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vfpdouble.c

/*
 *  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/ptrace.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 = 62 - 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 u32 (* const fop_extfns[32])(int dd, int unused, int dm, u32 fpscr) = {
      [FEXT_TO_IDX(FEXT_FCPY)]      = vfp_double_fcpy,
      [FEXT_TO_IDX(FEXT_FABS)]      = vfp_double_fabs,
      [FEXT_TO_IDX(FEXT_FNEG)]      = vfp_double_fneg,
      [FEXT_TO_IDX(FEXT_FSQRT)]     = vfp_double_fsqrt,
      [FEXT_TO_IDX(FEXT_FCMP)]      = vfp_double_fcmp,
      [FEXT_TO_IDX(FEXT_FCMPE)]     = vfp_double_fcmpe,
      [FEXT_TO_IDX(FEXT_FCMPZ)]     = vfp_double_fcmpz,
      [FEXT_TO_IDX(FEXT_FCMPEZ)]    = vfp_double_fcmpez,
      [FEXT_TO_IDX(FEXT_FCVT)]      = vfp_double_fcvts,
      [FEXT_TO_IDX(FEXT_FUITO)]     = vfp_double_fuito,
      [FEXT_TO_IDX(FEXT_FSITO)]     = vfp_double_fsito,
      [FEXT_TO_IDX(FEXT_FTOUI)]     = vfp_double_ftoui,
      [FEXT_TO_IDX(FEXT_FTOUIZ)]    = vfp_double_ftouiz,
      [FEXT_TO_IDX(FEXT_FTOSI)]     = vfp_double_ftosi,
      [FEXT_TO_IDX(FEXT_FTOSIZ)]    = vfp_double_ftosiz,
};




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 u32 (* const fop_fns[16])(int dd, int dn, int dm, u32 fpscr) = {
      [FOP_TO_IDX(FOP_FMAC)]  = vfp_double_fmac,
      [FOP_TO_IDX(FOP_FNMAC)] = vfp_double_fnmac,
      [FOP_TO_IDX(FOP_FMSC)]  = vfp_double_fmsc,
      [FOP_TO_IDX(FOP_FNMSC)] = vfp_double_fnmsc,
      [FOP_TO_IDX(FOP_FMUL)]  = vfp_double_fmul,
      [FOP_TO_IDX(FOP_FNMUL)] = vfp_double_fnmul,
      [FOP_TO_IDX(FOP_FADD)]  = vfp_double_fadd,
      [FOP_TO_IDX(FOP_FSUB)]  = vfp_double_fsub,
      [FOP_TO_IDX(FOP_FDIV)]  = vfp_double_fdiv,
};

#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 = vfp_get_dm(inst);
      unsigned int vecitr, veclen, vecstride;
      u32 (*fop)(int, int, s32, u32);

      veclen = fpscr & FPSCR_LENGTH_MASK;
      vecstride = (1 + ((fpscr & FPSCR_STRIDE_MASK) == FPSCR_STRIDE_MASK)) * 2;

      /*
       * fcvtds takes an sN register number as destination, not dN.
       * It also always operates on scalars.
       */
      if ((inst & FEXT_MASK) == FEXT_FCVT) {
            veclen = 0;
            dest = vfp_get_sd(inst);
      } else
            dest = vfp_get_dd(inst);

      /*
       * If destination bank is zero, vector length is always '1'.
       * ARM DDI0100F C5.1.3, C5.3.2.
       */
      if (FREG_BANK(dest) == 0)
            veclen = 0;

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

      fop = (op == FOP_EXT) ? fop_extfns[FEXT_TO_IDX(inst)] : fop_fns[FOP_TO_IDX(op)];
      if (!fop)
            goto invalid;

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

            if (op == FOP_EXT && (inst & FEXT_MASK) == FEXT_FCVT)
                  pr_debug("VFP: itr%d (s%u) = op[%u] (d%u)\n",
                         vecitr >> FPSCR_LENGTH_BIT,
                         dest, dn, dm);
            else if (op == FOP_EXT)
                  pr_debug("VFP: itr%d (d%u) = op[%u] (d%u)\n",
                         vecitr >> FPSCR_LENGTH_BIT,
                         dest, dn, dm);
            else
                  pr_debug("VFP: itr%d (d%u) = (d%u) op[%u] (d%u)\n",
                         vecitr >> FPSCR_LENGTH_BIT,
                         dest, dn, FOP_TO_IDX(op), dm);

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

            exceptions |= except;

            /*
             * This ensures that comparisons only operate on scalars;
             * comparisons always return with one FPSCR status bit set.
             */
            if (except & (FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V))
                  break;

            /*
             * CHECK: It appears to be undefined whether we stop when
             * we encounter an exception.  We continue.
             */

            dest = FREG_BANK(dest) + ((FREG_IDX(dest) + vecstride) & 6);
            dn = FREG_BANK(dn) + ((FREG_IDX(dn) + vecstride) & 6);
            if (FREG_BANK(dm) != 0)
                  dm = FREG_BANK(dm) + ((FREG_IDX(dm) + vecstride) & 6);
      }
      return exceptions;

 invalid:
      return ~0;
}

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