stdarg.h and especially stddef.h are textual and so everything they
declare gets precompiled into all of their clients' pcm files. They
shouldn't directly declare anything though, their purpose is to select
what submodules get imported, and not to add duplicate declarations to
all of their clients. Make it so that they always ignore their header
guards, even without modules, and declare them in separate header files
so that they only go into the stdarg/stddef pcms. Still declare them in
case clients rely on them.

Such APIs are useful in lock implementations

fir.cuda_free operation was wrongly generated for dummy argument.

An earlier commit provided a way to decouple DXIL version from Shader
Model version by representing the DXIL version as `SubArch` in the DXIL 
Target Triple and adding corresponding valid DXIL Arch types.

This change constructs DXIL target triple with DXIL version that is
deduced from Shader Model version specified in the following scenarios:

1. When compilation target profile is specified: 
For e.g., DXIL target triple `dxilv1.8-unknown-shader6.8-library` is
constructed when `-T lib_6_8` is specified. 
2. When DXIL target triple without DXIL version is specified:
For e.g., DXIL target triple `dxilv1.8-pc-shadermodel6.8-library` is
constructed when `-mtriple=dxil-pc-shadermodel6.8-library` is specified.

Updated relevant HLSL tests that check for target triple. 

Validated that Clang (`check-clang`) and LLVM (`check-llvm`) regression
tests pass.

Address review comments for PR91214.

Use add_custom_command instead of add_custom_target to generate
SBLanguages.h.

This implements the HLSL 202x conforming literals feature.

The feature proposal is available here:

https://github.com/microsoft/hlsl-specs/blob/main/proposals/0017-conforming-literals.md

The language specification for this behavior is available in (poorly
rendered) HTML or PDF:
https://microsoft.github.io/hlsl-specs/specs/hlsl.html#Lex.Literal.Float
https://microsoft.github.io/hlsl-specs/specs/hlsl.pdf

The main implementation details are:
1) Unsuffixed floating literals are `float`.
2) The integer `ll` suffix specifies `int64_t (aka long)` which is
64-bit because HLSL has no defined `long` keyword or `long long` type.

Resolves #85714

This adds a document to describe the DXContainer format and the
structures of data inside the file.

Resolves #88775

Revert the portion of https://github.com/llvm/llvm-project/pull/75125
which modified the LIBOMP_HEADERS_INSTALL_PATH in standalone build.

This change is harmful for real standalone builds (i.e. builds where we
build openmp by itself), since it tries to overwrite the `omp.h` inside
the build compiler. For all-in-one builds with clang, testing shows this
change is unnecessary as https://github.com/llvm/llvm-project/pull/88007
already set up that build configuration so that omp.h will be put into
the project build's `clang` resource directory.

[coro][CoroSplit] Use `llvm.lifetime.end` to compute putting objects on the frame vs the stack (#90265)

The current logic for using lifetime intrinsics to determine whether a
coroutine alloca should live on the coroutine frame or stack doesn't
consider `llvm.lifetime.end`. As a result, some allocas are incorrectly
placed on the stack even though their lifetimes may outlive the stack.
For example, SimplifyCFG may generate code that drops the corresponding
`llvm.lifetime.end` of an `llvm.lifetime.start`, and that code is
incorrectly handled by the existing logic.

To fix this, new logic is introduced where if an alloca's address is
escaped, and there is a path from an `llvm.lifetime.start` to a
coroutine suspend point (e.g. `llvm.coro.suspend`) without an
`llvm.lifetime.end`, then we know the object lives beyond the suspension
point and therefore must go on the coroutine frame.

Fixes https://github.com/llvm/llvm-project/issues/86580

Insert the barrier after the last _executed_ copy, not the most recently
inserted copy.
This fixes https://github.com/llvm/llvm-project/issues/91205.

We need to update DW_AT_comp_dir/DW_AT_dwo_name TU in the
.debug_info.dwo section so that the path is correct. Refactored helper
functions to make it easier for next step.

This uses non-volatile registers for the first four (six on Windows)
registers used for `preserve_none` argument passing. This allows these
registers to stay "pinned", even if the body of the `preserve_none`
function contains calls to other "normal" functions.

Example:

```c
void boring(void);

__attribute__((preserve_none)) void (continuation)(void *, void *, void *, void *);

__attribute__((preserve_none)) void entry(void *a, void *b, void *c, void *d)
{
    boring();
    __attribute__((musttail)) return continuation(a, b, c, d);
}
``` 

Before:

```asm
pushq   %rax
movq    %rcx, %rbx
movq    %rdx, %r14
movq    %rsi, %r15
movq    %rdi, %r12
callq   boring@PLT
movq    %r12, %rdi
movq    %r15, %rsi
movq    %r14, %rdx
movq    %rbx, %rcx
popq    %rax
jmp     continuation@PLT
```

After:

```asm
pushq   %rax
callq   boring@PLT
popq    %rax
jmp     continuation@PLT
```

This change updates the logic that determines whether an `emitc.expression`
result is translated into a dedicated variable assignment. Due to how
the translation of `emitc.subscript` currently works, a previously
inline-able `emitc.expression` would produce incorrect C++ if its single user 
was a `emitc.subscript` operation.

