------- Comment #3 from vvv at ru dot ru 2009-05-10 18:08 -------
(In reply to comment #2)
> This should have been done already with cgraph order.
Unfortunately, I can see inverse order only in separate source file. Inverse
but not optimized.
Example:
// file order1.c
#include <stdio.h>
main(int argc, char **argv)
{int i,j,k,l;
i=func1();
j=func2();
k=func3();
l=func4();
printf("%d %d %d %d\n",i,j,k,l);
}
=====================================
// file order2.c
int func1(){ return(F(4));}
int func2(){ return(F(3));}
int func3(){ return(F(2));}
int func4(){ return(F(1));}
=====================================
// file order3.c
int F(int x){ return(x);}
# gcc --version
gcc (GCC) 4.5.0 20090508 (experimental)
# gcc -o order order3.c order2.c order1.c -O2
# objdump -d order
0000000000400520 <F>:
400520: 89 f8 mov %edi,%eax
400522: c3 retq
0000000000400530 <func4>:
400530: bf 01 00 00 00 mov $0x1,%edi
400535: 31 c0 xor %eax,%eax
400537: e9 e4 ff ff ff jmpq 400520 <F>
0000000000400540 <func3>:
400540: bf 02 00 00 00 mov $0x2,%edi
400545: 31 c0 xor %eax,%eax
400547: e9 d4 ff ff ff jmpq 400520 <F>
0000000000400550 <func2>:
400550: bf 03 00 00 00 mov $0x3,%edi
400555: 31 c0 xor %eax,%eax
400557: e9 c4 ff ff ff jmpq 400520 <F>
0000000000400560 <func1>:
400560: bf 04 00 00 00 mov $0x4,%edi
400565: 31 c0 xor %eax,%eax
400567: e9 b4 ff ff ff jmpq 400520 <F>
0000000000400570 <main>:
400570: 48 89 5c 24 e8 mov %rbx,-0x18(%rsp)
400575: 48 89 6c 24 f0 mov %rbp,-0x10(%rsp)
40057a: 31 c0 xor %eax,%eax
40057c: 4c 89 64 24 f8 mov %r12,-0x8(%rsp)
400581: 48 83 ec 18 sub $0x18,%rsp
400585: e8 d6 ff ff ff callq 400560 <func1>
40058a: 89 c3 mov %eax,%ebx
40058c: 31 c0 xor %eax,%eax
40058e: e8 bd ff ff ff callq 400550 <func2>
400593: 89 c5 mov %eax,%ebp
400595: 31 c0 xor %eax,%eax
400597: e8 a4 ff ff ff callq 400540 <func3>
40059c: 41 89 c4 mov %eax,%r12d
40059f: 31 c0 xor %eax,%eax
4005a1: e8 8a ff ff ff callq 400530 <func4>
4005a6: 44 89 e1 mov %r12d,%ecx
4005a9: 41 89 c0 mov %eax,%r8d
4005ac: 89 ea mov %ebp,%edx
4005ae: 89 de mov %ebx,%esi
4005b0: 48 8b 6c 24 08 mov 0x8(%rsp),%rbp
4005b5: 48 8b 1c 24 mov (%rsp),%rbx
4005b9: 4c 8b 64 24 10 mov 0x10(%rsp),%r12
4005be: bf bc 06 40 00 mov $0x4006bc,%edi
4005c3: 31 c0 xor %eax,%eax
4005c5: 48 83 c4 18 add $0x18,%rsp
4005c9: e9 42 fe ff ff jmpq 400410 <pri...@plt>
=====================================
But optimal:
0000000000400520 <main>:
400520: 48 89 5c 24 e8 mov %rbx,-0x18(%rsp)
400525: 48 89 6c 24 f0 mov %rbp,-0x10(%rsp)
40052a: 31 c0 xor %eax,%eax
40052c: 4c 89 64 24 f8 mov %r12,-0x8(%rsp)
400531: 48 83 ec 18 sub $0x18,%rsp
400535: e8 46 00 00 00 callq 400580 <func1>
40053a: 89 c3 mov %eax,%ebx
40053c: 31 c0 xor %eax,%eax
40053e: e8 4d 00 00 00 callq 400590 <func2>
400543: 89 c5 mov %eax,%ebp
400545: 31 c0 xor %eax,%eax
400547: e8 54 00 00 00 callq 4005a0 <func3>
40054c: 41 89 c4 mov %eax,%r12d
40054f: 31 c0 xor %eax,%eax
400551: e8 5a 00 00 00 callq 4005b0 <func4>
400556: 44 89 e1 mov %r12d,%ecx
400559: 41 89 c0 mov %eax,%r8d
40055c: 89 ea mov %ebp,%edx
40055e: 89 de mov %ebx,%esi
400560: 48 8b 6c 24 08 mov 0x8(%rsp),%rbp
400565: 48 8b 1c 24 mov (%rsp),%rbx
400569: 4c 8b 64 24 10 mov 0x10(%rsp),%r12
40056e: bf bc 06 40 00 mov $0x4006bc,%edi
400573: 31 c0 xor %eax,%eax
400575: 48 83 c4 18 add $0x18,%rsp
400579: e9 92 fe ff ff jmpq 400410 <pri...@plt>
0000000000400580 <func1>:
400580: bf 01 00 00 00 mov $0x1,%edi
400585: 31 c0 xor %eax,%eax
400587: e9 34 00 00 00 jmpq 4005c0 <F>
0000000000400590 <func2>:
400590: bf 02 00 00 00 mov $0x2,%edi
400595: 31 c0 xor %eax,%eax
400597: e9 24 00 00 00 jmpq 4005c0 <F>
00000000004005a0 <func3>:
4005a0: bf 03 00 00 00 mov $0x3,%edi
4005a5: 31 c0 xor %eax,%eax
4005a7: e9 14 00 00 00 jmpq 4005c0 <F>
00000000004005b0 <func4>:
4005b0: bf 04 00 00 00 mov $0x4,%edi
4005b5: 31 c0 xor %eax,%eax
4005b7: e9 04 00 00 00 jmpq 4005c0 <F>
00000000004005c0 <F>:
4005c0: 89 f8 mov %edi,%eax
4005c2: c3 retq
===========
BTW, how about reordering idea for data?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40093
