calculate_crc32c: Add SSE4.2 implementation on x86

Derived from an implementation by Mark Adler.

The fast loop performs three simultaneous CRCs over subsets of the data
before composing them.  This takes advantage of certain properties of
the CRC32 implementation in Intel hardware.  (The CRC instruction takes 1
cycle but has 2-3 cycles of latency.)

The CRC32 instruction does not manipulate FPU state.

i386 does not have the crc32q instruction, so avoid it there.  Otherwise
the implementation is identical to amd64.

Add basic userland tests to verify correctness on a variety of inputs.

PR:		216467
Reported by:	Ben RUBSON <ben.rubson at gmail.com>
Reviewed by:	kib@, markj@ (earlier version)
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D9342

sys/conf/files.amd64

@@ -593,6 +593,11 @@ compat/ndis/subr_pe.c		optional	ndisapi pci
 compat/ndis/subr_usbd.c		optional	ndisapi pci
 compat/ndis/winx64_wrap.S	optional	ndisapi pci
 #
+crc32_sse42.o			standard				\
+	dependency	"$S/libkern/x86/crc32_sse42.c"			\
+	compile-with	"${CC} -c ${CFLAGS:N-nostdinc} ${WERROR} ${PROF} -msse4 ${.IMPSRC}" \
+	no-implicit-rule						\
+	clean		"crc32_sse42.o"
 libkern/memmove.c		standard
 libkern/memset.c		standard
 #

sys/conf/files.i386

@@ -554,6 +554,11 @@ kern/kern_clocksource.c		standard
 kern/imgact_aout.c		optional compat_aout
 kern/imgact_gzip.c		optional gzip
 kern/subr_sfbuf.c		standard
+crc32_sse42.o			standard				\
+	dependency	"$S/libkern/x86/crc32_sse42.c"			\
+	compile-with	"${CC} -c ${CFLAGS:N-nostdinc} ${WERROR} ${PROF} -msse4 ${.IMPSRC}" \
+	no-implicit-rule						\
+	clean		"crc32_sse42.o"
 libkern/divdi3.c		standard
 libkern/ffsll.c			standard
 libkern/flsll.c			standard

sys/libkern/crc32.c

@@ -46,8 +46,14 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/libkern.h>
 #include <sys/systm.h>
 
+#if defined(__amd64__) || defined(__i386__)
+#include <machine/md_var.h>
+#include <machine/specialreg.h>
+#endif
+
 const uint32_t crc32_tab[] = {
 	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
 	0xe963a535, 0x9e6495a3,	0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
@@ -749,6 +755,11 @@ calculate_crc32c(uint32_t crc32c,
     const unsigned char *buffer,
     unsigned int length)
 {
+#if defined(__amd64__) || defined(__i386__)
+	if ((cpu_feature2 & CPUID2_SSE42) != 0) {
+		return (sse42_crc32c(crc32c, buffer, length));
+	} else
+#endif
 	if (length < 4) {
 		return (singletable_crc32c(crc32c, buffer, length));
 	} else {

