aco: add support for remapping color attachments

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27263>

src/amd/compiler/aco_instruction_selection.cpp

@@ -12689,8 +12689,14 @@ select_ps_epilog(Program* program, void* pinfo, ac_shader_config* config,
    } else {
       for (unsigned i = 0; i < MAX_DRAW_BUFFERS; i++) {
          struct aco_export_mrt* mrt = &mrts[mrt_num];
-         if (export_fs_mrt_color(&ctx, einfo, colors[i], i, mrt))
+         const uint8_t cb_idx = einfo->color_map[i];
+
+         if (cb_idx == 0xff || !einfo->colors[cb_idx].used)
+            continue;
+
+         if (export_fs_mrt_color(&ctx, einfo, colors[cb_idx], i, mrt)) {
             mrt->target += mrt_num++;
+         }
       }
    }
 

src/amd/compiler/aco_shader_info.h

@@ -47,6 +47,7 @@ struct aco_vs_prolog_info {
 
 struct aco_ps_epilog_info {
    struct ac_arg colors[MAX_DRAW_BUFFERS];
+   uint8_t color_map[MAX_DRAW_BUFFERS];
 
    uint32_t spi_shader_col_format;
 

src/amd/vulkan/radv_aco_shader_info.h

@@ -82,6 +82,8 @@ radv_aco_convert_ps_epilog_key(struct aco_ps_epilog_info *aco_info, const struct
    ASSIGN_FIELD(alpha_to_one);
 
    memcpy(aco_info->colors, radv_args->colors, sizeof(aco_info->colors));
+   for (uint32_t i = 0; i < MAX_RTS; i++)
+      aco_info->color_map[i] = i;
    aco_info->depth = radv_args->depth;
    aco_info->stencil = radv_args->stencil;
    aco_info->samplemask = radv_args->sample_mask;

src/gallium/drivers/radeonsi/si_shader_aco.c

@@ -323,6 +323,7 @@ si_aco_build_ps_epilog(struct aco_compiler_options *options,
       .skip_null_export = options->gfx_level >= GFX10 && !key->ps_epilog.uses_discard,
       .broadcast_last_cbuf = key->ps_epilog.states.last_cbuf,
       .alpha_func = key->ps_epilog.states.alpha_func,
+      .color_map = { 0, 1, 2, 3, 4, 5, 6, 7 },
    };
 
    struct si_shader_args args;