[Bug]: Function Multi Versioning: fix crashes, adjust names, priorities and mangling, support Android API 23-29, rcpc3 and mops features.

[ilinpv]

Description

Improve Function Multi Versioning support in NDK.

• Support Android API 23+
• New features:
  • rcpc3 - Load-Acquire RCpc instructions version 3.
  • mops - Memory Copy and Memory Set instructions.
• Adjust feature priorities, names, and mangling in accordance with the specification https://github.com/ARM-software/acle/blob/main/main/acle.md#function-multi-versioning
• Fix various crashes

Upstream bug

llvm/llvm-project#65669
llvm/llvm-project#81043

Commit to cherry-pick

LLVM commits to cherry-pick
llvm/llvm-project@30b0fdf
llvm/llvm-project@8ec50d6
llvm/llvm-project@b04fe22
llvm/llvm-project@e5fe3d2
llvm/llvm-project@1be0d9d
llvm/llvm-project@179ba12
llvm/llvm-project@f214933
llvm/llvm-project@99d7433
llvm/llvm-project@b42b7c8
llvm/llvm-project@e81ef46

Affected versions

r26

Canary version

No response

Host OS

Linux, Windows

Host OS version

Ubuntu 22.04 LTS

Affected ABIs

arm64-v8a

[ilinpv]

Preparing patch of cherry-picks to llvm-r487747 for next NDK respin.

[DanAlbert]

These aren't regressions, are they? FMV wasn't in r25 at all, I thought.

[pirama-arumuga-nainar]

IIUC, it's a new feature in r26 toolchain that's broken at launch. One exception is that llvm/llvm-project@b04fe22 seems like a feature rather than a bug fix to me.

[DanAlbert]

I'm inclined to say that we should not be backporting changes for experimental clang features that were not ready yet when we branched the toolchain. If these had been filed before we reached the release candidate that'd probably be a different story, but it's hard to justify risking the stability of the release with fixes for unfinished features. We did that last year with r25 and aiui that was the cause of #1862. It's critical that point releases do not introduce regresssions, so unless the cherry-pick is fixing a regression from the previous major release, it's not typically a candidate.