sys/libkern/x86/crc32_sse42.c

@@ -0,0 +1,288 @@
+/*
+ * Derived from crc32c.c version 1.1 by Mark Adler.
+ *
+ * Copyright (C) 2013 Mark Adler
+ *
+ * This software is provided 'as-is', without any express or implied warranty.
+ * In no event will the author be held liable for any damages arising from the
+ * use of this software.
+ *
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented; you must not
+ *    claim that you wrote the original software. If you use this software
+ *    in a product, an acknowledgment in the product documentation would be
+ *    appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ *    misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
+ *
+ * Mark Adler
+ * madler@alumni.caltech.edu
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+/*
+ * This file is compiled in userspace in order to run ATF unit tests.
+ */
+#ifdef USERSPACE_TESTING
+#include <stdint.h>
+#else
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/libkern.h>
+#include <sys/systm.h>
+#endif
+
+#include <nmmintrin.h>
+
+/* CRC-32C (iSCSI) polynomial in reversed bit order. */
+#define POLY	0x82f63b78
+
+/*
+ * Block sizes for three-way parallel crc computation.  LONG and SHORT must
+ * both be powers of two.
+ */
+#define LONG	8192
+#define SHORT	256
+
+/* Tables for hardware crc that shift a crc by LONG and SHORT zeros. */
+static uint32_t crc32c_long[4][256];
+static uint32_t crc32c_short[4][256];
+
+/*
+ * Multiply a matrix times a vector over the Galois field of two elements,
+ * GF(2).  Each element is a bit in an unsigned integer.  mat must have at
+ * least as many entries as the power of two for most significant one bit in
+ * vec.
+ */
+static inline uint32_t
+gf2_matrix_times(uint32_t *mat, uint32_t vec)
+{
+	uint32_t sum;
+
+	sum = 0;
+	while (vec) {
+		if (vec & 1)
+			sum ^= *mat;
+		vec >>= 1;
+		mat++;
+	}
+	return (sum);
+}
+
+/*
+ * Multiply a matrix by itself over GF(2).  Both mat and square must have 32
+ * rows.
+ */
+static inline void
+gf2_matrix_square(uint32_t *square, uint32_t *mat)
+{
+	int n;
+
+	for (n = 0; n < 32; n++)
+		square[n] = gf2_matrix_times(mat, mat[n]);
+}
+
+/*
+ * Construct an operator to apply len zeros to a crc.  len must be a power of
+ * two.  If len is not a power of two, then the result is the same as for the
+ * largest power of two less than len.  The result for len == 0 is the same as
+ * for len == 1.  A version of this routine could be easily written for any
+ * len, but that is not needed for this application.
+ */
+static void
+crc32c_zeros_op(uint32_t *even, size_t len)
+{
+	uint32_t odd[32];       /* odd-power-of-two zeros operator */
+	uint32_t row;
+	int n;
+
+	/* put operator for one zero bit in odd */
+	odd[0] = POLY;              /* CRC-32C polynomial */
+	row = 1;
+	for (n = 1; n < 32; n++) {
+		odd[n] = row;
+		row <<= 1;
+	}
+
+	/* put operator for two zero bits in even */
+	gf2_matrix_square(even, odd);
+
+	/* put operator for four zero bits in odd */
+	gf2_matrix_square(odd, even);
+
+	/*
+	 * first square will put the operator for one zero byte (eight zero
+	 * bits), in even -- next square puts operator for two zero bytes in
+	 * odd, and so on, until len has been rotated down to zero
+	 */
+	do {
+		gf2_matrix_square(even, odd);
+		len >>= 1;
+		if (len == 0)
+			return;
+		gf2_matrix_square(odd, even);
+		len >>= 1;
+	} while (len);
+
+	/* answer ended up in odd -- copy to even */
+	for (n = 0; n < 32; n++)
+		even[n] = odd[n];
+}
+
+/*
+ * Take a length and build four lookup tables for applying the zeros operator
+ * for that length, byte-by-byte on the operand.
+ */
+static void
+crc32c_zeros(uint32_t zeros[][256], size_t len)
+{
+	uint32_t op[32];
+	uint32_t n;
+
+	crc32c_zeros_op(op, len);
+	for (n = 0; n < 256; n++) {
+		zeros[0][n] = gf2_matrix_times(op, n);
+		zeros[1][n] = gf2_matrix_times(op, n << 8);
+		zeros[2][n] = gf2_matrix_times(op, n << 16);
+		zeros[3][n] = gf2_matrix_times(op, n << 24);
+	}
+}
+
+/* Apply the zeros operator table to crc. */
+static inline uint32_t
+crc32c_shift(uint32_t zeros[][256], uint32_t crc)
+{
+
+	return (zeros[0][crc & 0xff] ^ zeros[1][(crc >> 8) & 0xff] ^
+	    zeros[2][(crc >> 16) & 0xff] ^ zeros[3][crc >> 24]);
+}
+
+/* Initialize tables for shifting crcs. */
+static void
+#ifdef USERSPACE_TESTING
+__attribute__((__constructor__))
+#endif
+crc32c_init_hw(void)
+{
+	crc32c_zeros(crc32c_long, LONG);
+	crc32c_zeros(crc32c_short, SHORT);
+}
+#ifdef _KERNEL
+SYSINIT(crc32c_sse42, SI_SUB_LOCK, SI_ORDER_ANY, crc32c_init_hw, NULL);
+#endif
+
+/* Compute CRC-32C using the Intel hardware instruction. */
+#ifdef USERSPACE_TESTING
+uint32_t sse42_crc32c(uint32_t, const unsigned char *, unsigned);
+#endif
+uint32_t
+sse42_crc32c(uint32_t crc, const unsigned char *buf, unsigned len)
+{
+#ifdef __amd64__
+	const size_t align = 8;
+#else
+	const size_t align = 4;
+#endif
+	const unsigned char *next, *end;
+	uint64_t crc0, crc1, crc2;      /* need to be 64 bits for crc32q */
+
+	next = buf;
+	crc0 = crc;
+
+	/* Compute the crc to bring the data pointer to an aligned boundary. */
+	while (len && ((uintptr_t)next & (align - 1)) != 0) {
+		crc0 = _mm_crc32_u8(crc0, *next);
+		next++;
+		len--;
+	}
+
+	/*
+	 * Compute the crc on sets of LONG*3 bytes, executing three independent
+	 * crc instructions, each on LONG bytes -- this is optimized for the
+	 * Nehalem, Westmere, Sandy Bridge, and Ivy Bridge architectures, which
+	 * have a throughput of one crc per cycle, but a latency of three
+	 * cycles.
+	 */
+	while (len >= LONG * 3) {
+		crc1 = 0;
+		crc2 = 0;
+		end = next + LONG;
+		do {
+#ifdef __amd64__
+			crc0 = _mm_crc32_u64(crc0, *(const uint64_t *)next);
+			crc1 = _mm_crc32_u64(crc1,
+			    *(const uint64_t *)(next + LONG));
+			crc2 = _mm_crc32_u64(crc2,
+			    *(const uint64_t *)(next + (LONG * 2)));
+#else
+			crc0 = _mm_crc32_u32(crc0, *(const uint32_t *)next);
+			crc1 = _mm_crc32_u32(crc1,
+			    *(const uint32_t *)(next + LONG));
+			crc2 = _mm_crc32_u32(crc2,
+			    *(const uint32_t *)(next + (LONG * 2)));
+#endif
+			next += align;
+		} while (next < end);
+		crc0 = crc32c_shift(crc32c_long, crc0) ^ crc1;
+		crc0 = crc32c_shift(crc32c_long, crc0) ^ crc2;
+		next += LONG * 2;
+		len -= LONG * 3;
+	}
+
+	/*
+	 * Do the same thing, but now on SHORT*3 blocks for the remaining data
+	 * less than a LONG*3 block
+	 */
+	while (len >= SHORT * 3) {
+		crc1 = 0;
+		crc2 = 0;
+		end = next + SHORT;
+		do {
+#ifdef __amd64__
+			crc0 = _mm_crc32_u64(crc0, *(const uint64_t *)next);
+			crc1 = _mm_crc32_u64(crc1,
+			    *(const uint64_t *)(next + SHORT));
+			crc2 = _mm_crc32_u64(crc2,
+			    *(const uint64_t *)(next + (SHORT * 2)));
+#else
+			crc0 = _mm_crc32_u32(crc0, *(const uint32_t *)next);
+			crc1 = _mm_crc32_u32(crc1,
+			    *(const uint32_t *)(next + SHORT));
+			crc2 = _mm_crc32_u32(crc2,
+			    *(const uint32_t *)(next + (SHORT * 2)));
+#endif
+			next += align;
+		} while (next < end);
+		crc0 = crc32c_shift(crc32c_short, crc0) ^ crc1;
+		crc0 = crc32c_shift(crc32c_short, crc0) ^ crc2;
+		next += SHORT * 2;
+		len -= SHORT * 3;
+	}
+
+	/* Compute the crc on the remaining bytes at native word size. */
+	end = next + (len - (len & (align - 1)));
+	while (next < end) {
+#ifdef __amd64__
+		crc0 = _mm_crc32_u64(crc0, *(const uint64_t *)next);
+#else
+		crc0 = _mm_crc32_u32(crc0, *(const uint32_t *)next);
+#endif
+		next += align;
+	}
+	len &= (align - 1);
+
+	/* Compute the crc for any trailing bytes. */
+	while (len) {
+		crc0 = _mm_crc32_u8(crc0, *next);
+		next++;
+		len--;
+	}
+
+	return ((uint32_t)crc0);
+}

