[llvm-dev] [RFC] Enable thread specific cl::opt values for multi-threaded support

[Yevgeny Rouban via llvm-dev]

On Sat, Oct 20, 2018 at 5:08 PM Nicolai Hähnle via llvm-dev <llvm-dev at lists.
llvm.org> wrote:

> Hi Yevgeny,
>
> Just to make sure I'm understanding this correctly: When a thread has a
> non-null option context, then options set in the global context will
> have no effect at all for that thread. Right? (That's what I would
> expect and what makes sense to me.)
>
> Yes, but the global context has no effect on your thread only for those
options that have been changed in this thread's context.
That is because a thread local copy of an option is created in the current
thread context when this option is set by this thread or another thread
with the same option context. If the option has not been set then its
global value is used.
For your case, I would suggest that you explicitly set a new thread option
context for every thread (or thread group) that uses LLVM. This way the
threads/groups will not affect each other and will use the options in the
copy-on-write way.
May be it makes sense to try playing with the tests in the patch to better
understand the use model.

Thanks.
-Yevgeny Rouban
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20181022/ec2c5748/attachment.html>