Seeing as Simon's gone to all the trouble of releasing the source to
Parrot now, I wondered what I could have a play with. I've did simple
Parrot assembler and thought about different types of bytecode. Like
bytecode for the Java virtual machine, which it turns out is stack
based. Could I convert JVM->PVM? I think so ;-)
[Yes, this is a proof of concept, and the parrot assembler will change
in many ways rsn, so this is just a head up to show it's possible]
Given the following Java code:
class HelloWorld {
public static void main (String args[]) {
int i = 1;
int j = 1;
while(i < 10) {
System.out.print(i);
System.out.print(j);
i++;
j += i;
}
}
}
(which prints out: 112336410515621728836945)
That actually gets translated into the the following JVM bytecode:
0 iconst_1
1 istore_1
2 iconst_1
3 istore_2
4 goto 28
7 getstatic #2 <Field java.io.PrintStream out>
10 iload_1
11 invokevirtual #3 <Method void print(int)>
14 getstatic #2 <Field java.io.PrintStream out>
17 iload_2
18 invokevirtual #3 <Method void print(int)>
21 iinc 1 1
24 iload_2
25 iload_1
26 iadd
27 istore_2
28 iload_1
29 bipush 10
31 if_icmplt 7
34 return
And my magic script (http://astray.com/java2parrot.pl.txt)
converts it to the following Parrot assembler code:
set_i_ic I1, 1
set_i I63, I1
set_i_ic I1, 1
set_i I62, I1
branch_ic LAAA
LAAB: set_i I1, I63
print_i I1
set_i I1, I62
print_i I1
inc_i I63
set_i I1, I62
set_i I2, I63
add_i I1, I1, I2
set_i I62, I1
LAAA: set_i I3, I63
set_i_ic I4, 10
lt_i_ic I3, I4, LAAB, LAAC
LAAC: end
which outputs:
I reg 1 is 1
I reg 1 is 1
I reg 1 is 2
I reg 1 is 3
I reg 1 is 3
I reg 1 is 6
I reg 1 is 4
I reg 1 is 10
I reg 1 is 5
I reg 1 is 15
I reg 1 is 6
I reg 1 is 21
I reg 1 is 7
I reg 1 is 28
I reg 1 is 8
I reg 1 is 36
I reg 1 is 9
I reg 1 is 45
Cool, huh. Much more on this soon! Leon
--
Leon Brocard.............................http://www.astray.com/
Iterative Software...........http://www.iterative-software.com/
... If you eat yogurt you'll have lots of culture
