--- /dev/null
+/*
+ * Copyright (C) 2013 ARM Ltd.
+ * Copyright (C) 2013 Linaro.
+ *
+ * This code is based on glibc cortex strings work originally authored by Linaro
+ * and re-licensed under GPLv2 for the Linux kernel. The original code can
+ * be found @
+ *
+ * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
+ * files/head:/src/aarch64/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+/*
+ * compare two strings
+ *
+ * Parameters:
+ * x0 - const string 1 pointer
+ * x1 - const string 2 pointer
+ * x2 - the maximal length to be compared
+ * Returns:
+ * x0 - an integer less than, equal to, or greater than zero if s1 is found,
+ * respectively, to be less than, to match, or be greater than s2.
+ */
+
+#define REP8_01 0x0101010101010101
+#define REP8_7f 0x7f7f7f7f7f7f7f7f
+#define REP8_80 0x8080808080808080
+
+/* Parameters and result. */
+src1 .req x0
+src2 .req x1
+limit .req x2
+result .req x0
+
+/* Internal variables. */
+data1 .req x3
+data1w .req w3
+data2 .req x4
+data2w .req w4
+has_nul .req x5
+diff .req x6
+syndrome .req x7
+tmp1 .req x8
+tmp2 .req x9
+tmp3 .req x10
+zeroones .req x11
+pos .req x12
+limit_wd .req x13
+mask .req x14
+endloop .req x15
+
+ENTRY(strncmp)
+ cbz limit, .Lret0
+ eor tmp1, src1, src2
+ mov zeroones, #REP8_01
+ tst tmp1, #7
+ b.ne .Lmisaligned8
+ ands tmp1, src1, #7
+ b.ne .Lmutual_align
+ /* Calculate the number of full and partial words -1. */
+ /*
+ * when limit is mulitply of 8, if not sub 1,
+ * the judgement of last dword will wrong.
+ */
+ 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.
+ */
+.Lloop_aligned:
+ ldr data1, [src1], #8
+ ldr data2, [src2], #8
+.Lstart_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 .Lloop_aligned
+
+ /*Not reached the limit, must have found the end or a diff. */
+ tbz limit_wd, #63, .Lnot_limit
+
+ /* Limit % 8 == 0 => all bytes significant. */
+ ands limit, limit, #7
+ b.eq .Lnot_limit
+
+ lsl limit, limit, #3 /* Bits -> bytes. */
+ mov mask, #~0
+CPU_BE( lsr mask, mask, limit )
+CPU_LE( lsl mask, mask, limit )
+ 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
+
+.Lnot_limit:
+ orr syndrome, diff, has_nul
+ b .Lcal_cmpresult
+
+.Lmutual_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. */
+ /* Big-endian. Early bytes are at MSB. */
+CPU_BE( lsl tmp2, tmp2, tmp3 ) /* Shift (tmp1 & 63). */
+ /* Little-endian. Early bytes are at LSB. */
+CPU_LE( lsr tmp2, tmp2, tmp3 ) /* Shift (tmp1 & 63). */
+
+ 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 .Lstart_realigned
+
+/*when src1 offset is not equal to src2 offset...*/
+.Lmisaligned8:
+ cmp limit, #8
+ b.lo .Ltiny8proc /*limit < 8... */
+ /*
+ * Get the align offset length to compare per byte first.
