diff mbox series

[5/6] x86/crc-t10dif: implement crc_t10dif using new template

Message ID 20241125041129.192999-6-ebiggers@kernel.org
State New
Headers show
Series x86: new optimized CRC functions, with VPCLMULQDQ support | expand

Commit Message

Eric Biggers Nov. 25, 2024, 4:11 a.m. UTC
From: Eric Biggers <ebiggers@google.com>

Instantiate crc-pclmul-template.S for crc_t10dif and delete the original
PCLMULQDQ optimized implementation.  This has the following advantages:

- Less CRC-variant-specific code.
- Full VPCLMULQDQ support, improving performance on newer CPUs.
- A faster final reduction from 128 bits.
- Support for i386.

Benchmark results on AMD Ryzen 9 9950X (Zen 5) using crc_kunit:

    	Length     Before        After
	------     ------        -----
	     1     435 MB/s      509 MB/s
	    16    1878 MB/s     1852 MB/s
	    64    4336 MB/s     6123 MB/s
	   127    5394 MB/s     8431 MB/s
	   128    5590 MB/s    10886 MB/s
	   200    5948 MB/s    13371 MB/s
	   256   15813 MB/s    19428 MB/s
	   511   14193 MB/s    25177 MB/s
	   512   18136 MB/s    35188 MB/s
	  1024   19878 MB/s    62569 MB/s
	  3173   21009 MB/s    77916 MB/s
	  4096   21249 MB/s    82295 MB/s
	 16384   21645 MB/s    89350 MB/s

The above results compare the state directly before this patch to the
state after this patch.  Note that performance was also improved earlier
by eliminating the indirect call associated with the crypto API.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 arch/x86/Kconfig                    |   2 +-
 arch/x86/lib/Makefile               |   2 +-
 arch/x86/lib/crc-pclmul-consts.h    |  48 +++-
 arch/x86/lib/crc-t10dif-glue.c      |  22 +-
 arch/x86/lib/crc16-msb-pclmul.S     |   6 +
 arch/x86/lib/crct10dif-pcl-asm_64.S | 332 ----------------------------
 6 files changed, 65 insertions(+), 347 deletions(-)
 create mode 100644 arch/x86/lib/crc16-msb-pclmul.S
 delete mode 100644 arch/x86/lib/crct10dif-pcl-asm_64.S
diff mbox series

Patch

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 687221b7ea851..3a47ef91ef177 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -75,11 +75,11 @@  config X86
 	select ARCH_HAS_CACHE_LINE_SIZE
 	select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
 	select ARCH_HAS_CPU_FINALIZE_INIT
 	select ARCH_HAS_CPU_PASID		if IOMMU_SVA
 	select ARCH_HAS_CRC32
-	select ARCH_HAS_CRC_T10DIF		if X86_64
+	select ARCH_HAS_CRC_T10DIF
 	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DEBUG_VIRTUAL
 	select ARCH_HAS_DEBUG_VM_PGTABLE	if !X86_PAE
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_DMA_OPS			if GART_IOMMU || XEN
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 8a59c61624c2f..08496e221a7d1 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -41,11 +41,11 @@  lib-$(CONFIG_MITIGATION_RETPOLINE) += retpoline.o
 obj-$(CONFIG_CRC32_ARCH) += crc32-x86.o
 crc32-x86-y := crc32-glue.o crc32-pclmul.o
 crc32-x86-$(CONFIG_64BIT) += crc32c-3way.o
 
 obj-$(CONFIG_CRC_T10DIF_ARCH) += crc-t10dif-x86.o
-crc-t10dif-x86-y := crc-t10dif-glue.o crct10dif-pcl-asm_64.o
+crc-t10dif-x86-y := crc-t10dif-glue.o crc16-msb-pclmul.o
 
 obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o
 obj-y += iomem.o
 
 ifeq ($(CONFIG_X86_32),y)
diff --git a/arch/x86/lib/crc-pclmul-consts.h b/arch/x86/lib/crc-pclmul-consts.h
index ed9a625cdd2a6..c3ca689eae3b8 100644
--- a/arch/x86/lib/crc-pclmul-consts.h
+++ b/arch/x86/lib/crc-pclmul-consts.h
@@ -1,14 +1,60 @@ 
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 /*
  * CRC constants generated by:
  *
- *	./scripts/crc/gen-crc-consts.py x86_pclmul crc32_lsb_0xedb88320
+ *	./scripts/crc/gen-crc-consts.py x86_pclmul crc16_msb_0x8bb7,crc32_lsb_0xedb88320
  *
  * Do not edit manually.
  */
 
