src/sksl/sksl_compute.sksl

// defines built-in interfaces supported by SkSL compute shaders

layout(builtin=24) in uint3 sk_NumWorkgroups;
layout(builtin=26) in uint3 sk_WorkgroupID;
layout(builtin=27) in uint3 sk_LocalInvocationID;
layout(builtin=28) in uint3 sk_GlobalInvocationID;
layout(builtin=29) in uint sk_LocalInvocationIndex;

$pure half4 read($readableTexture2D t, uint2 pos);
void write($writableTexture2D t, uint2 pos, half4 color);

$pure uint width($genTexture2D t);
$pure uint height($genTexture2D t);

// Control-barrier with memory-ordering constraints applied to
// workgroup shared memory only.
void workgroupBarrier();

// Control-barrier with memory-ordering constraints applied to
// uniform and storage-buffer memory.
void storageBarrier();