Hello,
I work with GCC4.5.1 version with SPARC-V8 target.
Working for embedded systems, I would be please to improve the code density.
When a caller function calls a callee function with short or char
arguments, the arguments are casted twice: inside the caller function
and inside the callee function, see the example. It is a waste of
performance in code density and speed!
I don't understand why there is a double casting. Is there any
optimization I could activate in GCC to remove it?
Best wishes,
Laurent poche
Example:
sparc-elf-gcc -o test.elf test.c -Os
short somme(char a, short b){
int i;
for (i=0; i<b; i++){
a+=a;
}
return a+b;
}
short somme2(char a, short b){
int i;
for (i=0; i<b; i++){
a+=b;
}
return a+2*b;
}
int main(){
volatile short b=1;
volatile char a=1, c=1;
b=somme(a,b);
b=somme(c,b);
b=somme(a,c);
b=somme2(a,b);
b=somme2(c,b);
b=somme2(a,c);
return 0;
}
0001024c <somme>:
1024c: 85 2a 60 10 sll %o1, 0x10, %g2
10250: 82 10 20 00 clr %g1
10254: 10 80 00 03 b 10260 <somme+0x14>
10258: 85 38 a0 10 sra %g2, 0x10, %g2
1025c: 82 00 60 01 inc %g1
10260: 80 a0 40 02 cmp %g1, %g2
10264: 26 bf ff fe bl,a 1025c <somme+0x10>
10268: 91 2a 20 01 sll %o0, 1, %o0
1026c: 91 2a 20 18 sll %o0, 0x18, %o0
10270: 91 3a 20 18 sra %o0, 0x18, %o0
10274: 81 c3 e0 08 retl
10278: 90 02 40 08 add %o1, %o0, %o0
000102b4 <main>:
102b4: 9d e3 bf 98 save %sp, -104, %sp
102b8: 82 10 20 01 mov 1, %g1
102bc: c2 37 bf fc sth %g1, [ %fp + -4 ]
102c0: c2 2f bf ff stb %g1, [ %fp + -1 ]
102c4: c2 2f bf fe stb %g1, [ %fp + -2 ]
102c8: d0 0f bf ff ldub [ %fp + -1 ], %o0
102cc: d2 17 bf fc lduh [ %fp + -4 ], %o1
102d0: 91 2a 20 18 sll %o0, 0x18, %o0
102d4: 93 2a 60 10 sll %o1, 0x10, %o1
102d8: 91 3a 20 18 sra %o0, 0x18, %o0
102dc: 7f ff ff dc call 1024c <somme>
102e0: 93 3a 60 10 sra %o1, 0x10, %o1
...
