Thanks very much!
David Brown wrote:
What sort of compile-time options have you got turned on? It looks to me
like this is compiled with all optomisations switched off, and full
debugging on, so that the compiler generates as debugger-friendly code as
possible. For example, a local copy of the parameter d is made on the
stack, and manipulated there rather than using a register, and r5 is set up
as a frame pointer so that any debugger can track local variables and the
stack.
It is usual to compile with at least -O, if not -O2 - gcc and gdb are
perfectly happy with debugging optomised code (although occasionally local
variables give odd values, or are optomised away altogether), and I find
they give far more understandable assembly code than unoptomised code.
mvh.,
David
I have simple delay loop as:
void delay(unsigned int d) {
while(d--){
nop();
nop();
}
}
I was expecting that this function will use only one register (r15), as
it doesn't declare anything. To my supprise dissassembly is very
complicated. Does anyone know why it is so? And what is add #6, r5
Also another thing: while(d--) syntax.
I understand above syn. as
AGAIN: cmp d
jnz X
add #-1,d
jmp AGAIN
X:
as opposite to while (--d) syntax which is realized as below.
void delay(unsigned int d) {
1140: 05 12 push r5 ;
1142: 04 12 push r4 ;
1144: 05 41 mov r1, r5 ;
1146: 35 50 06 00 add #6, r5 ;#0x0006
114a: 21 83 decd r1 ;
114c: 04 41 mov r1, r4 ;
114e: 84 4f 00 00 mov r15, 0(r4) ;
while(d--) {
1152: b4 53 00 00 add #-1, 0(r4) ;r3 As==11
1156: b4 93 00 00 cmp #-1, 0(r4) ;r3 As==11
115a: 01 20 jnz $+4 ;abs 0x115e
115c: 03 3c jmp $+8 ;abs 0x1164
nop();
115e: 03 43 nop
nop();
1160: 03 43 nop
1162: f7 3f jmp $-16 ;abs 0x1152
}
}
1164: 21 53 incd r1 ;
1166: 34 41 pop r4 ;
1168: 35 41 pop r5 ;
116a: 30 41 ret
-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Mspgcc-users mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/mspgcc-users
-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Mspgcc-users mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/mspgcc-users
