General Computer Science 320201 GenCS I & II Lecture ... - Kwarc

call pushes the return address (of the call statement in the L(VM) program)
then it jumps to the first body instruction.
[proc 2 26,
con 0, arg 2, leq, cjp 5,
con 1, return,
con 1, arg 2, sub, arg 1,
call 0, arg 1, mul,
return,
con 2, con 10, call 0,
halt]
arg i pushes the i th argument onto the stack
[proc 2 26,
con 0, arg 2, leq, cjp 5,
con 1, return,
con 1, arg 2, sub, arg 1,
call 0, arg 1, mul,
return,
con 2, con 10, call 0,
halt]
Comparison turns out false, so we push 0.
[proc 2 26,
con 0, arg 2, leq, cjp 5,
con 1, return,
con 1, arg 2, sub, arg 1,
call 0, arg 1, mul,
return,
con 2, con 10, call 0,
halt]
cjp pops the truth value and jumps (on false).
[proc 2 26,
con 0, arg 2, leq, cjp 5,
con 1, return,
con 1, arg 2, sub, arg 1,
call 0, arg 1, mul,
return,
con 2, con 10, call 0,
halt]
we first push 1
2
0
32 0
10 -1
2 -2
0
32 0
10 -1
2 -2
32 0
10 -1
2 -2
2
1
32 0
10 -1
2 -2
then we push the second argument (from the call frame position −2)
[proc 2 26,
con 0, arg 2, leq, cjp 5,
con 1, return,
con 1, arg 2, sub, arg 1,
call 0, arg 1, mul,
return,
con 2, con 10, call 0,
halt]
172
1
32 0
10 -1
2 -2