On 9/7/06, Rana Dasgupta <[EMAIL PROTECTED]> wrote:
Hi Mikhail,
Sorry I left this thread for a while. Are you implementing VMMagic
support in .OPT currently, and prototyping with bump allocation? I am
just
trying to understand in what order we are doing this.
I'm implementing VMMagics and going to use it to prototype bump pointer
allocation. I hope I will finish VMMagic OPT package in a several weeks.
Would it be possible to list the fastpath helpers so that the java
interfaces to access them could be defined? All of them don't need magic
classes support and one of us could just write them. I don't know the list
of intrinsics implemented already in .JET. Can we just use them as is, and
what else ( other than TLS access, call support ) would need to be added?
The list of the helpers with fast path to be written in Java:
1) object allocation
2) array allocation
3) monitor enters
4) monitor exits
5) I hope we can move some profiling helpers to Java and to remove the
knowledge about their implementation from JIT.
6) write and read barriers
7) back branch polling helper
8) ? Some TI helpers ?
VM gurus, have you anything to add to this list?
+ I think that TLS and call support are enough.
BTW, there may be a small omission in the example below..if I am reading
this right...
IMO "newCurrent = oldCurrent + size" is OK. May be the source of the problem
is the variable name, i.e. 'ceiling' is always >= 'current' in my example.
Thanks,
Rana
On 8/28/06, Mikhail Fursov <[EMAIL PROTECTED]> wrote:
> Folks,
> Here is the example of fast allocation helper written in Java with the
> help
> of VMMagic
> If nobody objects I'm starting to implement VMMagic support in
> Jitrino.OPTthis week.
>
>
>
> private static final int GC_TLS_OFFSET = 10;
> private static final int GC_CURRENT_OFFSET= GC_TLS_OFFSET + 0;
> private static final int GC_CEILING_OFFSET= GC_TLS_OFFSET + 4;
> private static final int OBJ_VTABLE_OFFSET = 0;
>
> //annotate with calling convention and real VM helper id/name
information
> private static Address slowAlloc(int vtable, int size) {throw new
> Error("must never be called!");}
>
> private static Address fastAlloc(int vtable, int size) {
> Address tlsBase = TLS.getAddress(); //load thread local client area
> address
>
> Address currentFieldAddress = tlsBase.plus(GC_CURRENT_OFFSET);
> Address ceilingFieldAddress = tlsBase.plus(GC_CEILING_OFFSET);
>
> Address newObjectAddress; //the result of the method
>
> // check if there is enough size to do allocation in thread local
> buffer
> Address current = currentFieldAddress.loadAddress();
> Address ceiling = ceilingFieldAddress.loadAddress();
> Address newCurrent = current.plus(size);
> if (newCurrent.LT(ceiling)) {
>> newCurrent = newCurrent.plus(-size);
currentFieldAddress.store(newCurrent.toWord());
> newObjectAddress = newCurrent;
> newObjectAddress.store(vtable, Offset.fromInt
(OBJ_VTABLE_OFFSET));
>
> } else {
> newObjectAddress = slowAlloc(vtable, size);
> }
> return newObjectAddress;
> }
>
> --
> Mikhail Fursov
>
>
--
Mikhail Fursov
