remove emulated TLS for OSX

[MartinNowak]

• native TLS supported since 2.072.0

[dlang-bot]

Thanks for your pull request, @MartinNowak!

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[PetarKirov]

CyberShadow/DAutoTest fails due to dlang/dlang.org#1796.

[jacob-carlborg]

@MartinNowak @ZombineDev 32bit is still using emulated TLS: https://github.com/dlang/dmd/blob/master/src/ddmd/toobj.d#L1239.

To elaborate, I never got the implementation to work on 32bit, although it's using the same scheme as far as I can see. Since 32bit macOS is basically a dead platform, Walter decided it wasn't worth spending time on it and the 64bit implementation was approved.

There are a few cases where 32bit macOS might still be interesting:

• The simulator (for iOS, WatchOS and TvOS) is actually running x86 code and not ARM code. iOS will soon be 64bit only as well, but I'm not sure about WatchOS. This assumes that someone actually cares about running DMD compiled code in the simulators. It might be enough with LDC

• As far as I understand, Guillaume Piolat is developing audio plugins on macOS and supports 32bit. I'm not sure if DMD is needed or if LDC is enough. I think the customers might be using old 32bit plugins which are not available for 64bit and therefore cannot move the main application to 64bit either

[ibuclaw]

Decide what to do about OSX 32bit.

As per @jacob-carlborg's comments

[MartinNowak]

Yes, smelled a bit as if 32-bit was still relying on this. Any reference to the OSX TLS implementation? Can't find any in dlang/dmd#5346, but I guess you didn't reverse engineer all of it @jacob-carlborg.
I found https://stackoverflow.com/a/29929949/2371032 which mentions TLS support in XCode 8.

[MartinNowak]

Decide what to do about OSX 32bit.

Keep as long as it's not much to keep.

[jacob-carlborg]

Any reference to the OSX TLS implementation?

There's no official reference, as far as I know. What I found out is documented here [1][2].

[1] https://github.com/dlang/dmd/blob/master/src/ddmd/toobj.d#L1212
[2] https://github.com/dlang/dmd/blob/master/src/ddmd/backend/el.c#L1285

[jacob-carlborg]

TLS was supported before Xcode 8. __thread was supported but not thread_local, IIRC.

[dnadlinger]

TLS is supported on OS X 10.7+.

[MartinNowak]

There's no official reference, as far as I know. What I found out is documented here [1][2].

Unfortunately doesn't document from what you derived this. Guess from their runtime linker and llvm/clang, right?

[jacob-carlborg]

Unfortunately doesn't document from what you derived this. Guess from their runtime linker and llvm/clang, right?

From dyld and looking at the assembly and object dumps from Clang.

[PetarKirov]

Darwin_64_32 fails consistently on autotester, so it looks we can't move forward with this PR. Please reopen, if I'm misunderstanding.