/*
 *  linux/arch/arm/vfp/vfpdouble.c
 *
 * This code is derived in part from John R. Housers softfloat library, which
 * carries the following notice:
 *
 * ===========================================================================
 * This C source file is part of the SoftFloat IEC/IEEE Floating-point
 * Arithmetic Package, Release 2.
 *
 * Written by John R. Hauser.  This work was made possible in part by the
 * International Computer Science Institute, located at Suite 600, 1947 Center
 * Street, Berkeley, California 94704.  Funding was partially provided by the
 * National Science Foundation under grant MIP-9311980.  The original version
 * of this code was written as part of a project to build a fixed-point vector
 * processor in collaboration with the University of California at Berkeley,
 * overseen by Profs. Nelson Morgan and John Wawrzynek.  More information
 * is available through the web page `http://HTTP.CS.Berkeley.EDU/~jhauser/
 * arithmetic/softfloat.html'.
 *
 * THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE.  Although reasonable effort
 * has been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT
 * TIMES RESULT IN INCORRECT BEHAVIOR.  USE OF THIS SOFTWARE IS RESTRICTED TO
 * PERSONS AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ANY
 * AND ALL LOSSES, COSTS, OR OTHER PROBLEMS ARISING FROM ITS USE.
 *
 * Derivative works are acceptable, even for commercial purposes, so long as
 * (1) they include prominent notice that the work is derivative, and (2) they
 * include prominent notice akin to these three paragraphs for those parts of
 * this code that are retained.
 * ===========================================================================
 */
#include <linux/kernel.h>
#include <linux/bitops.h>

#include <asm/div64.h>
#include <asm/vfp.h>

#include "vfpinstr.h"
#include "vfp.h"

static struct vfp_double vfp_double_default_qnan = {
        .exponent       = 2047,
        .sign           = 0,
        .significand    = VFP_DOUBLE_SIGNIFICAND_QNAN,
};

static void vfp_double_dump(const char *str, struct vfp_double *d)
{
        pr_debug("VFP: %s: sign=%d exponent=%d significand=%016llx\n",
                 str, d->sign != 0, d->exponent, d->significand);
}

static void vfp_double_normalise_denormal(struct vfp_double *vd)
{
        int bits = 31 - fls(vd->significand >> 32);
        if (bits == 31)
                bits = 63 - fls(vd->significand);

        vfp_double_dump("normalise_denormal: in", vd);

        if (bits) {
                vd->exponent -= bits - 1;
                vd->significand <<= bits;
        }

        vfp_double_dump("normalise_denormal: out", vd);
}

u32 vfp_double_normaliseround(int dd, struct vfp_double *vd, u32 fpscr, u32 exceptions, const char *func)
{
        u64 significand, incr;
        int exponent, shift, underflow;
        u32 rmode;

        vfp_double_dump("pack: in", vd);

        /*
         * Infinities and NaNs are a special case.
         */
        if (vd->exponent == 2047 && (vd->significand == 0 || exceptions))
                goto pack;

        /*
         * Special-case zero.
         */
        if (vd->significand == 0) {
                vd->exponent = 0;
                goto pack;
        }

        exponent = vd->exponent;
        significand = vd->significand;

        shift = 32 - fls(significand >> 32);
        if (shift == 32)
                shift = 64 - fls(significand);
        if (shift) {
                exponent -= shift;
                significand <<= shift;
        }

#ifdef DEBUG
        vd->exponent = exponent;
        vd->significand = significand;
        vfp_double_dump("pack: normalised", vd);
#endif

        /*
         * Tiny number?
         */
        underflow = exponent < 0;
        if (underflow) {
                significand = vfp_shiftright64jamming(significand, -exponent);
                exponent = 0;
#ifdef DEBUG
                vd->exponent = exponent;
                vd->significand = significand;
                vfp_double_dump("pack: tiny number", vd);
#endif
                if (!(significand & ((1ULL << (VFP_DOUBLE_LOW_BITS + 1)) - 1)))
                        underflow = 0;
        }

        /*
         * Select rounding increment.
         */
        incr = 0;
        rmode = fpscr & FPSCR_RMODE_MASK;

        if (rmode == FPSCR_ROUND_NEAREST) {
                incr = 1ULL << VFP_DOUBLE_LOW_BITS;
                if ((significand & (1ULL << (VFP_DOUBLE_LOW_BITS + 1))) == 0)
                        incr -= 1;
        } else if (rmode == FPSCR_ROUND_TOZERO) {
                incr = 0;
        } else if ((rmode == FPSCR_ROUND_PLUSINF) ^ (vd->sign != 0))
                incr = (1ULL << (VFP_DOUBLE_LOW_BITS + 1)) - 1;

        pr_debug("VFP: rounding increment = 0x%08llx\n", incr);

        /*
         * Is our rounding going to overflow?
         */
        if ((significand + incr) < significand) {
                exponent += 1;
                significand = (significand >> 1) | (significand & 1);
                incr >>= 1;
#ifdef DEBUG
                vd->exponent = exponent;
                vd->significand = significand;
                vfp_double_dump("pack: overflow", vd);
#endif
        }

        /*
         * If any of the low bits (which will be shifted out of the
         * number) are non-zero, the result is inexact.
         */
        if (significand & ((1 << (VFP_DOUBLE_LOW_BITS + 1)) - 1))
                exceptions |= FPSCR_IXC;

