On 09/07/15 23:17, Basile Starynkevitch wrote: > (this is triggered by a question on the Ocaml mailing list asking about > SystemZ backend in Ocaml; SystemZ is today a backend for GCC & probably > GCCJIT) > > We might want to support better good garbage collection schemes in GCC, > particularily in GCCJIT. This is a > thing that LLVM is known to be weak at, and we might aim to do much > better. If we did, good frontends for > good functional languages (e.g. F#, Ocaml, Haskell) might in the future > profit of GCC technology. And even a Javascript engine based on GCCJIT > could profit. > > A good GC is very probably a precise (sometimes generational copying) GC > with write barriers > (read the http://gchandbook.org/ for more, or at least the wikipage > about garbage collection). So a good GC is changing pointers. > > So we need to know where, and provide a mechanism for, pointer values > are located in the call stack (of the GCCJIT generated code), and > probably provide some write barrier machinery.
It's going to be very hard. All our experience with GCJ shows that a true precise GC in GCC is going to require major surgery in many places. The HotSpot optimizing compilers are written with GC as a basic requirement and it touches many places. Andrew.
