Rev 1408 | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1627 | serge | 1 | /* memcmp() Author: Kees J. Bot */ |
| 2 | /* 2 Jan 1994 */ |
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| 1408 | serge | 3 | |
| 1627 | serge | 4 | /* int memcmp(const void *s1, const void *s2, size_t n) */ |
| 5 | /* Compare two chunks of memory. */ |
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| 6 | /* */ |
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| 7 | #include "asm.h" |
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| 1408 | serge | 8 | |
| 1627 | serge | 9 | ENTRY(memcmp) |
| 10 | cld |
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| 11 | push %ebp |
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| 12 | movl %esp, %ebp |
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| 13 | push %esi |
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| 14 | push %edi |
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| 15 | movl 8(%ebp), %esi /* String s1 */ |
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| 16 | movl 12(%ebp), %edi /* String s2 */ |
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| 17 | movl 16(%ebp), %ecx /* Length */ |
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| 18 | cmpl $16, %ecx |
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| 19 | jb cbyte /* Don't bother being smart with short arrays */ |
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| 20 | movl %esi, %eax |
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| 21 | orl %edi, %eax |
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| 22 | testb $1, %al |
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| 23 | jne cbyte /* Bit 0 set, use byte compare */ |
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| 24 | testb $2, %al |
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| 25 | jne cword /* Bit 1 set, use word compare */ |
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| 26 | clword: |
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| 27 | shrdl $2, %ecx, %eax /* Save low two bits of ecx in eax */ |
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| 28 | shrl $2, %ecx |
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| 1408 | serge | 29 | |
| 1627 | serge | 30 | repe cmpsl /* Compare longwords */ |
| 31 | subl $4, %esi |
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| 32 | subl $4, %edi |
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| 33 | incl %ecx /* Recompare the last longword */ |
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| 34 | shldl $2, %eax, %ecx /* And any excess bytes */ |
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| 35 | jmp last |
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| 36 | cword: |
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| 37 | shrdl $1, %ecx, %eax /* Save low bit of ecx in eax */ |
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| 38 | shrl $1, %ecx |
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| 1408 | serge | 39 | |
| 1627 | serge | 40 | repe cmpsw /* Compare words */ |
| 41 | subl $2, %esi |
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| 42 | subl $2, %edi |
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| 43 | incl %ecx /* Recompare the last word */ |
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| 44 | shldl $1, %eax, %ecx /* And one more byte? */ |
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| 45 | cbyte: |
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| 46 | testl %ecx, %ecx /* Set 'Z' flag if ecx = 0 */ |
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| 47 | last: |
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| 48 | repe cmpsb /* Look for the first differing byte */ |
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| 49 | seta %al /* al = (s1 > s2) */ |
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| 50 | setb %ah /* ah = (s1 < s2) */ |
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| 51 | subb %ah, %al |
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| 52 | movsbl %al, %eax /* eax = (s1 > s2) - (s1 < s2), i.e. -1, 0, 1 */ |
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| 53 | movl %esi, %edx /* For bcmp() to play with */ |
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| 54 | pop %edi |
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| 55 | pop %esi |
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| 56 | pop %ebp |
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| 1408 | serge | 57 | ret |