For reference, here's the bytecode for tak in Erjang [JAD'ed bytecode
even further below].
In the actual generated code, it moves things around quite a bit in
local variables, but that is because of the way I translate BEAM to
JVM by keeping a "stack" in the local variables. All function calls
then do aload_0, aload_1, ... aload_N before a function call with
N-1. I'm assuming that the JVM will see through all these register
moves and optimize them away.
tak is very easy to translate for Erjang, because a simple local
analysis says that it doesn't suspend. So because of that it
generates very straightforward code. This is often the case for
"leafs" in the call graph.
Except for all the extra moving things around in variables, this is
what it does. The only "issue" with this is that Erjang cannot
suspend the thread while running in this loop (i.e. Kilim is not
pushed on this code). The check_exit() at the end of the loop is
there to make sure I can kill the process. is_ge() and dec()
[decrement] are native method on EObject.
static EObject tak(EProc proc, EObject X, EObject Y, EObject Z)
{
do {
if (Y.is_ge(X)) { return Z; }
EObject X1 = tak(proc, X.dec(), Y, Z);
EObject Y1 = tak(proc, Y.dec(), Z, X);
EObject Z1 = tak(proc, Z.dec(), X, Y);
X = X1; Y = Y1; Z = Z1;
proc.check_exit();
} while (true);
}
Kresten
-----[actual generated code]----
Method name:"tak__3" public static Signature:
(erjang.EProc,erjang.EObject,erjang.EObject,erjang.EObject)erjang.EObject
Attribute "Code", length:170, max_stack:4, max_locals:9, code_length:
138
0: goto 3
3: aload_2
4: aload_1
5: invokevirtual <Method erjang.EObject.is_ge
(erjang.EObject)boolean>
8: ifeq 15
11: aload_3
12: astore_1
13: aload_1
14: areturn
15: getstatic <Field erjang.ERT.NIL erjang.ENil>
18: dup
19: nop
20: astore 5
22: dup
23: nop
24: astore 6
26: dup
27: nop
28: astore 7
30: nop
31: astore 8
33: aload_1
34: invokevirtual <Method erjang.EObject.dec ()erjang.EObject>
37: astore 4
39: aload_1
40: astore 5
42: aload 4
44: astore_1
45: aload_3
46: astore 7
48: aload_2
49: astore 6
51: aload_0
52: aload_1
53: aload_2
54: aload_3
55: invokestatic <Method erjang.m.bench_tak.bench_tak.tak__3
(erjang.EProc,erjang.EObject,erjang.EObject,erjang.EObject)erjang.EObject>
58: astore_1
59: aload 6
61: invokevirtual <Method erjang.EObject.dec ()erjang.EObject>
64: astore_2
65: aload_1
66: astore 8
68: aload 5
70: astore_3
71: aload_2
72: astore_1
73: aload 7
75: astore_2
76: aload_0
77: aload_1
78: aload_2
79: aload_3
80: invokestatic <Method erjang.m.bench_tak.bench_tak.tak__3
(erjang.EProc,erjang.EObject,erjang.EObject,erjang.EObject)erjang.EObject>
83: astore_1
84: aload 7
86: invokevirtual <Method erjang.EObject.dec ()erjang.EObject>
89: astore_2
90: aload_1
91: astore 4 93: aload 6
95: astore_3
96: aload_2
97: astore_1
98: aload 5
100: astore_2
101: aload 4
103: astore 5
105: getstatic <Field erjang.ERT.NIL erjang.ENil>
108: astore 7
110: getstatic <Field erjang.ERT.NIL erjang.ENil>
113: astore 6
115: aload_0
116: aload_1
117: aload_2
118: aload_3
119: invokestatic <Method erjang.m.bench_tak.bench_tak.tak__3
(erjang.EProc,erjang.EObject,erjang.EObject,erjang.EObject)erjang.EObject>
122: astore_1
123: aload 5
125: astore_2
126: aload_1
127: astore_3
128: aload 8
130: astore_1
131: aload_0
132: invokevirtual <Method erjang.EProc.check_exit ()void>
135: goto 3
Here's the JAD'ed version of the same code.
public static EObject tak__3(EProc eproc, EObject eobject, EObject
eobject1, EObject eobject2)
{
do
{
if(eobject1.is_ge(eobject))
{
eobject = eobject2;
return eobject;
}
EObject obj;
EObject obj1;
EObject obj2;
EObject obj3 = obj2 = obj1 = obj = ERT.NIL;
EObject eobject3 = eobject.dec();
obj = eobject;
eobject = eobject3;
obj2 = eobject2;
obj1 = eobject1;
eobject = tak__3(eproc, eobject, eobject1, eobject2);
eobject1 = obj1.dec();
obj3 = eobject;
eobject2 = obj;
eobject = eobject1;
eobject1 = obj2;
eobject = tak__3(eproc, eobject, eobject1, eobject2);
eobject1 = obj2.dec();
eobject3 = eobject;
eobject2 = obj1;
eobject = eobject1;
eobject1 = obj;
obj = eobject3;
obj2 = ERT.NIL;
obj1 = ERT.NIL;
eobject = tak__3(eproc, eobject, eobject1, eobject2);
eobject1 = obj;
eobject2 = eobject;
eobject = obj3;
eproc.check_exit();
} while(true);
}
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