[LLVMdev] RFC: Atomics.h

[Owen Anderson]

On May 16, 2009, at 7:47 PM, Luke Dalessandro wrote:

> Owen Anderson wrote:
>> Some of you may have noticed that I addedd include/llvm/System/ 
>> Atomics.h
>> to the repository briefly, which will be used for adding support for
>> threading in LLVM.
>
> Just out of curiosity, is there a design document somewhere for the  
> plan
> for threading?

Not as yet.  Chris may have ideas in this direction, but I don't think  
they're been written down anywhere.  For now, I'm just trying to  
enhance the thread-safety of some obviously unsafe pieces of code.

> Also, atomic ops are usually pretty low level things used for
> nonblocking algorithms or to build higher level locking constructs. Is
> that the plan here too? It seems like you'd want to avoid anything too
> fancy since LLVM has to run on so many different architectures with
> their variety of memory semantics, etc.

I totally agree.  However, at least one case of thread-unsafety  
(ManagedStatic), has proven very-difficult-to-impossible to implement  
correctly without using lower-level operations.

--Owen
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