[Mesa-dev] [PATCH 1/2] radeonsi: disable ReZ

[Marek Olšák]

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

This is a serious performance fix. Discovered by luck.

Cc: 12.0 <mesa-stable at lists.freedesktop.org>
---
 src/gallium/drivers/radeonsi/si_state_shaders.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/gallium/drivers/radeonsi/si_state_shaders.c b/src/gallium/drivers/radeonsi/si_state_shaders.c
index c41c519..be5c659 100644
--- a/src/gallium/drivers/radeonsi/si_state_shaders.c
+++ b/src/gallium/drivers/radeonsi/si_state_shaders.c
@@ -801,34 +801,31 @@ static void si_shader_ps(struct si_shader *shader)
 	si_pm4_set_reg(pm4, R_00B028_SPI_SHADER_PGM_RSRC1_PS,
 		       S_00B028_VGPRS((shader->config.num_vgprs - 1) / 4) |
 		       S_00B028_SGPRS((shader->config.num_sgprs - 1) / 8) |
 		       S_00B028_DX10_CLAMP(1) |
 		       S_00B028_FLOAT_MODE(shader->config.float_mode));
 	si_pm4_set_reg(pm4, R_00B02C_SPI_SHADER_PGM_RSRC2_PS,
 		       S_00B02C_EXTRA_LDS_SIZE(shader->config.lds_size) |
 		       S_00B02C_USER_SGPR(SI_PS_NUM_USER_SGPR) |
 		       S_00B32C_SCRATCH_EN(shader->config.scratch_bytes_per_wave > 0));
 
-	/* Prefer RE_Z if the shader is complex enough. The requirement is either:
-	 * - the shader uses at least 2 VMEM instructions, or
-	 * - the code size is at least 50 2-dword instructions or 100 1-dword
-	 *   instructions.
+	/* DON'T USE EARLY_Z_THEN_RE_Z !!!
+	 *
+	 * It decreases performance by 15% in DiRT: Showdown on Ultra settings.
+	 * And it has pretty complex shaders.
 	 *
 	 * Shaders with side effects that must execute independently of the
 	 * depth test require LATE_Z.
 	 */
 	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;
 }
 
 static void si_shader_init_pm4_state(struct si_screen *sscreen,
                                      struct si_shader *shader)
 {
 	switch (shader->selector->type) {
 	case PIPE_SHADER_VERTEX:
 		if (shader->key.vs.as_ls)
-- 
2.7.4