[Mesa-dev] [PATCH] i965/blorp: Special-case the clear color in MSAA resolves
Jason Ekstrand
jason at jlekstrand.net
Wed May 11 04:45:59 UTC 2016
The current MSAA resolve code has a special-case for if the MCS value is 0.
In this case we can only sample once because we know that all values are in
slice 0. This commit adds a second optimization that detecs the magic MCS
value that indicates the clear color and grabs the color from a push
constant and avoids sampling altogether. On a microbenchmark written by
Neil Roberts that tests resolving surfaces with just clear color, this
improves performance by 60% for 8x, 40% for 4x, and 28% for 2x MSAA on my
SKL gte3 laptop. The benchmark can be found on the ML archive:
https://lists.freedesktop.org/archives/mesa-dev/2016-February/108077.html
---
src/mesa/drivers/dri/i965/brw_blorp.h | 4 +-
src/mesa/drivers/dri/i965/brw_blorp_blit.cpp | 72 ++++++++++++++++++++++++++--
2 files changed, 71 insertions(+), 5 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_blorp.h b/src/mesa/drivers/dri/i965/brw_blorp.h
index 5f7569c..550c6c5 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp.h
+++ b/src/mesa/drivers/dri/i965/brw_blorp.h
@@ -197,7 +197,9 @@ struct brw_blorp_wm_push_constants
uint32_t src_z;
/* Pad out to an integral number of registers */
- uint32_t pad[5];
+ uint32_t pad;
+
+ union gl_color_union clear_color;
};
#define BRW_BLORP_NUM_PUSH_CONSTANT_DWORDS \
diff --git a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
index 97e3908..314034e 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
@@ -346,6 +346,7 @@ struct brw_blorp_blit_vars {
nir_variable *offset;
} u_x_transform, u_y_transform;
nir_variable *u_src_z;
+ nir_variable *u_clear_color;
/* gl_FragCoord */
nir_variable *frag_coord;
@@ -374,6 +375,7 @@ brw_blorp_blit_vars_init(nir_builder *b, struct brw_blorp_blit_vars *v,
LOAD_UNIFORM(y_transform.multiplier, glsl_float_type())
LOAD_UNIFORM(y_transform.offset, glsl_float_type())
LOAD_UNIFORM(src_z, glsl_uint_type())
+ LOAD_UNIFORM(clear_color, glsl_vec4_type())
#undef DECL_UNIFORM
@@ -858,7 +860,8 @@ static nir_ssa_def *
blorp_nir_manual_blend_average(nir_builder *b, nir_ssa_def *pos,
unsigned tex_samples,
enum intel_msaa_layout tex_layout,
- enum brw_reg_type dst_type)
+ enum brw_reg_type dst_type,
+ struct brw_blorp_blit_vars *v)
{
/* If non-null, this is the outer-most if statement */
nir_if *outer_if = NULL;
@@ -867,9 +870,53 @@ blorp_nir_manual_blend_average(nir_builder *b, nir_ssa_def *pos,
nir_local_variable_create(b->impl, glsl_vec4_type(), "color");
nir_ssa_def *mcs = NULL;
- if (tex_layout == INTEL_MSAA_LAYOUT_CMS)
+ if (tex_layout == INTEL_MSAA_LAYOUT_CMS) {
mcs = blorp_nir_txf_ms_mcs(b, pos);
+ /* The MCS buffer stores a packed value that provides a mapping from
+ * samples to array slices. The magic value of all ones means that all
+ * samples have the clear color. In this case, we can short-circuit the
+ * sampling process and just use the clear color that we pushed into the
+ * shader.
+ */
+ nir_ssa_def *is_clear_color;
+ switch (tex_samples) {
+ case 2:
+ /* Empirical evidence suggests that the value returned from the
+ * sampler is not always 0x3 for clear color so we need to mask it.
