/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (C) 2016 Gvozden Nešković. All rights reserved.
 */

#include <sys/vdev_raidz_impl.h>

/*
 * Provide native CPU scalar routines.
 * Support 32bit and 64bit CPUs.
 */
#if ((~(0x0ULL)) >> 24) == 0xffULL
#define ELEM_SIZE       4
typedef uint32_t iv_t;
#elif ((~(0x0ULL)) >> 56) == 0xffULL
#define ELEM_SIZE       8
typedef uint64_t iv_t;
#endif

/*
 * Vector type used in scalar implementation
 *
 * The union is expected to be of native CPU register size. Since addition
 * uses XOR operation, it can be performed an all byte elements at once.
 * Multiplication requires per byte access.
 */
typedef union {
        iv_t e;
        uint8_t b[ELEM_SIZE];
} v_t;

/*
 * Precomputed lookup tables for multiplication by a constant
 *
 * Reconstruction path requires multiplication by a constant factors. Instead of
 * performing two step lookup (log & exp tables), a direct lookup can be used
 * instead. Multiplication of element 'a' by a constant 'c' is obtained as:
 *
 *      r = vdev_raidz_mul_lt[c_log][a];
 *
 * where c_log = vdev_raidz_log2[c]. Log of coefficient factors is used because
 * they are faster to obtain while solving the syndrome equations.
 *
 * PERFORMANCE NOTE:
 * Even though the complete lookup table uses 64kiB, only relatively small
 * portion of it is used at the same time. Following shows number of accessed
 * bytes for different cases:
 *      - 1 failed disk: 256B (1 mul. coefficient)
 *      - 2 failed disks: 512B (2 mul. coefficients)
 *      - 3 failed disks: 1536B (6 mul. coefficients)
 *
 * Size of actually accessed lookup table regions is only larger for
 * reconstruction of 3 failed disks, when compared to traditional log/exp
 * method. But since the result is obtained in one lookup step performance is
 * doubled.
 */
static uint8_t vdev_raidz_mul_lt[256][256] __attribute__((aligned(256)));

static void
raidz_init_scalar(void)
{
        int c, i;
        for (c = 0; c < 256; c++)
                for (i = 0; i < 256; i++)
                        vdev_raidz_mul_lt[c][i] = gf_mul(c, i);

}

#define PREFETCHNTA(ptr, offset)        {}
#define PREFETCH(ptr, offset)           {}

#define XOR_ACC(src, acc)       acc.e ^= ((v_t *)src)[0].e
#define XOR(src, acc)           acc.e ^= src.e
#define ZERO(acc)               acc.e = 0
#define COPY(src, dst)          dst = src
#define LOAD(src, val)          val = ((v_t *)src)[0]
#define STORE(dst, val)         ((v_t *)dst)[0] = val

/*
 * Constants used for optimized multiplication by 2.
 */
static const struct {
        iv_t mod;
        iv_t mask;
        iv_t msb;
} scalar_mul2_consts = {
#if ELEM_SIZE == 8
        .mod    = 0x1d1d1d1d1d1d1d1dULL,
        .mask   = 0xfefefefefefefefeULL,
        .msb    = 0x8080808080808080ULL,
#else
        .mod    = 0x1d1d1d1dULL,
        .mask   = 0xfefefefeULL,
        .msb    = 0x80808080ULL,
#endif
};

#define MUL2_SETUP() {}

#define MUL2(a)                                                         \
{                                                                       \
        iv_t _mask;                                                     \
                                                                        \
        _mask = (a).e & scalar_mul2_consts.msb;                         \
        _mask = (_mask << 1) - (_mask >> 7);                            \
        (a).e = ((a).e << 1) & scalar_mul2_consts.mask;                 \
        (a).e = (a).e ^ (_mask & scalar_mul2_consts.mod);               \
}

#define MUL4(a)                                                         \
{                                                                       \
        MUL2(a);                                                        \
        MUL2(a);                                                        \
}

