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Faculty of Computer Science © 2006 CMPUT 229 Subroutines - Part 2 Calling Itself.

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1 Faculty of Computer Science © 2006 CMPUT 229 Subroutines - Part 2 Calling Itself

2 © 2006 Department of Computing Science CMPUT 229 Calling Itself int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); }

3 © 2006 Department of Computing Science CMPUT 229 Linking a Recursive Procedure int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC D0 A6 SP

4 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10004000 3 Memory SP$8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC D0 $12345678 A6 $00008014 SP $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

5 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $12345678 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC D0 $00008010 A6 $0000800C SP A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

6 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $12345678 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC D0 $00008010 A6 $0000800C SP A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

7 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $12345678 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 3 D0 $00008010 A6 $0000800C SP A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

8 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $12345678 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008010 A6 $0000800C SP A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

9 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $12345678 2 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008010 A6 $0000800C SP A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

10 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $12345678 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008010 A6 $00008008 SP A6 Assuming that call to subroutine fact is at address $100024FC $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

11 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008004 A6 $00008000 SP A6 $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

12 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008004 A6 $00008000 SP A6 $1000 2500 M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

13 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008004 A6 $00008000 SP A6 $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

14 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00008004 A6 $00008000 SP A6 $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

15 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00008004 A6 $00008000 SP A6 $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

16 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00008004 A6 $00007FFC SP A6 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

17 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FF8 A6 $00007FF4 SP A6 $00008004 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

18 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FF8 A6 $00007FF4 SP A6 $00008004 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

19 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FF8 A6 $00007FF4 SP A6 $00008004 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

20 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 0 D0 $00007FF8 A6 $00007FF4 SP A6 $00008004 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

21 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 0 D0 $00007FF8 A6 $00007FF4 SP A6 $00008004 0 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

22 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6)Compare with Zero BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 0 D0 $00007FF8 A6 $00007FF0 SP A6 $00008004 0 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $7FEC $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

23 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 0 D0 $00007FEC A6 $00007FE8 SP A6 $00008004 0 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

24 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 0 D0 $00007FEC A6 $00007FE8 SP A6 $00008004 0 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

25 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FEC A6 $00007FE8 SP A6 $00008004 0 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

26 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FEC A6 $00007FE8 SP A6 $00008004 0 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

27 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FEC A6 $00007FE8 SP A6 $00008004 0 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

28 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FF8 A6 $00007FF0 SP A6 $00008004 0 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

29 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADDQ.L #4,SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FF8 A6 $00007FF4 SP A6 $00008004 0 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

30 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP/A6 $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FF8 A6 $00007FF8 SP $00008004 0 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

31 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FF8 A6 $00007FF0 SP $00008004 0 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 SP/A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

32 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00007FF8 A6 $00007FF0 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 SP/A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

33 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00008004 A6 $00007FFC SP A6 $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

34 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory SP $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 1 D0 $00008004 A6 $00008000 SP A6 $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

35 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008004 A6 $00008004 SP SP/A6 $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

36 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 2 $12345678 $0008010 2 $10002500 $10004000 6 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008004 A6 $00008004 SP SP/A6 $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

37 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 2 $12345678 $0008010 2 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008010 A6 $00008008 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

38 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 2 $12345678 $0008010 2 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008010 A6 $00008008 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

39 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 2 $12345678 $0008010 2 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008010 A6 $00008010 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 SP/A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

40 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 2 $12345678 $0008010 2 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 6 D0 $00008010 A6 $00008010 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 SP/A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

41 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 6 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 6 D0 $00008010 A6 $00008010 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 SP/A6 $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

42 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 6 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 6 D0 $12345678 A6 $00008014 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 SP $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

43 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 6 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 6 D0 $12345678 A6 $00008018 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 SP $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

44 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 6 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 6 D0 $12345678 A6 $00008018 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $00007FF8 $7FEC 1 $7FE8 SP $1000 3FFBMOVEQ#3,(SP) $1000 3FFCBSRfact $1000 4000….

