[Mesa-dev] [PATCH] i965/blorp: Use LRP instruction to do manual blending.

[Paul Berry]

On 5 March 2013 15:56, Matt Turner <mattst88 at gmail.com> wrote:

> Replaces (samples - 1) ADDs and a MUL with (samples - 1) LRPs.
> ---
>  src/mesa/drivers/dri/i965/brw_blorp_blit.cpp |   31
> +++++++++++--------------
>  1 files changed, 14 insertions(+), 17 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
> b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
> index 37524ad..4d1ba90 100644
> --- a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
> @@ -1376,12 +1376,11 @@ brw_blorp_blit_program::manual_blend(unsigned
> num_samples)
>      * For integer formats, we replace the add operations with average
>      * operations and skip the final division.
>      */
> -   typedef struct brw_instruction *(*brw_op2_ptr)(struct brw_compile *,
> -                                                  struct brw_reg,
> -                                                  struct brw_reg,
> -                                                  struct brw_reg);
> -   brw_op2_ptr combine_op =
> -      key->texture_data_type == BRW_REGISTER_TYPE_F ? brw_ADD : brw_AVG;
> +   struct brw_reg zero_point_five;
> +   if (key->texture_data_type == BRW_REGISTER_TYPE_F) {
> +      brw_MOV(&func, zero_point_five, brw_imm_f(0.5f));
> +   }
> +
>

It looks like you're not initializing the struct zero_point_five.  You need
to allocate a register in brw_blorp_blit_program::alloc_regs() and then
store it in this.

Other than that the patch looks good.


>     unsigned stack_depth = 0;
>     for (unsigned i = 0; i < num_samples; ++i) {
>        assert(stack_depth == _mesa_bitcount(i)); /* Loop invariant */
> @@ -1423,9 +1422,17 @@ brw_blorp_blit_program::manual_blend(unsigned
> num_samples)
>
>           /* TODO: should use a smaller loop bound for non_RGBA formats */
>           for (int k = 0; k < 4; ++k) {
> -            combine_op(&func, offset(texture_data[stack_depth - 1], 2*k),
> +            if (key->texture_data_type == BRW_REGISTER_TYPE_F) {
> +               /* LRP operands are (a, y, x). */
> +               brw_LRP(&func, offset(texture_data[stack_depth - 1], 2*k),
> +                       zero_point_five,
> +                       offset(vec8(texture_data[stack_depth]), 2*k),
> +                       offset(vec8(texture_data[stack_depth - 1]), 2*k));
> +            } else {
> +               brw_AVG(&func, offset(texture_data[stack_depth - 1], 2*k),
>                         offset(vec8(texture_data[stack_depth - 1]), 2*k),
>                         offset(vec8(texture_data[stack_depth]), 2*k));
> +            }
>           }
>        }
>     }
> @@ -1433,16 +1440,6 @@ brw_blorp_blit_program::manual_blend(unsigned
> num_samples)
>     /* We should have just 1 sample on the stack now. */
>     assert(stack_depth == 1);
>
> -   if (key->texture_data_type == BRW_REGISTER_TYPE_F) {
> -      /* Scale the result down by a factor of num_samples */
> -      /* TODO: should use a smaller loop bound for non-RGBA formats */
> -      for (int j = 0; j < 4; ++j) {
> -         brw_MUL(&func, offset(texture_data[0], 2*j),
> -                 offset(vec8(texture_data[0]), 2*j),
> -                 brw_imm_f(1.0/num_samples));
> -      }
> -   }
> -
>     if (key->tex_layout == INTEL_MSAA_LAYOUT_CMS)
>        brw_ENDIF(&func);
>  }
> --
> 1.7.8.6
>
>
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