strrchr.S revision 1.1
1 /* 2 * Written by J.T. Conklin <jtc (at) acorntoolworks.com> 3 * Public domain. 4 */ 5 6 #include <machine/asm.h> 7 8 #if defined(LIBC_SCCS) 9 RCSID("$NetBSD: strrchr.S,v 1.1 2005/12/20 19:28:51 christos Exp $") 10 #endif 11 12 #ifdef RINDEX 13 ENTRY(rindex) 14 #else 15 ENTRY(strrchr) 16 #endif 17 movzbq %sil,%rcx 18 19 /* zero return value */ 20 xorq %rax,%rax 21 22 /* 23 * Align to word boundary. 24 * Consider unrolling loop? 25 */ 26 .Lalign: 27 testb $7,%dil 28 je .Lword_aligned 29 movb (%rdi),%dl 30 cmpb %cl,%dl 31 cmoveq %rdi,%rax 32 incq %rdi 33 testb %dl,%dl 34 jne .Lalign 35 jmp .Ldone 36 37 .Lword_aligned: 38 /* copy char to all bytes in word */ 39 movb %cl,%ch 40 movq %rcx,%rdx 41 salq $16,%rcx 42 orq %rdx,%rcx 43 movq %rcx,%rdx 44 salq $32,%rcx 45 orq %rdx,%rcx 46 47 movabsq $0x0101010101010101,%r8 48 movabsq $0x8080808080808080,%r9 49 50 /* Check whether any byte in the word is equal to ch or 0. */ 51 _ALIGN_TEXT 52 .Lloop: 53 movq (%rdi),%rdx 54 addq $8,%rdi 55 movq %rdx,%rsi 56 subq %r8,%rdx 57 xorq %rcx,%rsi 58 subq %r8,%rsi 59 orq %rsi,%rdx 60 testq %r9,%rdx 61 je .Lloop 62 63 /* 64 * In rare cases, the above loop may exit prematurely. We must 65 * return to the loop if none of the bytes in the word match 66 * ch or are equal to 0. 67 */ 68 69 movb -8(%rdi),%dl 70 cmpb %cl,%dl /* 1st byte == ch? */ 71 jne 1f 72 leaq -8(%rdi),%rax 73 1: testb %dl,%dl /* 1st byte == 0? */ 74 je .Ldone 75 76 movb -7(%rdi),%dl 77 cmpb %cl,%dl /* 2nd byte == ch? */ 78 jne 1f 79 leaq -7(%rdi),%rax 80 1: testb %dl,%dl /* 2nd byte == 0? */ 81 je .Ldone 82 83 movb -6(%rdi),%dl 84 cmpb %cl,%dl /* 3rd byte == ch? */ 85 jne 1f 86 leaq -6(%rdi),%rax 87 1: testb %dl,%dl /* 3rd byte == 0? */ 88 je .Ldone 89 90 movb -5(%rdi),%dl 91 cmpb %cl,%dl /* 4th byte == ch? */ 92 jne 1f 93 leaq -5(%rdi),%rax 94 1: testb %dl,%dl /* 4th byte == 0? */ 95 je .Ldone 96 97 movb -4(%rdi),%dl 98 cmpb %cl,%dl /* 5th byte == ch? */ 99 jne 1f 100 leaq -4(%rdi),%rax 101 1: testb %dl,%dl /* 5th byte == 0? */ 102 je .Ldone 103 104 movb -3(%rdi),%dl 105 cmpb %cl,%dl /* 6th byte == ch? */ 106 jne 1f 107 leaq -3(%rdi),%rax 108 1: testb %dl,%dl /* 6th byte == 0? */ 109 je .Ldone 110 111 movb -2(%rdi),%dl 112 cmpb %cl,%dl /* 7th byte == ch? */ 113 jne 1f 114 leaq -2(%rdi),%rax 115 1: testb %dl,%dl /* 7th byte == 0? */ 116 je .Ldone 117 118 movb -1(%rdi),%dl 119 cmpb %cl,%dl /* 8th byte == ch? */ 120 jne 1f 121 leaq -1(%rdi),%rax 122 1: testb %dl,%dl /* 8th byte == 0? */ 123 jne .Lloop 124 125 .Ldone: 126 ret 127
Indexes created Fri Oct 03 02:09:57 GMT 2025