strlen-armv7.S: Import latest strlen cortex-strings code.
Import the latest version of strlen from the Linaro cortex-strings package. This version is faster across a variety of block size and alignments on ARMv7. newlib/ChangeLog: 2013-06-21 Will Newton <will.newton@linaro.org> * libc/machine/arm/strlen-armv7.S: Import latest strlen code from Linaro cortex-strings.
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Will Newton
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2013-06-21 Will Newton <will.newton@linaro.org>
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* libc/machine/arm/strlen-armv7.S: Import latest strlen
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code from Linaro cortex-strings.
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2013-06-21 Will Newton <will.newton@linaro.org>
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* MAINTAINERS: Add Will Newton to Write After Approval.
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@ -1,4 +1,4 @@
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/* Copyright (c) 2010-2011, Linaro Limited
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/* Copyright (c) 2010-2011,2013 Linaro Limited
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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@ -28,100 +28,130 @@
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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Written by Dave Gilbert <david.gilbert@linaro.org>
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This strlen routine is optimised on a Cortex-A9 and should work on
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all ARMv7 processors. This routine is reasonably fast for short
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strings, but is probably slower than a simple implementation if all
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your strings are very short */
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@ 2011-02-08 david.gilbert@linaro.org
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@ Extracted from local git 6848613a
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@ 2011-10-13 david.gilbert@linaro.org
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@ Extracted from cortex-strings bzr rev 63
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@ Integrate to newlib, flip to ldrd
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@ Pull in Endian macro from my memchr
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Assumes:
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ARMv6T2, AArch32
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*/
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#include "arm_asm.h"
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@ NOTE: This ifdef MUST match the ones in arm/strlen.c
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@ We fallback to the one in arm/strlen.c for size optimised or
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@ for older arch's
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/* NOTE: This ifdef MUST match the ones in arm/strlen.c
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We fallback to the one in arm/strlen.c for size optimised or
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for older architectures. */
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#if defined(_ISA_ARM_7) || defined(__ARM_ARCH_6T2__) && \
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!(defined (__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED) || \
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(defined (__thumb__) && !defined (__thumb2__)))
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@ this lets us check a flag in a 00/ff byte easily in either endianness
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.macro def_fn f p2align=0
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.text
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.p2align \p2align
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.global \f
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.type \f, %function
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\f:
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.endm
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#ifdef __ARMEB__
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#define CHARTSTMASK(c) 1<<(31-(c*8))
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#define S2LO lsl
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#define S2HI lsr
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#else
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#define CHARTSTMASK(c) 1<<(c*8)
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#define S2LO lsr
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#define S2HI lsl
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#endif
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@------------------------------------------------------------------------------
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/* This code requires Thumb. */
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.thumb
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.syntax unified
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.arch armv7-a
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.thumb_func
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.align 2
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.p2align 4,,15
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.global strlen
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.type strlen,%function
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strlen:
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@ r0 = string
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@ returns count of bytes in string not including terminator
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mov r1, r0
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push { r4,r6 }
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mvns r6, #0 @ all F
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movs r4, #0
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tst r0, #7
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beq 2f
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/* Parameters and result. */
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#define srcin r0
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#define result r0
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1:
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ldrb r2, [r1], #1
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tst r1, #7 @ Hit alignment yet?
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cbz r2, 10f @ Exit if we found the 0
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bne 1b
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/* Internal variables. */
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#define src r1
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#define data1a r2
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#define data1b r3
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#define const_m1 r12
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#define const_0 r4
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#define tmp1 r4 /* Overlaps const_0 */
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#define tmp2 r5
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@ So we're now aligned
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2:
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ldrd r2,r3,[r1],#8
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uadd8 r2, r2, r6 @ Par add 0xff - sets the GE bits for bytes!=0
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sel r2, r4, r6 @ bytes are 00 for none-00 bytes,
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@ or ff for 00 bytes - NOTE INVERSION
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uadd8 r3, r3, r6 @ Par add 0xff - sets the GE bits for bytes!=0
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sel r3, r2, r6 @ chained...bytes are 00 for none-00 bytes,
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@ or ff for 00 bytes - NOTE INVERSION
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cmp r3, #0
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beq 2b
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def_fn strlen p2align=6
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pld [srcin, #0]
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strd r4, r5, [sp, #-8]!
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bic src, srcin, #7
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mvn const_m1, #0
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ands tmp1, srcin, #7 /* (8 - bytes) to alignment. */
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pld [src, #32]
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bne.w .Lmisaligned8
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mov const_0, #0
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mov result, #-8
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.Lloop_aligned:
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/* Bytes 0-7. */
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ldrd data1a, data1b, [src]
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pld [src, #64]
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add result, result, #8
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.Lstart_realigned:
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uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
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sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
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uadd8 data1b, data1b, const_m1
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sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
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cbnz data1b, .Lnull_found
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strlenendtmp:
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@ One (or more) of the bytes we loaded was 0 - but which one?
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@ r2 has the mask corresponding to the first loaded word
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@ r3 has a combined mask of the two words - but if r2 was all-non 0
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@ then it's just the 2nd words
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cmp r2, #0
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itte eq
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moveq r2, r3 @ the end is in the 2nd word
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subeq r1,r1,#3
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subne r1,r1,#7
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/* Bytes 8-15. */
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ldrd data1a, data1b, [src, #8]
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uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
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add result, result, #8
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sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
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uadd8 data1b, data1b, const_m1
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sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
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cbnz data1b, .Lnull_found
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@ r1 currently points to the 2nd byte of the word containing the 0
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tst r2, # CHARTSTMASK(0) @ 1st character
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bne 10f
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adds r1,r1,#1
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tst r2, # CHARTSTMASK(1) @ 2nd character
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ittt eq
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addeq r1,r1,#1
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tsteq r2, # (3<<15) @ 2nd & 3rd character
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@ If not the 3rd must be the last one
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addeq r1,r1,#1
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/* Bytes 16-23. */
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ldrd data1a, data1b, [src, #16]
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uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
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add result, result, #8
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sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
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uadd8 data1b, data1b, const_m1
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sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
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cbnz data1b, .Lnull_found
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10:
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@ r0 is still at the beginning, r1 is pointing 1 byte after the nul
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sub r0, r1, r0
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subs r0, r0, #1
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pop { r4, r6 }
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/* Bytes 24-31. */
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ldrd data1a, data1b, [src, #24]
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add src, src, #32
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uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
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add result, result, #8
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sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
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uadd8 data1b, data1b, const_m1
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sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
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cmp data1b, #0
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beq .Lloop_aligned
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.Lnull_found:
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cmp data1a, #0
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itt eq
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addeq result, result, #4
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moveq data1a, data1b
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#ifndef __ARMEB__
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rev data1a, data1a
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#endif
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clz data1a, data1a
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ldrd r4, r5, [sp], #8
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add result, result, data1a, lsr #3 /* Bits -> Bytes. */
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bx lr
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.Lmisaligned8:
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ldrd data1a, data1b, [src]
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and tmp2, tmp1, #3
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rsb result, tmp1, #0
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lsl tmp2, tmp2, #3 /* Bytes -> bits. */
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tst tmp1, #4
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pld [src, #64]
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S2HI tmp2, const_m1, tmp2
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orn data1a, data1a, tmp2
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itt ne
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ornne data1b, data1b, tmp2
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movne data1a, const_m1
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mov const_0, #0
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b .Lstart_realigned
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.size strlen, . - strlen
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#endif
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