[Mesa-dev] [PATCH 04/11] i965/vec4: Use the actual channels used in pack_uniform_registers

[Jason Ekstrand]

On Fri, Oct 2, 2015 at 12:32 AM, Iago Toral <itoral at igalia.com> wrote:
> On Wed, 2015-09-30 at 18:41 -0700, Jason Ekstrand wrote:
>> Previously, pack_uniform_registers worked based on the size of the uniform
>> as given to us when we initially set up the uniforms.  However, we have to
>> walk through the uniforms and figure out liveness anyway, so we migh as
>> well record the number of channels used as we go.  This may also allow us
>> to pack things tighter in a few cases.
>> ---
>>  src/mesa/drivers/dri/i965/brw_vec4.cpp | 52 +++++++++++++++++++++++++---------
>>  1 file changed, 38 insertions(+), 14 deletions(-)
>>
>> diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
>> index 407698f..f0fa07e 100644
>> --- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
>> +++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
>> @@ -518,11 +518,11 @@ vec4_visitor::split_uniform_registers()
>>  void
>>  vec4_visitor::pack_uniform_registers()
>>  {
>> -   bool uniform_used[this->uniforms];
>> +   uint8_t chans_used[this->uniforms];
>>     int new_loc[this->uniforms];
>>     int new_chan[this->uniforms];
>>
>> -   memset(uniform_used, 0, sizeof(uniform_used));
>> +   memset(chans_used, 0, sizeof(chans_used));
>>     memset(new_loc, 0, sizeof(new_loc));
>>     memset(new_chan, 0, sizeof(new_chan));
>>
>> @@ -532,10 +532,36 @@ vec4_visitor::pack_uniform_registers()
>>      */
>>     foreach_block_and_inst(block, vec4_instruction, inst, cfg) {
>>        for (int i = 0 ; i < 3; i++) {
>> -      if (inst->src[i].file != UNIFORM)
>> -         continue;
>> +         if (inst->src[i].file != UNIFORM)
>> +            continue;
>
> The switch statement below should go before the loop.

Will do.

>> +         unsigned readmask;
>> +         switch (inst->opcode) {
>> +         case VEC4_OPCODE_PACK_BYTES:
>> +         case BRW_OPCODE_DP4:
>> +         case BRW_OPCODE_DPH:
>> +            readmask = 0xf;
>> +            break;
>> +         case BRW_OPCODE_DP3:
>> +            readmask = 0x7;
>> +            break;
>> +         case BRW_OPCODE_DP2:
>> +            readmask = 0x3;
>> +            break;
>
> I don't know if there are other opcodes that could also be
> special-handled like these, but if there are we are only missing the
> opportunity to do tighter packing for them (which we are not doing now
> anyway)...
>
> Reviewed-by: Iago Toral Quiroga <itoral at igalia.com>
>
>> +         default:
>> +            readmask = inst->dst.writemask;
>> +            break;
>> +         }
>> +
>> +         int reg = inst->src[i].reg;
>> +
>> +         for (int c = 0; c < 4; c++) {
>> +            if (!(readmask & (1 << c)))
>> +               continue;
>>
>> -      uniform_used[inst->src[i].reg] = true;
>> +            chans_used[reg] = MAX2(chans_used[reg],
>> +                                   BRW_GET_SWZ(inst->src[i].swizzle, c) + 1);
>> +         }
>>        }
>>     }
>>
>> @@ -546,17 +572,15 @@ vec4_visitor::pack_uniform_registers()
>>      */
>>     for (int src = 0; src < uniforms; src++) {
>>        assert(src < uniform_array_size);
>> -      int size = this->uniform_vector_size[src];
>> +      int size = chans_used[src];
>>
>> -      if (!uniform_used[src]) {
>> -      this->uniform_vector_size[src] = 0;
>> -      continue;
>> -      }
>> +      if (size == 0)
>> +         continue;
>>
>>        int dst;
>>        /* Find the lowest place we can slot this uniform in. */
>>        for (dst = 0; dst < src; dst++) {
>> -      if (this->uniform_vector_size[dst] + size <= 4)
>> +      if (chans_used[dst] + size <= 4)
>>           break;
>>        }
>>
>> @@ -565,7 +589,7 @@ vec4_visitor::pack_uniform_registers()
>>        new_chan[src] = 0;
>>        } else {
>>        new_loc[src] = dst;
>> -      new_chan[src] = this->uniform_vector_size[dst];
>> +      new_chan[src] = chans_used[dst];
>>
>>        /* Move the references to the data */
>>        for (int j = 0; j < size; j++) {
>> @@ -573,8 +597,8 @@ vec4_visitor::pack_uniform_registers()
>>              stage_prog_data->param[src * 4 + j];
>>        }
>>
>> -      this->uniform_vector_size[dst] += size;
>> -      this->uniform_vector_size[src] = 0;
>> +      chans_used[dst] += size;
>> +      chans_used[src] = 0;
>>        }
>>
>>        new_uniform_count = MAX2(new_uniform_count, dst + 1);
>
>