src/broadcom/compiler/v3d_nir_lower_blend.c

/*
 * Copyright 2025 Raspberry Pi Ltd
 * SPDX-License-Identifier: MIT
 */

#include "util/format/u_format.h"
#include "compiler/nir/nir_builder.h"
#include "compiler/nir/nir_format_convert.h"
#include "compiler/nir/nir_lower_blend.h"
#include "v3d_compiler.h"

bool
v3d_nir_lower_blend(nir_shader *nir, struct v3d_compile *c)
{
   if (!c->fs_key->software_blend)
      return false;

   nir_lower_blend_options options = {
      /* logic op is handled elsewhere in the compiler */
      .logicop_enable = false,
      .scalar_blend_const = true,
   };

   bool lower_blend = false;
   for (unsigned rt = 0; rt < V3D_MAX_DRAW_BUFFERS; rt++) {
      if (!(c->fs_key->cbufs & (1 << rt))) {
         static const nir_lower_blend_channel replace = {
            .func = PIPE_BLEND_ADD,
            .src_factor = PIPE_BLENDFACTOR_ONE,
            .dst_factor = PIPE_BLENDFACTOR_ZERO,
         };

         options.rt[rt].rgb = replace;
         options.rt[rt].alpha = replace;
         continue;
      }

      lower_blend = true;

      /* Colour write mask is handled by the hardware. */
      options.rt[rt].colormask = 0xf;

      options.format[rt] = c->fs_key->color_fmt[rt].format;

      options.rt[rt].rgb.func = c->fs_key->blend[rt].rgb_func;
      options.rt[rt].alpha.func = c->fs_key->blend[rt].alpha_func;
      options.rt[rt].rgb.dst_factor = c->fs_key->blend[rt].rgb_dst_factor;
      options.rt[rt].alpha.dst_factor = c->fs_key->blend[rt].alpha_dst_factor;
      options.rt[rt].rgb.src_factor = c->fs_key->blend[rt].rgb_src_factor;
      options.rt[rt].alpha.src_factor = c->fs_key->blend[rt].alpha_src_factor;
   }

   return lower_blend && nir_lower_blend(nir, &options);
}