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_div(union ieee754dp x, union ieee754dp y)
  13{
  14        u64 rm;
  15        int re;
  16        u64 bm;
  17
  18        COMPXDP;
  19        COMPYDP;
  20
  21        EXPLODEXDP;
  22        EXPLODEYDP;
  23
  24        ieee754_clearcx();
  25
  26        FLUSHXDP;
  27        FLUSHYDP;
  28
  29        switch (CLPAIR(xc, yc)) {
  30        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  31        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  32        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  33        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  34        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  35                return ieee754dp_nanxcpt(y);
  36
  37        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  38        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  39        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  40        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  41        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  42        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  43                return ieee754dp_nanxcpt(x);
  44
  45        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  46        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  47        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  48        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  49                return y;
  50
  51        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  52        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  53        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  54        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  55        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  56                return x;
  57
  58
  59        /*
  60         * Infinity handling
  61         */
  62        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  63                ieee754_setcx(IEEE754_INVALID_OPERATION);
  64                return ieee754dp_indef();
  65
  66        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  67        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  68        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  69                return ieee754dp_zero(xs ^ ys);
  70
  71        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  72        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  73        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  74                return ieee754dp_inf(xs ^ ys);
  75
  76        /*
  77         * Zero handling
  78         */
  79        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  80                ieee754_setcx(IEEE754_INVALID_OPERATION);
  81                return ieee754dp_indef();
  82
  83        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  84        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  85                ieee754_setcx(IEEE754_ZERO_DIVIDE);
  86                return ieee754dp_inf(xs ^ ys);
  87
  88        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
  89        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
  90                return ieee754dp_zero(xs == ys ? 0 : 1);
  91
  92        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
  93                DPDNORMX;
  94                fallthrough;
  95        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
  96                DPDNORMY;
  97                break;
  98
  99        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 100                DPDNORMX;
 101                break;
 102
 103        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 104                break;
 105        }
 106        assert(xm & DP_HIDDEN_BIT);
 107        assert(ym & DP_HIDDEN_BIT);
 108
 109        /* provide rounding space */
 110        xm <<= 3;
 111        ym <<= 3;
 112
 113        /* now the dirty work */
 114
 115        rm = 0;
 116        re = xe - ye;
 117
 118        for (bm = DP_MBIT(DP_FBITS + 2); bm; bm >>= 1) {
 119                if (xm >= ym) {
 120                        xm -= ym;
 121                        rm |= bm;
 122                        if (xm == 0)
 123                                break;
 124                }
 125                xm <<= 1;
 126        }
 127
 128        rm <<= 1;
 129        if (xm)
 130                rm |= 1;        /* have remainder, set sticky */
 131
 132        assert(rm);
 133
 134        /*
 135         * Normalise rm to rounding precision ?
 136         */
 137        while ((rm >> (DP_FBITS + 3)) == 0) {
 138                rm <<= 1;
 139                re--;
 140        }
 141
 142        return ieee754dp_format(xs == ys ? 0 : 1, re, rm);
 143}
 144