memchr.S revision 1.3
1 1.3 christos /* 2 1.3 christos * Written by J.T. Conklin <jtc (at) acorntoolworks.com> 3 1.3 christos * Public domain. 4 1.1 christos */ 5 1.1 christos 6 1.1 christos #include <machine/asm.h> 7 1.1 christos 8 1.1 christos #if defined(LIBC_SCCS) 9 1.2 dsl RCSID("$NetBSD: memchr.S,v 1.3 2009/07/19 23:45:29 christos Exp $") 10 1.1 christos #endif 11 1.1 christos 12 1.3 christos ENTRY(memchr) 13 1.3 christos movzbq %sil,%rcx 14 1.3 christos 15 1.3 christos /* 16 1.3 christos * Align to word boundary. 17 1.3 christos * Consider unrolling loop? 18 1.3 christos */ 19 1.3 christos testq %rdx,%rdx /* nbytes == 0? */ 20 1.3 christos je .Lzero 21 1.3 christos .Lalign: 22 1.3 christos testb $7,%dil 23 1.3 christos je .Lword_aligned 24 1.3 christos movq %rdi,%rax 25 1.3 christos cmpb (%rdi),%cl 26 1.3 christos je .Ldone 27 1.3 christos incq %rdi 28 1.3 christos decq %rdx 29 1.3 christos jnz .Lalign 30 1.3 christos jmp .Lzero 31 1.3 christos 32 1.3 christos .Lword_aligned: 33 1.3 christos /* copy char to all bytes in word */ 34 1.3 christos movb %cl,%ch 35 1.3 christos movq %rcx,%rsi 36 1.3 christos salq $16,%rcx 37 1.3 christos orq %rsi,%rcx 38 1.3 christos movq %rcx,%rsi 39 1.3 christos salq $32,%rcx 40 1.3 christos orq %rsi,%rcx 41 1.2 dsl 42 1.2 dsl movabsq $0x0101010101010101,%r8 43 1.3 christos movabsq $0x8080808080808080,%r9 44 1.1 christos 45 1.3 christos _ALIGN_TEXT 46 1.3 christos .Lloop: 47 1.3 christos cmpq $7,%rdx /* nbytes > 8 */ 48 1.3 christos jbe .Lbyte 49 1.3 christos movq (%rdi),%rsi 50 1.3 christos addq $8,%rdi 51 1.3 christos xorq %rcx,%rsi 52 1.3 christos subq $8,%rdx 53 1.3 christos subq %r8,%rsi 54 1.3 christos testq %r9,%rsi 55 1.3 christos je .Lloop 56 1.3 christos 57 1.3 christos /* 58 1.3 christos * In rare cases, the above loop may exit prematurely. We must 59 1.3 christos * return to the loop if none of the bytes in the word are 60 1.3 christos * equal to ch. 61 1.3 christos */ 62 1.3 christos 63 1.3 christos leaq -8(%rdi),%rax 64 1.3 christos cmpb -8(%rdi),%cl /* 1st byte == ch? */ 65 1.3 christos je .Ldone 66 1.3 christos 67 1.3 christos leaq -7(%rdi),%rax 68 1.3 christos cmpb -7(%rdi),%cl /* 2nd byte == ch? */ 69 1.3 christos je .Ldone 70 1.3 christos 71 1.3 christos leaq -6(%rdi),%rax 72 1.3 christos cmpb -6(%rdi),%cl /* 3rd byte == ch? */ 73 1.3 christos je .Ldone 74 1.3 christos 75 1.3 christos leaq -5(%rdi),%rax 76 1.3 christos cmpb -5(%rdi),%cl /* 4th byte == ch? */ 77 1.3 christos je .Ldone 78 1.3 christos 79 1.3 christos leaq -4(%rdi),%rax 80 1.3 christos cmpb -4(%rdi),%cl /* 5th byte == ch? */ 81 1.3 christos je .Ldone 82 1.3 christos 83 1.3 christos leaq -3(%rdi),%rax 84 1.3 christos cmpb -3(%rdi),%cl /* 6th byte == ch? */ 85 1.3 christos je .Ldone 86 1.3 christos 87 1.3 christos leaq -2(%rdi),%rax 88 1.3 christos cmpb -2(%rdi),%cl /* 7th byte == ch? */ 89 1.3 christos je .Ldone 90 1.3 christos 91 1.3 christos leaq -1(%rdi),%rax 92 1.3 christos cmpb -1(%rdi),%cl /* 7th byte == ch? */ 93 1.3 christos jne .Lloop 94 1.3 christos ret 95 1.1 christos 96 1.3 christos .Lbyte: 97 1.3 christos testq %rdx,%rdx 98 1.3 christos je .Lzero 99 1.3 christos .Lbyte_loop: 100 1.3 christos movq %rdi,%rax 101 1.3 christos cmpb (%rdi),%cl 102 1.3 christos je .Ldone 103 1.3 christos incq %rdi 104 1.3 christos decq %rdx 105 1.3 christos jnz .Lbyte_loop 106 1.3 christos 107 1.3 christos .Lzero: 108 1.3 christos xorq %rax,%rax 109 1.1 christos 110 1.3 christos .Ldone: 111 1.1 christos ret 112
Indexes created Thu Sep 25 08:09:54 GMT 2025