Structs are split to remove builtin members to create valid SPIR-V. In this
process, an outer structure array dimension may be propegated onto the
now-removed builtin variables. For example, a mystruct[3].position ->
position[3]. The copy between the split and unsplit forms would handle
this in some cases, but not if the array dimension was at different levels
of aggregate.
It now does this, but may not handle arbitrary composite types. Unclear if
that has any semantic meaning for builtins though.
This needs some render testing, but is destined to be part of master.
This also leads to a variety of other simplifications.
- IO are global symbols, so only need one list of linkage nodes (deferred)
- no longer need parse-context-wide 'inEntryPoint' state, entry-point is localized
- several parts of splitting/flattening are now localized
When copying split types with mixtures of user variables and buitins,
where the builtins are extracted, there is a parallel structures traversal.
The traversal was not obtaining the derefenced types in the array case.
