C++0x memory model code gen

[Andrew MacLeod]

I've created a wiki page with the changes to codegen for the C++ memory 
model that we're working on implementing.

http://gcc.gnu.org/wiki/Atomic/GCCMM/CodeGen

in a nutshell, it expands the set of __sync atomic builtin's to take 
another parameter for memory model, and then allow machine descriptions 
to customize the code for any specific combination.

It's already at version 2.0, I'm sure there will be more updates.

Please question, comment, or criticize!

Andrew

I've also started trying to figure out what optimizations can really be 
performed on atomic accesses with synchronization and how/whether we'll 
do them. Let me know if you have even a vague understanding of this 
arcane subject and want to have some input early :-)