+ * After this process, one string's address will be aligned.*/
+ and tmp1, src1, #7
+ neg tmp1, tmp1
+ add tmp1, tmp1, #8
+ and tmp2, src2, #7
+ neg tmp2, tmp2
+ add tmp2, tmp2, #8
+ subs tmp3, tmp1, tmp2
+ csel pos, tmp1, tmp2, hi /*Choose the maximum. */
+ /*
+ * Here, limit is not less than 8, so directly run .Ltinycmp
+ * without checking the limit.*/
+ sub limit, limit, pos
+.Ltinycmp:
+ ldrb data1w, [src1], #1
+ ldrb data2w, [src2], #1
+ subs pos, pos, #1
+ ccmp data1w, #1, #0, ne /* NZCV = 0b0000. */
+ ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
+ b.eq .Ltinycmp
+ cbnz pos, 1f /*find the null or unequal...*/
+ cmp data1w, #1
+ ccmp data1w, data2w, #0, cs
+ b.eq .Lstart_align /*the last bytes are equal....*/
+1:
+ sub result, data1, data2
+ ret
+
+.Lstart_align:
+ lsr limit_wd, limit, #3
+ cbz limit_wd, .Lremain8
+ /*process more leading bytes to make str1 aligned...*/
+ ands xzr, src1, #7
+ b.eq .Lrecal_offset
+ add src1, src1, tmp3 /*tmp3 is positive in this branch.*/
+ add src2, src2, tmp3
+ ldr data1, [src1], #8
+ ldr data2, [src2], #8
+
+ sub limit, limit, tmp3
+ lsr limit_wd, limit, #3
+ 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, ne/*if limit_wd is 0,will finish the cmp*/
+ bics has_nul, tmp1, tmp2
+ ccmp endloop, #0, #0, eq /*has_null is ZERO: no null byte*/
+ b.ne .Lunequal_proc
+ /*How far is the current str2 from the alignment boundary...*/
+ and tmp3, tmp3, #7
+.Lrecal_offset:
+ neg pos, tmp3
+.Lloopcmp_proc:
+ /*
+ * Divide the eight bytes into two parts. First,backwards the src2
+ * to an alignment boundary,load eight bytes from the SRC2 alignment
+ * boundary,then compare with the relative bytes from SRC1.
+ * If all 8 bytes are equal,then start the second part's comparison.
+ * Otherwise finish the comparison.
+ * This special handle can garantee all the accesses are in the
+ * thread/task space in avoid to overrange access.
+ */
+ ldr data1, [src1,pos]
+ ldr data2, [src2,pos]
+ sub tmp1, data1, zeroones
+ orr tmp2, data1, #REP8_7f
+ bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
+ eor diff, data1, data2 /* Non-zero if differences found. */
+ csinv endloop, diff, xzr, eq
+ cbnz endloop, .Lunequal_proc
+
+ /*The second part process*/
+ ldr data1, [src1], #8
+ ldr data2, [src2], #8
+ 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, ne/*if limit_wd is 0,will finish the cmp*/
+ bics has_nul, tmp1, tmp2
+ ccmp endloop, #0, #0, eq /*has_null is ZERO: no null byte*/
+ b.eq .Lloopcmp_proc
+
+.Lunequal_proc:
+ orr syndrome, diff, has_nul
+ cbz syndrome, .Lremain8
+.Lcal_cmpresult:
+ /*
+ * reversed the byte-order as big-endian,then CLZ can find the most
+ * significant zero bits.
+ */
+CPU_LE( rev syndrome, syndrome )
+CPU_LE( rev data1, data1 )
+CPU_LE( rev data2, data2 )
+ /*
+ * 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.
+ */
+CPU_BE( cbnz has_nul, 1f )
+CPU_BE( cmp data1, data2 )
+CPU_BE( cset result, ne )
+CPU_BE( cneg result, result, lo )
+CPU_BE( ret )
+CPU_BE( 1: )
+ /* Re-compute the NUL-byte detection, using a byte-reversed value.*/
+CPU_BE( rev tmp3, data1 )
+CPU_BE( sub tmp1, tmp3, zeroones )
+CPU_BE( orr tmp2, tmp3, #REP8_7f )
+CPU_BE( bic has_nul, tmp1, tmp2 )
+CPU_BE( rev has_nul, has_nul )
+CPU_BE( orr syndrome, diff, has_nul )
+ /*
+ * 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
+ 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
+
+.Lremain8:
+ /* Limit % 8 == 0 => all bytes significant. */
+ ands limit, limit, #7
+ b.eq .Lret0
+.Ltiny8proc:
+ ldrb data1w, [src1], #1
+ ldrb data2w, [src2], #1
+ subs limit, limit, #1
+
+ ccmp data1w, #1, #0, ne /* NZCV = 0b0000. */
+ ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
+ b.eq .Ltiny8proc
+ sub result, data1, data2
+ ret
+
+.Lret0:
+ mov result, #0
+ ret
+ENDPROC(strncmp)
Code Review / kvmfornfv.git / blobdiff