1 /* 2 * strlen - calculate the length of a string 3 * 4 * Copyright (c) 2010-2020, Arm Limited. 5 * SPDX-License-Identifier: MIT 6 */ 7 8 #if __ARM_ARCH >= 6 && __ARM_ARCH_ISA_THUMB == 2 9 10 /* 11 Assumes: 12 ARMv6T2, AArch32 13 14 */ 15 16 #include "../asmdefs.h" 17 18 #ifdef __ARMEB__ 19 #define S2LO lsl 20 #define S2HI lsr 21 #else 22 #define S2LO lsr 23 #define S2HI lsl 24 #endif 25 26 /* This code requires Thumb. */ 27 .thumb 28 .syntax unified 29 30 /* Parameters and result. */ 31 #define srcin r0 32 #define result r0 33 34 /* Internal variables. */ 35 #define src r1 36 #define data1a r2 37 #define data1b r3 38 #define const_m1 r12 39 #define const_0 r4 40 #define tmp1 r4 /* Overlaps const_0 */ 41 #define tmp2 r5 42 43 ENTRY (__strlen_armv6t2) 44 pld [srcin, #0] 45 strd r4, r5, [sp, #-8]! 46 bic src, srcin, #7 47 mvn const_m1, #0 48 ands tmp1, srcin, #7 /* (8 - bytes) to alignment. */ 49 pld [src, #32] 50 bne.w L(misaligned8) 51 mov const_0, #0 52 mov result, #-8 53 L(loop_aligned): 54 /* Bytes 0-7. */ 55 ldrd data1a, data1b, [src] 56 pld [src, #64] 57 add result, result, #8 58 L(start_realigned): 59 uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */ 60 sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */ 61 uadd8 data1b, data1b, const_m1 62 sel data1b, data1a, const_m1 /* Only used if d1a == 0. */ 63 cbnz data1b, L(null_found) 64 65 /* Bytes 8-15. */ 66 ldrd data1a, data1b, [src, #8] 67 uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */ 68 add result, result, #8 69 sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */ 70 uadd8 data1b, data1b, const_m1 71 sel data1b, data1a, const_m1 /* Only used if d1a == 0. */ 72 cbnz data1b, L(null_found) 73 74 /* Bytes 16-23. */ 75 ldrd data1a, data1b, [src, #16] 76 uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */ 77 add result, result, #8 78 sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */ 79 uadd8 data1b, data1b, const_m1 80 sel data1b, data1a, const_m1 /* Only used if d1a == 0. */ 81 cbnz data1b, L(null_found) 82 83 /* Bytes 24-31. */ 84 ldrd data1a, data1b, [src, #24] 85 add src, src, #32 86 uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */ 87 add result, result, #8 88 sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */ 89 uadd8 data1b, data1b, const_m1 90 sel data1b, data1a, const_m1 /* Only used if d1a == 0. */ 91 cmp data1b, #0 92 beq L(loop_aligned) 93 94 L(null_found): 95 cmp data1a, #0 96 itt eq 97 addeq result, result, #4 98 moveq data1a, data1b 99 #ifndef __ARMEB__ 100 rev data1a, data1a 101 #endif 102 clz data1a, data1a 103 ldrd r4, r5, [sp], #8 104 add result, result, data1a, lsr #3 /* Bits -> Bytes. */ 105 bx lr 106 107 L(misaligned8): 108 ldrd data1a, data1b, [src] 109 and tmp2, tmp1, #3 110 rsb result, tmp1, #0 111 lsl tmp2, tmp2, #3 /* Bytes -> bits. */ 112 tst tmp1, #4 113 pld [src, #64] 114 S2HI tmp2, const_m1, tmp2 115 orn data1a, data1a, tmp2 116 itt ne 117 ornne data1b, data1b, tmp2 118 movne data1a, const_m1 119 mov const_0, #0 120 b L(start_realigned) 121 122 END (__strlen_armv6t2) 123 124 #endif /* __ARM_ARCH >= 6 && __ARM_ARCH_ISA_THUMB == 2 */ 125