46 lines
1.1 KiB
ArmAsm
46 lines
1.1 KiB
ArmAsm
/* memset() Author: Kees J. Bot */
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/* 2 Jan 1994 */
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/* void *memset(void *s, int c, size_t n) */
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/* Set a chunk of memory to the same byte value. */
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/* */
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#include <machine/asm.h>
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ENTRY(memset)
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push %ebp
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movl %esp, %ebp
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push %edi
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movl 8(%ebp), %edi /* The string */
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movzbl 12(%ebp), %eax /* The fill byte */
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movl 16(%ebp), %ecx /* Length */
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cld
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cmpl $16, %ecx
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jb sbyte /* Don't bother being smart with short arrays */
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testl $1, %edi
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jne sbyte /* Bit 0 set, use byte store */
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testl $2, %edi
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jne sword /* Bit 1 set, use word store */
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slword:
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movb %al, %ah
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movl %eax, %edx
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sall $16, %edx
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orl %edx, %eax /* One byte to four bytes */
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shrdl $2, %ecx, %edx /* Save low two bits of ecx in edx */
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shrl $2, %ecx
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rep stosl /* Store longwords. */
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shldl $2, %edx, %ecx /* Restore low two bits */
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sword:
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movb %al, %ah /* One byte to two bytes */
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shrl $1, %ecx
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rep stosw /* Store words */
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adcl %ecx, %ecx /* One more byte? */
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sbyte:
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rep stosb /* Store bytes */
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done:
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movl 8(%ebp), %eax /* Return some value you have no need for */
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pop %edi
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pop %ebp
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ret
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