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/*
* strlen - calculate the length of a string
*
* Copyright (c) 2010-2020, Arm Limited.
* SPDX-License-Identifier: MIT
*/
#if __ARM_ARCH >= 6 && __ARM_ARCH_ISA_THUMB == 2
/*
Assumes:
ARMv6T2, AArch32
*/
#include "../asmdefs.h"
#ifdef __ARMEB__
#define S2LO lsl
#define S2HI lsr
#else
#define S2LO lsr
#define S2HI lsl
#endif
/* This code requires Thumb. */
.thumb
.syntax unified
/* Parameters and result. */
#define srcin r0
#define result r0
/* Internal variables. */
#define src r1
#define data1a r2
#define data1b r3
#define const_m1 r12
#define const_0 r4
#define tmp1 r4 /* Overlaps const_0 */
#define tmp2 r5
ENTRY (__strlen_armv6t2)
pld [srcin, #0]
strd r4, r5, [sp, #-8]!
bic src, srcin, #7
mvn const_m1, #0
ands tmp1, srcin, #7 /* (8 - bytes) to alignment. */
pld [src, #32]
bne.w L(misaligned8)
mov const_0, #0
mov result, #-8
L(loop_aligned):
/* Bytes 0-7. */
ldrd data1a, data1b, [src]
pld [src, #64]
add result, result, #8
L(start_realigned):
uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
uadd8 data1b, data1b, const_m1
sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
cbnz data1b, L(null_found)
/* Bytes 8-15. */
ldrd data1a, data1b, [src, #8]
uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
add result, result, #8
sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
uadd8 data1b, data1b, const_m1
sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
cbnz data1b, L(null_found)
/* Bytes 16-23. */
ldrd data1a, data1b, [src, #16]
uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
add result, result, #8
sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
uadd8 data1b, data1b, const_m1
sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
cbnz data1b, L(null_found)
/* Bytes 24-31. */
ldrd data1a, data1b, [src, #24]
add src, src, #32
uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
add result, result, #8
sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
uadd8 data1b, data1b, const_m1
sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
cmp data1b, #0
beq L(loop_aligned)
L(null_found):
cmp data1a, #0
itt eq
addeq result, result, #4
moveq data1a, data1b
#ifndef __ARMEB__
rev data1a, data1a
#endif
clz data1a, data1a
ldrd r4, r5, [sp], #8
add result, result, data1a, lsr #3 /* Bits -> Bytes. */
bx lr
L(misaligned8):
ldrd data1a, data1b, [src]
and tmp2, tmp1, #3
rsb result, tmp1, #0
lsl tmp2, tmp2, #3 /* Bytes -> bits. */
tst tmp1, #4
pld [src, #64]
S2HI tmp2, const_m1, tmp2
orn data1a, data1a, tmp2
itt ne
ornne data1b, data1b, tmp2
movne data1a, const_m1
mov const_0, #0
b L(start_realigned)
END (__strlen_armv6t2)
#endif /* __ARM_ARCH >= 6 && __ARM_ARCH_ISA_THUMB == 2 */
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