Is there a modern GC for D?

[Robert Jacques]

Based on a thread on the DMD concurrency mailing list I've begun to get a  
sinking regarding the future of the garbage collector in D: most of the  
work in GC algorithms has gone into functional and (mostly) pure-OO  
languages, leaving a multi-paradigm systems programming language like D  
out in the cold. So far, I know mark-sweep and mark-region algorithms in  
either serial, parallel or thread-local forms should work. But based on  
Java we'd really like incremental, generational and/or concurrent options.  
So I'd like to ask people to help brainstorm some ideas.

Some things I've run into:
-structs/pointers/slices/etc make finding memory meta information, like  
mark-bits or ref-counts, non-trivial.
-C function calls and assembler blocks make code instrumentation  
questionable.
-Getting concurrent GC code correct is very hard. Boehm's algorithm, for  
instance, looks extremely racy.

Thanks!