[Mesa-dev] [PATCH 2/2] radeonsi: use re-Z

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

This can increase perf for shaders that kill pixels (kill, alpha-test,
alpha-to-coverage).
---
 src/gallium/drivers/radeonsi/si_shader.h        |  1 +
 src/gallium/drivers/radeonsi/si_state.c         |  6 +++---
 src/gallium/drivers/radeonsi/si_state_shaders.c | 16 +++++++++++++---
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/src/gallium/drivers/radeonsi/si_shader.h b/src/gallium/drivers/radeonsi/si_shader.h
index ff5c24d..637d264 100644
--- a/src/gallium/drivers/radeonsi/si_shader.h
+++ b/src/gallium/drivers/radeonsi/si_shader.h
@@ -365,6 +365,7 @@ struct si_shader {
 	struct r600_resource		*scratch_bo;
 	union si_shader_key		key;
 	bool				is_binary_shared;
+	unsigned			z_order;
 
 	/* The following data is all that's needed for binary shaders. */
 	struct radeon_shader_binary	binary;
diff --git a/src/gallium/drivers/radeonsi/si_state.c b/src/gallium/drivers/radeonsi/si_state.c
index 2dfdbeb..b23b17a 100644
--- a/src/gallium/drivers/radeonsi/si_state.c
+++ b/src/gallium/drivers/radeonsi/si_state.c
@@ -1339,10 +1339,10 @@ static void si_emit_db_render_state(struct si_context *sctx, struct r600_atom *s
 		            sctx->ps_db_shader_control;
 
 	/* Bug workaround for smoothing (overrasterization) on SI. */
-	if (sctx->b.chip_class == SI && sctx->smoothing_enabled)
+	if (sctx->b.chip_class == SI && sctx->smoothing_enabled) {
+		db_shader_control &= C_02880C_Z_ORDER;
 		db_shader_control |= S_02880C_Z_ORDER(V_02880C_LATE_Z);
-	else
-		db_shader_control |= S_02880C_Z_ORDER(V_02880C_EARLY_Z_THEN_LATE_Z);
+	}
 
 	/* Disable the gl_SampleMask fragment shader output if MSAA is disabled. */
 	if (sctx->framebuffer.nr_samples <= 1 || (rs && !rs->multisample_enable))
diff --git a/src/gallium/drivers/radeonsi/si_state_shaders.c b/src/gallium/drivers/radeonsi/si_state_shaders.c
index a6753a7..c220185 100644
--- a/src/gallium/drivers/radeonsi/si_state_shaders.c
+++ b/src/gallium/drivers/radeonsi/si_state_shaders.c
@@ -789,6 +789,13 @@ static void si_shader_ps(struct si_shader *shader)
 		       S_00B02C_EXTRA_LDS_SIZE(shader->config.lds_size) |
 		       S_00B02C_USER_SGPR(num_user_sgprs) |
 		       S_00B32C_SCRATCH_EN(shader->config.scratch_bytes_per_wave > 0));
+
+	/* Prefer RE_Z if the shader is complex enough. */
+	if (info->num_memory_instructions >= 2 ||
+	    shader->binary.code_size > 100*4)
+		shader->z_order = V_02880C_EARLY_Z_THEN_RE_Z;
+	else
+		shader->z_order = V_02880C_EARLY_Z_THEN_LATE_Z;
 }
 
 static void si_shader_init_pm4_state(struct si_shader *shader)
@@ -1985,15 +1992,18 @@ bool si_update_shaders(struct si_context *sctx)
 	si_update_vgt_shader_config(sctx);
 
 	if (sctx->ps_shader.cso) {
-		unsigned db_shader_control =
-			sctx->ps_shader.cso->db_shader_control |
-			S_02880C_KILL_ENABLE(si_get_alpha_test_func(sctx) != PIPE_FUNC_ALWAYS);
+		unsigned db_shader_control;
 
 		r = si_shader_select(ctx, &sctx->ps_shader);
 		if (r)
 			return false;
 		si_pm4_bind_state(sctx, ps, sctx->ps_shader.current->pm4);
 
+		db_shader_control =
+			sctx->ps_shader.cso->db_shader_control |
+			S_02880C_KILL_ENABLE(si_get_alpha_test_func(sctx) != PIPE_FUNC_ALWAYS) |
+			S_02880C_Z_ORDER(sctx->ps_shader.current->z_order);
+
 		if (si_pm4_state_changed(sctx, ps) || si_pm4_state_changed(sctx, vs) ||
 		    sctx->sprite_coord_enable != rs->sprite_coord_enable ||
 		    sctx->flatshade != rs->flatshade) {
-- 
2.5.0