[Mesa-dev] [PATCH v2] i965/blorp: Special-case the clear color in MSAA resolves
Ilia Mirkin
imirkin at alum.mit.edu
Thu May 12 02:44:22 UTC 2016
On Wed, May 11, 2016 at 10:42 PM, Jason Ekstrand <jason at 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)),
> + 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;
Prepare to get yelled at by all the ubsan people... I think they want 1U here.
> + 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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