        /*
         * Do our rounding.
         */
        significand += incr;

        /*
         * Infinity?
         */
        if (exponent >= 2046) {
                exceptions |= FPSCR_OFC | FPSCR_IXC;
                if (incr == 0) {
                        vd->exponent = 2045;
                        vd->significand = 0x7fffffffffffffffULL;
                } else {
                        vd->exponent = 2047;            /* infinity */
                        vd->significand = 0;
                }
        } else {
                if (significand >> (VFP_DOUBLE_LOW_BITS + 1) == 0)
                        exponent = 0;
                if (exponent || significand > 0x8000000000000000ULL)
                        underflow = 0;
                if (underflow)
                        exceptions |= FPSCR_UFC;
                vd->exponent = exponent;
                vd->significand = significand >> 1;
        }

 pack:
        vfp_double_dump("pack: final", vd);
        {
                s64 d = vfp_double_pack(vd);
                pr_debug("VFP: %s: d(d%d)=%016llx exceptions=%08x\n", func,
                         dd, d, exceptions);
                vfp_put_double(d, dd);
        }
        return exceptions;
}

/*
 * Propagate the NaN, setting exceptions if it is signalling.
 * 'n' is always a NaN.  'm' may be a number, NaN or infinity.
 */
static u32
vfp_propagate_nan(struct vfp_double *vdd, struct vfp_double *vdn,
                  struct vfp_double *vdm, u32 fpscr)
{
        struct vfp_double *nan;
        int tn, tm = 0;

        tn = vfp_double_type(vdn);

        if (vdm)
                tm = vfp_double_type(vdm);

        if (fpscr & FPSCR_DEFAULT_NAN)
                /*
                 * Default NaN mode - always returns a quiet NaN
                 */
                nan = &vfp_double_default_qnan;
        else {
                /*
                 * Contemporary mode - select the first signalling
                 * NAN, or if neither are signalling, the first
                 * quiet NAN.
                 */
                if (tn == VFP_SNAN || (tm != VFP_SNAN && tn == VFP_QNAN))
                        nan = vdn;
                else
                        nan = vdm;
                /*
                 * Make the NaN quiet.
                 */
                nan->significand |= VFP_DOUBLE_SIGNIFICAND_QNAN;
        }

        *vdd = *nan;

        /*
         * If one was a signalling NAN, raise invalid operation.
         */
        return tn == VFP_SNAN || tm == VFP_SNAN ? FPSCR_IOC : VFP_NAN_FLAG;
}

/*
 * Extended operations
 */
static u32 vfp_double_fabs(int dd, int unused, int dm, u32 fpscr)
{
        vfp_put_double(vfp_double_packed_abs(vfp_get_double(dm)), dd);
        return 0;
}

static u32 vfp_double_fcpy(int dd, int unused, int dm, u32 fpscr)
{
        vfp_put_double(vfp_get_double(dm), dd);
        return 0;
}

static u32 vfp_double_fneg(int dd, int unused, int dm, u32 fpscr)
{
        vfp_put_double(vfp_double_packed_negate(vfp_get_double(dm)), dd);
        return 0;
}

static u32 vfp_double_fsqrt(int dd, int unused, int dm, u32 fpscr)
{
        struct vfp_double vdm, vdd;
        int ret, tm;

        vfp_double_unpack(&vdm, vfp_get_double(dm));
        tm = vfp_double_type(&vdm);
        if (tm & (VFP_NAN|VFP_INFINITY)) {
                struct vfp_double *vdp = &vdd;

                if (tm & VFP_NAN)
                        ret = vfp_propagate_nan(vdp, &vdm, NULL, fpscr);
                else if (vdm.sign == 0) {
 sqrt_copy:
                        vdp = &vdm;
                        ret = 0;
                } else {
 sqrt_invalid:
                        vdp = &vfp_double_default_qnan;
                        ret = FPSCR_IOC;
                }
                vfp_put_double(vfp_double_pack(vdp), dd);
                return ret;
        }

        /*
         * sqrt(+/- 0) == +/- 0
         */
        if (tm & VFP_ZERO)
                goto sqrt_copy;

        /*
         * Normalise a denormalised number
         */
        if (tm & VFP_DENORMAL)
                vfp_double_normalise_denormal(&vdm);

        /*
         * sqrt(<0) = invalid
         */
        if (vdm.sign)
                goto sqrt_invalid;

        vfp_double_dump("sqrt", &vdm);

        /*
         * Estimate the square root.
         */
        vdd.sign = 0;
        vdd.exponent = ((vdm.exponent - 1023) >> 1) + 1023;
        vdd.significand = (u64)vfp_estimate_sqrt_significand(vdm.exponent, vdm.significand >> 32) << 31;

        vfp_double_dump("sqrt estimate1", &vdd);

        vdm.significand >>= 1 + (vdm.exponent & 1);
        vdd.significand += 2 + vfp_estimate_div128to64(vdm.significand, 0, vdd.significand);

        vfp_double_dump("sqrt estimate2", &vdd);

