OpEntryPoint declares the list of variables in Input and Output
storage classes that are used. Use that information to skip creating
other variables from such storage classes that are unused by the entry
point.
After that change, is not necessary to use remove dead variables for
those types of variables; and because of that is also not necessary to
lower initalizers for output variables.
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8456>
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