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 _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