+/*
+ * CRC folding constants generated for most-significant-bit-first CRC-16 using
+ * G(x) = x^16 + x^15 + x^11 + x^9 + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1
+ */
+static const struct {
+	u8 bswap_mask[16];
+	u64 fold_across_2048_bits_consts[2];
+	u64 fold_across_1024_bits_consts[2];
+	u64 fold_across_512_bits_consts[2];
+	u64 fold_across_256_bits_consts[2];
+	u64 fold_across_128_bits_consts[2];
+	u8 shuf_table[48];
+	u64 barrett_reduction_consts[2];
+} crc16_msb_0x8bb7_consts __cacheline_aligned __maybe_unused = {
+	.bswap_mask = {15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0},
+	.fold_across_2048_bits_consts = {
+		0x22c6,	/* x^(2048+0) mod G(x) */
+		0x9f16,	/* x^(2048+64) mod G(x) */
+	},
+	.fold_across_1024_bits_consts = {
+		0x6123,	/* x^(1024+0) mod G(x) */
+		0x2295,	/* x^(1024+64) mod G(x) */
+	},
+	.fold_across_512_bits_consts = {
+		0x1069,	/* x^(512+0) mod G(x) */
+		0xdd31,	/* x^(512+64) mod G(x) */
+	},
+	.fold_across_256_bits_consts = {
+		0x857d,	/* x^(256+0) mod G(x) */
+		0x7acc,	/* x^(256+64) mod G(x) */
+	},
+	.fold_across_128_bits_consts = {
+		0xa010,	/* x^(128+0) mod G(x) */
+		0x1faa,	/* x^(128+64) mod G(x) */
+	},
+	.shuf_table = {
+		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+		 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15,
+		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	},
+	.barrett_reduction_consts = {
+		0xf65a57f81d33a48a,	/* floor(x^80 / G(x)) - x^64 */
+		0x18bb7,	/* G(x) */
+	},
+};
+
 /*
  * CRC folding constants generated for least-significant-bit-first CRC-32 using
  * G(x) = x^32 + x^26 + x^23 + x^22 + x^16 + x^12 + x^11 + x^10 + x^8 + x^7 +
  *        x^5 + x^4 + x^2 + x + 1
  */
diff --git a/arch/x86/lib/crc-t10dif-glue.c b/arch/x86/lib/crc-t10dif-glue.c
index 13f07ddc9122c..f4cfffdb19ceb 100644
--- a/arch/x86/lib/crc-t10dif-glue.c
+++ b/arch/x86/lib/crc-t10dif-glue.c
@@ -1,39 +1,37 @@ 
 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
- * CRC-T10DIF using PCLMULQDQ instructions
+ * CRC-T10DIF using [V]PCLMULQDQ instructions
  *
  * Copyright 2024 Google LLC
  */
 
 #include <asm/cpufeatures.h>
 #include <asm/simd.h>
-#include <crypto/internal/simd.h>
 #include <linux/crc-t10dif.h>
 #include <linux/module.h>
+#include "crc-pclmul-consts.h"
+#include "crc-pclmul-template-glue.h"
 
 static DEFINE_STATIC_KEY_FALSE(have_pclmulqdq);
 
-asmlinkage u16 crc_t10dif_pcl(u16 init_crc, const u8 *buf, size_t len);
+DECLARE_CRC_PCLMUL_FUNCS(crc16_msb, u16);
 
 u16 crc_t10dif_arch(u16 crc, const u8 *p, size_t len)
 {
-	if (len >= 16 &&
-	    static_key_enabled(&have_pclmulqdq) && crypto_simd_usable()) {
-		kernel_fpu_begin();
-		crc = crc_t10dif_pcl(crc, p, len);
-		kernel_fpu_end();
-		return crc;
-	}
+	CRC_PCLMUL(crc, p, len, crc16_msb, crc16_msb_0x8bb7_consts,
+		   have_pclmulqdq, false);
 	return crc_t10dif_generic(crc, p, len);
 }
 EXPORT_SYMBOL(crc_t10dif_arch);
 
 static int __init crc_t10dif_x86_init(void)
 {
-	if (boot_cpu_has(X86_FEATURE_PCLMULQDQ))
+	if (boot_cpu_has(X86_FEATURE_PCLMULQDQ)) {
 		static_branch_enable(&have_pclmulqdq);
+		INIT_CRC_PCLMUL(crc16_msb);
+	}
 	return 0;
 }
 arch_initcall(crc_t10dif_x86_init);
 
 static void __exit crc_t10dif_x86_exit(void)
@@ -45,7 +43,7 @@  bool crc_t10dif_is_optimized(void)
 {
 	return static_key_enabled(&have_pclmulqdq);
 }
 EXPORT_SYMBOL(crc_t10dif_is_optimized);
 