        /*
         * And now adjust.
         */
        if ((vdd.significand & VFP_DOUBLE_LOW_BITS_MASK) <= 5) {
                if (vdd.significand < 2) {
                        vdd.significand = ~0ULL;
                } else {
                        u64 termh, terml, remh, reml;
                        vdm.significand <<= 2;
                        mul64to128(&termh, &terml, vdd.significand, vdd.significand);
                        sub128(&remh, &reml, vdm.significand, 0, termh, terml);
                        while ((s64)remh < 0) {
                                vdd.significand -= 1;
                                shift64left(&termh, &terml, vdd.significand);
                                terml |= 1;
                                add128(&remh, &reml, remh, reml, termh, terml);
                        }
                        vdd.significand |= (remh | reml) != 0;
                }
        }
        vdd.significand = vfp_shiftright64jamming(vdd.significand, 1);

        return vfp_double_normaliseround(dd, &vdd, fpscr, 0, "fsqrt");
}

/*
 * Equal        := ZC
 * Less than    := N
 * Greater than := C
 * Unordered    := CV
 */
static u32 vfp_compare(int dd, int signal_on_qnan, int dm, u32 fpscr)
{
        s64 d, m;
        u32 ret = 0;

        m = vfp_get_double(dm);
        if (vfp_double_packed_exponent(m) == 2047 && vfp_double_packed_mantissa(m)) {
                ret |= FPSCR_C | FPSCR_V;
                if (signal_on_qnan || !(vfp_double_packed_mantissa(m) & (1ULL << (VFP_DOUBLE_MANTISSA_BITS - 1))))
                        /*
                         * Signalling NaN, or signalling on quiet NaN
                         */
                        ret |= FPSCR_IOC;
        }

        d = vfp_get_double(dd);
        if (vfp_double_packed_exponent(d) == 2047 && vfp_double_packed_mantissa(d)) {
                ret |= FPSCR_C | FPSCR_V;
                if (signal_on_qnan || !(vfp_double_packed_mantissa(d) & (1ULL << (VFP_DOUBLE_MANTISSA_BITS - 1))))
                        /*
                         * Signalling NaN, or signalling on quiet NaN
                         */
                        ret |= FPSCR_IOC;
        }

        if (ret == 0) {
                if (d == m || vfp_double_packed_abs(d | m) == 0) {
                        /*
                         * equal
                         */
                        ret |= FPSCR_Z | FPSCR_C;
                } else if (vfp_double_packed_sign(d ^ m)) {
                        /*
                         * different signs
                         */
                        if (vfp_double_packed_sign(d))
                                /*
                                 * d is negative, so d < m
                                 */
                                ret |= FPSCR_N;
                        else
                                /*
                                 * d is positive, so d > m
                                 */
                                ret |= FPSCR_C;
                } else if ((vfp_double_packed_sign(d) != 0) ^ (d < m)) {
                        /*
                         * d < m
                         */
                        ret |= FPSCR_N;
                } else if ((vfp_double_packed_sign(d) != 0) ^ (d > m)) {
                        /*
                         * d > m
                         */
                        ret |= FPSCR_C;
                }
        }

        return ret;
}

static u32 vfp_double_fcmp(int dd, int unused, int dm, u32 fpscr)
{
        return vfp_compare(dd, 0, dm, fpscr);
}

static u32 vfp_double_fcmpe(int dd, int unused, int dm, u32 fpscr)
{
        return vfp_compare(dd, 1, dm, fpscr);
}

static u32 vfp_double_fcmpz(int dd, int unused, int dm, u32 fpscr)
{
        return vfp_compare(dd, 0, VFP_REG_ZERO, fpscr);
}

static u32 vfp_double_fcmpez(int dd, int unused, int dm, u32 fpscr)
{
        return vfp_compare(dd, 1, VFP_REG_ZERO, fpscr);
}

static u32 vfp_double_fcvts(int sd, int unused, int dm, u32 fpscr)
{
        struct vfp_double vdm;
        struct vfp_single vsd;
        int tm;
        u32 exceptions = 0;

        vfp_double_unpack(&vdm, vfp_get_double(dm));

        tm = vfp_double_type(&vdm);

        /*
         * If we have a signalling NaN, signal invalid operation.
         */
        if (tm == VFP_SNAN)
                exceptions = FPSCR_IOC;

        if (tm & VFP_DENORMAL)
                vfp_double_normalise_denormal(&vdm);

        vsd.sign = vdm.sign;
        vsd.significand = vfp_hi64to32jamming(vdm.significand);

        /*
         * If we have an infinity or a NaN, the exponent must be 255
         */
        if (tm & (VFP_INFINITY|VFP_NAN)) {
                vsd.exponent = 255;
                if (tm == VFP_QNAN)
                        vsd.significand |= VFP_SINGLE_SIGNIFICAND_QNAN;
                goto pack_nan;
        } else if (tm & VFP_ZERO)
                vsd.exponent = 0;
        else
                vsd.exponent = vdm.exponent - (1023 - 127);

        return vfp_single_normaliseround(sd, &vsd, fpscr, exceptions, "fcvts");

 pack_nan:
        vfp_put_float(vfp_single_pack(&vsd), sd);
        return exceptions;
}

static u32 vfp_double_fuito(int dd, int unused, int dm, u32 fpscr)
{
        struct vfp_double vdm;
        u32 m = vfp_get_float(dm);