This removes the GISel versions of isREVMask, isTRNMask, isUZPMask and
isZipMask. They are combined with the existing versions from SDAG into
AArch64PerfectShuffle.h.

This appears to have been missed because later cpus don't inherit from Nehalem tuning much.

Noticed while cleaning up for #90985

Need to use the last address of the vectorized stores for the strided
stores, not the first one, to correctly store the data.

This change refactors RenderFloatingPointOptions() to eliminate some
excessively complicated logic and a redundant switch statement. The
logic being simplified is an artifact of the original -ffp-model
implementation, and over time it has become unnecessary.

The handling of diagnostics related to the -ffp-contract option is
still a bit convoluted after this change. I will address that in a
subsequent patch because I think it will make sense to make some minor
changes to the driver behavior when that is cleaned up. The current
patch should not make any change to observable behavior of the driver.

I was cleaning up this portion of the code and realized these are
completely unused.

In some cases we see strings from categories being part of "data"
sections (Ex:`__objc_const`), not part of of sections marked as
`cstring_literals`. Since lld treats these sections differently we need
to explicitly implement support for reading strings from the
non-`cstring_literals` sections.

Adding a test that previously would result in an assert.

When generating categories, clang sometimes will generate references in
the `.addrsig` section to the various category data items. Since we may
erase such items after merging them, we also need to remove them from
the `.addrsig` section - otherwise this will cause runtime asserts with
the `.addrsig` section trying to access invalid data.

Implementation wise, we use a hashset to keep track of all erased
`InputSection`'s and then go through all `.addrsig` sections and remove
references to any erased `InputSection`.

Currently RISCVDeadRegisterDefinitions runs after vsetvli insertion, but
in #70549 vsetvli insertion runs after vector regalloc and as a result
we no longer convert some vsetvli a0, a0s to vsetvli x0, a0. This patch
moves it to after vector regalloc, but before scalar regalloc so we
still get the benefits of reducing register pressure.

These two are very similar to the other 'var-list' variants, except they
require that the type of the variable be a pointer.  This patch
implements that restriction.

Besides duplicating code, privatizing variables in every section
causes problems when synchronization barriers are used. This
happens because each section is executed by a given thread, which
will cause the program to hang if not all running threads execute
the barrier operation.

Fixes https://github.com/llvm/llvm-project/issues/72824

Because LiveVariables has been run, we no longer need to lookup the
users in MachineRegisterInfo anymore and can instead just check for the
dead flag.

Need to check that the signed operand has an extra sign bit to be sure
that we do not skip signedness, when trying to minimize bitwidth for
smin/smax intrinsics.

Fix the issue that `char` constants are converted to `uint64_t` in the
wrong way when doing the inlining.

This reverts commit 11066449.

As noted in the original patch, this was designed to reverted once
https://reviews.llvm.org/D142479 and https://reviews.llvm.org/D142660
landed, which has long since happened.

`SBProcess::GetMemoryRegionInfo` uses `qMemoryRegionInfo` packet to get
memory region info, but this is not supported in gdb-server and causing
downstream lldb test failures. This change ignores the the error from
`SBProcess::GetMemoryRegionInfo` .

Reported by @tedwoodward @jerinphilip.

Revert "Reapply "Use an abbrev to reduce size of VALUE_GUID records in ThinLTO summaries" (#90610)" (#91194)

Reverts llvm/llvm-project#90692

Breaking PPC buildbots. The bots are not meant to test LLD, but are
running a test that is using an old version of LLD without the change
(so is incompatible). Revert until a fix is found.

Adds more FP test macros for the upcoming test adds for #61092 and the
issues opened from it: #88768, #88769, #88770, #88771, #88772.

Fix bug in `{EXPECT,ASSERT}_FP_EXCEPTION`. `EXPECT_FP_EXCEPTION(0)`
seems to be used to test that an exception did not happen, but it always
does `EXPECT_GE(... & 0, 0)` which never fails.

Update and refactor tests that break after the above bug fix. An
interesting way things broke after the above change is that
`ForceRoundingMode` and `quick_get_round()` were raising the inexact
exception, breaking a lot of the `atan*` tests.

The changes for all files other than `FPMatcher.h` and
`libc/test/src/math/smoke/RoundToIntegerTest.h` should have the same
semantics as before. For `RoundToIntegerTest.h`, lines 56-58 before the
changes do not always hold since this test is used for functions with
different exception and errno behavior like `lrint` and `lround`. I've
deleted those lines for now, but tests for those cases should be added
for the different nearest int functions to account for this.

Adding @nickdesaulniers for review.

Fixes #90285.

This relands #90348 with a fix for a [buildbot
failure](https://lab.llvm.org/buildbot/#/builders/216/builds/38446)
caused by the test being run with `-fno-rtti`.

Pre-commit tests for an upcoming patch.