1 ; Copyright (c) 2010-2011, Linaro Limited 2 ; All rights reserved. 3 ; 4 ; Redistribution and use in source and binary forms, with or without 5 ; modification, are permitted provided that the following conditions 6 ; are met: 7 ; 8 ; * Redistributions of source code must retain the above copyright 9 ; notice, this list of conditions and the following disclaimer. 10 ; 11 ; * Redistributions in binary form must reproduce the above copyright 12 ; notice, this list of conditions and the following disclaimer in the 13 ; documentation and/or other materials provided with the distribution. 14 ; 15 ; * Neither the name of Linaro Limited nor the names of its 16 ; contributors may be used to endorse or promote products derived 17 ; from this software without specific prior written permission. 18 ; 19 ; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 ; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 ; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 ; A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 ; HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 ; SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 ; LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 ; DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 ; THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 ; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 ; OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 ; 31 32 ; 33 ; Written by Dave Gilbert <david.gilbert (a] linaro.org> 34 ; 35 ; This memchr routine is optimised on a Cortex-A9 and should work on 36 ; all ARMv7 processors. It has a fast past for short sizes, and has 37 ; an optimised path for large data sets; the worst case is finding the 38 ; match early in a large data set. 39 ; 40 41 42 ; 2011-02-07 david.gilbert (a] linaro.org 43 ; Extracted from local git a5b438d861 44 ; 2011-07-14 david.gilbert (a] linaro.org 45 ; Import endianness fix from local git ea786f1b 46 ; 2011-12-07 david.gilbert (a] linaro.org 47 ; Removed unneeded cbz from align loop 48 49 ; this lets us check a flag in a 00/ff byte easily in either endianness 50 #define CHARTSTMASK(c) 1<<(c*8) 51 52 EXPORT InternalMemScanMem8 53 AREA ScanMem, CODE, READONLY 54 THUMB 55 56 InternalMemScanMem8 57 ; r0 = start of memory to scan 58 ; r1 = length 59 ; r2 = character to look for 60 ; returns r0 = pointer to character or NULL if not found 61 uxtb r2, r2 ; Don't think we can trust the caller to actually pass a char 62 63 cmp r1, #16 ; If it's short don't bother with anything clever 64 blt L20 65 66 tst r0, #7 ; If it's already aligned skip the next bit 67 beq L10 68 69 ; Work up to an aligned point 70 L5 71 ldrb r3, [r0],#1 72 subs r1, r1, #1 73 cmp r3, r2 74 beq L50 ; If it matches exit found 75 tst r0, #7 76 bne L5 ; If not aligned yet then do next byte 77 78 L10 79 ; At this point, we are aligned, we know we have at least 8 bytes to work with 80 push {r4-r7} 81 orr r2, r2, r2, lsl #8 ; expand the match word across to all bytes 82 orr r2, r2, r2, lsl #16 83 bic r4, r1, #7 ; Number of double words to work with 84 mvns r7, #0 ; all F's 85 movs r3, #0 86 87 L15 88 ldmia r0!, {r5,r6} 89 subs r4, r4, #8 90 eor r5, r5, r2 ; Get it so that r5,r6 have 00's where the bytes match the target 91 eor r6, r6, r2 92 uadd8 r5, r5, r7 ; Parallel add 0xff - sets the GE bits for anything that wasn't 0 93 sel r5, r3, r7 ; bytes are 00 for none-00 bytes, or ff for 00 bytes - NOTE INVERSION 94 uadd8 r6, r6, r7 ; Parallel add 0xff - sets the GE bits for anything that wasn't 0 95 sel r6, r5, r7 ; chained....bytes are 00 for none-00 bytes, or ff for 00 bytes - NOTE INVERSION 96 cbnz r6, L60 97 bne L15 ; (Flags from the subs above) If not run out of bytes then go around again 98 99 pop {r4-r7} 100 and r2, r2, #0xff ; Get r2 back to a single character from the expansion above 101 and r1, r1, #7 ; Leave the count remaining as the number after the double words have been done 102 103 L20 104 cbz r1, L40 ; 0 length or hit the end already then not found 105 106 L21 ; Post aligned section, or just a short call 107 ldrb r3, [r0], #1 108 subs r1, r1, #1 109 eor r3, r3, r2 ; r3 = 0 if match - doesn't break flags from sub 110 cbz r3, L50 111 bne L21 ; on r1 flags 112 113 L40 114 movs r0, #0 ; not found 115 bx lr 116 117 L50 118 subs r0, r0, #1 ; found 119 bx lr 120 121 L60 ; We're here because the fast path found a hit - now we have to track down exactly which word it was 122 ; r0 points to the start of the double word after the one that was tested 123 ; r5 has the 00/ff pattern for the first word, r6 has the chained value 124 cmp r5, #0 125 itte eq 126 moveq r5, r6 ; the end is in the 2nd word 127 subeq r0, r0, #3 ; Points to 2nd byte of 2nd word 128 subne r0, r0, #7 ; or 2nd byte of 1st word 129 130 ; r0 currently points to the 3rd byte of the word containing the hit 131 tst r5, #CHARTSTMASK(0) ; 1st character 132 bne L61 133 adds r0, r0, #1 134 tst r5, #CHARTSTMASK(1) ; 2nd character 135 ittt eq 136 addeq r0, r0 ,#1 137 tsteq r5, #(3 << 15) ; 2nd & 3rd character 138 ; If not the 3rd must be the last one 139 addeq r0, r0, #1 140 141 L61 142 pop {r4-r7} 143 subs r0, r0, #1 144 bx lr 145 146 END 147 148