        vdm.sign = 0;
        vdm.exponent = 1023 + 63 - 1;
        vdm.significand = (u64)m;

        return vfp_double_normaliseround(dd, &vdm, fpscr, 0, "fuito");
}

static u32 vfp_double_fsito(int dd, int unused, int dm, u32 fpscr)
{
        struct vfp_double vdm;
        u32 m = vfp_get_float(dm);

        vdm.sign = (m & 0x80000000) >> 16;
        vdm.exponent = 1023 + 63 - 1;
        vdm.significand = vdm.sign ? -m : m;

        return vfp_double_normaliseround(dd, &vdm, fpscr, 0, "fsito");
}

static u32 vfp_double_ftoui(int sd, int unused, int dm, u32 fpscr)
{
        struct vfp_double vdm;
        u32 d, exceptions = 0;
        int rmode = fpscr & FPSCR_RMODE_MASK;
        int tm;

        vfp_double_unpack(&vdm, vfp_get_double(dm));

        /*
         * Do we have a denormalised number?
         */
        tm = vfp_double_type(&vdm);
        if (tm & VFP_DENORMAL)
                exceptions |= FPSCR_IDC;

        if (tm & VFP_NAN)
                vdm.sign = 0;

        if (vdm.exponent >= 1023 + 32) {
                d = vdm.sign ? 0 : 0xffffffff;
                exceptions = FPSCR_IOC;
        } else if (vdm.exponent >= 1023 - 1) {
                int shift = 1023 + 63 - vdm.exponent;
                u64 rem, incr = 0;

                /*
                 * 2^0 <= m < 2^32-2^8
                 */
                d = (vdm.significand << 1) >> shift;
                rem = vdm.significand << (65 - shift);

                if (rmode == FPSCR_ROUND_NEAREST) {
                        incr = 0x8000000000000000ULL;
                        if ((d & 1) == 0)
                                incr -= 1;
                } else if (rmode == FPSCR_ROUND_TOZERO) {
                        incr = 0;
                } else if ((rmode == FPSCR_ROUND_PLUSINF) ^ (vdm.sign != 0)) {
                        incr = ~0ULL;
                }

                if ((rem + incr) < rem) {
                        if (d < 0xffffffff)
                                d += 1;
                        else
                                exceptions |= FPSCR_IOC;
                }

                if (d && vdm.sign) {
                        d = 0;
                        exceptions |= FPSCR_IOC;
                } else if (rem)
                        exceptions |= FPSCR_IXC;
        } else {
                d = 0;
                if (vdm.exponent | vdm.significand) {
                        exceptions |= FPSCR_IXC;
                        if (rmode == FPSCR_ROUND_PLUSINF && vdm.sign == 0)
                                d = 1;
                        else if (rmode == FPSCR_ROUND_MINUSINF && vdm.sign) {
                                d = 0;
                                exceptions |= FPSCR_IOC;
                        }
                }
        }

        pr_debug("VFP: ftoui: d(s%d)=%08x exceptions=%08x\n", sd, d, exceptions);

        vfp_put_float(d, sd);

        return exceptions;
}

static u32 vfp_double_ftouiz(int sd, int unused, int dm, u32 fpscr)
{
        return vfp_double_ftoui(sd, unused, dm, FPSCR_ROUND_TOZERO);
}

static u32 vfp_double_ftosi(int sd, int unused, int dm, u32 fpscr)
{
        struct vfp_double vdm;
        u32 d, exceptions = 0;
        int rmode = fpscr & FPSCR_RMODE_MASK;
        int tm;

        vfp_double_unpack(&vdm, vfp_get_double(dm));
        vfp_double_dump("VDM", &vdm);

        /*
         * Do we have denormalised number?
         */
        tm = vfp_double_type(&vdm);
        if (tm & VFP_DENORMAL)
                exceptions |= FPSCR_IDC;

        if (tm & VFP_NAN) {
                d = 0;
                exceptions |= FPSCR_IOC;
        } else if (vdm.exponent >= 1023 + 32) {
                d = 0x7fffffff;
                if (vdm.sign)
                        d = ~d;
                exceptions |= FPSCR_IOC;
        } else if (vdm.exponent >= 1023 - 1) {
                int shift = 1023 + 63 - vdm.exponent;   /* 58 */
                u64 rem, incr = 0;

                d = (vdm.significand << 1) >> shift;
                rem = vdm.significand << (65 - shift);

                if (rmode == FPSCR_ROUND_NEAREST) {
                        incr = 0x8000000000000000ULL;
                        if ((d & 1) == 0)
                                incr -= 1;
                } else if (rmode == FPSCR_ROUND_TOZERO) {
                        incr = 0;
                } else if ((rmode == FPSCR_ROUND_PLUSINF) ^ (vdm.sign != 0)) {
                        incr = ~0ULL;
                }

                if ((rem + incr) < rem && d < 0xffffffff)
                        d += 1;
                if (d > 0x7fffffff + (vdm.sign != 0)) {
                        d = 0x7fffffff + (vdm.sign != 0);
                        exceptions |= FPSCR_IOC;
                } else if (rem)
                        exceptions |= FPSCR_IXC;

