On Wed, May 11, 2016 at 7:42 PM, Jason Ekstrand <ja...@jlekstrand.net> wrote:
> 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 | 101 > +++++++++++++++++++++++++-- > 2 files changed, 100 insertions(+), 5 deletions(-) > > diff --git a/src/mesa/drivers/dri/i965/brw_blorp.h > b/src/mesa/drivers/dri/i965/brw_blorp.h > index 15114d0..9d71ca4 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 514a316..45b696d 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)), > This needs to be nir_iand. Fixed locally... > + 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++) { > @@ -1341,7 +1389,7 @@ 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); > @@ -1493,6 +1541,48 @@ compute_msaa_layout_for_pipeline(struct brw_context > *brw, unsigned num_samples, > } > > > +static union gl_color_union > +brw_blorp_get_clear_color_for_mt(struct brw_context *brw, > + struct intel_mipmap_tree *mt, > + unsigned swizzle) > +{ > + union gl_color_union color; > + if (brw->gen >= 9) { > + color = mt->gen9_fast_clear_color; > + } else if (_mesa_is_format_integer(mt->format)) { > + color.i[0] = (mt->fast_clear_color_value & (1 << 31)) != 0; > + color.i[1] = (mt->fast_clear_color_value & (1 << 30)) != 0; > + color.i[2] = (mt->fast_clear_color_value & (1 << 29)) != 0; > + color.i[3] = (mt->fast_clear_color_value & (1 << 28)) != 0; > + } else { > + color.f[0] = (mt->fast_clear_color_value & (1 << 31)) != 0; > + color.f[1] = (mt->fast_clear_color_value & (1 << 30)) != 0; > + color.f[2] = (mt->fast_clear_color_value & (1 << 29)) != 0; > + color.f[3] = (mt->fast_clear_color_value & (1 << 28)) != 0; > + } > + > + if (swizzle != SWIZZLE_NOOP) { > + union gl_color_union orig_color = color; > + for (unsigned i = 0; i < 4; i++) { > + unsigned s = GET_SWZ(swizzle, i); > + if (s <= SWIZZLE_W) { > + color.i[i] = orig_color.i[s]; > + } else if (s == SWIZZLE_ZERO) { > + color.i[i] = 0; > + } else { > + assert(s == SWIZZLE_ONE); > + if (_mesa_is_format_integer(mt->format)) > + color.i[i] = 1; > + else > + color.f[i] = 1; > + } > + } > + } > + > + return color; > +} > + > + > /** > * Note: if the src (or dst) is a 2D multisample array texture on Gen7+ > using > * INTEL_MSAA_LAYOUT_UMS or INTEL_MSAA_LAYOUT_CMS, src_layer (dst_layer) > is > @@ -1665,6 +1755,9 @@ brw_blorp_blit_miptrees(struct brw_context *brw, > params.src.num_samples <= 1 && params.dst.num_samples <= 1) > wm_prog_key.bilinear_filter = true; > > + params.wm_push_consts.clear_color = > + brw_blorp_get_clear_color_for_mt(brw, src_mt, src_swizzle); > + > 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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