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    Subject[PATCH 08/14] crc32: Add slice-by-8 algorithm to existing code
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    Date
    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.

    From: Bob Pearson <rpearson@systemfabricworks.com>
    Signed-off-by: Bob Pearson <rpearson@systemfabricworks.com>
    [djwong@us.ibm.com: Minor changelog tweaks]
    Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
    ---
    lib/crc32.c | 40 ++++++++++++++++++++++++++++------------
    lib/crc32defs.h | 29 +++++++++++++++++++++--------
    lib/gen_crc32table.c | 43 +++++++++++++++++++++++++++----------------
    3 files changed, 76 insertions(+), 36 deletions(-)


    diff --git a/lib/crc32.c b/lib/crc32.c
    index 157b35f..6311712 100644
    --- a/lib/crc32.c
    +++ b/lib/crc32.c
    @@ -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;
    + 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

    diff --git a/lib/crc32defs.h b/lib/crc32defs.h
    index daa3a5e..8181592 100644
    --- a/lib/crc32defs.h
    +++ b/lib/crc32defs.h
    @@ -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
    diff --git a/lib/gen_crc32table.c b/lib/gen_crc32table.c
    index 99ac744..0d9edd1 100644
    --- a/lib/gen_crc32table.c
    +++ b/lib/gen_crc32table.c
    @@ -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");
    }



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