This improves type safety and is less verbose. Use SimpleTy only where
an integer is needed like switches or emitting a VBR.

---------

Co-authored-by: Sergei Barannikov <barannikov88@gmail.com>

This is a generalization of the LookupPtrRegClass mechanism.
AMDGPU has several use cases for swapping the register class of
instruction operands based on the subtarget, but none of them
really fit into the box of being pointer-like.

The current system requires manual management of an arbitrary integer
ID. For the AMDGPU use case, this would end up being around 40 new
entries to manage.

This just introduces the base infrastructure. I have ports of all
the target specific usage of PointerLikeRegClass ready.

Rename `getXYZInstructionsByEnumValue()` to just `getXYZInstructions`
and drop the `ByEnumValue` in the name.

- Add various instruction subclass/sub-slice accessors to
`CodeGenTarget`.
- Delete unused `inst_begin` and `inst_end` iterators.
- Rename `Instructions` to `InstructionMap` and `getInstructions` to
`getInstructionMap` to better represent their meaning.
- Use these new accessors in InstrInfoEmitter

This method doesn't use anything from CodeGenTarget, so it seems to
belong in CodeGenRegBank.

Pointers already have a well-defined null value.

These properties are only valid on ComplexPatterns. Having them as flags
is more convenient because one can now use "let = ... in" syntax to set
these flags on several patterns at a time. This is also less error-prone
as it makes it impossible to specify these properties on records derived
from SDPatternOperator.

Pull Request: https://github.com/llvm/llvm-project/pull/119599

The former is a wrapper for the latter with two differences: Other is
mapped to "UNKNOWN" (rather than "MVT::Other"), and iPTR(Any) are mapped
to "TLI.getPointerTy()" rather than "MVT::iPTR(Any)".

The only uses are in FastISelMap::printFunctionDefinitions. Most of
these uses are just a form of name mangling to ensure uniqueness, so the
actual string isn't important (and, in the case of MVT::iPTR(Any), were
both to be used, they would clash). Two uses are for a case statement,
which requires the expression to be a constant (of the right type), but
neither UNKNOWN nor TLI.getPointerTy() are constants, so would not work
there. The remaining uses are where an expression is needed, so UNKNOWN
similarly doesn't work, though TLI.getPointerTy() could in this case.
However, neither iPTR nor iPTRAny are supposed to make it this far
through TableGen, and should instead have been replaced with concrete
types, so this case should not be hit. Moreover, for almost all of these
uses, the name is passed to getLegalCName, which will strip an MVT::
prefix but will leave TLI.getPointerTy() unchanged, which is not a valid
C identifier, nor component thereof.

Thus, delete this unnecessary, and mostly-broken, wrapper and just use
the underlying getEnumName. This has been verified to have no effect on
the generated files for any in-tree target, including experimental ones.

Reviewers: arsenm

Reviewed By: arsenm

Pull Request: https://github.com/llvm/llvm-project/pull/113731