KHR_parallel_shader_compile

var ext = gl.getExtension('KHR_parallel_shader_compile');

// Assuming lists of `shaders` and `programs`:
for (const x of shaders)
    gl.compileShader(x); // Never check compile status unless subsequent linking fails.
for (const x of programs)
    gl.linkProgram(x);

// Generator yielding a progress ratio [0.0, 1.0].
// Without the extension, this will jank and only check one program per generation.
function* linkingProgress(programs) {
    const ext = gl.getExtension('KHR_parallel_shader_compile');
    let todo = programs.slice();
    while (todo.length) {
        if (ext) {
            todo = todo.filter(x => !gl.getProgramParameter(x, ext.COMPLETION_STATUS_KHR));
        } else {
            const x = todo.pop();
            gl.getProgramParameter(x, gl.LINK_STATUS);
        }
        if (!todo.length)
            return;
        yield 1.0 - (todo.length / programs.length);
    }
}