/* * Written by J.T. Conklin <jtc@acorntoolworks.com> * Public domain. */ #include <machine/asm.h> #if defined(LIBC_SCCS) RCSID("$NetBSD: strcpy.S,v 1.2 2014/03/22 19:38:46 jakllsch Exp $") #endif /* * This strcpy implementation copies a byte at a time until the * source pointer is aligned to a word boundary, it then copies by * words until it finds a word containing a zero byte, and finally * copies by bytes until the end of the string is reached. * * While this may result in unaligned stores if the source and * destination pointers are unaligned with respect to each other, * it is still faster than either byte copies or the overhead of * an implementation suitable for machines with strict alignment * requirements. */ ENTRY(strcpy) pushl %ebx movl 8(%esp),%ecx movl 12(%esp),%eax /* * Align source to a word boundary. * Consider unrolling loop? */ _ALIGN_TEXT .Lalign: testl $3,%eax je .Lword_aligned movb (%eax),%bl incl %eax movb %bl,(%ecx) incl %ecx testb %bl,%bl jne .Lalign jmp .Ldone _ALIGN_TEXT .Lloop: movl %ebx,(%ecx) addl $4,%ecx .Lword_aligned: movl (%eax),%ebx addl $4,%eax leal -0x01010101(%ebx),%edx testl $0x80808080,%edx je .Lloop /* * In rare cases, the above loop may exit prematurely. We must * return to the loop if none of the bytes in the word equal 0. */ movb %bl,(%ecx) incl %ecx testb %bl,%bl je .Ldone movb %bh,(%ecx) incl %ecx testb %bh,%bh je .Ldone shrl $16,%ebx movb %bl,(%ecx) incl %ecx testb %bl,%bl je .Ldone movb %bh,(%ecx) incl %ecx testb %bh,%bh jne .Lword_aligned .Ldone: movl 8(%esp),%eax popl %ebx ret END(strcpy) |