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

[Iago Toral]

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.

> +         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);