#define MUL(c, a)                                                       \
{                                                                       \
        const uint8_t *mul_lt = vdev_raidz_mul_lt[c];                   \
        switch (ELEM_SIZE) {                                            \
        case 8:                                                         \
                a.b[7] = mul_lt[a.b[7]];                                \
                a.b[6] = mul_lt[a.b[6]];                                \
                a.b[5] = mul_lt[a.b[5]];                                \
                a.b[4] = mul_lt[a.b[4]];                                \
                /* falls through */                                     \
        case 4:                                                         \
                a.b[3] = mul_lt[a.b[3]];                                \
                a.b[2] = mul_lt[a.b[2]];                                \
                a.b[1] = mul_lt[a.b[1]];                                \
                a.b[0] = mul_lt[a.b[0]];                                \
                break;                                                  \
        }                                                               \
}

#define raidz_math_begin()      {}
#define raidz_math_end()        {}

#define SYN_STRIDE              1

#define ZERO_DEFINE()           v_t d0
#define ZERO_STRIDE             1
#define ZERO_D                  d0

#define COPY_DEFINE()           v_t d0
#define COPY_STRIDE             1
#define COPY_D                  d0

#define ADD_DEFINE()            v_t d0
#define ADD_STRIDE              1
#define ADD_D                   d0

#define MUL_DEFINE()            v_t d0
#define MUL_STRIDE              1
#define MUL_D                   d0

#define GEN_P_STRIDE            1
#define GEN_P_DEFINE()          v_t p0
#define GEN_P_P                 p0

#define GEN_PQ_STRIDE           1
#define GEN_PQ_DEFINE()         v_t d0, c0
#define GEN_PQ_D                d0
#define GEN_PQ_C                c0

#define GEN_PQR_STRIDE          1
#define GEN_PQR_DEFINE()        v_t d0, c0
#define GEN_PQR_D               d0
#define GEN_PQR_C               c0

#define SYN_Q_DEFINE()          v_t d0, x0
#define SYN_Q_D                 d0
#define SYN_Q_X                 x0


#define SYN_R_DEFINE()          v_t d0, x0
#define SYN_R_D                 d0
#define SYN_R_X                 x0


#define SYN_PQ_DEFINE()         v_t d0, x0
#define SYN_PQ_D                d0
#define SYN_PQ_X                x0


#define REC_PQ_STRIDE           1
#define REC_PQ_DEFINE()         v_t x0, y0, t0
#define REC_PQ_X                x0
#define REC_PQ_Y                y0
#define REC_PQ_T                t0


#define SYN_PR_DEFINE()         v_t d0, x0
#define SYN_PR_D                d0
#define SYN_PR_X                x0

#define REC_PR_STRIDE           1
#define REC_PR_DEFINE()         v_t x0, y0, t0
#define REC_PR_X                x0
#define REC_PR_Y                y0
#define REC_PR_T                t0


#define SYN_QR_DEFINE()         v_t d0, x0
#define SYN_QR_D                d0
#define SYN_QR_X                x0


#define REC_QR_STRIDE           1
#define REC_QR_DEFINE()         v_t x0, y0, t0
#define REC_QR_X                x0
#define REC_QR_Y                y0
#define REC_QR_T                t0


#define SYN_PQR_DEFINE()        v_t d0, x0
#define SYN_PQR_D               d0
#define SYN_PQR_X               x0

#define REC_PQR_STRIDE          1
#define REC_PQR_DEFINE()        v_t x0, y0, z0, xs0, ys0
#define REC_PQR_X               x0
#define REC_PQR_Y               y0
#define REC_PQR_Z               z0
#define REC_PQR_XS              xs0
#define REC_PQR_YS              ys0

#include "vdev_raidz_math_impl.h"

