[Mesa-dev] [PATCH] i965/fs: Strip trailing contant zeroes in sample messages

[Neil Roberts]

Matt Turner <mattst88 at gmail.com> writes:

>> +   foreach_block_and_inst(block, fs_inst, inst, cfg) {
>> +      if ((inst->opcode == SHADER_OPCODE_TEX ||
>> +           inst->opcode == SHADER_OPCODE_TXF) &&
>> +          !inst->shadow_compare) {
>> +         fs_inst *load_payload = (fs_inst *) inst->prev;
>> +
>> +         if (load_payload->is_head_sentinel() ||
>> +             load_payload->opcode != SHADER_OPCODE_LOAD_PAYLOAD)
>> +            continue;
>
> We can't guarantee that the load_payload isn't used by another texture
> later in the program, and since you need to change the texture
> operation's mlen, I think you need to check that the load_payload
> isn't used after this texture operation.
>
> To do that, (1) add an ip variable and initialize it to -1, (2) add
> ip++ as the first statement in the foreach_block_and_inst loop, (3)
> add some code to this check similar to in
> brw_fs_saturate_propagation.cpp using this->live_intervals.

Hrm, I'm not modifying the LOAD_PAYLOAD instruction, only the
SHADRE_OPCODE_TEX/TXF instruction. If there is a later instruction that
is using the LOAD_PAYLOAD, won't that end up making it's own dependency
on the MOV instructions so they won't get removed?

>> +   OPT(opt_zero_samples);
>
> I think you're probably right that this can be done after the
> optimization loop. I guess it's possible that we might trim a texture
> payload down and it'll then be the same as an existing payload and we
> can then CSE them. I'd be interested to see if putting it inside the
> optimization loop improves anything.

Hrm, it might be worth trying. However, as I mentioned above, I'm not
modifying the LOAD_PAYLOAD instruction so it probably won't hit the
example you mentioned.

Thanks for the review.

Regards,
- Neil