Goal is simply to reduce direct usage of getLength and setLength so that
if we end up moving memset.pattern (whose length is in elements) there
are fewer places to audit.

lifetime.start and lifetime.end are primarily intended for use on
allocas, to enable stack coloring and other liveness optimizations. This
is necessary because all (static) allocas are hoisted into the entry
block, so lifetime markers are the only way to convey the actual
lifetimes.

However, lifetime.start and lifetime.end are currently *allowed* to be
used on non-alloca pointers. We don't actually do this in practice, but
just the mere fact that this is possible breaks the core purpose of the
lifetime markers, which is stack coloring of allocas. Stack coloring can
only work correctly if all lifetime markers for an alloca are
analyzable.

* If a lifetime marker may operate on multiple allocas via a select/phi,
we don't know which lifetime actually starts/ends and handle it
incorrectly (https://github.com/llvm/llvm-project/issues/104776).
* Stack coloring operates on the assumption that all lifetime markers
are visible, and not, for example, hidden behind a function call or
escaped pointer. It's not possible to change this, as part of the
purpose of lifetime markers is that they work even in the presence of
escaped pointers, where simple use analysis is insufficient.

I don't think there is any way to have coherent semantics for lifetime
markers on allocas, while also permitting them on arbitrary pointer
values.

This PR restricts lifetimes to operate on allocas only. As a followup, I
will also drop the size argument, which is superfluous if we always
operate on an alloca. (This change also renders various code handling
lifetime markers on non-alloca dead. I plan to clean up that kind of
code after dropping the size argument as well.)

In practice, I've only found a few places that currently produce
lifetimes on non-allocas:

* CoroEarly replaces the promise alloca with the result of an intrinsic,
which will later be replaced back with an alloca. I think this is the
only place where there is some legitimate loss of functionality, but I
don't think this is particularly important (I don't think we'd expect
the promise in a coroutine to admit useful lifetime optimization.)
* SafeStack moves unsafe allocas onto a separate frame. We can safely
drop lifetimes here, as SafeStack performs its own stack coloring.
* Similar for AddressSanitizer, it also moves allocas into separate
memory.
* LSR sometimes replaces the lifetime argument with a GEP chain of the
alloca (where the offsets ultimately cancel out). This is just
unnecessary. (Fixed separately in
https://github.com/llvm/llvm-project/pull/149492.)
* InferAddrSpaces sometimes makes lifetimes operate on an addrspacecast
of an alloca. I don't think this is necessary.

Stop using hardcoded function named and check availability. This only fixes
the forced usage via command line in the pass itself; the implementations
inside of TargetLoweringBase hide additional call emission.

Avoid hardcoding the function name, and query if it's really
supported or not.

Add a new `CreateIntrinsic` overload with no `Types`, useful for
creating calls to non-overloaded intrinsics that don't need additional
mangling.

Identified with misc-include-cleaner.

Just insert addrspacecast in cases where the alloca uses a
different address space, since I don't know what else you
could possibly do.

This pull request corrects multiple occurrences of the typo "avaliable"
to "available" across the LLVM and Clang codebase. These changes improve
the clarity and accuracy of comments and documentation. Specific
modifications are in the following files:

1. clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp:
Updated comments in readability checks for cognitive complexity.
2. llvm/include/llvm/ExecutionEngine/Orc/ExecutionUtils.h: Corrected
documentation for JITDylib responsibilities.
3. llvm/include/llvm/Target/TargetMacroFusion.td: Fixed descriptions for
FusionPredicate variables.
4. llvm/lib/CodeGen/SafeStack.cpp: Improved comments on DominatorTree
availability.
5. llvm/lib/Target/RISCV/RISCVSchedSiFive7.td: Enhanced resource usage
descriptions for vector units.
6. llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp: Updated invariant
description in shift-detect idiom logic.
7. llvm/test/MC/ARM/mve-fp-registers.s: Amended ARM MVE register
availability notes.
8. mlir/lib/Bytecode/Reader/BytecodeReader.cpp: Adjusted forward
reference descriptions for bytecode reader operations.

These changes have no impact on code functionality, focusing solely on
documentation clarity.

Co-authored-by: wangqiang <wangqiang1@kylinos.cn>

Convert almost every instance of:
  CreateCall(Intrinsic::getOrInsertDeclaration(...), ...)
to the equivalent CreateIntrinsic call.

Rename the function to reflect its correct behavior and to be consistent
with `Module::getOrInsertFunction`. This is also in preparation of
adding a new `Intrinsic::getDeclaration` that will have behavior similar
to `Module::getFunction` (i.e, just lookup, no creation).