DEFINE_GEN_METHODS(scalar);
DEFINE_REC_METHODS(scalar);

boolean_t
raidz_will_scalar_work(void)
{
        return (B_TRUE); /* always */
}

const raidz_impl_ops_t vdev_raidz_scalar_impl = {
        .init = raidz_init_scalar,
        .fini = NULL,
        .gen = RAIDZ_GEN_METHODS(scalar),
        .rec = RAIDZ_REC_METHODS(scalar),
        .is_supported = &raidz_will_scalar_work,
        .name = "scalar"
};

/* Powers of 2 in the RAID-Z Galois field. */
const uint8_t vdev_raidz_pow2[256] __attribute__((aligned(256))) = {
        0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80,
        0x1d, 0x3a, 0x74, 0xe8, 0xcd, 0x87, 0x13, 0x26,
        0x4c, 0x98, 0x2d, 0x5a, 0xb4, 0x75, 0xea, 0xc9,
        0x8f, 0x03, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc0,
        0x9d, 0x27, 0x4e, 0x9c, 0x25, 0x4a, 0x94, 0x35,
        0x6a, 0xd4, 0xb5, 0x77, 0xee, 0xc1, 0x9f, 0x23,
        0x46, 0x8c, 0x05, 0x0a, 0x14, 0x28, 0x50, 0xa0,
        0x5d, 0xba, 0x69, 0xd2, 0xb9, 0x6f, 0xde, 0xa1,
        0x5f, 0xbe, 0x61, 0xc2, 0x99, 0x2f, 0x5e, 0xbc,
        0x65, 0xca, 0x89, 0x0f, 0x1e, 0x3c, 0x78, 0xf0,
        0xfd, 0xe7, 0xd3, 0xbb, 0x6b, 0xd6, 0xb1, 0x7f,
        0xfe, 0xe1, 0xdf, 0xa3, 0x5b, 0xb6, 0x71, 0xe2,
        0xd9, 0xaf, 0x43, 0x86, 0x11, 0x22, 0x44, 0x88,
        0x0d, 0x1a, 0x34, 0x68, 0xd0, 0xbd, 0x67, 0xce,
        0x81, 0x1f, 0x3e, 0x7c, 0xf8, 0xed, 0xc7, 0x93,
        0x3b, 0x76, 0xec, 0xc5, 0x97, 0x33, 0x66, 0xcc,
        0x85, 0x17, 0x2e, 0x5c, 0xb8, 0x6d, 0xda, 0xa9,
        0x4f, 0x9e, 0x21, 0x42, 0x84, 0x15, 0x2a, 0x54,
        0xa8, 0x4d, 0x9a, 0x29, 0x52, 0xa4, 0x55, 0xaa,
        0x49, 0x92, 0x39, 0x72, 0xe4, 0xd5, 0xb7, 0x73,
        0xe6, 0xd1, 0xbf, 0x63, 0xc6, 0x91, 0x3f, 0x7e,
        0xfc, 0xe5, 0xd7, 0xb3, 0x7b, 0xf6, 0xf1, 0xff,
        0xe3, 0xdb, 0xab, 0x4b, 0x96, 0x31, 0x62, 0xc4,
        0x95, 0x37, 0x6e, 0xdc, 0xa5, 0x57, 0xae, 0x41,
        0x82, 0x19, 0x32, 0x64, 0xc8, 0x8d, 0x07, 0x0e,
        0x1c, 0x38, 0x70, 0xe0, 0xdd, 0xa7, 0x53, 0xa6,
        0x51, 0xa2, 0x59, 0xb2, 0x79, 0xf2, 0xf9, 0xef,
        0xc3, 0x9b, 0x2b, 0x56, 0xac, 0x45, 0x8a, 0x09,
        0x12, 0x24, 0x48, 0x90, 0x3d, 0x7a, 0xf4, 0xf5,
        0xf7, 0xf3, 0xfb, 0xeb, 0xcb, 0x8b, 0x0b, 0x16,
        0x2c, 0x58, 0xb0, 0x7d, 0xfa, 0xe9, 0xcf, 0x83,
        0x1b, 0x36, 0x6c, 0xd8, 0xad, 0x47, 0x8e, 0x01
};

