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Diffstat (limited to 'sysdeps/aarch64/strnlen.S')
| -rw-r--r-- | sysdeps/aarch64/strnlen.S | 165 |
1 files changed, 0 insertions, 165 deletions
diff --git a/sysdeps/aarch64/strnlen.S b/sysdeps/aarch64/strnlen.S deleted file mode 100644 index 8a4767b75e..0000000000 --- a/sysdeps/aarch64/strnlen.S +++ /dev/null @@ -1,165 +0,0 @@ -/* strnlen - calculate the length of a string with limit. - - Copyright (C) 2013-2017 Free Software Foundation, Inc. - - This file is part of the GNU C Library. - - 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> - -/* Assumptions: - * - * ARMv8-a, AArch64 - */ - -/* Arguments and results. */ -#define srcin x0 -#define len x0 -#define limit x1 - -/* Locals and temporaries. */ -#define src x2 -#define data1 x3 -#define data2 x4 -#define data2a x5 -#define has_nul1 x6 -#define has_nul2 x7 -#define tmp1 x8 -#define tmp2 x9 -#define tmp3 x10 -#define tmp4 x11 -#define zeroones x12 -#define pos x13 -#define limit_wd x14 - -#define REP8_01 0x0101010101010101 -#define REP8_7f 0x7f7f7f7f7f7f7f7f -#define REP8_80 0x8080808080808080 - -ENTRY_ALIGN_AND_PAD (__strnlen, 6, 9) - DELOUSE (0) - DELOUSE (1) - DELOUSE (2) - cbz limit, L(hit_limit) - mov zeroones, #REP8_01 - bic src, srcin, #15 - ands tmp1, srcin, #15 - b.ne L(misaligned) - /* Calculate the number of full and partial words -1. */ - sub limit_wd, limit, #1 /* Limit != 0, so no underflow. */ - lsr limit_wd, limit_wd, #4 /* Convert to Qwords. */ - - /* NUL detection works on the principle that (X - 1) & (~X) & 0x80 - (=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and - can be done in parallel across the entire word. */ - /* The inner loop deals with two Dwords at a time. This has a - slightly higher start-up cost, but we should win quite quickly, - especially on cores with a high number of issue slots per - cycle, as we get much better parallelism out of the operations. */ - - /* Start of critial section -- keep to one 64Byte cache line. */ -L(loop): - ldp data1, data2, [src], #16 -L(realigned): - sub tmp1, data1, zeroones - orr tmp2, data1, #REP8_7f - sub tmp3, data2, zeroones - orr tmp4, data2, #REP8_7f - bic has_nul1, tmp1, tmp2 - bic has_nul2, tmp3, tmp4 - subs limit_wd, limit_wd, #1 - orr tmp1, has_nul1, has_nul2 - ccmp tmp1, #0, #0, pl /* NZCV = 0000 */ - b.eq L(loop) - /* End of critical section -- keep to one 64Byte cache line. */ - - orr tmp1, has_nul1, has_nul2 - cbz tmp1, L(hit_limit) /* No null in final Qword. */ - - /* We know there's a null in the final Qword. The easiest thing - to do now is work out the length of the string and return - MIN (len, limit). */ - - sub len, src, srcin - cbz has_nul1, L(nul_in_data2) -#ifdef __AARCH64EB__ - mov data2, data1 -#endif - sub len, len, #8 - mov has_nul2, has_nul1 -L(nul_in_data2): -#ifdef __AARCH64EB__ - /* For big-endian, carry propagation (if the final byte in the - string is 0x01) means we cannot use has_nul directly. The - easiest way to get the correct byte is to byte-swap the data - and calculate the syndrome a second time. */ - rev data2, data2 - sub tmp1, data2, zeroones - orr tmp2, data2, #REP8_7f - bic has_nul2, tmp1, tmp2 -#endif - sub len, len, #8 - rev has_nul2, has_nul2 - clz pos, has_nul2 - add len, len, pos, lsr #3 /* Bits to bytes. */ - cmp len, limit - csel len, len, limit, ls /* Return the lower value. */ - RET - -L(misaligned): - /* Deal with a partial first word. - We're doing two things in parallel here; - 1) Calculate the number of words (but avoiding overflow if - limit is near ULONG_MAX) - to do this we need to work out - limit + tmp1 - 1 as a 65-bit value before shifting it; - 2) Load and mask the initial data words - we force the bytes - before the ones we are interested in to 0xff - this ensures - early bytes will not hit any zero detection. */ - sub limit_wd, limit, #1 - neg tmp4, tmp1 - cmp tmp1, #8 - - and tmp3, limit_wd, #15 - lsr limit_wd, limit_wd, #4 - mov tmp2, #~0 - - ldp data1, data2, [src], #16 - lsl tmp4, tmp4, #3 /* Bytes beyond alignment -> bits. */ - add tmp3, tmp3, tmp1 - -#ifdef __AARCH64EB__ - /* Big-endian. Early bytes are at MSB. */ - lsl tmp2, tmp2, tmp4 /* Shift (tmp1 & 63). */ -#else - /* Little-endian. Early bytes are at LSB. */ - lsr tmp2, tmp2, tmp4 /* Shift (tmp1 & 63). */ -#endif - add limit_wd, limit_wd, tmp3, lsr #4 - - orr data1, data1, tmp2 - orr data2a, data2, tmp2 - - csinv data1, data1, xzr, le - csel data2, data2, data2a, le - b L(realigned) - -L(hit_limit): - mov len, limit - RET -END (__strnlen) -libc_hidden_def (__strnlen) -weak_alias (__strnlen, strnlen) -libc_hidden_def (strnlen) |