Some clients do not want to emit a terminator after each sub-sequence
(they have other means of determining the length of sub-sequences).
This moves `Term` argument from `emit` method to the constructor and
makes it optional. It couldn't be made optional while still on the
`emit` method because if the terminator wasn't specified, it has to be
taken into account in `layout` method as well.
The fact that `layout` method was called is now recorded in a dedicated
member variable, `IsLaidOut`. `Entries != 0` can no longer be used to
reliably check if `layout` method was called because it may be zero for
a different reason: the terminator wasn't specified and all added
sequences (if any) were empty.
This reduces the size of `*LaneMaskLists` and `*SubRegIdxLists` a bit
and resolves the removed TODO.
- Replace use of std::isalnum/ispunct with StringExtras version to avoid
possibly locale dependent behavior.
- Remove `static` from printChar (do its deduplicated when linking).
- Use range based for loops and structured bindings.
- No need to use `llvm::` for code in llvm namespace.
Refactor of the llvm-tblgen source into:
- a "Basic" library, which contains the bare minimum utilities to build
`llvm-min-tablegen`
- a "Common" library which contains all of the helpers for TableGen
backends. Such helpers can be shared by more than one backend, and even
unit tested (e.g. CodeExpander is, maybe we can add more over time)
Fixes#80647
