I'm assuming that the temporaries are the things being moved around here ?.
It is not so much a matter of moving things around, but a matter of allocating (and renumbering) parrot (or for JIT) processor registers. These are of course mainly temporaries, but even when you have some find_lexical/do_something/store_lexical, imcc selects the best register for all involved ops, temps or "variables" it doesn't really matter.
The only question I have here , how does imcc identify loops ?. I've been using "if goto" to loop around , which is exactly the way assembly does it. But that sounds like a lot of work identifying the loops and optimising accordingly.
Here are basic blocks, the CFG and loop info of 0 set I0, 10 1 x: 1 unless I0, y 2 dec I0 2 print I0 2 print "\n" 2 branch x 3 y: 3 end
Dumping the CFG: ------------------------------- 0 (0) -> 1 <- 1 (1) -> 2 3 <- 2 0 2 (1) -> 1 <- 1 3 (0) -> <- 1
Loop info --------- loop 0, depth 1, size 2, entry 0, contains blocks: 1 2
To make it more clear -- identifying tight loops and the usage weights
correctly. 10 uses of $I0 outside the loop vs 1 use of $I1 inside a 100
times loop. Which will be come first ?.
This is basically the current score calculation used for register allocation:
r->score = r->use_count + (r->lhs_use_count << 2);
r->score += 1 << (loop_depth * 3);
Gopal
leo