                if (vdm.sign)
                        d = -d;
        } else {
                d = 0;
                if (vdm.exponent | vdm.significand) {
                        exceptions |= FPSCR_IXC;
                        if (rmode == FPSCR_ROUND_PLUSINF && vdm.sign == 0)
                                d = 1;
                        else if (rmode == FPSCR_ROUND_MINUSINF && vdm.sign)
                                d = -1;
                }
        }

        pr_debug("VFP: ftosi: d(s%d)=%08x exceptions=%08x\n", sd, d, exceptions);

        vfp_put_float((s32)d, sd);

        return exceptions;
}

static u32 vfp_double_ftosiz(int dd, int unused, int dm, u32 fpscr)
{
        return vfp_double_ftosi(dd, unused, dm, FPSCR_ROUND_TOZERO);
}


static struct op fops_ext[32] = {
        [FEXT_TO_IDX(FEXT_FCPY)]        = { vfp_double_fcpy,   0 },
        [FEXT_TO_IDX(FEXT_FABS)]        = { vfp_double_fabs,   0 },
        [FEXT_TO_IDX(FEXT_FNEG)]        = { vfp_double_fneg,   0 },
        [FEXT_TO_IDX(FEXT_FSQRT)]       = { vfp_double_fsqrt,  0 },
        [FEXT_TO_IDX(FEXT_FCMP)]        = { vfp_double_fcmp,   OP_SCALAR },
        [FEXT_TO_IDX(FEXT_FCMPE)]       = { vfp_double_fcmpe,  OP_SCALAR },
        [FEXT_TO_IDX(FEXT_FCMPZ)]       = { vfp_double_fcmpz,  OP_SCALAR },
        [FEXT_TO_IDX(FEXT_FCMPEZ)]      = { vfp_double_fcmpez, OP_SCALAR },
        [FEXT_TO_IDX(FEXT_FCVT)]        = { vfp_double_fcvts,  OP_SCALAR|OP_SD },
        [FEXT_TO_IDX(FEXT_FUITO)]       = { vfp_double_fuito,  OP_SCALAR|OP_SM },
        [FEXT_TO_IDX(FEXT_FSITO)]       = { vfp_double_fsito,  OP_SCALAR|OP_SM },
        [FEXT_TO_IDX(FEXT_FTOUI)]       = { vfp_double_ftoui,  OP_SCALAR|OP_SD },
        [FEXT_TO_IDX(FEXT_FTOUIZ)]      = { vfp_double_ftouiz, OP_SCALAR|OP_SD },
        [FEXT_TO_IDX(FEXT_FTOSI)]       = { vfp_double_ftosi,  OP_SCALAR|OP_SD },
        [FEXT_TO_IDX(FEXT_FTOSIZ)]      = { vfp_double_ftosiz, OP_SCALAR|OP_SD },
};




static u32
vfp_double_fadd_nonnumber(struct vfp_double *vdd, struct vfp_double *vdn,
                          struct vfp_double *vdm, u32 fpscr)
{
        struct vfp_double *vdp;
        u32 exceptions = 0;
        int tn, tm;

        tn = vfp_double_type(vdn);
        tm = vfp_double_type(vdm);

        if (tn & tm & VFP_INFINITY) {
                /*
                 * Two infinities.  Are they different signs?
                 */
                if (vdn->sign ^ vdm->sign) {
                        /*
                         * different signs -> invalid
                         */
                        exceptions = FPSCR_IOC;
                        vdp = &vfp_double_default_qnan;
                } else {
                        /*
                         * same signs -> valid
                         */
                        vdp = vdn;
                }
        } else if (tn & VFP_INFINITY && tm & VFP_NUMBER) {
                /*
                 * One infinity and one number -> infinity
                 */
                vdp = vdn;
        } else {
                /*
                 * 'n' is a NaN of some type
                 */
                return vfp_propagate_nan(vdd, vdn, vdm, fpscr);
        }
        *vdd = *vdp;
        return exceptions;
}

static u32
vfp_double_add(struct vfp_double *vdd, struct vfp_double *vdn,
               struct vfp_double *vdm, u32 fpscr)
{
        u32 exp_diff;
        u64 m_sig;

        if (vdn->significand & (1ULL << 63) ||
            vdm->significand & (1ULL << 63)) {
                pr_info("VFP: bad FP values in %s\n", __func__);
                vfp_double_dump("VDN", vdn);
                vfp_double_dump("VDM", vdm);
        }

        /*
         * Ensure that 'n' is the largest magnitude number.  Note that
         * if 'n' and 'm' have equal exponents, we do not swap them.
         * This ensures that NaN propagation works correctly.
         */
        if (vdn->exponent < vdm->exponent) {
                struct vfp_double *t = vdn;
                vdn = vdm;
                vdm = t;
        }

        /*
         * Is 'n' an infinity or a NaN?  Note that 'm' may be a number,
         * infinity or a NaN here.
         */
        if (vdn->exponent == 2047)
                return vfp_double_fadd_nonnumber(vdd, vdn, vdm, fpscr);

        /*
         * We have two proper numbers, where 'vdn' is the larger magnitude.
         *
         * Copy 'n' to 'd' before doing the arithmetic.
         */
        *vdd = *vdn;

        /*
         * Align 'm' with the result.
         */
        exp_diff = vdn->exponent - vdm->exponent;
        m_sig = vfp_shiftright64jamming(vdm->significand, exp_diff);

