1/* 2 * Written by J.T. Conklin <jtc@acorntoolworks.com> 3 * Public domain. 4 */ 5 6#include <machine/asm.h> 7 8#if defined(LIBC_SCCS) 9 RCSID("$NetBSD: strcmp.S,v 1.2 2014/03/22 19:16:34 jakllsch Exp $") 10#endif 11 12ENTRY(strcmp) 13 /* 14 * Align s1 to word boundary. 15 * Consider unrolling loop? 16 */ 17.Ls1align: 18 testb $7,%dil 19 je .Ls1aligned 20 movb (%rdi),%al 21 incq %rdi 22 movb (%rsi),%dl 23 incq %rsi 24 testb %al,%al 25 je .Ldone 26 cmpb %al,%dl 27 je .Ls1align 28 jmp .Ldone 29 30 /* 31 * Check whether s2 is aligned to a word boundary. If it is, we 32 * can compare by words. Otherwise we have to compare by bytes. 33 */ 34.Ls1aligned: 35 testb $7,%sil 36 jne .Lbyte_loop 37 38 movabsq $0x0101010101010101,%r8 39 subq $8,%rdi 40 movabsq $0x8080808080808080,%r9 41 subq $8,%rsi 42 43 _ALIGN_TEXT 44.Lword_loop: 45 movq 8(%rdi),%rax 46 addq $8,%rdi 47 movq 8(%rsi),%rdx 48 addq $8,%rsi 49 cmpq %rax,%rdx 50 jne .Lbyte_loop 51 subq %r8,%rdx 52 notq %rax 53 andq %rax,%rdx 54 testq %r9,%rdx 55 je .Lword_loop 56 57 _ALIGN_TEXT 58.Lbyte_loop: 59 movb (%rdi),%al 60 incq %rdi 61 movb (%rsi),%dl 62 incq %rsi 63 testb %al,%al 64 je .Ldone 65 cmpb %al,%dl 66 je .Lbyte_loop 67 68.Ldone: 69 movzbq %al,%rax 70 movzbq %dl,%rdx 71 subq %rdx,%rax 72 ret 73END(strcmp) 74