-MODULE_DESCRIPTION("CRC-T10DIF using PCLMULQDQ instructions");
+MODULE_DESCRIPTION("CRC-T10DIF using [V]PCLMULQDQ instructions");
 MODULE_LICENSE("GPL");
diff --git a/arch/x86/lib/crc16-msb-pclmul.S b/arch/x86/lib/crc16-msb-pclmul.S
new file mode 100644
index 0000000000000..14e90ce199314
--- /dev/null
+++ b/arch/x86/lib/crc16-msb-pclmul.S
@@ -0,0 +1,6 @@ 
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+// Copyright 2024 Google LLC
+
+#include "crc-pclmul-template.S"
+
+DEFINE_CRC_PCLMUL_FUNCS(crc16_msb, /* bits= */ 16, /* lsb= */ 0)
diff --git a/arch/x86/lib/crct10dif-pcl-asm_64.S b/arch/x86/lib/crct10dif-pcl-asm_64.S
deleted file mode 100644
index 5286db5b8165e..0000000000000
--- a/arch/x86/lib/crct10dif-pcl-asm_64.S
+++ /dev/null
@@ -1,332 +0,0 @@ 
-########################################################################
-# Implement fast CRC-T10DIF computation with SSE and PCLMULQDQ instructions
-#
-# Copyright (c) 2013, Intel Corporation
-#
-# Authors:
-#     Erdinc Ozturk <erdinc.ozturk@intel.com>
-#     Vinodh Gopal <vinodh.gopal@intel.com>
-#     James Guilford <james.guilford@intel.com>
-#     Tim Chen <tim.c.chen@linux.intel.com>
-#
-# This software is available to you under a choice of one of two
-# licenses.  You may choose to be licensed under the terms of the GNU
-# General Public License (GPL) Version 2, available from the file
-# COPYING in the main directory of this source tree, or the
-# OpenIB.org BSD license below:
-#
-# Redistribution and use in source and binary forms, with or without
-# modification, are permitted provided that the following conditions are
-# met:
-#
-# * Redistributions of source code must retain the above copyright
-#   notice, this list of conditions and the following disclaimer.
-#
-# * Redistributions in binary form must reproduce the above copyright
-#   notice, this list of conditions and the following disclaimer in the
-#   documentation and/or other materials provided with the
-#   distribution.
-#
-# * Neither the name of the Intel Corporation nor the names of its
-#   contributors may be used to endorse or promote products derived from
-#   this software without specific prior written permission.
-#
-#
-# THIS SOFTWARE IS PROVIDED BY INTEL CORPORATION ""AS IS"" AND ANY
-# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
-# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTEL CORPORATION OR
-# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
-# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
-# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
-# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
-# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
-# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
-# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#
-#       Reference paper titled "Fast CRC Computation for Generic
-#	Polynomials Using PCLMULQDQ Instruction"
-#       URL: http://www.intel.com/content/dam/www/public/us/en/documents
-#  /white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf
