anv/pipeline: More aggressively optimize away color attachments

Instead of just looking at the number of color attachments, look at
which ones are actually used by the subpass.  This lets us potentially
throw away chunks of the fragment shader.  In DXVK, for example, all
subpasses have 8 attachments and most are VK_ATTACHMENT_UNUSED so this
is very helpful in that case.

Reviewed-by: Timothy Arceri <[email protected]>

1 files changed, 13 insertions, 5 deletions

diff --git a/src/intel/vulkan/anv_pipeline.c b/src/intel/vulkan/anv_pipeline.c
index 914e5132763..d795d77d9ba 100644
--- a/src/intel/vulkan/anv_pipeline.c
+++ b/src/intel/vulkan/anv_pipeline.c
@@ -339,7 +339,14 @@ populate_wm_prog_key(const struct anv_pipeline *pipeline,
    /* XXX Vulkan doesn't appear to specify */
    key->clamp_fragment_color = false;
 
-   key->nr_color_regions = pipeline->subpass->color_count;
+   assert(pipeline->subpass->color_count <= MAX_RTS);
+   for (uint32_t i = 0; i < pipeline->subpass->color_count; i++) {
+      if (pipeline->subpass->color_attachments[i].attachment !=
+          VK_ATTACHMENT_UNUSED)
+         key->color_outputs_valid |= (1 << i);
+   }
+
+   key->nr_color_regions = _mesa_bitcount(key->color_outputs_valid);
 
    key->replicate_alpha = key->nr_color_regions > 1 &&
                           info->pMultisampleState &&
@@ -904,8 +911,8 @@ anv_pipeline_compile_fs(struct anv_pipeline *pipeline,
             continue;
 
          const unsigned rt = var->data.location - FRAG_RESULT_DATA0;
-         /* Out-of-bounds */
-         if (rt >= key.nr_color_regions)
+         /* Unused or out-of-bounds */
+         if (rt >= MAX_RTS || !(key.color_outputs_valid & (1 << rt)))
             continue;
 
          const unsigned array_len =
@@ -936,8 +943,8 @@ anv_pipeline_compile_fs(struct anv_pipeline *pipeline,
             continue;
 
          const unsigned rt = var->data.location - FRAG_RESULT_DATA0;
-         if (rt >= key.nr_color_regions) {
-            /* Out-of-bounds, throw it away */
+         if (rt >= MAX_RTS || !(key.color_outputs_valid & (1 << rt))) {
+            /* Unused or out-of-bounds, throw it away */
             deleted_output = true;
             var->data.mode = nir_var_local;
             exec_node_remove(&var->node);
@@ -967,6 +974,7 @@ anv_pipeline_compile_fs(struct anv_pipeline *pipeline,
        * the key accordingly.
        */
       key.nr_color_regions = num_rts;
+      key.color_outputs_valid = (1 << num_rts) - 1;
 
       assert(num_rts <= max_rt);
       map.surface_to_descriptor -= num_rts;