llvm dev - Oct 2017 - emulated-tls & lld lto

Hi,

When targetting android (which doesn't support tls) I have to pass -mllvm
-emulated-tls to get a working executable, however lld fails with:

lld.exe: error: TLS attribute mismatch:
f_t31_RemObjects.Elements.System.SynchronizationContext.fCurrent
 >>> defined in 
 >>> defined in lto.tmp

Where
@f_t31_RemObjects.Elements.System.SynchronizationContext.fCurrent = hidden
thread_local global %._RemObjects.Elements.System.SynchronizationContext* null

when linking two bitcode files. I'm currently having a bit of trouble
reproducing this with a simple testcase so I wanted to ask if anyone knows what
could cause this?

This happens in SymbolTable::insert, the first time it inserts a symbol when
loading the Archive file, which sets it as TLS symbol. The second time when it
actually did LTO and it's not TLS anymore.

Carlo Kok
RemObjects Software
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I also cannot create a testcase that reproduces tihs.

What I find odd is that given

@a = hidden thread_local global i32 42, align 4

llc with -emulated-tl produces the symbols "__emutls_v.a" and
"__emutls_t.a", but not "a".

Any idea how
f_t31_RemObjects.Elements.System.SynchronizationContext.fCurrent is
showing up in lto.tmp?

Thanks,
Rafael

Carlo Kok via llvm-dev <llvm-dev at lists.llvm.org> writes:
> Hi,
>
> When targetting android (which doesn't support tls) I have to pass
-mllvm -emulated-tls to get a working executable, however lld fails with:
>
> lld.exe: error: TLS attribute mismatch:
f_t31_RemObjects.Elements.System.SynchronizationContext.fCurrent
>  >>> defined in 
>  >>> defined in lto.tmp
>
> Where
> @f_t31_RemObjects.Elements.System.SynchronizationContext.fCurrent = hidden
thread_local global %._RemObjects.Elements.System.SynchronizationContext* null
>
> when linking two bitcode files. I'm currently having a bit of trouble
reproducing this with a simple testcase so I wanted to ask if anyone knows what
could cause this?
>
> This happens in SymbolTable::insert, the first time it inserts a symbol
when loading the Archive file, which sets it as TLS symbol. The second time when
it actually did LTO and it's not TLS anymore.
>
> Carlo Kok
> RemObjects Software
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