RecordLayout::UnadjustedAlignment was documented as "Maximum of the
alignments of the record members in characters", but
RecordLayout::getUnadjustedAlignment(), which just returns
UnadjustedAlignment, was documented as getting "the record alignment in
characters, before alignment adjustement." These are not the same thing:
the former excludes alignment of base classes, the latter takes it into
account. ItaniumRecordLayoutBuilder::LayoutBase was setting it according
to the former, but the AAPCS calling convention handling, currently the
only user, relies on it being set according to the latter.

Fixes #135551.

This fixes two bugs in the ABI for over-sized bitfields for ARM and
AArch64:

The container type picked for an over-sized bitfield already contributes
to the alignment of the structure, but it should also contribute to the
"unadjusted alignment" which is used by the ARM and AArch64 PCS.

AAPCS64 defines the bitfield layout algorithm for over-sized bitfields
as picking a container which is the fundamental integer data type with
the largest size less than or equal to the bit-field width. Since
AAPCS64 has a 128-bit integer fundamental data type, we need to consider
Int128 as a container type for AArch64.

This patch makes determining alignment and width of BitInt to be target
ABI specific and makes it consistent with [Procedure Call Standard for
the Arm® 64-bit Architecture
(AArch64)](https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst)
for AArch64 targets.

When emitting the storage (or memory copy operations) for constant
initializers, the decision whether to split a constant structure or
array store into a sequence of field stores or to use `memcpy` is
based upon the optimization level and the size of the initializer.
In afe8b93ffdfef5d8879e1894b9d7dda40dee2b8d, we extended this by
allowing constants to be split when the array (or struct) type does
not match the type of data the address to the object (constant) is
expected to contain. This may happen when `emitStoresForConstant` is
called by `EmitAutoVarInit`, as the element type of the address gets
shrunk. When this occurs, let the initializer be split into a bunch
of stores only under `-ftrivial-auto-var-init=pattern`.

Fixes: https://github.com/llvm/llvm-project/issues/84178.

Recommit of 0d2860b795879f4dd152963b52f969b53b136899 with extra test
cases fixed.

A common user mistake is specifying a target of aarch64-none-eabi or
arm-none-elf whereas the correct names are aarch64-none-elf &
arm-none-eabi. Currently if a target of aarch64-none-eabi is specified
then the Generic_ELF toolchain is used, unlike aarch64-none-elf which
will use the BareMetal toolchain. This is unlikely to be intended by the
user so issue a warning that the target is invalid.

The target parser is liberal in what input it accepts so invalid triples
may yield behaviour that's sufficiently close to what the user intended.
Therefore invalid triples were used in many tests. This change updates
those tests to use valid triples.
One test (gnu-mcount.c) relies on the Generic_ELF toolchain behaviour so
change it to explicitly specify aarch64-unknown-none-gnu as the target.

Reviewed By: peter.smith, DavidSpickett

Differential Revision: https://reviews.llvm.org/D153430

Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.

Test updates are made as a separate patch: D108453

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D105169

This reverts commit aacfbb953eb705af2ecfeb95a6262818fa85dd92.

Revert "Fix lit test failures in CodeGenCoroutines"

This reverts commit 63fff0f5bffe20fa2c84a45a41161afa0043cb34.

Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.

Test updates are made as a separate patch: D108453

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D105169

[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default (2)

This patch updates test files after D105169.
Autogenerated test codes are changed by `utils/update_cc_test_checks.py,` and non-autogenerated test codes are changed as follows:

(1) I wrote a python script that (partially) updates the tests using regex: {F18594904} The script is not perfect, but I believe it gives hints about which patterns are updated to have `noundef` attached.

(2) The remaining tests are updated manually.

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D108453

Resolve lit failures in clang after 8ca4b3e's land

Fix lit test failures in clang-ppc* and clang-x64-windows-msvc

Fix missing failures in clang-ppc64be* and retry fixing clang-x64-windows-msvc

Fix internal_clone(aarch64) inline assembly

This reverts commit 7584ef766a7219b6ee5a400637206d26e0fa98ac.