On Thu, May 6, 2010 at 5:43 PM, Andrew MacLeod <amacl...@redhat.com> wrote: > I've been working for a while on understanding how the new memory model and > Atomics work, and what the impacts are on GCC. > > It would be ideal to get as many of these changes into GCC 4.6 as possible. > I've started work on some of the modifications and testing, and the overall > impact on GCC shouldn't be *too* bad :-) > > The plan is to localize the changes as much as possible, and any intrusive > bits like optimization changes will be controlled by a flag enabling us to > keep the current behaviour when we want it. > > I've put together a document summarizing how the memory model works, and how > I propose to make the changes. I've converted it to wiki pages. Maybe no > one will laugh at my choice of document format this time :-) > > The document is linked off the Atomics wiki page, or directly here: > http://gcc.gnu.org/wiki/Atomic/GCCMM > > It consists mainly of describing the 2 primary aspects of the memory model > which affects us > - Optimization changes to avoid introducing new data races > - Implementation of atomic variables and synchronization modes > as well as a new infrastructure to test these types of things. > > I'm sure I've screwed something up while doing it, and I will proofread it > later today again and tweak it further. > > Please point out anything that isn't clear, or is downright wrong. > Especially in the testing methodology since its all new stuff. > Suggestions for improvements on any of the plan are welcome as well.
First let me say that the C++ memory model is crap when it forces data-races to be avoided for unannotated data like the examples for packed data. Well, I hope that instead of just disabling optimizations you will help to improve their implementation to be able to optimize in a conformant manner. Richard. > Andrew > > > >
