radeonsi: eliminate VS outputs that aren't used by PS at runtime

A past commit added the ability to compile "optimized" shader variants
asynchronously (not stalling the app).

This commit builds upon that and adds what is basically a runtime shader
linker. If a VS output isn't used by the currently-bound PS, a new VS
compilation is started without that output. The new shader variant
is used when it's ready.

All apps using separate shader objects I've seen had unused VS outputs.

Eliminating unused/useless VS outputs also eliminates the corresponding
vertex attribute loads.

Tested-by: Edmondo Tommasina <[email protected]>
Reviewed-by: Nicolai Hähnle <[email protected]>

1 files changed, 25 insertions, 1 deletions

diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
index 2b432244331..abe30e54a58 100644
--- a/src/gallium/drivers/radeonsi/si_shader.c
+++ b/src/gallium/drivers/radeonsi/si_shader.c
@@ -2281,6 +2281,26 @@ static void si_llvm_export_vs(struct lp_build_tgsi_context *bld_base,
 	for (i = 0; i < noutput; i++) {
 		semantic_name = outputs[i].name;
 		semantic_index = outputs[i].sid;
+		bool export_param = true;
+
+		switch (semantic_name) {
+		case TGSI_SEMANTIC_POSITION: /* ignore these */
+		case TGSI_SEMANTIC_PSIZE:
+		case TGSI_SEMANTIC_CLIPVERTEX:
+		case TGSI_SEMANTIC_EDGEFLAG:
+			break;
+		case TGSI_SEMANTIC_GENERIC:
+		case TGSI_SEMANTIC_CLIPDIST:
+			if (shader->key.opt.hw_vs.kill_outputs &
+			    (1ull << si_shader_io_get_unique_index(semantic_name, semantic_index)))
+				export_param = false;
+			break;
+		default:
+			if (shader->key.opt.hw_vs.kill_outputs2 &
+			    (1u << si_shader_io_get_unique_index2(semantic_name, semantic_index)))
+				export_param = false;
+			break;
+		}
 
 handle_semantic:
 		/* Select the correct target */
@@ -2304,6 +2324,8 @@ handle_semantic:
 			break;
 		case TGSI_SEMANTIC_COLOR:
 		case TGSI_SEMANTIC_BCOLOR:
+			if (!export_param)
+				continue;
 			target = V_008DFC_SQ_EXP_PARAM + param_count;
 			assert(i < ARRAY_SIZE(shader->info.vs_output_param_offset));
 			shader->info.vs_output_param_offset[i] = param_count;
@@ -2325,6 +2347,8 @@ handle_semantic:
 		case TGSI_SEMANTIC_FOG:
 		case TGSI_SEMANTIC_TEXCOORD:
 		case TGSI_SEMANTIC_GENERIC:
+			if (!export_param)
+				continue;
 			target = V_008DFC_SQ_EXP_PARAM + param_count;
 			assert(i < ARRAY_SIZE(shader->info.vs_output_param_offset));
 			shader->info.vs_output_param_offset[i] = param_count;
@@ -7083,7 +7107,7 @@ int si_compile_tgsi_shader(struct si_screen *sscreen,
 	si_init_shader_ctx(&ctx, sscreen, shader, tm);
 	ctx.separate_prolog = !is_monolithic;
 
-	memset(shader->info.vs_output_param_offset, 0xff,
+	memset(shader->info.vs_output_param_offset, EXP_PARAM_UNDEFINED,
 	       sizeof(shader->info.vs_output_param_offset));
 
 	shader->info.uses_instanceid = sel->info.uses_instanceid;