--- /dev/null
+/* Copyright (C) 2011 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Code contributed by Dave Gilbert <david.gilbert@linaro.org>
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#include <sysdep.h>
+
+@ This memchr routine is optimised on a Cortex-A9 and should work on all ARMv7
+@ and ARMv6T2 processors. It has a fast path for short sizes, and has an
+@ optimised path for large data sets; the worst case is finding the match early
+@ in a large data set.
+@ Note: The use of cbz/cbnz means it's Thumb only
+
+@ 2011-07-15 david.gilbert@linaro.org
+@ Copy from Cortex strings release 21 and change license
+@ http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/view/head:/src/linaro-a9/memchr.S
+@ Change function declarations/entry/exit
+@ 2011-12-01 david.gilbert@linaro.org
+@ Add some fixes from comments received (including use of ldrd instead ldm)
+@ 2011-12-07 david.gilbert@linaro.org
+@ Removed cbz from align loop - can't be taken
+
+@ this lets us check a flag in a 00/ff byte easily in either endianness
+#ifdef __ARMEB__
+#define CHARTSTMASK(c) 1<<(31-(c*8))
+#else
+#define CHARTSTMASK(c) 1<<(c*8)
+#endif
+ .syntax unified
+
+ .text
+ .thumb
+
+@ ---------------------------------------------------------------------------
+ .thumb_func
+ .global memchr
+ .type memchr,%function
+ENTRY(memchr)
+ @ r0 = start of memory to scan
+ @ r1 = character to look for
+ @ r2 = length
+ @ returns r0 = pointer to character or NULL if not found
+ and r1,r1,#0xff @ Don't think we can trust the caller to actually pass a char
+
+ cmp r2,#16 @ If it's short don't bother with anything clever
+ blt 20f
+
+ tst r0, #7 @ If it's already aligned skip the next bit
+ beq 10f
+
+ @ Work up to an aligned point
+5:
+ ldrb r3, [r0],#1
+ subs r2, r2, #1
+ cmp r3, r1
+ beq 50f @ If it matches exit found
+ tst r0, #7
+ bne 5b @ If not aligned yet then do next byte
+
+10:
+ @ At this point, we are aligned, we know we have at least 8 bytes to work with
+ push {r4,r5,r6,r7}
+ cfi_adjust_cfa_offset (16)
+ cfi_rel_offset (r4, 0)
+ cfi_rel_offset (r5, 4)
+ cfi_rel_offset (r6, 8)
+ cfi_rel_offset (r7, 12)
+
+ cfi_remember_state
+
+ orr r1, r1, r1, lsl #8 @ expand the match word across to all bytes
+ orr r1, r1, r1, lsl #16
+ bic r4, r2, #7 @ Number of double words to work with * 8
+ mvns r7, #0 @ all F's
+ movs r3, #0
+
+15:
+ ldrd r5,r6, [r0],#8
+ subs r4, r4, #8
+ eor r5,r5, r1 @ Get it so that r5,r6 have 00's where the bytes match the target
+ eor r6,r6, r1
+ uadd8 r5, r5, r7 @ Parallel add 0xff - sets the GE bits for anything that wasn't 0
+ sel r5, r3, r7 @ bytes are 00 for none-00 bytes, or ff for 00 bytes - NOTE INVERSION
+ uadd8 r6, r6, r7 @ Parallel add 0xff - sets the GE bits for anything that wasn't 0
+ sel r6, r5, r7 @ chained....bytes are 00 for none-00 bytes, or ff for 00 bytes - NOTE INVERSION
+ cbnz r6, 60f
+ bne 15b @ (Flags from the subs above) If not run out of bytes then go around again
+
+ pop {r4,r5,r6,r7}
+ cfi_adjust_cfa_offset (-16)
+ cfi_restore (r4)
+ cfi_restore (r5)
+ cfi_restore (r6)
+ cfi_restore (r7)
+
+ and r1,r1,#0xff @ Get r1 back to a single character from the expansion above
+ and r2,r2,#7 @ Leave the count remaining as the number after the double words have been done
+
+20:
+ cbz r2, 40f @ 0 length or hit the end already then not found
+
+21: @ Post aligned section, or just a short call
+ ldrb r3,[r0],#1
+ subs r2,r2,#1
+ eor r3,r3,r1 @ r3 = 0 if match - doesn't break flags from sub
+ cbz r3, 50f
+ bne 21b @ on r2 flags
+
+40:
+ movs r0,#0 @ not found
+ DO_RET(lr)
+
+50:
+ subs r0,r0,#1 @ found
+ DO_RET(lr)
+
+60: @ We're here because the fast path found a hit - now we have to track down exactly which word it was
+ @ r0 points to the start of the double word after the one that was tested
+ @ r5 has the 00/ff pattern for the first word, r6 has the chained value
+ cfi_restore_state
+ cmp r5, #0
+ itte eq
+ moveq r5, r6 @ the end is in the 2nd word
+ subeq r0,r0,#3 @ Points to 2nd byte of 2nd word
+ subne r0,r0,#7 @ or 2nd byte of 1st word
+
+ @ r0 currently points to the 2nd byte of the word containing the hit
+ tst r5, # CHARTSTMASK(0) @ 1st character
+ bne 61f
+ adds r0,r0,#1
+ tst r5, # CHARTSTMASK(1) @ 2nd character
+ ittt eq
+ addeq r0,r0,#1
+ tsteq r5, # (3<<15) @ 2nd & 3rd character
+ @ If not the 3rd must be the last one
+ addeq r0,r0,#1
+
+61:
+ pop {r4,r5,r6,r7}
+ cfi_adjust_cfa_offset (-16)
+ cfi_restore (r4)
+ cfi_restore (r5)
+ cfi_restore (r6)
+ cfi_restore (r7)
+
+ subs r0,r0,#1
+ DO_RET(lr)
+
+END(memchr)
+libc_hidden_builtin_def (memchr)
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