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_div(union ieee754sp x, union ieee754sp y)
  13{
  14        unsigned int rm;
  15        int re;
  16        unsigned int bm;
  17
  18        COMPXSP;
  19        COMPYSP;
  20
  21        EXPLODEXSP;
  22        EXPLODEYSP;
  23
  24        ieee754_clearcx();
  25
  26        FLUSHXSP;
  27        FLUSHYSP;
  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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_inf(xs ^ ys);
  87
  88        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
  89        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
  90                return ieee754sp_zero(xs == ys ? 0 : 1);
  91
  92        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
  93                SPDNORMX;
  94                /* fall through */
  95
  96        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
  97                SPDNORMY;
  98                break;
  99
 100        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 101                SPDNORMX;
 102                break;
 103
 104        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 105                break;
 106        }
 107        assert(xm & SP_HIDDEN_BIT);
 108        assert(ym & SP_HIDDEN_BIT);
 109
 110        /* provide rounding space */
 111        xm <<= 3;
 112        ym <<= 3;
 113
 114        /* now the dirty work */
 115
 116        rm = 0;
 117        re = xe - ye;
 118
 119        for (bm = SP_MBIT(SP_FBITS + 2); bm; bm >>= 1) {
 120                if (xm >= ym) {
 121                        xm -= ym;
 122                        rm |= bm;
 123                        if (xm == 0)
 124                                break;
 125                }
 126                xm <<= 1;
 127        }
 128
 129        rm <<= 1;
 130        if (xm)
 131                rm |= 1;        /* have remainder, set sticky */
 132
 133        assert(rm);
 134
 135        /* normalise rm to rounding precision ?
 136         */
 137        while ((rm >> (SP_FBITS + 3)) == 0) {
 138                rm <<= 1;
 139                re--;
 140        }
 141
 142        return ieee754sp_format(xs == ys ? 0 : 1, re, rm);
 143}
 144