        /*
         * If the signs are different, we are really subtracting.
         */
        if (vdn->sign ^ vdm->sign) {
                m_sig = vdn->significand - m_sig;
                if ((s64)m_sig < 0) {
                        vdd->sign = vfp_sign_negate(vdd->sign);
                        m_sig = -m_sig;
                } else if (m_sig == 0) {
                        vdd->sign = (fpscr & FPSCR_RMODE_MASK) ==
                                      FPSCR_ROUND_MINUSINF ? 0x8000 : 0;
                }
        } else {
                m_sig += vdn->significand;
        }
        vdd->significand = m_sig;

        return 0;
}

static u32
vfp_double_multiply(struct vfp_double *vdd, struct vfp_double *vdn,
                    struct vfp_double *vdm, u32 fpscr)
{
        vfp_double_dump("VDN", vdn);
        vfp_double_dump("VDM", vdm);

        /*
         * Ensure that 'n' is the largest magnitude number.  Note that
         * if 'n' and 'm' have equal exponents, we do not swap them.
         * This ensures that NaN propagation works correctly.
         */
        if (vdn->exponent < vdm->exponent) {
                struct vfp_double *t = vdn;
                vdn = vdm;
                vdm = t;
                pr_debug("VFP: swapping M <-> N\n");
        }

        vdd->sign = vdn->sign ^ vdm->sign;

        /*
         * If 'n' is an infinity or NaN, handle it.  'm' may be anything.
         */
        if (vdn->exponent == 2047) {
                if (vdn->significand || (vdm->exponent == 2047 && vdm->significand))
                        return vfp_propagate_nan(vdd, vdn, vdm, fpscr);
                if ((vdm->exponent | vdm->significand) == 0) {
                        *vdd = vfp_double_default_qnan;
                        return FPSCR_IOC;
                }
                vdd->exponent = vdn->exponent;
                vdd->significand = 0;
                return 0;
        }

        /*
         * If 'm' is zero, the result is always zero.  In this case,
         * 'n' may be zero or a number, but it doesn't matter which.
         */
        if ((vdm->exponent | vdm->significand) == 0) {
                vdd->exponent = 0;
                vdd->significand = 0;
                return 0;
        }

        /*
         * We add 2 to the destination exponent for the same reason
         * as the addition case - though this time we have +1 from
         * each input operand.
         */
        vdd->exponent = vdn->exponent + vdm->exponent - 1023 + 2;
        vdd->significand = vfp_hi64multiply64(vdn->significand, vdm->significand);

        vfp_double_dump("VDD", vdd);
        return 0;
}

#define NEG_MULTIPLY    (1 << 0)
#define NEG_SUBTRACT    (1 << 1)

static u32
vfp_double_multiply_accumulate(int dd, int dn, int dm, u32 fpscr, u32 negate, char *func)
{
        struct vfp_double vdd, vdp, vdn, vdm;
        u32 exceptions;

        vfp_double_unpack(&vdn, vfp_get_double(dn));
        if (vdn.exponent == 0 && vdn.significand)
                vfp_double_normalise_denormal(&vdn);

        vfp_double_unpack(&vdm, vfp_get_double(dm));
        if (vdm.exponent == 0 && vdm.significand)
                vfp_double_normalise_denormal(&vdm);

        exceptions = vfp_double_multiply(&vdp, &vdn, &vdm, fpscr);
        if (negate & NEG_MULTIPLY)
                vdp.sign = vfp_sign_negate(vdp.sign);

        vfp_double_unpack(&vdn, vfp_get_double(dd));
        if (negate & NEG_SUBTRACT)
                vdn.sign = vfp_sign_negate(vdn.sign);

        exceptions |= vfp_double_add(&vdd, &vdn, &vdp, fpscr);

        return vfp_double_normaliseround(dd, &vdd, fpscr, exceptions, func);
}

/*
 * Standard operations
 */

/*
 * sd = sd + (sn * sm)
 */
static u32 vfp_double_fmac(int dd, int dn, int dm, u32 fpscr)
{
        return vfp_double_multiply_accumulate(dd, dn, dm, fpscr, 0, "fmac");
}

/*
 * sd = sd - (sn * sm)
 */
static u32 vfp_double_fnmac(int dd, int dn, int dm, u32 fpscr)
{
        return vfp_double_multiply_accumulate(dd, dn, dm, fpscr, NEG_MULTIPLY, "fnmac");
}

/*
 * sd = -sd + (sn * sm)
 */
static u32 vfp_double_fmsc(int dd, int dn, int dm, u32 fpscr)
{
        return vfp_double_multiply_accumulate(dd, dn, dm, fpscr, NEG_SUBTRACT, "fmsc");
}

/*
 * sd = -sd - (sn * sm)
 */
static u32 vfp_double_fnmsc(int dd, int dn, int dm, u32 fpscr)
{
        return vfp_double_multiply_accumulate(dd, dn, dm, fpscr, NEG_SUBTRACT | NEG_MULTIPLY, "fnmsc");
}

