--emulated-tls explanation?

[IGotD-]

On Tuesday, 13 October 2020 at 12:00:34 UTC, Denis Feklushkin 
wrote:
>
> It is implemented inside of LLVM?
> Can you provide link to right declaration?
>
> Google full of "__tls_get_addr()" form
>

Sorry, I can't because it is a mess. I think that __tls_get_addr 
is connected to an ELF standard for thread-local storage.

https://akkadia.org/drepper/tls.pdf

Note that the document doesn't include ARM but Itanium and other 
unusual CPUs. However declaration of __tls_get_addr is stated 
there for other CPUs than ARM. I've seen other versions of 
__tls_get_addr out there as well and it can be architecture 
dependent. Also keep in mind that I use ARMv7-ar as reference 
point here, I cannot 100% say that it is the same for Cortex M3. 
The RunTime ABI for ARM

http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=C3E4EA7E008BA776DF7E0F54C8F7CCF1?doi=10.1.1.352.5218&rep=rep1&type=pdf

isn't really that helpful either.