1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_RUNTIME_ARCH_ARM_MEMCMP16_ARM_S_ 18 #define ART_RUNTIME_ARCH_ARM_MEMCMP16_ARM_S_ 19 20 #include "asm_support_arm.S" 21 22 /* 23 * Optimized memcmp16() for ARM9. 24 * This would not be optimal on XScale or ARM11, where more prefetching 25 * and use of pld will be needed. 26 * The 2 major optimzations here are 27 * (1) The main loop compares 16 bytes at a time 28 * (2) The loads are scheduled in a way they won't stall 29 */ 30 31 ARM_ENTRY __memcmp16 32 pld [r0, #0] 33 pld [r1, #0] 34 35 /* take of the case where length is nul or the buffers are the same */ 36 cmp r0, r1 37 cmpne r2, #0 38 moveq r0, #0 39 bxeq lr 40 41 /* since r0 hold the result, move the first source 42 * pointer somewhere else 43 */ 44 45 mov r3, r0 46 47 /* make sure we have at least 12 words, this simplify things below 48 * and avoid some overhead for small blocks 49 */ 50 51 cmp r2, #12 52 bpl 0f 53 54 /* small blocks (less then 12 words) */ 55 pld [r0, #32] 56 pld [r1, #32] 57 58 1: ldrh r0, [r3], #2 59 ldrh ip, [r1], #2 60 subs r0, r0, ip 61 bxne lr 62 subs r2, r2, #1 63 bne 1b 64 bx lr 65 66 67 /* save registers */ 68 0: push {r4, lr} 69 .cfi_def_cfa_offset 8 70 .cfi_rel_offset r4, 0 71 .cfi_rel_offset lr, 4 72 73 /* align first pointer to word boundary */ 74 tst r3, #2 75 beq 0f 76 77 ldrh r0, [r3], #2 78 ldrh ip, [r1], #2 79 sub r2, r2, #1 80 subs r0, r0, ip 81 /* restore registers and return */ 82 popne {r4, lr} 83 bxne lr 84 85 86 0: /* here the first pointer is aligned, and we have at least 3 words 87 * to process. 88 */ 89 90 /* see if the pointers are congruent */ 91 eor r0, r3, r1 92 ands r0, r0, #2 93 bne 5f 94 95 /* congruent case, 16 half-words per iteration 96 * We need to make sure there are at least 16+2 words left 97 * because we effectively read ahead one long word, and we could 98 * read past the buffer (and segfault) if we're not careful. 99 */ 100 101 ldr ip, [r1] 102 subs r2, r2, #(16 + 2) 103 bmi 1f 104 105 0: 106 pld [r3, #64] 107 pld [r1, #64] 108 ldr r0, [r3], #4 109 ldr lr, [r1, #4]! 110 eors r0, r0, ip 111 ldreq r0, [r3], #4 112 ldreq ip, [r1, #4]! 113 eorseq r0, r0, lr 114 ldreq r0, [r3], #4 115 ldreq lr, [r1, #4]! 116 eorseq r0, r0, ip 117 ldreq r0, [r3], #4 118 ldreq ip, [r1, #4]! 119 eorseq r0, r0, lr 120 ldreq r0, [r3], #4 121 ldreq lr, [r1, #4]! 122 eorseq r0, r0, ip 123 ldreq r0, [r3], #4 124 ldreq ip, [r1, #4]! 125 eorseq r0, r0, lr 126 ldreq r0, [r3], #4 127 ldreq lr, [r1, #4]! 128 eorseq r0, r0, ip 129 ldreq r0, [r3], #4 130 ldreq ip, [r1, #4]! 131 eorseq r0, r0, lr 132 bne 2f 133 subs r2, r2, #16 134 bhs 0b 135 136 /* do we have at least 2 words left? */ 137 1: adds r2, r2, #(16 - 2 + 2) 138 bmi 4f 139 140 /* finish off 2 words at a time */ 141 3: ldr r0, [r3], #4 142 ldr ip, [r1], #4 143 eors r0, r0, ip 144 bne 2f 145 subs r2, r2, #2 146 bhs 3b 147 148 /* are we done? */ 149 4: adds r2, r2, #2 150 bne 8f 151 /* restore registers and return */ 152 mov r0, #0 153 pop {r4, lr} 154 .cfi_restore r4 155 .cfi_restore lr 156 .cfi_adjust_cfa_offset -8 157 bx lr 158 159 2: /* the last 2 words are different, restart them */ 160 ldrh r0, [r3, #-4] 161 ldrh ip, [r1, #-4] 162 subs r0, r0, ip 163 ldrheq r0, [r3, #-2] 164 ldrheq ip, [r1, #-2] 165 subseq r0, r0, ip 166 /* restore registers and return */ 167 pop {r4, lr} 168 .cfi_restore r4 169 .cfi_restore lr 170 .cfi_adjust_cfa_offset -8 171 bx lr 172 173 /* process the last few words */ 174 8: ldrh r0, [r3], #2 175 ldrh ip, [r1], #2 176 subs r0, r0, ip 177 bne 9f 178 subs r2, r2, #1 179 bne 8b 180 181 9: /* restore registers and return */ 182 pop {r4, lr} 183 .cfi_restore r4 184 .cfi_restore lr 185 .cfi_adjust_cfa_offset -8 186 bx lr 187 188 189 5: /*************** non-congruent case ***************/ 190 191 /* align the unaligned pointer */ 192 bic r1, r1, #3 193 ldr lr, [r1], #4 194 sub r2, r2, #8 195 196 6: 197 pld [r3, #64] 198 pld [r1, #64] 199 mov ip, lr, lsr #16 200 ldr lr, [r1], #4 201 ldr r0, [r3], #4 202 orr ip, ip, lr, lsl #16 203 eors r0, r0, ip 204 moveq ip, lr, lsr #16 205 ldreq lr, [r1], #4 206 ldreq r0, [r3], #4 207 orreq ip, ip, lr, lsl #16 208 eorseq r0, r0, ip 209 moveq ip, lr, lsr #16 210 ldreq lr, [r1], #4 211 ldreq r0, [r3], #4 212 orreq ip, ip, lr, lsl #16 213 eorseq r0, r0, ip 214 moveq ip, lr, lsr #16 215 ldreq lr, [r1], #4 216 ldreq r0, [r3], #4 217 orreq ip, ip, lr, lsl #16 218 eorseq r0, r0, ip 219 bne 7f 220 subs r2, r2, #8 221 bhs 6b 222 sub r1, r1, #2 223 /* are we done? */ 224 adds r2, r2, #8 225 moveq r0, #0 226 beq 9b 227 /* finish off the remaining bytes */ 228 b 8b 229 230 7: /* fix up the 2 pointers and fallthrough... */ 231 sub r1, r1, #2 232 b 2b 233 END __memcmp16 234 235 236 #endif // ART_RUNTIME_ARCH_ARM_MEMCMP16_ARM_S_ 237
