[Mesa-dev] [PATCH 22/20] radeonsi: disable early Z if the fragment shader writes to memory

[Nicolai Hähnle]

From: Nicolai Hähnle <nicolai.haehnle at amd.com>

Empirically, both the EXEC_ON_* flags and LATE_Z are necessary.
---
 src/gallium/drivers/radeonsi/si_state_shaders.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/gallium/drivers/radeonsi/si_state_shaders.c b/src/gallium/drivers/radeonsi/si_state_shaders.c
index 5fe1f79..7251092 100644
--- a/src/gallium/drivers/radeonsi/si_state_shaders.c
+++ b/src/gallium/drivers/radeonsi/si_state_shaders.c
@@ -794,9 +794,15 @@ static void si_shader_ps(struct si_shader *shader)
 	 * - the shader uses at least 2 VMEM instructions, or
 	 * - the code size is at least 50 2-dword instructions or 100 1-dword
 	 *   instructions.
+	 *
+	 * Shaders with side effects that must execute independently of the
+	 * depth test require LATE_Z.
 	 */
-	if (info->num_memory_instructions >= 2 ||
-	    shader->binary.code_size > 100*4)
+	if (info->writes_memory &&
+	    !info->properties[TGSI_PROPERTY_FS_EARLY_DEPTH_STENCIL])
+		shader->z_order = V_02880C_LATE_Z;
+	else 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;
@@ -1157,6 +1163,10 @@ static void *si_create_shader_selector(struct pipe_context *ctx,
 	if (sel->info.properties[TGSI_PROPERTY_FS_EARLY_DEPTH_STENCIL])
 		sel->db_shader_control |= S_02880C_DEPTH_BEFORE_SHADER(1);
 
+	if (sel->info.writes_memory)
+		sel->db_shader_control |= S_02880C_EXEC_ON_HIER_FAIL(1) |
+					  S_02880C_EXEC_ON_NOOP(1);
+
 	/* Compile the main shader part for use with a prolog and/or epilog. */
 	if (sel->type != PIPE_SHADER_GEOMETRY &&
 	    !sscreen->use_monolithic_shaders) {
-- 
2.5.0