[LLVMdev] Proposal for a new LLVM concurrency memory model

[Dan Gohman]

On Apr 26, 2010, at 1:15 PM, Alistair Lynn wrote:

> Hi David-
> 
> On 26 Apr 2010, at 21:05, David Greene wrote:
> 
>> What's a "trap" and "trap value?"  Is it some C++0X or Java thing?
>> It needs to be defined.
> 
> See LangRef.html

Yes; it was just added 4 days ago, for an unrelated purpose.  It's an
interesting concept which on the surface seems to be a good fit, though
there are some complicating issues.

Here's one:

In the "load widening" section of the proposed memory model, if there's
a race condition on the high bits of a widened load, but the high bits
are never observed, the low bits should remain defined. However, that's
not how the current trap concept works (yet).

Dan