Hi .
I successfully passed function arguments through registers in gcc-3.3.
Every thing seems okay except there is a reshuffling of registers
happening once the arguments are passed in registers.
see the below example code snippet.
int add(short int x,short int y,short int z)
{
return x+y+z;
}
main()
{
int a=5,b=6,c=7,d;
d=add(a,b,c);
}
and the objdump of add function is
00000134 <_add>:
134: c3 30 000030c3 mov r3,r0
136: c3 01 000001c3 mov r0,r1
138: c3 12 000012c3 mov r1,r2
13a: 00 0c 00000c00 add r0,r3,r0
13c: 80 00 00000080 add r0,r0,r1
13e: 04 08 00000804 rts
The arguments are clearly passed in to r0,r1,r2 but my compiler
reshuffled them to r3,r0,r1
my return value of a function goes to r0. since i declared r0-r3 as 1 in
CALL_USED_REGISTERS ,r0-r3
are not pushed in stack.
Can any one help me to avoid the reshuffling of registers ..the idle
case should be
00000134 <_add>:
134: add r0, r0,r1 ==> r0=r0+r1
138: add r0, r0, r2==> r0 = r0+r2
13c: rts
since the required values are already in r0,r1,r2.
PS: I am using gcc-3.3
Thanks,
Sumanth G
