[Mesa-dev] [PATCH 1/4] radv: move emitting VGT_GS_MODE into the HW VS path

[Samuel Pitoiset]

It's useless for NGG anyways.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
---
 src/amd/vulkan/radv_pipeline.c | 43 ++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 10 deletions(-)

diff --git a/src/amd/vulkan/radv_pipeline.c b/src/amd/vulkan/radv_pipeline.c
index fdeb31c453e..686fd371f0f 100644
--- a/src/amd/vulkan/radv_pipeline.c
+++ b/src/amd/vulkan/radv_pipeline.c
@@ -3272,27 +3272,18 @@ radv_pipeline_generate_vgt_gs_mode(struct radeon_cmdbuf *ctx_cs,
 		pipeline->shaders[MESA_SHADER_TESS_EVAL] :
 		pipeline->shaders[MESA_SHADER_VERTEX];
 	unsigned vgt_primitiveid_en = 0;
-	uint32_t vgt_gs_mode = 0;
 
-	if (radv_pipeline_has_gs(pipeline)) {
-		const struct radv_shader_variant *gs =
-			pipeline->shaders[MESA_SHADER_GEOMETRY];
-
-		vgt_gs_mode = ac_vgt_gs_mode(gs->info.gs.vertices_out,
-		                             pipeline->device->physical_device->rad_info.chip_class);
-	} else if (radv_pipeline_has_ngg(pipeline)) {
+	if (radv_pipeline_has_ngg(pipeline)) {
 		bool enable_prim_id =
 			outinfo->export_prim_id || vs->info.info.uses_prim_id;
 
 		vgt_primitiveid_en |= S_028A84_PRIMITIVEID_EN(enable_prim_id) |
 				      S_028A84_NGG_DISABLE_PROVOK_REUSE(enable_prim_id);
 	} else if (outinfo->export_prim_id || vs->info.info.uses_prim_id) {
-		vgt_gs_mode = S_028A40_MODE(V_028A40_GS_SCENARIO_A);
 		vgt_primitiveid_en |= S_028A84_PRIMITIVEID_EN(1);
 	}
 
 	radeon_set_context_reg(ctx_cs, R_028A84_VGT_PRIMITIVEID_EN, vgt_primitiveid_en);
-	radeon_set_context_reg(ctx_cs, R_028A40_VGT_GS_MODE, vgt_gs_mode);
 }
 
 static void
@@ -3370,6 +3361,38 @@ radv_pipeline_generate_hw_vs(struct radeon_cmdbuf *ctx_cs,
 	                       cull_dist_mask << 8 |
 	                       clip_dist_mask);
 
+	/* We always write VGT_GS_MODE in the VS state, because every switch
+	 * between different shader pipelines involving a different GS or no GS
+	 * at all involves a switch of the VS (different GS use different copy
+	 * shaders). On the other hand, when the API switches from a GS to no
+	 * GS and then back to the same GS used originally, the GS state is not
+	 * sent again.
+	 */
+	unsigned vgt_gs_mode;
+	if (!radv_pipeline_has_gs(pipeline)) {
+		const struct radv_vs_output_info *outinfo =
+			get_vs_output_info(pipeline);
+		const struct radv_shader_variant *vs =
+			pipeline->shaders[MESA_SHADER_TESS_EVAL] ?
+			pipeline->shaders[MESA_SHADER_TESS_EVAL] :
+			pipeline->shaders[MESA_SHADER_VERTEX];
+		unsigned mode = V_028A40_GS_OFF;
+
+		/* PrimID needs GS scenario A. */
+		if (outinfo->export_prim_id || vs->info.info.uses_prim_id)
+			mode = V_028A40_GS_SCENARIO_A;
+
+		vgt_gs_mode = S_028A40_MODE(mode);
+	} else {
+		const struct radv_shader_variant *gs =
+			pipeline->shaders[MESA_SHADER_GEOMETRY];
+
+		vgt_gs_mode = ac_vgt_gs_mode(gs->info.gs.vertices_out,
+		                             pipeline->device->physical_device->rad_info.chip_class);
+	}
+
+	radeon_set_context_reg(ctx_cs, R_028A40_VGT_GS_MODE, vgt_gs_mode);
+
 	if (pipeline->device->physical_device->rad_info.chip_class <= GFX8)
 		radeon_set_context_reg(ctx_cs, R_028AB4_VGT_REUSE_OFF,
 		                       outinfo->writes_viewport_index);
-- 
2.22.0