45 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008010 A6 $00008008 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,D0 $1000 3FFCBSRfact $1000 4000…. $00007FF8 $7FEC 1 $7FE8 A6

46 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 3 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 2 D0 $00008010 A6 $00008014 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,D0 $1000 3FFCBSRfact $1000 4000…. $00007FF8 $7FEC 1 $7FE8

47 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 6 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 6 D0 $00008010 A6 $00008010 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,D0 $1000 3FFCBSRfact $1000 4000…. $00007FF8 $7FEC 1 $7FE8 SP/A6

48 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 6 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 6 D0 $00008010 A6 $00008010 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,D0 $1000 3FFCBSRfact $1000 4000…. $00007FF8 $7FEC 1 $7FE8 SP/A6

49 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 6 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 6 D0 $12345678 A6 $00008010 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,D0 $1000 3FFCBSRfact $1000 4000…. $00007FF8 $7FEC 1 $7FE8 SP

50 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 6 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 6 D0 $12345678 A6 $00008010 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,D0 $1000 3FFCBSRfact $1000 4000…. $00007FF8 $7FEC 1 $7FE8 SP

51 © 2006 Department of Computing Science CMPUT 229 Example: fact(3) int fact ( int n ) { if (n < 1) return(1); else return(n * fact(n-1)); } M68K assembly: fact:LINK A6,#-4 TST.L 8(A6) BGTL6 MOVEQ #1,D0 MOVE.L D0,-4(A6) BRA L5 L6: MOVE.L 8(A6),D0n  1 SUBQ.L #1,D0D0  n-1 MOVE.L D0,(SP) BSR fact ADD.L#4, SP MULS.L 8(A6),D0 MOVE.L D0,-4(A6) L5: MOVE.L -4(A6),D0 UNLK A6 RTS $10002500 1 $12345678 $0008010 2 $10002500 $10004000 6 Memory $8014 $8018 $8010 $800C $8008 $8004 $8000 $7FFC 6 D0 $12345678 A6 $00008010 SP $00008004 1 $10002500 $7FF8 $7FF4 $7FF0 $1000 2500 $1000 3FFBMOVEQ#3,D0 $1000 3FFCBSRfact $1000 4000…. $00007FF8 $7FEC 1 $7FE8 SP

52 © 2006 Department of Computing Science CMPUT 229 Other Data Stored in the Stack $sp  High Address  Low Address $fp Before procedure call $sp  High Address  Low Address $fp After procedure call $sp  High Address  Low Address $fp During procedure call Saved argument registers Saved return reg. Saved registers Local arrays and structures Patt.-Hen. pp 139

53 © 2006 Department of Computing Science CMPUT 229 ASCII Code Patt.-Hen., pp 142

54 © 2006 Department of Computing Science CMPUT 229 A Procedure that Doesn’t Call Another Procedure void strcpy ( char x[ ], char y[ ]) { int i; i = 0; while ((x[i] = y[i]) != 0) i = i + 1; } Parameter Passing Convention base of array x[ ]  A0 base of array y[ ]  A1 Assumption i  D0 M68K assembly: strcpy ADD.L#4, SPRoom in stack for 1 more item MOVED0, (SP) Save D0 into stack MOVEQ#0, D0i  0 L1:MOVE.B(A1,D0), D4D4  y[i] MOVE.B(A0,D0), D5D5  y[i] TST D5if y[I] = 0 BEQL2done ADDQ#1, D0 i  i + 1 BRA L1Repeat L2:MOVE.L(SP), D0Restore D0 ADD.L#-4, SP pop one word off stack RTS return

55 © 2006 Department of Computing Science CMPUT 229 A Procedure that Doesn’t Call Another Procedure save D0 in stack void strcpy ( char x[ ], char y[ ]) { int i; i = 0; while ((x[i] = y[i]) != 0) i = i + 1; } M68K assembly: strcpy ADD.L#4, SPRoom in stack for 1 more item MOVED0, (SP) Save D0 into stack MOVEQ#0, D0i  0 L1:MOVE.B(A1,D0), D4D4  y[i] MOVE.B(A0,D0), D5D5  y[i] TST D5if y[I] = 0 BEQL2done ADDQ#1, D0 i  i + 1 BRA L1Repeat L2:MOVE.L(SP), D0Restore D0 ADD.L#-4, SP pop one word off stack RTS return Parameter Passing Convention base of array x[ ]  A0 base of array y[ ]  A1 Assumption i  D0