/* Logs of 2 in the RAID-Z Galois field. */
const uint8_t vdev_raidz_log2[256] __attribute__((aligned(256))) = {
        0x00, 0x00, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6,
        0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b,
        0x04, 0x64, 0xe0, 0x0e, 0x34, 0x8d, 0xef, 0x81,
        0x1c, 0xc1, 0x69, 0xf8, 0xc8, 0x08, 0x4c, 0x71,
        0x05, 0x8a, 0x65, 0x2f, 0xe1, 0x24, 0x0f, 0x21,
        0x35, 0x93, 0x8e, 0xda, 0xf0, 0x12, 0x82, 0x45,
        0x1d, 0xb5, 0xc2, 0x7d, 0x6a, 0x27, 0xf9, 0xb9,
        0xc9, 0x9a, 0x09, 0x78, 0x4d, 0xe4, 0x72, 0xa6,
        0x06, 0xbf, 0x8b, 0x62, 0x66, 0xdd, 0x30, 0xfd,
        0xe2, 0x98, 0x25, 0xb3, 0x10, 0x91, 0x22, 0x88,
        0x36, 0xd0, 0x94, 0xce, 0x8f, 0x96, 0xdb, 0xbd,
        0xf1, 0xd2, 0x13, 0x5c, 0x83, 0x38, 0x46, 0x40,
        0x1e, 0x42, 0xb6, 0xa3, 0xc3, 0x48, 0x7e, 0x6e,
        0x6b, 0x3a, 0x28, 0x54, 0xfa, 0x85, 0xba, 0x3d,
        0xca, 0x5e, 0x9b, 0x9f, 0x0a, 0x15, 0x79, 0x2b,
        0x4e, 0xd4, 0xe5, 0xac, 0x73, 0xf3, 0xa7, 0x57,
        0x07, 0x70, 0xc0, 0xf7, 0x8c, 0x80, 0x63, 0x0d,
        0x67, 0x4a, 0xde, 0xed, 0x31, 0xc5, 0xfe, 0x18,
        0xe3, 0xa5, 0x99, 0x77, 0x26, 0xb8, 0xb4, 0x7c,
        0x11, 0x44, 0x92, 0xd9, 0x23, 0x20, 0x89, 0x2e,
        0x37, 0x3f, 0xd1, 0x5b, 0x95, 0xbc, 0xcf, 0xcd,
        0x90, 0x87, 0x97, 0xb2, 0xdc, 0xfc, 0xbe, 0x61,
        0xf2, 0x56, 0xd3, 0xab, 0x14, 0x2a, 0x5d, 0x9e,
        0x84, 0x3c, 0x39, 0x53, 0x47, 0x6d, 0x41, 0xa2,
        0x1f, 0x2d, 0x43, 0xd8, 0xb7, 0x7b, 0xa4, 0x76,
        0xc4, 0x17, 0x49, 0xec, 0x7f, 0x0c, 0x6f, 0xf6,
        0x6c, 0xa1, 0x3b, 0x52, 0x29, 0x9d, 0x55, 0xaa,
        0xfb, 0x60, 0x86, 0xb1, 0xbb, 0xcc, 0x3e, 0x5a,
        0xcb, 0x59, 0x5f, 0xb0, 0x9c, 0xa9, 0xa0, 0x51,
        0x0b, 0xf5, 0x16, 0xeb, 0x7a, 0x75, 0x2c, 0xd7,
        0x4f, 0xae, 0xd5, 0xe9, 0xe6, 0xe7, 0xad, 0xe8,
        0x74, 0xd6, 0xf4, 0xea, 0xa8, 0x50, 0x58, 0xaf,
};