#119969 adds a couple of new methods to this class, which will need to
be overridden by these targets.

Part of #119709.

Pull Request: https://github.com/llvm/llvm-project/pull/119968

Identified with misc-include-cleaner.

Utilize common API in PPCTargetParser
(https://github.com/llvm/llvm-project/pull/97541) to set default CPU
with same interfaces for LLC.
This will update AIX default CPU to pwr7 and LoP powerppc64 default CPU
to ppc64.

Some targets only pass a TargetMachine & to their subtarget constructor
and require a static_cast to their target-specific TargetMachine subclass
to create *InstructionSelector.

These 3 targets already have the correct TargetMachine subclass
reference so no cast is needed.

Replace it with a forward declaration instead. Analysis.h is pulled in
by all passes, but not all passes need to access the module.

This removes the uses of target flags to disable subreg liveness,
relying on the `-enable-subreg-liveness` flag instead. The
`-enable-subreg-liveness` flag has been changed to take precedence over
the subtarget if set, and one use of `Subtarget->enableSubRegLiveness()`
has been changed to `MRI->subRegLivenessEnabled()` to make sure the
option properly applies.

Under some circumstance (library loaded with the main program), TLS
initial-exec model can be applied to local-dynamic access(es). We
could use some simple heuristic to decide the update at function level:
* If there is equal or less than a number of TLS local-dynamic access(es)
in the function, use TLS initial-exec model. (the threshold which default to
1 is controlled by hidden option)

Following the aix-small-local-exec-tls target attribute, this patch adds
a target attribute for an AIX-specific option in llc that informs the
compiler that it can use a faster access sequence for the local-dynamic
TLS model (formally named aix-small-local-dynamic-tls) when TLS
variables are less than ~32KB in size.

The patch either produces an addi/la with a displacement off of module
handle (return value from .__tls_get_mod) when the address is
calculated, or it produces an addi/la followed by a load/store when the
address is calculated and used for further accesses.

---------

Co-authored-by: Amy Kwan <amy.kwan1@ibm.com>

Exploit the per global code model attribute on AIX. On AIX we need to
update both the code sequence used to access the global (either 1 or 2
instructions for small and large code model respectively) and the
storage mapping class that we emit the toc entry.

---------

Co-authored-by: Amy Kwan <akwan0907@gmail.com>

The following tests fail when built with Address
and Undefined sanitizers:
CodeGen/PowerPC/basic-toc-data-def.ll
CodeGen/PowerPC/toc-data-large-array2.ll

Subtarget may be null in emitGlobalVariable, for example in the testcase
where we have no functions in the IR. The fix moves this function from
PPCSubtarget to a static helper function. This only fails with
sanitizers because the Subtarget is not used in the member function.