ToT / 14 does not build on OpenBSD/amd64

[brad0]

At the moment the ToT / 14 will not build on OpenBSD/amd64. I ran into this a few months ago and
then forgot about it.

It seems to be caused by this commit.. a0a5964
https://reviews.llvm.org/D105466

I have e-mailed some of our developers to see if they can comment on the diff and why it might be failing as is.

ld: error: undefined symbol: LLVMRTDyldTLSSpace
>>> referenced by llvm-rtdyld.cpp
>>>               tools/llvm-rtdyld/CMakeFiles/llvm-rtdyld.dir/llvm-rtdyld.cpp.o:(TrivialMemoryManager::allocateTLSSection(unsigned long, unsigned int, unsigned int, llvm::StringRef))
c++: error: linker command failed with exit code 1 (use -v to see invocation)

[llvmbot]

@llvm/issue-subscribers-backend-x86

[tstellar]

@MoritzS @lhames Should we revert this? a0a5964

[lhames]

@brad0 Does adding __linux__ to the condition fix the issue? If so I think we should just do that for now

@MoritzS Do you need this to work for BSD too? If so, would you be willing to investigate a longer term fix?

[MoritzS]

I used #if defined(__x86_64__) && defined(__ELF__) as a proxy to test for whether the target uses the ELF x86-64 TLS ABI. I'm not familiar with OpenBSD, does it use a different ABI? If adding __linux__ fixes this, I would also be in favor to just do that.

[brad0]

I'll check to see if that builds when I get home in a number of hours. But just to add to this.. OpenBSD currently does not have native TLS support. We're using the emulated TLS support.

[brad0]

I used #if defined(__x86_64__) && defined(__ELF__) as a proxy to test for whether the target uses the ELF x86-64 TLS ABI. I'm not familiar with OpenBSD, does it use a different ABI? If adding __linux__ fixes this, I would also be in favor to just do that.

I changed #if defined(__x86_64__) && defined(__ELF__) to #if defined(__x86_64__) && defined(__ELF__) && !defined(__OpenBSD__) and it built Ok.

[MoritzS]

Ok, that's good to know. Thanks for testing, @brad0. To be safe I think we should use defined(__linux__) instead of !define(__OpenBSD__). I only tested this extensively on linux and even the test case itself only runs on linux.

[brad0]

Ok, that's good to know. Thanks for testing, @brad0. To be safe I think we should use defined(__linux__) instead of !define(__OpenBSD__). I only tested this extensively on linux and even the test case itself only runs on linux.

Ah, it's disabling the code either way on OpenBSD. I had suggested !OpenBSD thinking other OS's like FreeBSD / NetBSD for example were Ok for TLS and ABI wise.

[brad0]

@MoritzS ?