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Diffstat (limited to 'sysdeps/arm/armv6t2/memchr.S')
| -rw-r--r-- | sysdeps/arm/armv6t2/memchr.S | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/sysdeps/arm/armv6t2/memchr.S b/sysdeps/arm/armv6t2/memchr.S new file mode 100644 index 0000000000..65bb94fe70 --- /dev/null +++ b/sysdeps/arm/armv6t2/memchr.S @@ -0,0 +1,187 @@ +/* Copyright (C) 2011-2014 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, see + <http://www.gnu.org/licenses/>. */ + +#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 +#ifdef NO_THUMB + .arm +#else + .thumb + .thumb_func +#endif + .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: + sfi_breg r0, \ + ldrb r3, [\B],#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 r6, r2, #7 @ Number of double words to work with * 8 + mvns r7, #0 @ all F's + movs r3, #0 + +15: + sfi_breg r0, \ + ldrd r4,r5, [\B],#8 +#ifndef NO_THUMB + subs r6, r6, #8 +#endif + eor r4,r4, r1 @ Get it so that r4,r5 have 00's where the bytes match the target + eor r5,r5, r1 + uadd8 r4, r4, r7 @ Parallel add 0xff - sets the GE bits for anything that wasn't 0 + sel r4, r3, r7 @ bytes are 00 for none-00 bytes, or ff for 00 bytes - NOTE INVERSION + uadd8 r5, r5, r7 @ Parallel add 0xff - sets the GE bits for anything that wasn't 0 + sel r5, r4, r7 @ chained....bytes are 00 for none-00 bytes, or ff for 00 bytes - NOTE INVERSION +#ifndef NO_THUMB + cbnz r5, 60f +#else + cmp r5, #0 + bne 60f + subs r6, r6, #8 +#endif + 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: +#ifndef NO_THUMB + cbz r2, 40f @ 0 length or hit the end already then not found +#else + cmp r2, #0 + beq 40f +#endif + +21: @ Post aligned section, or just a short call + sfi_breg r0, \ + ldrb r3,[\B],#1 +#ifndef NO_THUMB + subs r2,r2,#1 + eor r3,r3,r1 @ r3 = 0 if match - doesn't break flags from sub + cbz r3, 50f +#else + eors r3, r3, r1 + beq 50f + subs r2, r2, #1 +#endif + 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 + @ r4 has the 00/ff pattern for the first word, r5 has the chained value + cfi_restore_state + cmp r4, #0 + itte eq + moveq r4, r5 @ 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 r4, # CHARTSTMASK(0) @ 1st character + bne 61f + adds r0,r0,#1 + tst r4, # CHARTSTMASK(1) @ 2nd character + ittt eq + addeq r0,r0,#1 + tsteq r4, # (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) |