>
> RESOLVED: Zero. It's tough to pick another number that is
> meaningful for all three element data types. In practice, apps
> are likely to set it to 0xFFFF or 0xFFFFFFFF.
>
> You can infer from this that applications are expected to set 0xFFFF for
> GL_UNSIGNED_SHORT and 0xFFFFFFFF for GL_UNSIGNED_LONG. Experimentation is
> the only way to know for sure. :(
>
>
> Fixes sporadic failures in the ES 3 instanced_arrays_primitive_**restart
>> conformance test when run in combination with other tests. No Piglit
>> regressions.
>>
>> Cc: Ian Romanick <i...@freedesktop.org
>> Cc: Paul Berry <stereotype...@gmail.com>
>> Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
>> ---
>> src/mesa/drivers/dri/i965/brw_**primitive_restart.c | 27
>> ++++++++++++++++-------
>> 1 file changed, 19 insertions(+), 8 deletions(-)
>>
>> diff --git a/src/mesa/drivers/dri/i965/**brw_primitive_restart.c
>> b/src/mesa/drivers/dri/i965/**brw_primitive_restart.c
>> index f824915..cf4a1ea 100644
>> --- a/src/mesa/drivers/dri/i965/**brw_primitive_restart.c
>> +++ b/src/mesa/drivers/dri/i965/**brw_primitive_restart.c
>> @@ -183,19 +183,30 @@ haswell_upload_cut_index(**struct brw_context *brw)
>> if (!intel->is_haswell)
>> return;
>>
>> - const unsigned cut_index_setting =
>> - ctx->Array._PrimitiveRestart ? HSW_CUT_INDEX_ENABLE : 0;
>> -
>> - BEGIN_BATCH(2);
>> - OUT_BATCH(_3DSTATE_VF << 16 | cut_index_setting | (2 - 2));
>> - OUT_BATCH(ctx->Array._**RestartIndex);
>> - ADVANCE_BATCH();
>> + if (ctx->Array._PrimitiveRestart) {
>> + int cut_index = ctx->Array._RestartIndex;
>> +
>> + if (brw->ib.type == GL_UNSIGNED_BYTE)
>> + cut_index &= 0xff;
>> + else if (brw->ib.type == GL_UNSIGNED_SHORT)
>> + cut_index &= 0xffff;
>> +
>> + BEGIN_BATCH(2);
>> + OUT_BATCH(_3DSTATE_VF << 16 | HSW_CUT_INDEX_ENABLE | (2 - 2));
>> + OUT_BATCH(cut_index);
>> + ADVANCE_BATCH();
>> + } else {
>> + BEGIN_BATCH(2);
>> + OUT_BATCH(_3DSTATE_VF << 16 | (2 - 2));
>> + OUT_BATCH(0);
>> + ADVANCE_BATCH();
>> + }
>> }
>>
>> const struct brw_tracked_state haswell_cut_index = {
>> .dirty = {
>> .mesa = _NEW_TRANSFORM,
>> - .brw = 0,
>> + .brw = BRW_NEW_INDEX_BUFFER,
>> .cache = 0,
>> },
>> .emit = haswell_upload_cut_index,
>>
>>
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