This pass is similar to propagate_invariance in the GLSL compiler. The
real "output" of this pass is that any algebraic operations which are
eventually consumed by an invariant variable get marked as "exact".
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Cc: "12.0" <mesa-stable@lists.freedesktop.org>
