gcj: mem leaks & speed.

Mon Feb 2 18:07:00 GMT 2004

Boehm, Hans wrote:
> Adding a conventional copied young generation to gcj is nontrivial. It
> would have to really be a "mostly copied" young generation, since we have to
> deal with ambiguous roots.

About a decade ago Elliot Moss's group (at U-Mass Amherst, I believe)
worked on precise GC for GNU Modula-3, modifying Gcc to generate
information for precise root information. The project kind of fizzled
out, probably though lack of funding, and because it was difficult to
do efficiently (and it was easy to do conservative collection).
Since then we've now implemented Dwarf-2 unwind information,
where the compiler generates a compact encoding of what registers
need to be restored on exception handling. I'm wandering whether
that model could be extended to tell the GC what it needs to know
for precise (and possibly copying) collection.
Native methods are a complication. For CNI we can modify g++ in
the same way we modify gcj. For JNI we probably don't want to
use compiler assist, bu use the strategies that other VMs use.
-- 
	--Per Bothner
per@bothner.com http://per.bothner.com/