vello/piet-gpu/shader/tile_alloc.comp
Elias Naur a5b6bda941 add support for element flags to shaders
Commit 9afa9b86b6 added Rust support for
encoding flags into elements. This change adds support to shaders by
introducing variant tag structs:

struct VariantTag {
    uint tag;
    uint flags;
}

and returning them from Variant_tag functions.

It also adds a flags argument to write functions for enum variants that
include TagFlags.

No functionality changes.

Updates #70

Signed-off-by: Elias Naur <mail@eliasnaur.com>
2021-03-19 12:50:12 +01:00

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// SPDX-License-Identifier: Apache-2.0 OR MIT OR Unlicense
// Allocation and initialization of tiles for paths.
#version 450
#extension GL_GOOGLE_include_directive : enable
#include "mem.h"
#include "setup.h"
#define LG_TILE_ALLOC_WG (7 + LG_WG_FACTOR)
#define TILE_ALLOC_WG (1 << LG_TILE_ALLOC_WG)
layout(local_size_x = TILE_ALLOC_WG, local_size_y = 1) in;
layout(set = 0, binding = 1) readonly buffer ConfigBuf {
Config conf;
};
#include "annotated.h"
#include "tile.h"
// scale factors useful for converting coordinates to tiles
#define SX (1.0 / float(TILE_WIDTH_PX))
#define SY (1.0 / float(TILE_HEIGHT_PX))
shared uint sh_tile_count[TILE_ALLOC_WG];
shared MallocResult sh_tile_alloc;
void main() {
if (mem_error != NO_ERROR) {
return;
}
uint th_ix = gl_LocalInvocationID.x;
uint element_ix = gl_GlobalInvocationID.x;
PathRef path_ref = PathRef(conf.tile_alloc.offset + element_ix * Path_size);
AnnotatedRef ref = AnnotatedRef(conf.anno_alloc.offset + element_ix * Annotated_size);
uint tag = Annotated_Nop;
if (element_ix < conf.n_elements) {
tag = Annotated_tag(conf.anno_alloc, ref).tag;
}
int x0 = 0, y0 = 0, x1 = 0, y1 = 0;
switch (tag) {
case Annotated_Fill:
case Annotated_FillImage:
case Annotated_Stroke:
case Annotated_BeginClip:
case Annotated_EndClip:
// Note: we take advantage of the fact that fills, strokes, and
// clips have compatible layout.
AnnoFill fill = Annotated_Fill_read(conf.anno_alloc, ref);
x0 = int(floor(fill.bbox.x * SX));
y0 = int(floor(fill.bbox.y * SY));
x1 = int(ceil(fill.bbox.z * SX));
y1 = int(ceil(fill.bbox.w * SY));
break;
}
x0 = clamp(x0, 0, int(conf.width_in_tiles));
y0 = clamp(y0, 0, int(conf.height_in_tiles));
x1 = clamp(x1, 0, int(conf.width_in_tiles));
y1 = clamp(y1, 0, int(conf.height_in_tiles));
Path path;
path.bbox = uvec4(x0, y0, x1, y1);
uint tile_count = (x1 - x0) * (y1 - y0);
if (tag == Annotated_EndClip) {
// Don't actually allocate tiles for an end clip, but we do want
// the path structure (especially bbox) allocated for it.
tile_count = 0;
}
sh_tile_count[th_ix] = tile_count;
uint total_tile_count = tile_count;
// Prefix sum of sh_tile_count
for (uint i = 0; i < LG_TILE_ALLOC_WG; i++) {
barrier();
if (th_ix >= (1 << i)) {
total_tile_count += sh_tile_count[th_ix - (1 << i)];
}
barrier();
sh_tile_count[th_ix] = total_tile_count;
}
if (th_ix == TILE_ALLOC_WG - 1) {
sh_tile_alloc = malloc(total_tile_count * Tile_size);
}
barrier();
MallocResult alloc_start = sh_tile_alloc;
if (alloc_start.failed) {
return;
}
if (element_ix < conf.n_elements) {
uint tile_subix = th_ix > 0 ? sh_tile_count[th_ix - 1] : 0;
Alloc tiles_alloc = slice_mem(alloc_start.alloc, Tile_size * tile_subix, Tile_size * tile_count);
path.tiles = TileRef(tiles_alloc.offset);
Path_write(conf.tile_alloc, path_ref, path);
}
// Zero out allocated tiles efficiently
uint total_count = sh_tile_count[TILE_ALLOC_WG - 1] * (Tile_size / 4);
uint start_ix = alloc_start.alloc.offset >> 2;
for (uint i = th_ix; i < total_count; i += TILE_ALLOC_WG) {
// Note: this interleaving is faster than using Tile_write
// by a significant amount.
write_mem(alloc_start.alloc, start_ix + i, 0);
}
}