56 © 2006 Department of Computing Science CMPUT 229 A Procedure that Doesn’t Call Another Procedure save $s0 in stack i  0 void strcpy ( char x[ ], char y[ ]) { int i; i = 0; while ((x[i] = y[i]) != 0) i = i + 1; } M68K assembly: strcpy ADD.L#4, SPRoom in stack for 1 more item MOVED0, (SP) Save D0 into stack MOVEQ#0, D0i  0 L1:MOVE.B(A1,D0), D4D4  y[i] MOVE.B(A0,D0), D5D5  y[i] TST D5if y[I] = 0 BEQL2done ADDQ#1, D0 i  i + 1 BRA L1Repeat L2:MOVE.L(SP), D0Restore D0 ADD.L#-4, SP pop one word off stack RTS return Parameter Passing Convention base of array x[ ]  A0 base of array y[ ]  A1 Assumption i  D0

57 © 2006 Department of Computing Science CMPUT 229 A Procedure that Doesn’t Call Another Procedure save $s0 in stack i  0 x[i]  y[i] void strcpy ( char x[ ], char y[ ]) { int i; i = 0; while ((x[i] = y[i]) != 0) i = i + 1; } M68K assembly: strcpy ADD.L#4, SPRoom in stack for 1 more item MOVED0, (SP) Save D0 into stack MOVEQ#0, D0i  0 L1:MOVE.B(A1,D0), D4D4  y[i] MOVE.BD4, (A0,D0)x[i]  y[i] TST D5if y[I] = 0 BEQL2done ADDQ#1, D0 i  i + 1 BRA L1Repeat L2:MOVE.L(SP), D0Restore D0 ADD.L#-4, SP pop one word off stack RTS return Parameter Passing Convention base of array x[ ]  A0 base of array y[ ]  A1 Assumption i  D0

58 © 2006 Department of Computing Science CMPUT 229 A Procedure that Doesn’t Call Another Procedure save $s0 in stack y[i] = 0? i  0 x[i]  y[i] void strcpy ( char x[ ], char y[ ]) { int i; i = 0; while ((x[i] = y[i]) != 0) i = i + 1; } M68K assembly: strcpy ADD.L#4, SPRoom in stack for 1 more item MOVED0, (SP) Save D0 into stack MOVEQ#0, D0i  0 L1:MOVE.B(A1,D0), D4D4  y[i] MOVE.BD4, (A0,D0)x[i]  y[i] TST D5if y[I] = 0 BEQL2done ADDQ#1, D0 i  i + 1 BRA L1Repeat L2:MOVE.L(SP), D0Restore D0 ADD.L#-4, SP pop one word off stack RTS return Parameter Passing Convention base of array x[ ]  A0 base of array y[ ]  A1 Assumption i  D0

59 © 2006 Department of Computing Science CMPUT 229 A Procedure that Doesn’t Call Another Procedure i  i + 1 save $s0 in stack no y[i] = 0? i  0 x[i]  y[i] void strcpy ( char x[ ], char y[ ]) { int i; i = 0; while ((x[i] = y[i]) != 0) i = i + 1; } M68K assembly: strcpy ADD.L#4, SPRoom in stack for 1 more item MOVED0, (SP) Save D0 into stack MOVEQ#0, D0i  0 L1:MOVE.B(A1,D0), D4D4  y[i] MOVE.BD4, (A0,D0)x[i]  y[i] TST D5if y[I] = 0 BEQL2done ADDQ#1, D0 i  i + 1 BRA L1Repeat L2:MOVE.L(SP), D0Restore D0 ADD.L#-4, SP pop one word off stack RTS return Parameter Passing Convention base of array x[ ]  A0 base of array y[ ]  A1 Assumption i  D0

60 © 2006 Department of Computing Science CMPUT 229 A Procedure that Doesn’t Call Another Procedure i  i + 1 save $s0 in stack no y[i] = 0? yes restore $s0 return i  0 x[i]  y[i] void strcpy ( char x[ ], char y[ ]) { int i; i = 0; while ((x[i] = y[i]) != 0) i = i + 1; } M68K assembly: strcpy ADD.L#4, SPRoom in stack for 1 more item MOVED0, (SP) Save D0 into stack MOVEQ#0, D0i  0 L1:MOVE.B(A1,D0), D4D4  y[i] MOVE.BD4, (A0,D0)x[i]  y[i] TST D5if y[I] = 0 BEQL2done ADDQ#1, D0 i  i + 1 BRA L1Repeat L2:MOVE.L(SP), D0Restore D0 ADD.L#-4, SP pop one word off stack RTS return Parameter Passing Convention base of array x[ ]  A0 base of array y[ ]  A1 Assumption i  D0

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