-#
-
-#include <linux/linkage.h>
-
-.text
-
-#define		init_crc	%edi
-#define		buf		%rsi
-#define		len		%rdx
-
-#define		FOLD_CONSTS	%xmm10
-#define		BSWAP_MASK	%xmm11
-
-# Fold reg1, reg2 into the next 32 data bytes, storing the result back into
-# reg1, reg2.
-.macro	fold_32_bytes	offset, reg1, reg2
-	movdqu	\offset(buf), %xmm9
-	movdqu	\offset+16(buf), %xmm12
-	pshufb	BSWAP_MASK, %xmm9
-	pshufb	BSWAP_MASK, %xmm12
-	movdqa	\reg1, %xmm8
-	movdqa	\reg2, %xmm13
-	pclmulqdq	$0x00, FOLD_CONSTS, \reg1
-	pclmulqdq	$0x11, FOLD_CONSTS, %xmm8
-	pclmulqdq	$0x00, FOLD_CONSTS, \reg2
-	pclmulqdq	$0x11, FOLD_CONSTS, %xmm13
-	pxor	%xmm9 , \reg1
-	xorps	%xmm8 , \reg1
-	pxor	%xmm12, \reg2
-	xorps	%xmm13, \reg2
-.endm
-
-# Fold src_reg into dst_reg.
-.macro	fold_16_bytes	src_reg, dst_reg
-	movdqa	\src_reg, %xmm8
-	pclmulqdq	$0x11, FOLD_CONSTS, \src_reg
-	pclmulqdq	$0x00, FOLD_CONSTS, %xmm8
-	pxor	%xmm8, \dst_reg
-	xorps	\src_reg, \dst_reg
-.endm
-
-#
-# u16 crc_t10dif_pcl(u16 init_crc, const *u8 buf, size_t len);
-#
-# Assumes len >= 16.
-#
-SYM_FUNC_START(crc_t10dif_pcl)
-
-	movdqa	.Lbswap_mask(%rip), BSWAP_MASK
-
-	# For sizes less than 256 bytes, we can't fold 128 bytes at a time.
-	cmp	$256, len
-	jl	.Lless_than_256_bytes
-
-	# Load the first 128 data bytes.  Byte swapping is necessary to make the
-	# bit order match the polynomial coefficient order.
-	movdqu	16*0(buf), %xmm0
-	movdqu	16*1(buf), %xmm1
-	movdqu	16*2(buf), %xmm2
-	movdqu	16*3(buf), %xmm3
-	movdqu	16*4(buf), %xmm4
-	movdqu	16*5(buf), %xmm5
-	movdqu	16*6(buf), %xmm6
-	movdqu	16*7(buf), %xmm7
-	add	$128, buf
-	pshufb	BSWAP_MASK, %xmm0
-	pshufb	BSWAP_MASK, %xmm1
-	pshufb	BSWAP_MASK, %xmm2
-	pshufb	BSWAP_MASK, %xmm3
-	pshufb	BSWAP_MASK, %xmm4
-	pshufb	BSWAP_MASK, %xmm5
-	pshufb	BSWAP_MASK, %xmm6
-	pshufb	BSWAP_MASK, %xmm7
-
-	# XOR the first 16 data *bits* with the initial CRC value.
-	pxor	%xmm8, %xmm8
-	pinsrw	$7, init_crc, %xmm8
-	pxor	%xmm8, %xmm0
-
-	movdqa	.Lfold_across_128_bytes_consts(%rip), FOLD_CONSTS
-
-	# Subtract 128 for the 128 data bytes just consumed.  Subtract another
-	# 128 to simplify the termination condition of the following loop.
-	sub	$256, len
-
-	# While >= 128 data bytes remain (not counting xmm0-7), fold the 128
-	# bytes xmm0-7 into them, storing the result back into xmm0-7.
-.Lfold_128_bytes_loop:
-	fold_32_bytes	0, %xmm0, %xmm1
-	fold_32_bytes	32, %xmm2, %xmm3
-	fold_32_bytes	64, %xmm4, %xmm5
-	fold_32_bytes	96, %xmm6, %xmm7
-	add	$128, buf
-	sub	$128, len
-	jge	.Lfold_128_bytes_loop
-
-	# Now fold the 112 bytes in xmm0-xmm6 into the 16 bytes in xmm7.
-
-	# Fold across 64 bytes.
-	movdqa	.Lfold_across_64_bytes_consts(%rip), FOLD_CONSTS
-	fold_16_bytes	%xmm0, %xmm4
-	fold_16_bytes	%xmm1, %xmm5
-	fold_16_bytes	%xmm2, %xmm6
-	fold_16_bytes	%xmm3, %xmm7
-	# Fold across 32 bytes.
-	movdqa	.Lfold_across_32_bytes_consts(%rip), FOLD_CONSTS
-	fold_16_bytes	%xmm4, %xmm6
-	fold_16_bytes	%xmm5, %xmm7
-	# Fold across 16 bytes.
-	movdqa	.Lfold_across_16_bytes_consts(%rip), FOLD_CONSTS
