This avoids doing a Triple -> std::string -> Triple round trip in lots
of places, now that the Module stores a Triple.

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

This will make it easy for callers to see issues with and fix up calls
to createTargetMachine after a future change to the params of
TargetMachine.

This matches other nearby enums.

For downstream users, this should be a fairly straightforward
replacement,
e.g. s/CodeGenOpt::Aggressive/CodeGenOptLevel::Aggressive
or s/CGFT_/CodeGenFileType::

This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated.  The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

This moves the registry higher in the LLVM library dependency stack.
Every client of the target registry needs to link against MC anyway to
actually use the target, so we might as well move this out of Support.

This allows us to ensure that Support doesn't have includes from MC/*.

Differential Revision: https://reviews.llvm.org/D111454

This helps to distinguish such tests from successfully passed ones.

Differential Revision: https://reviews.llvm.org/D102754

Summary:
After D70211, Pass.h does not include InitializePasses.h anymore, so
these files need to include InitializePasses.h directly.

Reviewers: rnk

Subscribers: MatzeB, mehdi_amini, zzheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70217

The previous one didn't fix everything.

llvm-svn: 354719

llvm-svn: 354712

Summary:
Prior to r310876 one of our out-of-tree targets was enabling IPRA by modifying
the TargetOptions::EnableIPRA. This no longer works on current trunk since the
useIPRA() hook overrides any values that are set in advance. This patch adjusts
the behaviour of the hook so that API users and useIPRA() can both enable it
but useIPRA() cannot disable it if the API user already enabled it.

Reviewers: arsenm

Reviewed By: arsenm

Subscribers: wdng, mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D38043

llvm-svn: 354692