This patch fixes:

  llvm/lib/CodeGen/GlobalISel/CombinerHelperCasts.cpp:167:21: error:
  unused variable 'DL' [-Werror,-Wunused-variable]

  llvm/lib/CodeGen/GlobalISel/LoadStoreOpt.cpp:320:15: error: unused
  variable 'DL' [-Werror,-Wunused-variable]

Identified with misc-include-cleaner.

Similar to https://github.com/llvm/llvm-project/pull/96902, this adds
`getDataLayout()` helpers to Function and GlobalValue, replacing the
current `getParent()->getDataLayout()` pattern.

During analysis, we incorrectly leave the offset part of an address info
struct
as zero, when in actual fact we failed to decompose it into base +
offset.
This results in incorrectly assuming that the address is adjacent to
another store
addr. To fix this we wrap the offset in an optional<> so we can
distinguish between
real zero and unknown.

Fixes issue #90242

Remove getSizeOrUnknown call when MachineMemOperand is created.  For Scalable
TypeSize, the MemoryType created becomes a scalable_vector.

2 MMOs that have scalable memory access can then use the updated BasicAA that
understands scalable LocationSize.

Original Patch by Harvin Iriawan
Co-authored-by: David Green <david.green@arm.com>

This is part of #70452 that changes the type used for the external
interface of MMO to LocationSize as opposed to uint64_t. This means the
constructors take LocationSize, and convert ~UINT64_C(0) to
LocationSize::beforeOrAfter(). The getSize methods return a
LocationSize.

This allows us to be more precise with unknown sizes, not accidentally
treating them as unsigned values, and in the future should allow us to
add proper scalable vector support but none of that is included in this
patch. It should mostly be an NFC.

Global ISel is still expected to use the underlying LLT as it needs, and
are not expected to see unknown sizes for generic operations. Most of
the changes are hopefully fairly mechanical, adding a lot of getValue()
calls and protecting them with hasValue() where needed.

This is similar to #83017 but for the areas in GlobalISel's
LoadStoreOpt, and should help simplify #70452 a little. It will likely
change a little again once the sizes can be scalable.

Before restoring `CodeGen/LowLevelType`, rename this to `LowLevelTypeUtils`.

Differential Revision: https://reviews.llvm.org/D148768