-	fold_16_bytes	%xmm6, %xmm7
-
-	# Add 128 to get the correct number of data bytes remaining in 0...127
-	# (not counting xmm7), following the previous extra subtraction by 128.
-	# Then subtract 16 to simplify the termination condition of the
-	# following loop.
-	add	$128-16, len
-
-	# While >= 16 data bytes remain (not counting xmm7), fold the 16 bytes
-	# xmm7 into them, storing the result back into xmm7.
-	jl	.Lfold_16_bytes_loop_done
-.Lfold_16_bytes_loop:
-	movdqa	%xmm7, %xmm8
-	pclmulqdq	$0x11, FOLD_CONSTS, %xmm7
-	pclmulqdq	$0x00, FOLD_CONSTS, %xmm8
-	pxor	%xmm8, %xmm7
-	movdqu	(buf), %xmm0
-	pshufb	BSWAP_MASK, %xmm0
-	pxor	%xmm0 , %xmm7
-	add	$16, buf
-	sub	$16, len
-	jge	.Lfold_16_bytes_loop
-
-.Lfold_16_bytes_loop_done:
-	# Add 16 to get the correct number of data bytes remaining in 0...15
-	# (not counting xmm7), following the previous extra subtraction by 16.
-	add	$16, len
-	je	.Lreduce_final_16_bytes
-
-.Lhandle_partial_segment:
-	# Reduce the last '16 + len' bytes where 1 <= len <= 15 and the first 16
-	# bytes are in xmm7 and the rest are the remaining data in 'buf'.  To do
-	# this without needing a fold constant for each possible 'len', redivide
-	# the bytes into a first chunk of 'len' bytes and a second chunk of 16
-	# bytes, then fold the first chunk into the second.
-
-	movdqa	%xmm7, %xmm2
-
-	# xmm1 = last 16 original data bytes
-	movdqu	-16(buf, len), %xmm1
-	pshufb	BSWAP_MASK, %xmm1
-
-	# xmm2 = high order part of second chunk: xmm7 left-shifted by 'len' bytes.
-	lea	.Lbyteshift_table+16(%rip), %rax
-	sub	len, %rax
-	movdqu	(%rax), %xmm0
-	pshufb	%xmm0, %xmm2
-
-	# xmm7 = first chunk: xmm7 right-shifted by '16-len' bytes.
-	pxor	.Lmask1(%rip), %xmm0
-	pshufb	%xmm0, %xmm7
-
-	# xmm1 = second chunk: 'len' bytes from xmm1 (low-order bytes),
-	# then '16-len' bytes from xmm2 (high-order bytes).
-	pblendvb	%xmm2, %xmm1	#xmm0 is implicit
-
-	# Fold the first chunk into the second chunk, storing the result in xmm7.
-	movdqa	%xmm7, %xmm8
-	pclmulqdq	$0x11, FOLD_CONSTS, %xmm7
-	pclmulqdq	$0x00, FOLD_CONSTS, %xmm8
-	pxor	%xmm8, %xmm7
-	pxor	%xmm1, %xmm7
-
-.Lreduce_final_16_bytes:
-	# Reduce the 128-bit value M(x), stored in xmm7, to the final 16-bit CRC
-
-	# Load 'x^48 * (x^48 mod G(x))' and 'x^48 * (x^80 mod G(x))'.
-	movdqa	.Lfinal_fold_consts(%rip), FOLD_CONSTS
-
-	# Fold the high 64 bits into the low 64 bits, while also multiplying by
-	# x^64.  This produces a 128-bit value congruent to x^64 * M(x) and
-	# whose low 48 bits are 0.
-	movdqa	%xmm7, %xmm0
-	pclmulqdq	$0x11, FOLD_CONSTS, %xmm7 # high bits * x^48 * (x^80 mod G(x))
-	pslldq	$8, %xmm0
-	pxor	%xmm0, %xmm7			  # + low bits * x^64
-
-	# Fold the high 32 bits into the low 96 bits.  This produces a 96-bit
-	# value congruent to x^64 * M(x) and whose low 48 bits are 0.
-	movdqa	%xmm7, %xmm0
-	pand	.Lmask2(%rip), %xmm0		  # zero high 32 bits
-	psrldq	$12, %xmm7			  # extract high 32 bits
-	pclmulqdq	$0x00, FOLD_CONSTS, %xmm7 # high 32 bits * x^48 * (x^48 mod G(x))
