[PATCHv2 4/6] arm64: lib: Implement optimized memcmp routine
zhichang.yuan at linaro.org
zhichang.yuan at linaro.org
Sun Apr 27 22:11:32 PDT 2014
From: "zhichang.yuan" <zhichang.yuan at linaro.org>
This patch, based on Linaro's Cortex Strings library, adds
an assembly optimized memcmp() function.
Signed-off-by: Zhichang Yuan <zhichang.yuan at linaro.org>
Signed-off-by: Deepak Saxena <dsaxena at linaro.org>
---
arch/arm64/include/asm/string.h | 3 +
arch/arm64/kernel/arm64ksyms.c | 1 +
arch/arm64/lib/Makefile | 2 +-
arch/arm64/lib/memcmp.S | 258 +++++++++++++++++++++++++++++++++++++++
4 files changed, 263 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/lib/memcmp.S
diff --git a/arch/arm64/include/asm/string.h b/arch/arm64/include/asm/string.h
index 3ee8b30..3a43305 100644
--- a/arch/arm64/include/asm/string.h
+++ b/arch/arm64/include/asm/string.h
@@ -34,4 +34,7 @@ extern void *memchr(const void *, int, __kernel_size_t);
#define __HAVE_ARCH_MEMSET
extern void *memset(void *, int, __kernel_size_t);
+#define __HAVE_ARCH_MEMCMP
+extern int memcmp(const void *, const void *, size_t);
+
#endif
diff --git a/arch/arm64/kernel/arm64ksyms.c b/arch/arm64/kernel/arm64ksyms.c
index 338b568..909c18e 100644
--- a/arch/arm64/kernel/arm64ksyms.c
+++ b/arch/arm64/kernel/arm64ksyms.c
@@ -48,6 +48,7 @@ EXPORT_SYMBOL(memset);
EXPORT_SYMBOL(memcpy);
EXPORT_SYMBOL(memmove);
EXPORT_SYMBOL(memchr);
+EXPORT_SYMBOL(memcmp);
/* atomic bitops */
EXPORT_SYMBOL(set_bit);
diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
index 328ce1a..112c67f 100644
--- a/arch/arm64/lib/Makefile
+++ b/arch/arm64/lib/Makefile
@@ -1,4 +1,4 @@
lib-y := bitops.o clear_user.o delay.o copy_from_user.o \
copy_to_user.o copy_in_user.o copy_page.o \
clear_page.o memchr.o memcpy.o memmove.o memset.o \
- strchr.o strrchr.o
+ memcmp.o strchr.o strrchr.o
diff --git a/arch/arm64/lib/memcmp.S b/arch/arm64/lib/memcmp.S
new file mode 100644
index 0000000..6ea0776
--- /dev/null
+++ b/arch/arm64/lib/memcmp.S
@@ -0,0 +1,258 @@
+/*
+ * 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 memory areas(when two memory areas' offset are different,
+* alignment handled by the hardware)
+*
+* Parameters:
+* x0 - const memory area 1 pointer
+* x1 - const memory area 2 pointer
+* x2 - the maximal compare byte length
+* Returns:
+* x0 - a compare result, maybe less than, equal to, or greater than ZERO
+*/
+
+/* 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
+endloop .req x7
+tmp1 .req x8
+tmp2 .req x9
+tmp3 .req x10
+pos .req x11
+limit_wd .req x12
+mask .req x13
+
+ENTRY(memcmp)
+ cbz limit, .Lret0
+ eor tmp1, src1, src2
+ tst tmp1, #7
+ b.ne .Lmisaligned8
+ ands tmp1, src1, #7
+ b.ne .Lmutual_align
+ sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
+ lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */
+ /*
+ * The input source addresses are at alignment boundary.
+ * Directly compare eight bytes each time.
+ */
+.Lloop_aligned:
+ ldr data1, [src1], #8
+ ldr data2, [src2], #8
+.Lstart_realigned:
+ subs limit_wd, limit_wd, #1
+ eor diff, data1, data2 /* Non-zero if differences found. */
+ csinv endloop, diff, xzr, cs /* Last Dword or differences. */
+ cbz endloop, .Lloop_aligned
+
+ /* Not reached the limit, must have found a diff. */
+ tbz limit_wd, #63, .Lnot_limit
+
+ /* Limit % 8 == 0 => the diff is in the last 8 bytes. */
+ ands limit, limit, #7
+ b.eq .Lnot_limit
+ /*
+ * The remained bytes less than 8. It is needed to extract valid data
+ * from last eight bytes of the intended memory range.
+ */
+ lsl limit, limit, #3 /* bytes-> bits. */
+ mov mask, #~0
+CPU_BE( lsr mask, mask, limit )
+CPU_LE( lsl mask, mask, limit )
+ bic data1, data1, mask
+ bic data2, data2, mask
+
+ orr diff, diff, mask
+ b .Lnot_limit
+
+.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.
+ */
+ bic src1, src1, #7
+ bic src2, src2, #7
+ ldr data1, [src1], #8
+ ldr data2, [src2], #8
+ /*
+ * We can not add limit with alignment offset(tmp1) here. Since the
+ * addition probably make the limit overflown.
