Currently, the more features a version has, the higher its priority is.
We are changing ACLE https://github.com/ARM-software/acle/pull/370 as
follows:

"Among any two versions, the higher priority version is determined by
 identifying the highest priority feature that is specified in exactly
 one of the versions, and selecting that version."

We need to be able to propagate information about FMV attribute strings
from C/C++ source to LLVM IR. This is necessary so that we can
distinguish which target-features are coming from the cmdline, which are
coming from the target attribute, and which are coming from feature
dependency expansion. We need this for static resolution of calls in
LLVM. Here's a motivating example:

Suppose you have target_version("i8mm+dotprod") and
target_version("fcma"). The first version clearly has higher priority.
Now suppose you specify -march=armv8-a+i8mm on the command line. Then
the versions would have target-features "+i8mm,+dotprod" and
"+i8mm,+fcma" respectively. If you are using those to deduce version
priority, then you would incorrectly deduce that the second version was
higher priority than the first.

Currently we need at least one more version other than the default to
trigger FMV. However we would like a header file declaration

__attribute__((target_version("default"))) void f(void);

to guarantee that there will be f.default

This patch introduces the Clang components of type sanitizer: a
sanitizer for type-based aliasing violations.

It is based on Hal Finkel's https://reviews.llvm.org/D32198.

The Clang changes are mostly formulaic, the one specific change being
that when the TBAA sanitizer is enabled, TBAA is always generated, even
at -O0.

It goes together with the corresponding LLVM changes
(https://github.com/llvm/llvm-project/pull/76259) and compiler-rt
changes (https://github.com/llvm/llvm-project/pull/76261)

PR: https://github.com/llvm/llvm-project/pull/76260

Re-apply #113148 after revert in #119331

If function pointer signing is enabled, sign personality function
pointer stored in `.DW.ref.__gxx_personality_v0` section with IA key,
0x7EAD = `ptrauth_string_discriminator("personality")` constant
discriminator and address diversity enabled.

Reverts llvm/llvm-project#113148

See buildbot failure
https://lab.llvm.org/buildbot/#/builders/190/builds/11048

If function pointer signing is enabled, sign personality function
pointer stored in `.DW.ref.__gxx_personality_v0` section with IA key,
0x7EAD = `ptrauth_string_discriminator("personality")` constant
discriminator and address diversity enabled.

Fixes #112205

--- 

Commit that introduced this feature -
https://github.com/llvm/llvm-project/commit/9306ef9750b7a319d59f6d3e4977e01e39b8f161

Currently we have code with target hooks in CodeGenModule shared between
X86 and AArch64 for sorting MultiVersionResolverOptions. Those are used
when generating IFunc resolvers for FMV. The RISCV target has different
criteria for sorting, therefore it repeats sorting after calling
CodeGenFunction::EmitMultiVersionResolver.

I am moving the FMV priority logic in TargetInfo, so that it can be
implemented by the TargetParser which then makes it possible to query it
from llvm. Here is an example why this is handy:
https://github.com/llvm/llvm-project/pull/87939

When dealing with cpu_specific GlobalDecl,
GetOrCreateMultiVersionResolver should immediately return the already
created llvm function if it exists.

Fixes https://github.com/llvm/llvm-project/issues/115299.