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ac/nir: optimize frag_coord <-> pixel_coord in ac_nir_lower_ps_early

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Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33024>
This commit is contained in:
Marek Olšák 2025-01-02 18:00:22 -05:00
parent 33134f9503
commit e57b52ff6c
2 changed files with 96 additions and 11 deletions
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11
src/amd/common/nir/ac_nir.h
View file

@ -275,8 +275,17 @@ typedef struct {
bool load_sample_positions_always_loads_current_ones;
bool dynamic_rasterization_samples;
int force_front_face; /* 0 -> keep, 1 -> set to true, -1 -> set to false */
bool optimize_frag_coord; /* TODO: remove this after RADV can handle it */
/* barycentrics:
/* frag_coord/pixel_coord:
* allow_pixel_coord && (ps_iter_samples == 1 || force_center_interp_no_msaa ||
* the fractional part of frag_coord.xy isn't used):
* * frag_coord.xy is replaced by u2f(pixel_coord) + 0.5.
* else:
* * pixel_coord is replaced by f2u16(frag_coord.xy)
* * ps_iter_samples == 0 means the state is unknown.
*
* barycentrics:
* ps_iter_samples >= 2:
* * All barycentrics are changed to per-sample interpolation except at_offset/at_sample.
* * barycentric_at_sample(sample_id) is replaced by barycentric_sample.

96
src/amd/common/nir/ac_nir_lower_ps_early.c
View file

@ -27,6 +27,8 @@ typedef struct {
bool frag_color_is_frag_data0;
bool seen_color0_alpha;
bool uses_fragcoord_xy_as_float;
bool use_fragcoord;
} lower_ps_early_state;
static nir_variable *
@ -432,6 +434,35 @@ lower_ps_intrinsic(nir_builder *b, nir_intrinsic_instr *intrin, void *state)
return true;
}
break;
case nir_intrinsic_load_frag_coord:
if (!s->options->optimize_frag_coord)
break;
/* Compute frag_coord.xy from pixel_coord. */
if (!s->use_fragcoord && nir_def_components_read(&intrin->def) & 0x3) {
nir_def *new_fragcoord_xy = nir_u2f32(b, nir_load_pixel_coord(b));
if (!b->shader->info.fs.pixel_center_integer)
new_fragcoord_xy = nir_fadd_imm(b, new_fragcoord_xy, 0.5);
nir_def *fragcoord = nir_load_frag_coord(b);
nir_def_replace(&intrin->def,
nir_vec4(b, nir_channel(b, new_fragcoord_xy, 0),
nir_channel(b, new_fragcoord_xy, 1),
nir_channel(b, fragcoord, 2),
nir_channel(b, fragcoord, 3)));
return true;
}
break;
case nir_intrinsic_load_pixel_coord:
if (!s->options->optimize_frag_coord)
break;
/* There is already a floating-point frag_coord.xy use in the shader. Don't add pixel_coord.
* Instead, compute pixel_coord from frag_coord.
*/
if (s->use_fragcoord) {
nir_def *new_pixel_coord = nir_f2u16(b, nir_channels(b, nir_load_frag_coord(b), 0x3));
nir_def_replace(&intrin->def, new_pixel_coord);
return true;
}
break;
default:
break;
}
@ -440,18 +471,51 @@ lower_ps_intrinsic(nir_builder *b, nir_intrinsic_instr *intrin, void *state)
}
static bool
gather_frag_color_dual_src_blend(nir_builder *b, nir_intrinsic_instr *intr, void *state)
gather_info(nir_builder *b, nir_intrinsic_instr *intr, void *state)
{
lower_ps_early_state *s = (lower_ps_early_state *)state;
/* FRAG_RESULT_COLOR can't broadcast results to all color buffers if another
* FRAG_RESULT_COLOR output exists with dual_src_blend_index=1. This happens
* with gl_SecondaryFragColorEXT in GLES.
*/
if (intr->intrinsic == nir_intrinsic_store_output &&
nir_intrinsic_io_semantics(intr).location == FRAG_RESULT_COLOR &&
nir_intrinsic_io_semantics(intr).dual_source_blend_index)
s->frag_color_is_frag_data0 = true;
switch (intr->intrinsic) {
case nir_intrinsic_store_output:
/* FRAG_RESULT_COLOR can't broadcast results to all color buffers if another
* FRAG_RESULT_COLOR output exists with dual_src_blend_index=1. This happens
* with gl_SecondaryFragColorEXT in GLES.
*/
if (nir_intrinsic_io_semantics(intr).location == FRAG_RESULT_COLOR &&
nir_intrinsic_io_semantics(intr).dual_source_blend_index)
s->frag_color_is_frag_data0 = true;
break;
case nir_intrinsic_load_frag_coord:
assert(intr->def.bit_size == 32);
nir_foreach_use(use, &intr->def) {
if (nir_src_parent_instr(use)->type == nir_instr_type_alu &&
nir_src_components_read(use) & 0x3) {
switch (nir_instr_as_alu(nir_src_parent_instr(use))->op) {
case nir_op_f2i8:
case nir_op_f2i16:
case nir_op_f2i32:
case nir_op_f2i64:
case nir_op_f2u8:
case nir_op_f2u16:
case nir_op_f2u32:
case nir_op_f2u64:
case nir_op_ftrunc:
case nir_op_ffloor:
continue;
default:
break;
}
}
s->uses_fragcoord_xy_as_float = true;
break;
}
break;
case nir_intrinsic_load_sample_pos:
s->uses_fragcoord_xy_as_float = true;
break;
default:
break;
}
return false;
}
@ -470,7 +534,19 @@ ac_nir_lower_ps_early(nir_shader *nir, const ac_nir_lower_ps_early_options *opti
};
/* Don't gather shader_info. Just gather the single thing we want to know. */
nir_shader_intrinsics_pass(nir, gather_frag_color_dual_src_blend, nir_metadata_all, &state);
nir_shader_intrinsics_pass(nir, gather_info, nir_metadata_all, &state);
/* The preferred option is replacing frag_coord by pixel_coord.xy + 0.5. The goal is to reduce
* input VGPRs to increase PS wave launch rate. pixel_coord uses 1 input VGPR, while
* frag_coord.xy uses 2 input VGPRs. It only helps performance if the number of input VGPRs
* decreases to an even number. If it only decreases to an odd number, it has no effect.
*
* TODO: estimate input VGPRs and don't lower to pixel_coord if their number doesn't decrease to
* an even number?
*/
state.use_fragcoord = state.options->ps_iter_samples != 1 &&
!state.options->force_center_interp_no_msaa &&
state.uses_fragcoord_xy_as_float;
bool progress = nir_shader_intrinsics_pass(nir, lower_ps_intrinsic,
nir_metadata_control_flow, &state);