Since constant-expressions are evaluated at shader creation time, they can be used anywhere you might use a literal.
Constant-expressions can also be used by a const_assert statement.
The shader will not compile if the expression evaluates to false.
// Declare a 'const'
const my_constant = 4;
// Assert at shader creation time that my_constant is even
const_assert (my_constant & 1) == 0;
// Use my_constant to declare an array size
alias my_array = array<i32, my_constant*2>;
// Use my_constant to specify the workgroup size of a compute entry point
@compute @workgroup_size(my_constant)
fn compute_main() {}
// Use my_constant as the argument to a @location attribute
struct VertexInput {
@location(my_constant) texcoords : vec2f,
};
@vertex
fn vertex_main(input : VertexInput) -> @builtin(position) vec4f {
return vec4f();
}