nir/lower_io: Use b2b for shader and function temporaries

This way we can avoid some unnecessary conversions because there's no
need to sanitize to 0/1 for scratch.

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5927>
1 file changed