[PATCH] D65718: [LangRef] Document forward-progress requirement

[JF Bastien via Phabricator via llvm-commits]

jfb added inline comments.


================
Comment at: llvm/docs/LangRef.rst:2497
+(including but not limited to accessing inaccessible memory, volatile or
+atomic memory access, or other forms of thread synchronization). Failure to
+cause a side-effect in a finite amount of time results in undefined behavior.
----------------
efriedma wrote:
> jfb wrote:
> > A relaxed atomic load is a sufficient side-effect?
> We want to consider a busy-wait loop like "while (foo){}", where "foo" is an atomic variable, as making forward progress; otherwise, there isn't any way to write such a loop.  We also want to allow erasing dead atomic loads.
> 
> We might need to modify the definition of a side-effect to make this work.
Right, I'm trying to understand what guarantees LLVM offers, and if they're the same or more than C++.
Where it makes sense I'd like this documented, with references.

http://eel.is/c++draft/intro.progress
http://eel.is/c++draft/intro.multithread#intro.races-3



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