[PATCH] D147849: [Android] Use ELF TLS for Android API level 29+

[Ryan Prichard via Phabricator via llvm-commits]

rprichard added a comment.

nit: In the description/commit message, the "when the API level is > 29" should be "when the API level is >= 29".

I think it's OK, but I'd like confirmation that it works with LTO?

One issue I noticed earlier was that the compiler flag (`-f[no-]emulated-tls`) doesn't work with LTO:

- The flag is ignored when the compiler is only outputting LLVM IR, and
- The flag is also ignored at link-time when the IR is converted to emutls-or-efltls machine code.

This link-time LTO setting can be changed using `-Wl,-plugin-opt,-emulated-tls={0,1}`.

It's not clear to me from the patch whether the new default applies when `-flto` is used to compile. (I suspect that it does, but a confirmation might be useful?)

Also: This is technically an ABI break, but it only applies when a thread-local variable is accessed across an ABI boundary, which seems unlikely/rare. It seems like the change is worth it, in any case.


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D147849