sys/sys/libkern.h

@@ -205,6 +205,11 @@ crc32(const void *buf, size_t size)
 uint32_t
 calculate_crc32c(uint32_t crc32c, const unsigned char *buffer,
     unsigned int length);
+#ifdef _KERNEL
+#if defined(__amd64__) || defined(__i386__)
+uint32_t sse42_crc32c(uint32_t, const unsigned char *, unsigned);
+#endif
+#endif
 
 
 LIBKERN_INLINE void *memset(void *, int, size_t);

tests/sys/kern/Makefile

@@ -29,13 +29,19 @@ NETBSD_ATF_TESTS_C+=	mqueue_test
 CFLAGS.mqueue_test+=	-I${SRCTOP}/tests
 LIBADD.mqueue_test+=	rt
 
+.if ${MACHINE_ARCH} == "amd64" || ${MACHINE_ARCH} == "i386"
+ATF_TESTS_C+=	libkern_crc32
+CFLAGS.libkern_crc32+=	-msse4 -DUSERSPACE_TESTING
+LDADD.libkern_crc32+=	${SRCTOP}/sys/libkern/x86/crc32_sse42.c
+.endif
+
 # subr_unit.c contains functions whose prototypes lie in headers that cannot be
 # included in userland.  But as far as subr_unit_test goes, they're effectively
 # static.  So it's ok to disable -Wmissing-prototypes for this program.
 CFLAGS.subr_unit.c+=	-Wno-missing-prototypes
 SRCS.subr_unit_test+=	subr_unit.c
 
-WARNS?=	5
+WARNS?=	3
 
 TESTS_SUBDIRS+=	acct
 TESTS_SUBDIRS+=	execve