diff options
Diffstat (limited to 'ports/sysdeps/aarch64/strncmp.S')
| -rw-r--r-- | ports/sysdeps/aarch64/strncmp.S | 204 |
1 files changed, 0 insertions, 204 deletions
diff --git a/ports/sysdeps/aarch64/strncmp.S b/ports/sysdeps/aarch64/strncmp.S deleted file mode 100644 index 468bff4a3e..0000000000 --- a/ports/sysdeps/aarch64/strncmp.S +++ /dev/null @@ -1,204 +0,0 @@ -/* Copyright (C) 2013-2014 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 - */ - -#define REP8_01 0x0101010101010101 -#define REP8_7f 0x7f7f7f7f7f7f7f7f -#define REP8_80 0x8080808080808080 - -/* Parameters and result. */ -#define src1 x0 -#define src2 x1 -#define limit x2 -#define result x0 - -/* Internal variables. */ -#define data1 x3 -#define data1w w3 -#define data2 x4 -#define data2w w4 -#define has_nul x5 -#define diff x6 -#define syndrome x7 -#define tmp1 x8 -#define tmp2 x9 -#define tmp3 x10 -#define zeroones x11 -#define pos x12 -#define limit_wd x13 -#define mask x14 -#define endloop x15 - -ENTRY_ALIGN_AND_PAD (strncmp, 6, 7) - cbz limit, L(ret0) - eor tmp1, src1, src2 - mov zeroones, #REP8_01 - tst tmp1, #7 - b.ne L(misaligned8) - ands tmp1, src1, #7 - b.ne L(mutual_align) - /* Calculate the number of full and partial words -1. */ - sub limit_wd, limit, #1 /* limit != 0, so no underflow. */ - lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */ - - /* 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. */ - /* Start of performance-critical section -- one 64B cache line. */ -L(loop_aligned): - ldr data1, [src1], #8 - ldr data2, [src2], #8 -L(start_realigned): - subs limit_wd, limit_wd, #1 - sub tmp1, data1, zeroones - orr tmp2, data1, #REP8_7f - eor diff, data1, data2 /* Non-zero if differences found. */ - csinv endloop, diff, xzr, pl /* Last Dword or differences. */ - bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */ - ccmp endloop, #0, #0, eq - b.eq L(loop_aligned) - /* End of performance-critical section -- one 64B cache line. */ - - /* Not reached the limit, must have found the end or a diff. */ - tbz limit_wd, #63, L(not_limit) - - /* Limit % 8 == 0 => all bytes significant. */ - ands limit, limit, #7 - b.eq L(not_limit) - - lsl limit, limit, #3 /* Bits -> bytes. */ - mov mask, #~0 -#ifdef __AARCH64EB__ - lsr mask, mask, limit -#else - lsl mask, mask, limit -#endif - bic data1, data1, mask - bic data2, data2, mask - - /* Make sure that the NUL byte is marked in the syndrome. */ - orr has_nul, has_nul, mask - -L(not_limit): - orr syndrome, diff, has_nul - -#ifndef __AARCH64EB__ - rev syndrome, syndrome - rev data1, data1 - /* The MS-non-zero bit of the syndrome marks either the first bit - that is different, or the top bit of the first zero byte. - Shifting left now will bring the critical information into the - top bits. */ - clz pos, syndrome - rev data2, data2 - lsl data1, data1, pos - lsl data2, data2, pos - /* But we need to zero-extend (char is unsigned) the value and then - perform a signed 32-bit subtraction. */ - lsr data1, data1, #56 - sub result, data1, data2, lsr #56 - RET -#else - /* For big-endian we cannot use the trick with the syndrome value - as carry-propagation can corrupt the upper bits if the trailing - bytes in the string contain 0x01. */ - /* However, if there is no NUL byte in the dword, we can generate - the result directly. We can't just subtract the bytes as the - MSB might be significant. */ - cbnz has_nul, 1f - cmp data1, data2 - cset result, ne - cneg result, result, lo - RET -1: - /* Re-compute the NUL-byte detection, using a byte-reversed value. */ - rev tmp3, data1 - sub tmp1, tmp3, zeroones - orr tmp2, tmp3, #REP8_7f - bic has_nul, tmp1, tmp2 - rev has_nul, has_nul - orr syndrome, diff, has_nul - clz pos, syndrome - /* The MS-non-zero bit of the syndrome marks either the first bit - that is different, or the top bit of the first zero byte. - Shifting left now will bring the critical information into the - top bits. */ - lsl data1, data1, pos - lsl data2, data2, pos - /* But we need to zero-extend (char is unsigned) the value and then - perform a signed 32-bit subtraction. */ - lsr data1, data1, #56 - sub result, data1, data2, lsr #56 - RET -#endif - -L(mutual_align): - /* Sources are mutually aligned, but are not currently at an - alignment boundary. Round down the addresses and then mask off - the bytes that precede the start point. - We also need to adjust the limit calculations, but without - overflowing if the limit is near ULONG_MAX. */ - bic src1, src1, #7 - bic src2, src2, #7 - ldr data1, [src1], #8 - neg tmp3, tmp1, lsl #3 /* 64 - bits(bytes beyond align). */ - ldr data2, [src2], #8 - mov tmp2, #~0 - sub limit_wd, limit, #1 /* limit != 0, so no underflow. */ -#ifdef __AARCH64EB__ - /* Big-endian. Early bytes are at MSB. */ - lsl tmp2, tmp2, tmp3 /* Shift (tmp1 & 63). */ -#else - /* Little-endian. Early bytes are at LSB. */ - lsr tmp2, tmp2, tmp3 /* Shift (tmp1 & 63). */ -#endif - and tmp3, limit_wd, #7 - lsr limit_wd, limit_wd, #3 - /* Adjust the limit. Only low 3 bits used, so overflow irrelevant. */ - add limit, limit, tmp1 - add tmp3, tmp3, tmp1 - orr data1, data1, tmp2 - orr data2, data2, tmp2 - add limit_wd, limit_wd, tmp3, lsr #3 - b L(start_realigned) - -L(ret0): - mov result, #0 - RET - - .p2align 6 -L(misaligned8): - sub limit, limit, #1 -1: - /* Perhaps we can do better than this. */ - ldrb data1w, [src1], #1 - ldrb data2w, [src2], #1 - subs limit, limit, #1 - ccmp data1w, #1, #0, cs /* NZCV = 0b0000. */ - ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */ - b.eq 1b - sub result, data1, data2 - RET -END (strncmp) -libc_hidden_builtin_def (strncmp) |