Function push_buffer 

fn push_buffer(
    seen: &mut BTreeMap<(*const u8, usize), u32>,
    buffers: &mut Vec<Buffer>,
    buffer: &Buffer,
) -> u32

Returns the index of buffer in buffers, adding it if not already present.

Multiple input arrays, e.g. slices of the same array, may reference the same buffer, so this checks by identity to ensure it is only emitted once