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crc32: add slice-by-8 algorithm to existing code 

Add slicing-by-8 algorithm to the existing slicing-by-4 algorithm.  This
consists of:

- extend largest BITS size from 32 to 64
- extend tables from tab[4][256] to up to tab[8][256]
- Add code for inner loop.

[djwong@us.ibm.com: Minor changelog tweaks]
Signed-off-by: Bob Pearson <rpearson@systemfabricworks.com>
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Bob Pearson 2012-03-23 15:02:24 -07:00 committed by Linus Torvalds
parent 9a1dbf6a29
commit 324eb0f17d
3 changed files with 75 additions and 35 deletions
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38
lib/crc32.c
View File

@ -47,25 +47,28 @@ MODULE_LICENSE("GPL");
#if CRC_LE_BITS > 8 || CRC_BE_BITS > 8
/* implements slicing-by-4 or slicing-by-8 algorithm */
static inline u32
crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
{
# ifdef __LITTLE_ENDIAN
# define DO_CRC(x) crc = t0[(crc ^ (x)) & 255] ^ (crc >> 8)
# define DO_CRC4 crc = t3[(crc) & 255] ^ \
t2[(crc >> 8) & 255] ^ \
t1[(crc >> 16) & 255] ^ \
t0[(crc >> 24) & 255]
# define DO_CRC4 (t3[(q) & 255] ^ t2[(q >> 8) & 255] ^ \
t1[(q >> 16) & 255] ^ t0[(q >> 24) & 255])
# define DO_CRC8 (t7[(q) & 255] ^ t6[(q >> 8) & 255] ^ \
t5[(q >> 16) & 255] ^ t4[(q >> 24) & 255])
# else
# define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8)
# define DO_CRC4 crc = t0[(crc) & 255] ^ \
t1[(crc >> 8) & 255] ^ \
t2[(crc >> 16) & 255] ^ \
t3[(crc >> 24) & 255]
# define DO_CRC4 (t0[(q) & 255] ^ t1[(q >> 8) & 255] ^ \
t2[(q >> 16) & 255] ^ t3[(q >> 24) & 255])
# define DO_CRC8 (t4[(q) & 255] ^ t5[(q >> 8) & 255] ^ \
t6[(q >> 16) & 255] ^ t7[(q >> 24) & 255])
# endif
const u32 *b;
size_t rem_len;
const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3];
const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7];
u32 q;
/* Align it */
if (unlikely((long)buf & 3 && len)) {
@ -73,13 +76,25 @@ crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
DO_CRC(*buf++);
} while ((--len) && ((long)buf)&3);
}
# if CRC_LE_BITS == 32
rem_len = len & 3;
/* load data 32 bits wide, xor data 32 bits wide. */
len = len >> 2;
# else
rem_len = len & 7;
len = len >> 3;
# endif
b = (const u32 *)buf;
for (--b; len; --len) {
crc ^= *++b; /* use pre increment for speed */
DO_CRC4;
q = crc ^ *++b; /* use pre increment for speed */
# if CRC_LE_BITS == 32
crc = DO_CRC4;
# else
crc = DO_CRC8;
q = *++b;
crc ^= DO_CRC4;
# endif
}
len = rem_len;
/* And the last few bytes */
@ -92,6 +107,7 @@ crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
return crc;
#undef DO_CRC
#undef DO_CRC4
#undef DO_CRC8
}
#endif

29
lib/crc32defs.h
View File

@ -6,29 +6,42 @@
#define CRCPOLY_LE 0xedb88320
#define CRCPOLY_BE 0x04c11db7
/* How many bits at a time to use. Valid values are 1, 2, 4, 8, and 32. */
/* For less performance-sensitive, use 4 or 8 */
/*
* How many bits at a time to use. Valid values are 1, 2, 4, 8, 32 and 64.
* For less performance-sensitive, use 4 or 8 to save table size.
* For larger systems choose same as CPU architecture as default.
* This works well on X86_64, SPARC64 systems. This may require some
* elaboration after experiments with other architectures.
*/
#ifndef CRC_LE_BITS
# define CRC_LE_BITS 32
# ifdef CONFIG_64BIT
# define CRC_LE_BITS 64
# else
# define CRC_LE_BITS 32
# endif
#endif
#ifndef CRC_BE_BITS
# define CRC_BE_BITS 32
# ifdef CONFIG_64BIT
# define CRC_BE_BITS 64
# else
# define CRC_BE_BITS 32
# endif
#endif
/*
* Little-endian CRC computation. Used with serial bit streams sent
* lsbit-first. Be sure to use cpu_to_le32() to append the computed CRC.
*/
#if CRC_LE_BITS > 32 || CRC_LE_BITS < 1 || CRC_LE_BITS == 16 || \
#if CRC_LE_BITS > 64 || CRC_LE_BITS < 1 || CRC_LE_BITS == 16 || \
CRC_LE_BITS & CRC_LE_BITS-1
# error "CRC_LE_BITS must be one of {1, 2, 4, 8, 32}"
# error "CRC_LE_BITS must be one of {1, 2, 4, 8, 32, 64}"
#endif
/*
* Big-endian CRC computation. Used with serial bit streams sent
* msbit-first. Be sure to use cpu_to_be32() to append the computed CRC.
*/
#if CRC_BE_BITS > 32 || CRC_BE_BITS < 1 || CRC_BE_BITS == 16 || \
#if CRC_BE_BITS > 64 || CRC_BE_BITS < 1 || CRC_BE_BITS == 16 || \
CRC_BE_BITS & CRC_BE_BITS-1
# error "CRC_BE_BITS must be one of {1, 2, 4, 8, 32}"
# error "CRC_BE_BITS must be one of {1, 2, 4, 8, 32, 64}"
#endif

