isvarying

int  isvarying(<type>x)

int  isvarying(<type>x[])

Returns 1 when the given variable is varying, or 0 when it is uniform. A variable is varying when it may have a different value for each processor in the VEX SIMD array. If a value is varying, shader execution will generally be slower - so this function can be useful when debugging shader performance. Any variable type can be passed to the isvarying() function.