1/* Optimized strcmp implementation for Power7 using 'cmpb' instruction 2 Copyright (C) 2014-2022 Free Software Foundation, Inc. 3 This file is part of the GNU C Library. 4 5 The GNU C Library is free software; you can redistribute it and/or 6 modify it under the terms of the GNU Lesser General Public 7 License as published by the Free Software Foundation; either 8 version 2.1 of the License, or (at your option) any later version. 9 10 The GNU C Library is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 Lesser General Public License for more details. 14 15 You should have received a copy of the GNU Lesser General Public 16 License along with the GNU C Library; if not, see 17 <https://www.gnu.org/licenses/>. */ 18 19/* The optimization is achieved here through cmpb instruction. 20 8byte aligned strings are processed with double word comparision 21 and unaligned strings are handled effectively with loop unrolling 22 technique */ 23 24#include <sysdep.h> 25 26#ifndef STRCMP 27# define STRCMP strcmp 28#endif 29 30/* int [r3] strcmp (const char *s1 [r3], const char *s2 [r4]) */ 31 32 .machine power7 33ENTRY_TOCLESS (STRCMP, 4) 34 CALL_MCOUNT 2 35 36 or r9, r3, r4 37 rldicl. r10, r9, 0, 61 /* are s1 and s2 8 byte aligned..? */ 38 bne cr0, L(process_unaligned_bytes) 39 li r5, 0 40 41 .align 4 42/* process input parameters on double word aligned boundary */ 43L(unrollDword): 44 ld r8,0(r3) 45 ld r10,0(r4) 46 cmpb r7,r8,r5 47 cmpdi cr7,r7,0 48 mr r9,r7 49 bne cr7,L(null_found) 50 cmpld cr7,r8,r10 51 bne cr7,L(different) 52 53 ld r8,8(r3) 54 ld r10,8(r4) 55 cmpb r7,r8,r5 56 cmpdi cr7,r7,0 57 mr r9,r7 58 bne cr7,L(null_found) 59 cmpld cr7,r8,r10 60 bne cr7,L(different) 61 62 ld r8,16(r3) 63 ld r10,16(r4) 64 cmpb r7,r8,r5 65 cmpdi cr7,r7,0 66 mr r9,r7 67 bne cr7,L(null_found) 68 cmpld cr7,r8,r10 69 bne cr7,L(different) 70 71 ld r8,24(r3) 72 ld r10,24(r4) 73 cmpb r7,r8,r5 74 cmpdi cr7,r7,0 75 mr r9,r7 76 bne cr7,L(null_found) 77 cmpld cr7,r8,r10 78 bne cr7,L(different) 79 80 addi r3, r3, 32 81 addi r4, r4, 32 82 beq cr7, L(unrollDword) 83 84 .align 4 85L(null_found): 86#ifdef __LITTLE_ENDIAN__ 87 neg r7,r9 88 and r9,r9,r7 89 li r7,-1 90 cntlzd r9,r9 91 subfic r9,r9,71 92 sld r9,r7,r9 93#else 94 cntlzd r9,r9 95 li r7,-1 96 addi r9,r9,8 97 srd r9,r7,r9 98#endif 99 or r8,r8,r9 100 or r10,r10,r9 101 102L(different): 103 cmpb r9,r8,r10 104#ifdef __LITTLE_ENDIAN__ 105 addi r7,r9,1 106 andc r9,r7,r9 107 cntlzd r9,r9 108 subfic r9,r9,63 109#else 110 not r9,r9 111 cntlzd r9,r9 112 subfic r9,r9,56 113#endif 114 srd r3,r8,r9 115 srd r10,r10,r9 116 rldicl r10,r10,0,56 117 rldicl r3,r3,0,56 118 subf r3,r10,r3 119 blr 120 121 .align 4 122L(process_unaligned_bytes): 123 lbz r9, 0(r3) /* load byte from s1 */ 124 lbz r10, 0(r4) /* load byte from s2 */ 125 cmpdi cr7, r9, 0 /* compare *s1 with NULL */ 126 beq cr7, L(diffOfNULL) /* if *s1 is NULL , return *s1 - *s2 */ 127 cmplw cr7, r9, r10 /* compare *s1 and *s2 */ 128 bne cr7, L(ComputeDiff) /* branch to compute difference and return */ 129 130 lbz r9, 1(r3) /* load next byte from s1 */ 131 lbz r10, 1(r4) /* load next byte from s2 */ 132 cmpdi cr7, r9, 0 /* compare *s1 with NULL */ 133 beq cr7, L(diffOfNULL) /* if *s1 is NULL , return *s1 - *s2 */ 134 cmplw cr7, r9, r10 /* compare *s1 and *s2 */ 135 bne cr7, L(ComputeDiff) /* branch to compute difference and return */ 136 137 lbz r9, 2(r3) /* unroll 3rd byte here */ 138 lbz r10, 2(r4) 139 cmpdi cr7, r9, 0 140 beq cr7, L(diffOfNULL) 141 cmplw cr7, r9, r10 142 bne 7, L(ComputeDiff) 143 144 lbz r9, 3(r3) /* unroll 4th byte now */ 145 lbz r10, 3(r4) 146 addi r3, r3, 4 /* increment s1 by unroll factor */ 147 cmpdi cr7, r9, 0 148 cmplw cr6, 9, r10 149 beq cr7, L(diffOfNULL) 150 addi r4, r4, 4 /* increment s2 by unroll factor */ 151 beq cr6, L(process_unaligned_bytes) /* unroll byte processing */ 152 153 .align 4 154L(ComputeDiff): 155 extsw r9, r9 156 subf r10, r10, r9 /* compute s1 - s2 */ 157 extsw r3, r10 158 blr /* return */ 159 160 .align 4 161L(diffOfNULL): 162 li r9, 0 163 subf r10, r10, r9 /* compute s1 - s2 */ 164 extsw r3, r10 /* sign extend result */ 165 blr /* return */ 166 167END (STRCMP) 168libc_hidden_builtin_def (strcmp) 169