LXR linux/arch/mips/math-emu/dp

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* IEEE754 floating point arithmetic
   3 * double precision: common utilities
   4 */
   5/*
   6 * MIPS floating point support
   7 * Copyright (C) 1994-2000 Algorithmics Ltd.
   8 */
   9
  10#include "ieee754dp.h"
  11
  12union ieee754dp ieee754dp_mul(union ieee754dp x, union ieee754dp y)
  13{
  14        int re;
  15        int rs;
  16        u64 rm;
  17        unsigned int lxm;
  18        unsigned int hxm;
  19        unsigned int lym;
  20        unsigned int hym;
  21        u64 lrm;
  22        u64 hrm;
  23        u64 t;
  24        u64 at;
  25
  26        COMPXDP;
  27        COMPYDP;
  28
  29        EXPLODEXDP;
  30        EXPLODEYDP;
  31
  32        ieee754_clearcx();
  33
  34        FLUSHXDP;
  35        FLUSHYDP;
  36
  37        switch (CLPAIR(xc, yc)) {
  38        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  39        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  40        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  41        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  42        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  43                return ieee754dp_nanxcpt(y);
  44
  45        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  46        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  47        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  48        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  49        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  50        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  51                return ieee754dp_nanxcpt(x);
  52
  53        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  54        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  55        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  56        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  57                return y;
  58
  59        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  60        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  61        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  62        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  63        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  64                return x;
  65
  66
  67        /*
  68         * Infinity handling
  69         */
  70        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  71        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  72                ieee754_setcx(IEEE754_INVALID_OPERATION);
  73                return ieee754dp_indef();
  74
  75        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  76        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  77        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  78        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  79        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  80                return ieee754dp_inf(xs ^ ys);
  81
  82        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  83        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
  84        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
  85        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  86        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  87                return ieee754dp_zero(xs ^ ys);
  88
  89
  90        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
  91                DPDNORMX;
  92                fallthrough;
  93        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
  94                DPDNORMY;
  95                break;
  96
  97        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
  98                DPDNORMX;
  99                break;
 100
 101        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 102                break;
 103        }
 104        /* rm = xm * ym, re = xe+ye basically */
 105        assert(xm & DP_HIDDEN_BIT);
 106        assert(ym & DP_HIDDEN_BIT);
 107
 108        re = xe + ye;
 109        rs = xs ^ ys;
 110
 111        /* shunt to top of word */
 112        xm <<= 64 - (DP_FBITS + 1);
 113        ym <<= 64 - (DP_FBITS + 1);
 114
 115        /*
 116         * Multiply 64 bits xm, ym to give high 64 bits rm with stickness.
 117         */
 118
 119        lxm = xm;
 120        hxm = xm >> 32;
 121        lym = ym;
 122        hym = ym >> 32;
 123
 124        lrm = DPXMULT(lxm, lym);
 125        hrm = DPXMULT(hxm, hym);
 126
 127        t = DPXMULT(lxm, hym);
 128
 129        at = lrm + (t << 32);
 130        hrm += at < lrm;
 131        lrm = at;
 132
 133        hrm = hrm + (t >> 32);
 134
 135        t = DPXMULT(hxm, lym);
 136
 137        at = lrm + (t << 32);
 138        hrm += at < lrm;
 139        lrm = at;
 140
 141        hrm = hrm + (t >> 32);
 142
 143        rm = hrm | (lrm != 0);
 144
 145        /*
 146         * Sticky shift down to normal rounding precision.
 147         */
 148        if ((s64) rm < 0) {
 149                rm = (rm >> (64 - (DP_FBITS + 1 + 3))) |
 150                     ((rm << (DP_FBITS + 1 + 3)) != 0);
 151                re++;
 152        } else {
 153                rm = (rm >> (64 - (DP_FBITS + 1 + 3 + 1))) |
 154                     ((rm << (DP_FBITS + 1 + 3 + 1)) != 0);
 155        }
 156        assert(rm & (DP_HIDDEN_BIT << 3));
 157
 158        return ieee754dp_format(rs, re, rm);
 159}
 160