In the process of determining whether two MachineOperands are equal and
calculating the hash of a MachineOperand, both MO_RegisterMask and
MO_RegisterLiveOut types were uniformly handled. However, when the type
is MO_RegisterLiveOut, calling getRegMask() triggers an assertion
failure. This PR addresses this issue.

Remove `TargetIntrinsicInfo` class as its practically unused (its pure
virtual with no subclasses) and its references in the code.

Following discussions in #110443, and the following earlier discussions
in https://lists.llvm.org/pipermail/llvm-dev/2017-October/117907.html,
https://reviews.llvm.org/D38482, https://reviews.llvm.org/D38489, this
PR attempts to overhaul the `TargetMachine` and `LLVMTargetMachine`
interface classes. More specifically:
1. Makes `TargetMachine` the only class implemented under
`TargetMachine.h` in the `Target` library.
2. `TargetMachine` contains target-specific interface functions that
relate to IR/CodeGen/MC constructs, whereas before (at least on paper)
it was supposed to have only IR/MC constructs. Any Target that doesn't
want to use the independent code generator simply does not implement
them, and returns either `false` or `nullptr`.
3. Renames `LLVMTargetMachine` to `CodeGenCommonTMImpl`. This renaming
aims to make the purpose of `LLVMTargetMachine` clearer. Its interface
was moved under the CodeGen library, to further emphasis its usage in
Targets that use CodeGen directly.
4. Makes `TargetMachine` the only interface used across LLVM and its
projects. With these changes, `CodeGenCommonTMImpl` is simply a set of
shared function implementations of `TargetMachine`, and CodeGen users
don't need to static cast to `LLVMTargetMachine` every time they need a
CodeGen-specific feature of the `TargetMachine`.
5. More importantly, does not change any requirements regarding library
linking.

cc @arsenm @aeubanks

Avoid excess layer of indirection.

Finally addresses https://reviews.llvm.org/D148769#4311232 :)

No behavior change.

This is rework of;
  - D30046 (LLT)

Since I have introduced `llvm-min-tblgen` as D146352, `llvm-tblgen`
may depend on `CodeGen`.

`LowLevlType.h` originally belonged to `CodeGen`. Almost all userse are
still under `CodeGen` or `Target`. I think `CodeGen` is the right place
to put `LowLevelType.h`.

`MachineValueType.h` may be moved as well. (later, D149024)

I have made many modules depend on `CodeGen`. It is consistent but
inefficient. It will be split out later, D148769

Besides, I had to isolate MVT and LLT in modmap, since
`llvm::PredicateInfo` clashes between `TableGen/CodeGenSchedule.h`
and `Transforms/Utils/PredicateInfo.h`.
(I think better to introduce namespace llvm::TableGen)

Depends on D145937, D146352, and D148768.

Differential Revision: https://reviews.llvm.org/D148767

The object contained in unique_ptr will be automatically deleted at the end of
the current scope. In createMachineFunction,

  auto TM = createTargetMachine();

creates a TM contained in unique_ptr, a reference of the TM is stored in a
MachineFunction object, but at the end of the function, the TM is deleted, so
later access to the TM(and contained STI, TRI ...) through MachineFunction
object is invalid.

So we should not use unique_ptr<BogusTargetMachine> in functions
createMachineFunction and createTargetMachine.

Differential Revision: https://reviews.llvm.org/D131790

Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D121332

This makes it possible for targets to define their own MCObjectFileInfo.
This MCObjectFileInfo is then used to determine things like section alignment.

This is a follow up to D101462 and prepares for the RISCV backend defining the
text section alignment depending on the enabled extensions.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D101921

This untangles the MCContext and the MCObjectFileInfo. There is a circular
dependency between MCContext and MCObjectFileInfo. Currently this dependency
also exists during construction: You can't contruct a MOFI without a MCContext
without constructing the MCContext with a dummy version of that MOFI first.
This removes this dependency during construction. In a perfect world,
MCObjectFileInfo wouldn't depend on MCContext at all, but only be stored in the
MCContext, like other MC information. This is future work.

This also shifts/adds more information to the MCContext making it more
available to the different targets. Namely:

- TargetTriple
- ObjectFileType
- SubtargetInfo

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D101462