-	pxor	%xmm0, %xmm7			  # + low bits
-
-	# Load G(x) and floor(x^48 / G(x)).
-	movdqa	.Lbarrett_reduction_consts(%rip), FOLD_CONSTS
-
-	# Use Barrett reduction to compute the final CRC value.
-	movdqa	%xmm7, %xmm0
-	pclmulqdq	$0x11, FOLD_CONSTS, %xmm7 # high 32 bits * floor(x^48 / G(x))
-	psrlq	$32, %xmm7			  # /= x^32
-	pclmulqdq	$0x00, FOLD_CONSTS, %xmm7 # *= G(x)
-	psrlq	$48, %xmm0
-	pxor	%xmm7, %xmm0		     # + low 16 nonzero bits
-	# Final CRC value (x^16 * M(x)) mod G(x) is in low 16 bits of xmm0.
-
-	pextrw	$0, %xmm0, %eax
-	RET
-
-.align 16
-.Lless_than_256_bytes:
-	# Checksumming a buffer of length 16...255 bytes
-
-	# Load the first 16 data bytes.
-	movdqu	(buf), %xmm7
-	pshufb	BSWAP_MASK, %xmm7
-	add	$16, buf
-
-	# XOR the first 16 data *bits* with the initial CRC value.
-	pxor	%xmm0, %xmm0
-	pinsrw	$7, init_crc, %xmm0
-	pxor	%xmm0, %xmm7
-
-	movdqa	.Lfold_across_16_bytes_consts(%rip), FOLD_CONSTS
-	cmp	$16, len
-	je	.Lreduce_final_16_bytes		# len == 16
-	sub	$32, len
-	jge	.Lfold_16_bytes_loop		# 32 <= len <= 255
-	add	$16, len
-	jmp	.Lhandle_partial_segment	# 17 <= len <= 31
-SYM_FUNC_END(crc_t10dif_pcl)
-
-.section	.rodata, "a", @progbits
-.align 16
-
-# Fold constants precomputed from the polynomial 0x18bb7
-# G(x) = x^16 + x^15 + x^11 + x^9 + x^8 + x^7 + x^5 + x^4 + x^2 + x^1 + x^0
-.Lfold_across_128_bytes_consts:
-	.quad		0x0000000000006123	# x^(8*128)	mod G(x)
-	.quad		0x0000000000002295	# x^(8*128+64)	mod G(x)
-.Lfold_across_64_bytes_consts:
-	.quad		0x0000000000001069	# x^(4*128)	mod G(x)
-	.quad		0x000000000000dd31	# x^(4*128+64)	mod G(x)
-.Lfold_across_32_bytes_consts:
-	.quad		0x000000000000857d	# x^(2*128)	mod G(x)
-	.quad		0x0000000000007acc	# x^(2*128+64)	mod G(x)
-.Lfold_across_16_bytes_consts:
-	.quad		0x000000000000a010	# x^(1*128)	mod G(x)
-	.quad		0x0000000000001faa	# x^(1*128+64)	mod G(x)
-.Lfinal_fold_consts:
-	.quad		0x1368000000000000	# x^48 * (x^48 mod G(x))
-	.quad		0x2d56000000000000	# x^48 * (x^80 mod G(x))
-.Lbarrett_reduction_consts:
-	.quad		0x0000000000018bb7	# G(x)
-	.quad		0x00000001f65a57f8	# floor(x^48 / G(x))
-
-.section	.rodata.cst16.mask1, "aM", @progbits, 16
-.align 16
-.Lmask1:
-	.octa	0x80808080808080808080808080808080
-
-.section	.rodata.cst16.mask2, "aM", @progbits, 16
-.align 16
-.Lmask2:
-	.octa	0x00000000FFFFFFFFFFFFFFFFFFFFFFFF
-
-.section	.rodata.cst16.bswap_mask, "aM", @progbits, 16
-.align 16
-.Lbswap_mask:
-	.octa	0x000102030405060708090A0B0C0D0E0F
-
-.section	.rodata.cst32.byteshift_table, "aM", @progbits, 32
-.align 16
-# For 1 <= len <= 15, the 16-byte vector beginning at &byteshift_table[16 - len]
-# is the index vector to shift left by 'len' bytes, and is also {0x80, ...,
-# 0x80} XOR the index vector to shift right by '16 - len' bytes.
-.Lbyteshift_table:
-	.byte		 0x0, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87
-	.byte		0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f
-	.byte		 0x0,  0x1,  0x2,  0x3,  0x4,  0x5,  0x6,  0x7
-	.byte		 0x8,  0x9,  0xa,  0xb,  0xc,  0xd,  0xe , 0x0