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Optimize getting the palette index for palette compression using SIMD. #2405

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Optimize getting the palette index for palette compression using SIMD. #2405

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37 changes: 26 additions & 11 deletions src/utils.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -1078,10 +1078,29 @@ pub fn DynamicPackedIntArray(size: comptime_int) type { // MARK: DynamicPackedIn
};
}

fn alignedFind(T: type, arr: []align(64) T, elem: T) ?usize {
const vectorLength = std.simd.suggestVectorLength(T) orelse 1;
const TInt = std.meta.Int(.unsigned, @bitSizeOf(T));
const Vector = @Vector(vectorLength, TInt);
const array: [*]Vector = @ptrCast(arr.ptr);
const len = std.math.divCeil(usize, arr.len, vectorLength) catch unreachable;
const compare: Vector = @splat(@bitCast(elem));
for(0..len) |i| {
const boolVec = compare == array[i];
const int: std.meta.Int(.unsigned, vectorLength) = @bitCast(boolVec);
if(int != 0) {
const result = i*vectorLength + @ctz(int);
if(result >= arr.len) return null;
return result;
}
}
return null;
}

pub fn PaletteCompressedRegion(T: type, size: comptime_int) type { // MARK: PaletteCompressedRegion
const Impl = struct {
data: DynamicPackedIntArray(size) = .{},
palette: []Atomic(T),
palette: []align(64) Atomic(T),
paletteOccupancy: []u32,
paletteLength: u32,
activePaletteEntries: u32,
Expand All @@ -1096,7 +1115,7 @@ pub fn PaletteCompressedRegion(T: type, size: comptime_int) type { // MARK: Pale
.impl = .init(impl),
};
impl.* = .{
.palette = main.globalAllocator.alloc(Atomic(T), 1),
.palette = main.globalAllocator.alignedAlloc(Atomic(T), .@"64", 1),
.paletteOccupancy = main.globalAllocator.alloc(u32, 1),
.paletteLength = 1,
.activePaletteEntries = 1,
Expand All @@ -1115,11 +1134,12 @@ pub fn PaletteCompressedRegion(T: type, size: comptime_int) type { // MARK: Pale
};
impl.* = .{
.data = dataDupe,
.palette = main.globalAllocator.dupe(Atomic(T), templateImpl.palette),
.palette = main.globalAllocator.alignedAlloc(Atomic(T), .@"64", templateImpl.palette.len),
.paletteOccupancy = main.globalAllocator.dupe(u32, templateImpl.paletteOccupancy),
.paletteLength = templateImpl.paletteLength,
.activePaletteEntries = templateImpl.activePaletteEntries,
};
@memcpy(impl.palette, templateImpl.palette);
}

pub fn initCapacity(self: *Self, paletteLength: u32) void {
Expand All @@ -1132,7 +1152,7 @@ pub fn PaletteCompressedRegion(T: type, size: comptime_int) type { // MARK: Pale
};
impl.* = .{
.data = DynamicPackedIntArray(size).initCapacity(bitSize),
.palette = main.globalAllocator.alloc(Atomic(T), bufferLength),
.palette = main.globalAllocator.alignedAlloc(Atomic(T), .@"64", bufferLength),
.paletteOccupancy = main.globalAllocator.alloc(u32, bufferLength),
.paletteLength = paletteLength,
.activePaletteEntries = 1,
Expand Down Expand Up @@ -1187,12 +1207,7 @@ pub fn PaletteCompressedRegion(T: type, size: comptime_int) type { // MARK: Pale
fn getOrInsertPaletteIndex(noalias self: *Self, val: T) u32 {
var impl = self.impl.raw;
std.debug.assert(impl.paletteLength <= impl.palette.len);
var paletteIndex: u32 = 0;
while(paletteIndex < impl.paletteLength) : (paletteIndex += 1) {
if(std.meta.eql(impl.palette[paletteIndex].load(.unordered), val)) {
break;
}
}
const paletteIndex = alignedFind(Atomic(T), impl.palette[0..impl.paletteLength], .init(val)) orelse impl.paletteLength;
if(paletteIndex == impl.paletteLength) {
if(impl.paletteLength == impl.palette.len) {
if(impl.data.bitSize == 16) {
Expand All @@ -1217,7 +1232,7 @@ pub fn PaletteCompressedRegion(T: type, size: comptime_int) type { // MARK: Pale
impl.paletteLength += 1;
std.debug.assert(impl.paletteLength <= impl.palette.len);
}
return paletteIndex;
return @intCast(paletteIndex);
}

pub fn setRawValue(noalias self: *Self, i: usize, paletteIndex: u32) void {
Expand Down