/*
 * sd = sn * sm
 */
static u32 vfp_double_fmul(int dd, int dn, int dm, u32 fpscr)
{
        struct vfp_double vdd, vdn, vdm;
        u32 exceptions;

        vfp_double_unpack(&vdn, vfp_get_double(dn));
        if (vdn.exponent == 0 && vdn.significand)
                vfp_double_normalise_denormal(&vdn);

        vfp_double_unpack(&vdm, vfp_get_double(dm));
        if (vdm.exponent == 0 && vdm.significand)
                vfp_double_normalise_denormal(&vdm);

        exceptions = vfp_double_multiply(&vdd, &vdn, &vdm, fpscr);
        return vfp_double_normaliseround(dd, &vdd, fpscr, exceptions, "fmul");
}

/*
 * sd = -(sn * sm)
 */
static u32 vfp_double_fnmul(int dd, int dn, int dm, u32 fpscr)
{
        struct vfp_double vdd, vdn, vdm;
        u32 exceptions;

        vfp_double_unpack(&vdn, vfp_get_double(dn));
        if (vdn.exponent == 0 && vdn.significand)
                vfp_double_normalise_denormal(&vdn);

        vfp_double_unpack(&vdm, vfp_get_double(dm));
        if (vdm.exponent == 0 && vdm.significand)
                vfp_double_normalise_denormal(&vdm);

        exceptions = vfp_double_multiply(&vdd, &vdn, &vdm, fpscr);
        vdd.sign = vfp_sign_negate(vdd.sign);

        return vfp_double_normaliseround(dd, &vdd, fpscr, exceptions, "fnmul");
}

/*
 * sd = sn + sm
 */
static u32 vfp_double_fadd(int dd, int dn, int dm, u32 fpscr)
{
        struct vfp_double vdd, vdn, vdm;
        u32 exceptions;

        vfp_double_unpack(&vdn, vfp_get_double(dn));
        if (vdn.exponent == 0 && vdn.significand)
                vfp_double_normalise_denormal(&vdn);

        vfp_double_unpack(&vdm, vfp_get_double(dm));
        if (vdm.exponent == 0 && vdm.significand)
                vfp_double_normalise_denormal(&vdm);

        exceptions = vfp_double_add(&vdd, &vdn, &vdm, fpscr);

        return vfp_double_normaliseround(dd, &vdd, fpscr, exceptions, "fadd");
}

/*
 * sd = sn - sm
 */
static u32 vfp_double_fsub(int dd, int dn, int dm, u32 fpscr)
{
        struct vfp_double vdd, vdn, vdm;
        u32 exceptions;

        vfp_double_unpack(&vdn, vfp_get_double(dn));
        if (vdn.exponent == 0 && vdn.significand)
                vfp_double_normalise_denormal(&vdn);

        vfp_double_unpack(&vdm, vfp_get_double(dm));
        if (vdm.exponent == 0 && vdm.significand)
                vfp_double_normalise_denormal(&vdm);

        /*
         * Subtraction is like addition, but with a negated operand.
         */
        vdm.sign = vfp_sign_negate(vdm.sign);

        exceptions = vfp_double_add(&vdd, &vdn, &vdm, fpscr);

        return vfp_double_normaliseround(dd, &vdd, fpscr, exceptions, "fsub");
}

/*
 * sd = sn / sm
 */
static u32 vfp_double_fdiv(int dd, int dn, int dm, u32 fpscr)
{
        struct vfp_double vdd, vdn, vdm;
        u32 exceptions = 0;
        int tm, tn;

        vfp_double_unpack(&vdn, vfp_get_double(dn));
        vfp_double_unpack(&vdm, vfp_get_double(dm));

        vdd.sign = vdn.sign ^ vdm.sign;

        tn = vfp_double_type(&vdn);
        tm = vfp_double_type(&vdm);

        /*
         * Is n a NAN?
         */
        if (tn & VFP_NAN)
                goto vdn_nan;

        /*
         * Is m a NAN?
         */
        if (tm & VFP_NAN)
                goto vdm_nan;

        /*
         * If n and m are infinity, the result is invalid
         * If n and m are zero, the result is invalid
         */
        if (tm & tn & (VFP_INFINITY|VFP_ZERO))
                goto invalid;

        /*
         * If n is infinity, the result is infinity
         */
        if (tn & VFP_INFINITY)
                goto infinity;

        /*
         * If m is zero, raise div0 exceptions
         */
        if (tm & VFP_ZERO)
                goto divzero;

        /*
         * If m is infinity, or n is zero, the result is zero
         */
        if (tm & VFP_INFINITY || tn & VFP_ZERO)
                goto zero;

        if (tn & VFP_DENORMAL)
                vfp_double_normalise_denormal(&vdn);
        if (tm & VFP_DENORMAL)
                vfp_double_normalise_denormal(&vdm);

