Dan Sugalski wrote:
At 7:09 PM +0100 10/27/02, Leopold Toetsch wrote:So the I-register access is substituted by access to 3 global integers.
Now, how would these globals be loaded? When are these »arg« OPs inserted?
Currently the register optimizer in jit.c does something very similar: Setting up register access for the most used parrot registers in one execution block + load and store add block begin/end.
This is definitely a Clever Thing, and one I've pondered on and off. It will definitely speed up some things, as there's less bytecode to chew through, there's more of a chance for optimization by the C compiler when parrot's being built, and generally more opportunity to cheat.
It would also solve the multi_keyed problem. The _get_keyed argument preparation could fetch the PMC out of the aggregate.
I'm currently leaning against it only because it doesn't ultimately help the JIT. What we have now is wildly cool and damn useful (and has anyone heard from Daniel lately, BTW?) but there's room for more optimizations.
Yes, that's correct. JIT wouldn't profit currently. But with an optimized stream of (micro-)Ops, having optimzed fetch/store opcodes not in (basic-) block but finer granularity, JIT could profit too. Also the JIT-optimizer now run at load time would be done at compile time, so JIT startup time would be cut down.
Now, on the other hand it *does* speed up the interpreter, so it's definitely not an idea to discard. But if we're going to (and I'd still like to hold off) I think we're better off with a few special versions of ops that target one or twi registers directly, perhaps register 0 and 1, rather than have a separate set of special-purpose registers.My hack with the 3 globals includes obviously some cheating, globals are a nono, when having multiple interpreters. But nethertheless we could produce an optimized PBC stream, where the 3*4 registers are treated as "fast" registers, with load/store to the 32*4 slower registers only when necessary. This would also fit neatly with my proposal WRT keyed access.
I was also thinking of the various fixed sized integer ops for JVM or C#. The load/store ops would prepare integers of needed size and do sign extension when necessary.
leo
