Here are 3 small cleanup patches for lib/string.c against 2.6.14-rc2-git3
The first patch does whitespace and CodingStyle cleanups. It removes some
blank lines, removes some trailing whitespace, adds spaces after commas and
a few similar changes.
The second patch removes a few pointless register keywords. register is
merely a compiler hint that access to the variable should be optimized, but
gcc (3.3.6 in my case) generates the exact same code with and without the
keyword, and even if gcc did something different with register present I think
it is doubtful we would want to optimize access to these variables - especially
since this is generic library code and there are supposed to be optimized
versions in asm/ for anything that really matters speed wise.
The third patch removes a few pointless explicit casts. The first two hunks of
the patch really belongs in patch 1, but I missed them on the first pass and
instead of redoing all 3 patches I stuck them in this one.
One odd sideeffect of patch 1 is that gcc generates an object file that is 4
bytes smaller with the patch applied, but it's not obvious to me how it
manages this saving since the patch only makes whitespace changes. I tried
doing an objdump -D of string.o before and after the patch and compared the
output with diff, but that didn't reveal the cause of the 4 saved bytes - odd.
I've included the objdump diff below - as you can see it really shouldn't
make any difference, but the fact remains that the sizes differ :
juhl@dragon:~/download/kernel/linux-2.6.14-rc2-git3$ ls -l lib/string.o.orig
-rw-r--r-- 1 juhl users 60912 2005-09-23 22:25 lib/string.o.orig
juhl@dragon:~/download/kernel/linux-2.6.14-rc2-git3$ ls -l lib/string.o
-rw-r--r-- 1 juhl users 60908 2005-09-23 23:05 lib/string.o
Disassembly of section .text:
@@ -9,46 +9,46 @@
3: 57 push %edi
4: 89 d7 mov %edx,%edi
6: 56 push %esi
- 7: 89 ce mov %ecx,%esi
- 9: 31 c9 xor %ecx,%ecx
+ 7: 31 d2 xor %edx,%edx
+ 9: 89 ce mov %ecx,%esi
b: 53 push %ebx
c: 31 db xor %ebx,%ebx
e: 83 ec 04 sub $0x4,%esp
- 11: 85 f6 test %esi,%esi
+ 11: 85 c9 test %ecx,%ecx
13: 89 45 f0 mov %eax,0xfffffff0(%ebp)
16: 74 48 je 60 <strnicmp+0x60>
18: 8b 45 f0 mov 0xfffffff0(%ebp),%eax
1b: 0f b6 1f movzbl (%edi),%ebx
1e: 47 inc %edi
- 1f: 0f b6 08 movzbl (%eax),%ecx
+ 1f: 0f b6 10 movzbl (%eax),%edx
22: 40 inc %eax
23: 89 45 f0 mov %eax,0xfffffff0(%ebp)
- 26: 84 c9 test %cl,%cl
+ 26: 84 d2 test %dl,%dl
28: 74 36 je 60 <strnicmp+0x60>
2a: 84 db test %bl,%bl
2c: 74 32 je 60 <strnicmp+0x60>
- 2e: 38 d9 cmp %bl,%cl
+ 2e: 38 da cmp %bl,%dl
30: 74 2a je 5c <strnicmp+0x5c>
- 32: 0f b6 c1 movzbl %cl,%eax
- 35: 89 ca mov %ecx,%edx
+ 32: 0f b6 c2 movzbl %dl,%eax
+ 35: 89 d1 mov %edx,%ecx
37: f6 80 00 00 00 00 01 testb $0x1,0x0(%eax)
3e: 74 03 je 43 <strnicmp+0x43>
- 40: 8d 51 20 lea 0x20(%ecx),%edx
+ 40: 8d 4a 20 lea 0x20(%edx),%ecx
43: 0f b6 c3 movzbl %bl,%eax
- 46: 89 d1 mov %edx,%ecx
- 48: 89 da mov %ebx,%edx
+ 46: 89 ca mov %ecx,%edx
+ 48: 89 d9 mov %ebx,%ecx
4a: f6 80 00 00 00 00 01 testb $0x1,0x0(%eax)
51: 74 03 je 56 <strnicmp+0x56>
- 53: 8d 53 20 lea 0x20(%ebx),%edx
- 56: 38 d1 cmp %dl,%cl
- 58: 89 d3 mov %edx,%ebx
+ 53: 8d 4b 20 lea 0x20(%ebx),%ecx
+ 56: 38 ca cmp %cl,%dl
+ 58: 89 cb mov %ecx,%ebx
5a: 75 04 jne 60 <strnicmp+0x60>
5c: 4e dec %esi
5d: 75 b9 jne 18 <strnicmp+0x18>
5f: 90 nop
60: 83 c4 04 add $0x4,%esp
- 63: 0f b6 d3 movzbl %bl,%edx
- 66: 0f b6 c1 movzbl %cl,%eax
+ 63: 0f b6 c2 movzbl %dl,%eax
+ 66: 0f b6 d3 movzbl %bl,%edx
69: 5b pop %ebx
6a: 5e pop %esi
6b: 5f pop %edi
Anyway, the patches have been compile tested, and a kernel with all 3 applied
boots just fine with no observable defects.
--
Jesper Juhl <[email protected]>
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