xref: /aosp_15_r20/external/skia/resources/sksl/compute/AtomicOperations.compute (revision c8dee2aa9b3f27cf6c858bd81872bdeb2c07ed17)

layout(local_size_x = 64) in;

layout(metal, binding = 0) buffer ssbo {
    atomicUint globalCounter;
};

workgroup atomic_uint localCounter;  // atomic_uint is a synonym for atomicUint

void main() {
    // Initialize the local counter.
    if (sk_LocalInvocationID.x == 0) {
        atomicStore(localCounter, 0);
    }

    // Synchronize the threads in the workgroup so they all see the initial value.
    workgroupBarrier();

    // All threads increment the counter.
    atomicAdd(localCounter, 1);

    // Synchronize the threads again to ensure they have all executed the increment
    // and the following load reads the same value across all threads in the
    // workgroup.
    workgroupBarrier();

    // Add the workgroup-only tally to the global counter.
    if (sk_LocalInvocationID.x == 0) {
        atomicAdd(globalCounter, atomicLoad(localCounter));
    }
}