1/* Optimized memrchr implementation for PowerPC32/POWER7 using cmpb insn. 2 Copyright (C) 2010-2022 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#include <sysdep.h> 20 21/* int [r3] memrchr (char *s [r3], int byte [r4], int size [r5]) */ 22 .machine power7 23ENTRY (__memrchr) 24 CALL_MCOUNT 25 add r7,r3,r5 /* Calculate the last acceptable address. */ 26 neg r0,r7 27 addi r7,r7,-1 28 mr r10,r3 29 clrrwi r6,r7,7 30 li r9,3<<5 31 dcbt r9,r6,16 /* Stream hint, decreasing addresses. */ 32 33 /* Replicate BYTE to word. */ 34 insrwi r4,r4,8,16 35 insrwi r4,r4,16,0 36 li r6,-4 37 li r9,-1 38 rlwinm r0,r0,3,27,28 /* Calculate padding. */ 39 clrrwi r8,r7,2 40 srw r9,r9,r0 41 cmplwi r5,16 42 clrrwi r0,r10,2 43 ble L(small_range) 44 45#ifdef __LITTLE_ENDIAN__ 46 lwzx r12,0,r8 47#else 48 lwbrx r12,0,r8 /* Load reversed word from memory. */ 49#endif 50 cmpb r3,r12,r4 /* Check for BYTE in WORD1. */ 51 and r3,r3,r9 52 cmplwi cr7,r3,0 /* If r3 == 0, no BYTEs have been found. */ 53 bne cr7,L(done) 54 55 mtcrf 0x01,r8 56 /* Are we now aligned to a doubleword boundary? If so, skip to 57 the main loop. Otherwise, go through the alignment code. */ 58 bf 29,L(loop_setup) 59 60 /* Handle WORD2 of pair. */ 61#ifdef __LITTLE_ENDIAN__ 62 lwzx r12,r8,r6 63#else 64 lwbrx r12,r8,r6 65#endif 66 addi r8,r8,-4 67 cmpb r3,r12,r4 68 cmplwi cr7,r3,0 69 bne cr7,L(done) 70 71L(loop_setup): 72 /* The last word we want to read in the loop below is the one 73 containing the first byte of the string, ie. the word at 74 s & ~3, or r0. The first word read is at r8 - 4, we 75 read 2 * cnt words, so the last word read will be at 76 r8 - 4 - 8 * cnt + 4. Solving for cnt gives 77 cnt = (r8 - r0) / 8 */ 78 sub r5,r8,r0 79 addi r8,r8,-4 80 srwi r9,r5,3 /* Number of loop iterations. */ 81 mtctr r9 /* Setup the counter. */ 82 83 /* Main loop to look for BYTE backwards in the string. 84 FIXME: Investigate whether 32 byte align helps with this 85 9 instruction loop. */ 86 .align 5 87L(loop): 88 /* Load two words, compare and merge in a 89 single register for speed. This is an attempt 90 to speed up the byte-checking process for bigger strings. */ 91 92#ifdef __LITTLE_ENDIAN__ 93 lwzx r12,0,r8 94 lwzx r11,r8,r6 95#else 96 lwbrx r12,0,r8 97 lwbrx r11,r8,r6 98#endif 99 cmpb r3,r12,r4 100 cmpb r9,r11,r4 101 or r5,r9,r3 /* Merge everything in one word. */ 102 cmplwi cr7,r5,0 103 bne cr7,L(found) 104 addi r8,r8,-8 105 bdnz L(loop) 106 107 /* We may have one more word to read. */ 108 cmplw r8,r0 109 bnelr 110 111#ifdef __LITTLE_ENDIAN__ 112 lwzx r12,0,r8 113#else 114 lwbrx r12,0,r8 115#endif 116 cmpb r3,r12,r4 117 cmplwi cr7,r3,0 118 bne cr7,L(done) 119 blr 120 121 .align 4 122L(found): 123 /* OK, one (or both) of the words contains BYTE. Check 124 the first word. */ 125 cmplwi cr6,r3,0 126 bne cr6,L(done) 127 128 /* BYTE must be in the second word. Adjust the address 129 again and move the result of cmpb to r3 so we can calculate the 130 pointer. */ 131 132 mr r3,r9 133 addi r8,r8,-4 134 135 /* r3 has the output of the cmpb instruction, that is, it contains 136 0xff in the same position as BYTE in the original 137 word from the string. Use that to calculate the pointer. 138 We need to make sure BYTE is *before* the end of the 139 range. */ 140L(done): 141 cntlzw r9,r3 /* Count leading zeros before the match. */ 142 cmplw r8,r0 /* Are we on the last word? */ 143 srwi r6,r9,3 /* Convert leading zeros to bytes. */ 144 addi r0,r6,-3 145 sub r3,r8,r0 146 cmplw cr7,r3,r10 147 bnelr 148 bgelr cr7 149 li r3,0 150 blr 151 152 .align 4 153L(null): 154 li r3,0 155 blr 156 157/* Deals with size <= 16. */ 158 .align 4 159L(small_range): 160 cmplwi r5,0 161 beq L(null) 162 163#ifdef __LITTLE_ENDIAN__ 164 lwzx r12,0,r8 165#else 166 lwbrx r12,0,r8 /* Load reversed word from memory. */ 167#endif 168 cmpb r3,r12,r4 /* Check for BYTE in WORD1. */ 169 and r3,r3,r9 170 cmplwi cr7,r3,0 171 bne cr7,L(done) 172 173 /* Are we done already? */ 174 cmplw r8,r0 175 addi r8,r8,-4 176 beqlr 177 178 .align 5 179L(loop_small): 180#ifdef __LITTLE_ENDIAN__ 181 lwzx r12,0,r8 182#else 183 lwbrx r12,0,r8 184#endif 185 cmpb r3,r12,r4 186 cmplw r8,r0 187 cmplwi cr7,r3,0 188 bne cr7,L(done) 189 addi r8,r8,-4 190 bne L(loop_small) 191 blr 192 193END (__memrchr) 194weak_alias (__memrchr, memrchr) 195libc_hidden_builtin_def (memrchr) 196