        /*
         * Ok, we have two numbers, we can perform division.
         */
        vdd.exponent = vdn.exponent - vdm.exponent + 1023 - 1;
        vdm.significand <<= 1;
        if (vdm.significand <= (2 * vdn.significand)) {
                vdn.significand >>= 1;
                vdd.exponent++;
        }
        vdd.significand = vfp_estimate_div128to64(vdn.significand, 0, vdm.significand);
        if ((vdd.significand & 0x1ff) <= 2) {
                u64 termh, terml, remh, reml;
                mul64to128(&termh, &terml, vdm.significand, vdd.significand);
                sub128(&remh, &reml, vdn.significand, 0, termh, terml);
                while ((s64)remh < 0) {
                        vdd.significand -= 1;
                        add128(&remh, &reml, remh, reml, 0, vdm.significand);
                }
                vdd.significand |= (reml != 0);
        }
        return vfp_double_normaliseround(dd, &vdd, fpscr, 0, "fdiv");

 vdn_nan:
        exceptions = vfp_propagate_nan(&vdd, &vdn, &vdm, fpscr);
 pack:
        vfp_put_double(vfp_double_pack(&vdd), dd);
        return exceptions;

 vdm_nan:
        exceptions = vfp_propagate_nan(&vdd, &vdm, &vdn, fpscr);
        goto pack;

 zero:
        vdd.exponent = 0;
        vdd.significand = 0;
        goto pack;

 divzero:
        exceptions = FPSCR_DZC;
 infinity:
        vdd.exponent = 2047;
        vdd.significand = 0;
        goto pack;

 invalid:
        vfp_put_double(vfp_double_pack(&vfp_double_default_qnan), dd);
        return FPSCR_IOC;
}

static struct op fops[16] = {
        [FOP_TO_IDX(FOP_FMAC)]  = { vfp_double_fmac,  0 },
        [FOP_TO_IDX(FOP_FNMAC)] = { vfp_double_fnmac, 0 },
        [FOP_TO_IDX(FOP_FMSC)]  = { vfp_double_fmsc,  0 },
        [FOP_TO_IDX(FOP_FNMSC)] = { vfp_double_fnmsc, 0 },
        [FOP_TO_IDX(FOP_FMUL)]  = { vfp_double_fmul,  0 },
        [FOP_TO_IDX(FOP_FNMUL)] = { vfp_double_fnmul, 0 },
        [FOP_TO_IDX(FOP_FADD)]  = { vfp_double_fadd,  0 },
        [FOP_TO_IDX(FOP_FSUB)]  = { vfp_double_fsub,  0 },
        [FOP_TO_IDX(FOP_FDIV)]  = { vfp_double_fdiv,  0 },
};

#define FREG_BANK(x)    ((x) & 0x0c)
#define FREG_IDX(x)     ((x) & 3)

u32 vfp_double_cpdo(u32 inst, u32 fpscr)
{
        u32 op = inst & FOP_MASK;
        u32 exceptions = 0;
        unsigned int dest;
        unsigned int dn = vfp_get_dn(inst);
        unsigned int dm;
        unsigned int vecitr, veclen, vecstride;
        struct op *fop;

        vecstride = (1 + ((fpscr & FPSCR_STRIDE_MASK) == FPSCR_STRIDE_MASK));

        fop = (op == FOP_EXT) ? &fops_ext[FEXT_TO_IDX(inst)] : &fops[FOP_TO_IDX(op)];

        /*
         * fcvtds takes an sN register number as destination, not dN.
         * It also always operates on scalars.
         */
        if (fop->flags & OP_SD)
                dest = vfp_get_sd(inst);
        else
                dest = vfp_get_dd(inst);

        /*
         * f[us]ito takes a sN operand, not a dN operand.
         */
        if (fop->flags & OP_SM)
                dm = vfp_get_sm(inst);
        else
                dm = vfp_get_dm(inst);

        /*
         * If destination bank is zero, vector length is always '1'.
         * ARM DDI0100F C5.1.3, C5.3.2.
         */
        if ((fop->flags & OP_SCALAR) || (FREG_BANK(dest) == 0))
                veclen = 0;
        else
                veclen = fpscr & FPSCR_LENGTH_MASK;

        pr_debug("VFP: vecstride=%u veclen=%u\n", vecstride,
                 (veclen >> FPSCR_LENGTH_BIT) + 1);

        if (!fop->fn)
                goto invalid;

        for (vecitr = 0; vecitr <= veclen; vecitr += 1 << FPSCR_LENGTH_BIT) {
                u32 except;
                char type;

                type = fop->flags & OP_SD ? 's' : 'd';
                if (op == FOP_EXT)
                        pr_debug("VFP: itr%d (%c%u) = op[%u] (d%u)\n",
                                 vecitr >> FPSCR_LENGTH_BIT,
                                 type, dest, dn, dm);
                else
                        pr_debug("VFP: itr%d (%c%u) = (d%u) op[%u] (d%u)\n",
                                 vecitr >> FPSCR_LENGTH_BIT,
                                 type, dest, dn, FOP_TO_IDX(op), dm);

                except = fop->fn(dest, dn, dm, fpscr);
                pr_debug("VFP: itr%d: exceptions=%08x\n",
                         vecitr >> FPSCR_LENGTH_BIT, except);

                exceptions |= except;

                /*
                 * CHECK: It appears to be undefined whether we stop when
                 * we encounter an exception.  We continue.
                 */
                dest = FREG_BANK(dest) + ((FREG_IDX(dest) + vecstride) & 3);
                dn = FREG_BANK(dn) + ((FREG_IDX(dn) + vecstride) & 3);
                if (FREG_BANK(dm) != 0)
                        dm = FREG_BANK(dm) + ((FREG_IDX(dm) + vecstride) & 3);
        }
        return exceptions;

 invalid:
        return ~0;
}