+ */
+ sub limit_wd, limit, #1/*limit != 0, so no underflow.*/
+ and tmp3, limit_wd, #7
+ lsr limit_wd, limit_wd, #3
+ add tmp3, tmp3, tmp1
+ add limit_wd, limit_wd, tmp3, lsr #3
+ add limit, limit, tmp1/* Adjust the limit for the extra. */
+
+ lsl tmp1, tmp1, #3/* Bytes beyond alignment -> bits.*/
+ neg tmp1, tmp1/* Bits to alignment -64. */
+ mov tmp2, #~0
+ /*mask off the non-intended bytes before the start address.*/
+CPU_BE( lsl tmp2, tmp2, tmp1 )/*Big-endian.Early bytes are at MSB*/
+ /* Little-endian. Early bytes are at LSB. */
+CPU_LE( lsr tmp2, tmp2, tmp1 )
+
+ orr data1, data1, tmp2
+ orr data2, data2, tmp2
+ b .Lstart_realigned
+
+ /*src1 and src2 have different alignment offset.*/
+.Lmisaligned8:
+ cmp limit, #8
+ b.lo .Ltiny8proc /*limit < 8: compare byte by byte*/
+
+ and tmp1, src1, #7
+ neg tmp1, tmp1
+ add tmp1, tmp1, #8/*valid length in the first 8 bytes of src1*/
+ and tmp2, src2, #7
+ neg tmp2, tmp2
+ add tmp2, tmp2, #8/*valid length in the first 8 bytes of src2*/
+ subs tmp3, tmp1, tmp2
+ csel pos, tmp1, tmp2, hi /*Choose the maximum.*/
+
+ sub limit, limit, pos
+ /*compare the proceeding bytes in the first 8 byte segment.*/
+.Ltinycmp:
+ ldrb data1w, [src1], #1
+ ldrb data2w, [src2], #1
+ subs pos, pos, #1
+ ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */
+ b.eq .Ltinycmp
+ cbnz pos, 1f /*diff occurred before the last byte.*/
+ cmp data1w, data2w
+ b.eq .Lstart_align
+1:
+ sub result, data1, data2
+ ret
+
+.Lstart_align:
+ lsr limit_wd, limit, #3
+ cbz limit_wd, .Lremain8
+
+ ands xzr, src1, #7
+ b.eq .Lrecal_offset
+ /*process more leading bytes to make src1 aligned...*/
+ add src1, src1, tmp3 /*backwards src1 to alignment boundary*/
+ add src2, src2, tmp3
+ sub limit, limit, tmp3
+ lsr limit_wd, limit, #3
+ cbz limit_wd, .Lremain8
+ /*load 8 bytes from aligned SRC1..*/
+ ldr data1, [src1], #8
+ ldr data2, [src2], #8
+
+ subs limit_wd, limit_wd, #1
+ eor diff, data1, data2 /*Non-zero if differences found.*/
+ csinv endloop, diff, xzr, ne
+ cbnz endloop, .Lunequal_proc
+ /*How far is the current SRC2 from the alignment boundary...*/
+ and tmp3, tmp3, #7
+
+.Lrecal_offset:/*src1 is aligned now..*/
+ neg pos, tmp3
+.Lloopcmp_proc:
+ /*
+ * Divide the eight bytes into two parts. First,backwards the src2
+ * to an alignment boundary,load eight bytes and compare from
+ * the SRC2 alignment boundary. 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]
+ eor diff, data1, data2 /* Non-zero if differences found. */
+ cbnz diff, .Lnot_limit
+
+ /*The second part process*/
+ ldr data1, [src1], #8
+ ldr data2, [src2], #8
+ eor diff, data1, data2 /* Non-zero if differences found. */
+ subs limit_wd, limit_wd, #1
+ csinv endloop, diff, xzr, ne/*if limit_wd is 0,will finish the cmp*/
+ cbz endloop, .Lloopcmp_proc
+.Lunequal_proc:
+ cbz diff, .Lremain8
+
+/*There is differnence occured in the latest comparison.*/
+.Lnot_limit:
+/*
+* For little endian,reverse the low significant equal bits into MSB,then
+* following CLZ can find how many equal bits exist.
+*/
+CPU_LE( rev diff, diff )
+CPU_LE( rev data1, data1 )
+CPU_LE( rev data2, data2 )
+
+ /*
+ * The MS-non-zero bit of DIFF marks either the first bit
+ * that is different, or the end of the significant data.
+ * Shifting left now will bring the critical information into the
+ * top bits.
+ */
+ clz pos, diff
+ lsl data1, data1, pos
+ lsl data2, data2, pos
+ /*
+ * We need to zero-extend (char is unsigned) the value and then
+ * perform a signed subtraction.
+ */
+ lsr data1, data1, #56
+ sub result, data1, data2, lsr #56
+ ret
+
+.Lremain8:
+ /* Limit % 8 == 0 =>. all data are equal.*/
+ ands limit, limit, #7
+ b.eq .Lret0
+
+.Ltiny8proc:
+ ldrb data1w, [src1], #1
+ ldrb data2w, [src2], #1
+ subs limit, limit, #1
+
+ ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */
+ b.eq .Ltiny8proc
+ sub result, data1, data2
+ ret
+.Lret0:
+ mov result, #0
+ ret
+ENDPROC(memcmp)
--
1.7.9.5
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