+ */
+ is_clear_color =
+ nir_ieq(b, nir_iand(b, nir_channel(b, mcs, 0), nir_imm_int(b, 0x3)),
+ nir_imm_int(b, 0x3));
+ break;
+ case 4:
+ is_clear_color =
+ nir_ieq(b, nir_channel(b, mcs, 0), nir_imm_int(b, 0xff));
+ break;
+ case 8:
+ is_clear_color =
+ nir_ieq(b, nir_channel(b, mcs, 0), nir_imm_int(b, ~0));
+ break;
+ case 16:
+ is_clear_color =
+ nir_ior(b, nir_ieq(b, nir_channel(b, mcs, 0), nir_imm_int(b, ~0)),
+ nir_ieq(b, nir_channel(b, mcs, 1), nir_imm_int(b, ~0)));
+ break;
+ default:
+ unreachable("Invalid sample count");
+ }
+
+ nir_if *if_stmt = nir_if_create(b->shader);
+ if_stmt->condition = nir_src_for_ssa(is_clear_color);
+ nir_cf_node_insert(b->cursor, &if_stmt->cf_node);
+
+ b->cursor = nir_after_cf_list(&if_stmt->then_list);
+ nir_store_var(b, color, nir_load_var(b, v->u_clear_color), 0xf);
+
+ b->cursor = nir_after_cf_list(&if_stmt->else_list);
+ outer_if = if_stmt;
+ }
+
/* We add together samples using a binary tree structure, e.g. for 4x MSAA:
*
* result = ((sample[0] + sample[1]) + (sample[2] + sample[3])) / 4
@@ -937,7 +984,8 @@ blorp_nir_manual_blend_average(nir_builder *b, nir_ssa_def *pos,
nir_store_var(b, color, texture_data[0], 0xf);
b->cursor = nir_after_cf_list(&if_stmt->else_list);
- outer_if = if_stmt;
+ if (!outer_if)
+ outer_if = if_stmt;
}
for (int j = 0; j < count_trailing_one_bits(i); j++) {
@@ -1345,7 +1393,7 @@ brw_blorp_build_nir_shader(struct brw_context *brw,
/* Gen7+ hardware doesn't automaticaly blend. */
color = blorp_nir_manual_blend_average(&b, src_pos, key->src_samples,
key->src_layout,
- key->texture_data_type);
+ key->texture_data_type, &v);
}
} else if (key->blend && key->blit_scaled) {
color = blorp_nir_manual_blend_bilinear(&b, src_pos, key->src_samples, key, &v);
@@ -1669,6 +1717,22 @@ brw_blorp_blit_miptrees(struct brw_context *brw,
params.src.num_samples <= 1 && params.dst.num_samples <= 1)
wm_prog_key.bilinear_filter = true;
+ union gl_color_union clear_color;
+ if (brw->gen >= 9) {
+ clear_color = src_mt->gen9_fast_clear_color;
+ } else if (_mesa_is_format_integer(src_mt->format)) {
+ clear_color.i[0] = (src_mt->fast_clear_color_value & (1 << 0)) != 0;
+ clear_color.i[1] = (src_mt->fast_clear_color_value & (1 << 1)) != 0;
+ clear_color.i[2] = (src_mt->fast_clear_color_value & (1 << 2)) != 0;
+ clear_color.i[3] = (src_mt->fast_clear_color_value & (1 << 3)) != 0;
+ } else {
+ clear_color.f[0] = (src_mt->fast_clear_color_value & (1 << 0)) != 0;
+ clear_color.f[1] = (src_mt->fast_clear_color_value & (1 << 1)) != 0;
+ clear_color.f[2] = (src_mt->fast_clear_color_value & (1 << 2)) != 0;
+ clear_color.f[3] = (src_mt->fast_clear_color_value & (1 << 3)) != 0;
+ }
+ params.wm_push_consts.clear_color = clear_color;
+
GLenum base_format = _mesa_get_format_base_format(src_mt->format);
if (base_format != GL_DEPTH_COMPONENT && /* TODO: what about depth/stencil? */
base_format != GL_STENCIL_INDEX &&
--
2.5.0.400.gff86faf
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