43
lib/gen_crc32table.c
View File

@ -1,23 +1,28 @@
#include <stdio.h>
#include "../include/generated/autoconf.h"
#include "crc32defs.h"
#include <inttypes.h>
#define ENTRIES_PER_LINE 4
#if CRC_LE_BITS <= 8
#define LE_TABLE_SIZE (1 << CRC_LE_BITS)
#if CRC_LE_BITS > 8
# define LE_TABLE_ROWS (CRC_LE_BITS/8)
# define LE_TABLE_SIZE 256
#else
#define LE_TABLE_SIZE 256
# define LE_TABLE_ROWS 1
# define LE_TABLE_SIZE (1 << CRC_LE_BITS)
#endif
#if CRC_BE_BITS <= 8
#define BE_TABLE_SIZE (1 << CRC_BE_BITS)
#if CRC_BE_BITS > 8
# define BE_TABLE_ROWS (CRC_BE_BITS/8)
# define BE_TABLE_SIZE 256
#else
#define BE_TABLE_SIZE 256
# define BE_TABLE_ROWS 1
# define BE_TABLE_SIZE (1 << CRC_BE_BITS)
#endif
static uint32_t crc32table_le[4][256];
static uint32_t crc32table_be[4][256];
static uint32_t crc32table_le[LE_TABLE_ROWS][256];
static uint32_t crc32table_be[BE_TABLE_ROWS][256];
/**
* crc32init_le() - allocate and initialize LE table data
@ -40,7 +45,7 @@ static void crc32init_le(void)
}
for (i = 0; i < LE_TABLE_SIZE; i++) {
crc = crc32table_le[0][i];
for (j = 1; j < 4; j++) {
for (j = 1; j < LE_TABLE_ROWS; j++) {
crc = crc32table_le[0][crc & 0xff] ^ (crc >> 8);
crc32table_le[j][i] = crc;
}
@ -64,18 +69,18 @@ static void crc32init_be(void)
}
for (i = 0; i < BE_TABLE_SIZE; i++) {
crc = crc32table_be[0][i];
for (j = 1; j < 4; j++) {
for (j = 1; j < BE_TABLE_ROWS; j++) {
crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
crc32table_be[j][i] = crc;
}
}
}
static void output_table(uint32_t (*table)[256], int len, char *trans)
static void output_table(uint32_t (*table)[256], int rows, int len, char *trans)
{
int i, j;
for (j = 0 ; j < 4; j++) {
for (j = 0 ; j < rows; j++) {
printf("{");
for (i = 0; i < len - 1; i++) {
if (i % ENTRIES_PER_LINE == 0)
@ -92,15 +97,21 @@ int main(int argc, char** argv)
if (CRC_LE_BITS > 1) {
crc32init_le();
printf("static const u32 crc32table_le[4][256] = {");
output_table(crc32table_le, LE_TABLE_SIZE, "tole");
printf("static const u32 __cacheline_aligned "
"crc32table_le[%d][%d] = {",
LE_TABLE_ROWS, LE_TABLE_SIZE);
output_table(crc32table_le, LE_TABLE_ROWS,
LE_TABLE_SIZE, "tole");
printf("};\n");
}
if (CRC_BE_BITS > 1) {
crc32init_be();
printf("static const u32 crc32table_be[4][256] = {");
output_table(crc32table_be, BE_TABLE_SIZE, "tobe");
printf("static const u32 __cacheline_aligned "
"crc32table_be[%d][%d] = {",
BE_TABLE_ROWS, BE_TABLE_SIZE);
output_table(crc32table_be, LE_TABLE_ROWS,
BE_TABLE_SIZE, "tobe");
printf("};\n");
}