This patch identifies shader exports to unbound CBs and removes them during
TGSI to LLVM IR lowering. The method is identical to the one used in the
gallium/r600 driver.
The GLSL lower_output_reads pass generates temporary copies for writes to
shader outputs. In the case of gl_FragData, this results in writes to every
MRT when one or more elements are written in the shader. When these MRTs
are unbound and masked out there is still a performance loss equivalent to
exports to bound, unmasked MRTs on SI.
Signed-off-by: Jay Cornwall <j...@jcornwall.me>
---
src/gallium/drivers/radeonsi/radeonsi_pipe.h | 1 +
src/gallium/drivers/radeonsi/radeonsi_shader.c | 6 ++++++
src/gallium/drivers/radeonsi/si_state.c | 15 +++++++++++++--
src/gallium/drivers/radeonsi/si_state.h | 1 +
4 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/src/gallium/drivers/radeonsi/radeonsi_pipe.h
b/src/gallium/drivers/radeonsi/radeonsi_pipe.h
index 26f7e09..bede043 100644
--- a/src/gallium/drivers/radeonsi/radeonsi_pipe.h
+++ b/src/gallium/drivers/radeonsi/radeonsi_pipe.h
@@ -148,6 +148,7 @@ struct r600_context {
unsigned fb_compressed_cb_mask;
unsigned pa_sc_line_stipple;
unsigned pa_su_sc_mode_cntl;
+ boolean dual_src_blend;
/* for saving when using blitter */
struct pipe_stencil_ref stencil_ref;
struct si_pipe_shader_selector *ps_shader;
diff --git a/src/gallium/drivers/radeonsi/radeonsi_shader.c
b/src/gallium/drivers/radeonsi/radeonsi_shader.c
index 80ee325..e4a9f56 100644
--- a/src/gallium/drivers/radeonsi/radeonsi_shader.c
+++ b/src/gallium/drivers/radeonsi/radeonsi_shader.c
@@ -995,6 +995,12 @@ handle_semantic:
semantic_name);
}
+ /* Shader is keyed on nr_cbufs, optimize out exports to
unbound CBs */
+ if (si_shader_ctx->type == TGSI_PROCESSOR_FRAGMENT &&
+ semantic_name == TGSI_SEMANTIC_COLOR &&
+ color_count >
si_shader_ctx->shader->key.ps.nr_cbufs)
+ continue;
+
si_llvm_init_export_args(bld_base, d, index, target,
args);
if (si_shader_ctx->type == TGSI_PROCESSOR_VERTEX &&
diff --git a/src/gallium/drivers/radeonsi/si_state.c
b/src/gallium/drivers/radeonsi/si_state.c
index da7c3d0..8109bde 100644
--- a/src/gallium/drivers/radeonsi/si_state.c
+++ b/src/gallium/drivers/radeonsi/si_state.c
@@ -27,6 +27,7 @@
#include "util/u_memory.h"
#include "util/u_framebuffer.h"
#include "util/u_blitter.h"
+#include "util/u_dual_blend.h"
#include "util/u_helpers.h"
#include "util/u_math.h"
#include "util/u_pack_color.h"
@@ -168,6 +169,8 @@ static void si_update_fb_blend_state(struct r600_context
*rctx)
si_pm4_set_reg(pm4, R_028238_CB_TARGET_MASK, mask);
si_pm4_set_state(rctx, fb_blend, pm4);
+
+ rctx->dual_src_blend = blend->dual_src_blend;
}
/*
@@ -309,6 +312,9 @@ static void *si_create_blend_state_mode(struct pipe_context
*ctx,
si_pm4_set_reg(pm4, R_028780_CB_BLEND0_CONTROL + i * 4,
blend_cntl);
}
+ /* only MRT0 has dual src blend */
+ blend->dual_src_blend = util_blend_state_is_dual(state, 0);
+
return blend;
}
@@ -2097,8 +2103,13 @@ static INLINE void si_shader_selector_key(struct
pipe_context *ctx,
if (rctx->queued.named.rasterizer->clip_plane_enable & 0xf)
key->vs.ucps_enabled |= 0x1;
} else if (sel->type == PIPE_SHADER_FRAGMENT) {
- if (sel->fs_write_all)
- key->ps.nr_cbufs = rctx->framebuffer.nr_cbufs;
+ /* Key on nr_cbufs to optimize unused EXPORTs. */
+ key->ps.nr_cbufs = rctx->framebuffer.nr_cbufs;
+
+ /* Dual-source blending only makes sense with nr_cbufs == 1. */
+ if (key->ps.nr_cbufs == 1 && rctx->dual_src_blend)
+ key->ps.nr_cbufs = 2;
+
key->ps.export_16bpc = rctx->export_16bpc;
if (rctx->queued.named.rasterizer) {
diff --git a/src/gallium/drivers/radeonsi/si_state.h
b/src/gallium/drivers/radeonsi/si_state.h
index 6dbf880..ca51496 100644
--- a/src/gallium/drivers/radeonsi/si_state.h
+++ b/src/gallium/drivers/radeonsi/si_state.h
@@ -34,6 +34,7 @@ struct si_state_blend {
struct si_pm4_state pm4;
uint32_t cb_target_mask;
bool alpha_to_one;
+ bool dual_src_blend;
};
struct si_state_viewport {
--
1.8.4.1
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