[PATCH] D115456: Implement on-demand TLS initialization for Microsoft CXX ABI

[Maurice Heumann via Phabricator via cfe-commits]

momo5502 added a comment.

In D115456#3216811 <https://reviews.llvm.org/D115456#3216811>, @majnemer wrote:

> This is looking great! Just a few more questions.
>
> What is the behavior with something like:
>
>   thread_local int x = 2;
>   int f() {
>     return x;
>   }
>
> I'm wondering if we need to move this logic <https://github.com/llvm/llvm-project/blob/1f07a4a5699b73582461880e716e6692cbe3d6a6/clang/lib/CodeGen/ItaniumCXXABI.cpp#L391-L392> into the generic C++ ABI implementation.

The MS compiler only emits the dynamic initializers for variables with constructors/destructors, just like it is currently done here for the Itanium ABI.
I also thought about adopting that behaviour, but I think threre are edge-cases when triggering dynamic TLS initialization even for constant variables is useful.
For example there might be custom TLS callbacks that can affect the value of this variable.

If desired, I can change it to match the behaviour of MS, but I thought it could be beneficial to diverge in this case.


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https://reviews.llvm.org/D115456