http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21150
Denis Vlasenko <vda.linux at googlemail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |vda.linux at googlemail dot
| |com
--- Comment #6 from Denis Vlasenko <vda.linux at googlemail dot com> 2013-01-18
11:12:18 UTC ---
Guess this can be closed now. All four cases look good:
$ cat helper-4.6.3-O2.asm
helper-4.6.3-O2.o: file format elf32-i386
...
00000000 <a>:
0: 0f b6 05 2d 00 00 00 movzbl 0x2d,%eax
7: 32 05 24 00 00 00 xor 0x24,%al
d: 32 05 00 00 00 00 xor 0x0,%al
13: 32 05 36 00 00 00 xor 0x36,%al
19: 32 05 3f 00 00 00 xor 0x3f,%al
1f: 32 05 09 00 00 00 xor 0x9,%al
25: 32 05 12 00 00 00 xor 0x12,%al
2b: 32 05 1b 00 00 00 xor 0x1b,%al
31: c3 ret
Disassembly of section .text.b:
00000000 <b>:
0: 0f b6 05 12 00 00 00 movzbl 0x12,%eax
7: 32 05 09 00 00 00 xor 0x9,%al
d: 32 05 00 00 00 00 xor 0x0,%al
13: 32 05 1b 00 00 00 xor 0x1b,%al
19: 32 05 24 00 00 00 xor 0x24,%al
1f: 32 05 2d 00 00 00 xor 0x2d,%al
25: 32 05 36 00 00 00 xor 0x36,%al
2b: 32 05 3f 00 00 00 xor 0x3f,%al
31: c3 ret
Disassembly of section .text.c:
00000000 <c>:
0: 0f b6 05 09 00 00 00 movzbl 0x9,%eax
7: 32 05 00 00 00 00 xor 0x0,%al
d: 32 05 12 00 00 00 xor 0x12,%al
13: 32 05 1b 00 00 00 xor 0x1b,%al
19: 32 05 24 00 00 00 xor 0x24,%al
1f: 32 05 2d 00 00 00 xor 0x2d,%al
25: 32 05 36 00 00 00 xor 0x36,%al
2b: 32 05 3f 00 00 00 xor 0x3f,%al
31: c3 ret
Disassembly of section .text.d:
00000000 <d>:
0: 0f b6 05 12 00 00 00 movzbl 0x12,%eax
7: 32 05 09 00 00 00 xor 0x9,%al
d: 32 05 00 00 00 00 xor 0x0,%al
13: 32 05 1b 00 00 00 xor 0x1b,%al
19: 32 05 24 00 00 00 xor 0x24,%al
1f: 32 05 2d 00 00 00 xor 0x2d,%al
25: 32 05 36 00 00 00 xor 0x36,%al
2b: 32 05 3f 00 00 00 xor 0x3f,%al
31: c3 ret
Curiously, -Os manages to squeeze two more bytes out of it.
helper-4.6.3-Os.o: file format elf32-i386
00000000 <a>:
0: a0 2d 00 00 00 mov 0x2d,%al
^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ better than movzbl
5: 33 05 24 00 00 00 xor 0x24,%eax << why %eax? oh well...
b: 33 05 00 00 00 00 xor 0x0,%eax
11: 32 05 36 00 00 00 xor 0x36,%al
17: 32 05 3f 00 00 00 xor 0x3f,%al
1d: 32 05 09 00 00 00 xor 0x9,%al
23: 32 05 12 00 00 00 xor 0x12,%al
29: 32 05 1b 00 00 00 xor 0x1b,%al
2f: c3 ret
