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

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* IEEE754 floating point arithmetic
   3 * single precision
   4 */
   5/*
   6 * MIPS floating point support
   7 * Copyright (C) 1994-2000 Algorithmics Ltd.
   8 */
   9
  10#include "ieee754sp.h"
  11
  12union ieee754sp ieee754sp_mul(union ieee754sp x, union ieee754sp y)
  13{
  14        int re;
  15        int rs;
  16        unsigned int rm;
  17        unsigned short lxm;
  18        unsigned short hxm;
  19        unsigned short lym;
  20        unsigned short hym;
  21        unsigned int lrm;
  22        unsigned int hrm;
  23        unsigned int t;
  24        unsigned int at;
  25
  26        COMPXSP;
  27        COMPYSP;
  28
  29        EXPLODEXSP;
  30        EXPLODEYSP;
  31
  32        ieee754_clearcx();
  33
  34        FLUSHXSP;
  35        FLUSHYSP;
  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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_zero(xs ^ ys);
  88
  89
  90        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
  91                SPDNORMX;
  92                fallthrough;
  93        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
  94                SPDNORMY;
  95                break;
  96
  97        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
  98                SPDNORMX;
  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 & SP_HIDDEN_BIT);
 106        assert(ym & SP_HIDDEN_BIT);
 107
 108        re = xe + ye;
 109        rs = xs ^ ys;
 110
 111        /* shunt to top of word */
 112        xm <<= 32 - (SP_FBITS + 1);
 113        ym <<= 32 - (SP_FBITS + 1);
 114
 115        /*
 116         * Multiply 32 bits xm, ym to give high 32 bits rm with stickness.
 117         */
 118        lxm = xm & 0xffff;
 119        hxm = xm >> 16;
 120        lym = ym & 0xffff;
 121        hym = ym >> 16;
 122
 123        lrm = lxm * lym;        /* 16 * 16 => 32 */
 124        hrm = hxm * hym;        /* 16 * 16 => 32 */
 125
 126        t = lxm * hym; /* 16 * 16 => 32 */
 127        at = lrm + (t << 16);
 128        hrm += at < lrm;
 129        lrm = at;
 130        hrm = hrm + (t >> 16);
 131
 132        t = hxm * lym; /* 16 * 16 => 32 */
 133        at = lrm + (t << 16);
 134        hrm += at < lrm;
 135        lrm = at;
 136        hrm = hrm + (t >> 16);
 137
 138        rm = hrm | (lrm != 0);
 139
 140        /*
 141         * Sticky shift down to normal rounding precision.
 142         */
 143        if ((int) rm < 0) {
 144                rm = (rm >> (32 - (SP_FBITS + 1 + 3))) |
 145                    ((rm << (SP_FBITS + 1 + 3)) != 0);
 146                re++;
 147        } else {
 148                rm = (rm >> (32 - (SP_FBITS + 1 + 3 + 1))) |
 149                     ((rm << (SP_FBITS + 1 + 3 + 1)) != 0);
 150        }
 151        assert(rm & (SP_HIDDEN_BIT << 3));
 152
 153        return ieee754sp_format(rs, re, rm);
 154}
 155