Some hardware (AGX, Imagination, Arm) really want to know the interpolation
qualifiers when compiling the vertex shader. Even though we need to handle this
dynamic for separate shaders, we can improve performance by linking.
nir_opt_varyings already has all the information to do this, so just do so.
Note this has to be done in common code for Gallium, which links varyings within
the GLSL linker but then presents the linked programs as separate shader
objects. This models that nicely, allowing Gallium drivers to optimize without
weird sidebands.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Marek Olšák <maraeo@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36501>