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_add(union ieee754dp x, union ieee754dp y)
  13{
  14        int s;
  15
  16        COMPXDP;
  17        COMPYDP;
  18
  19        EXPLODEXDP;
  20        EXPLODEYDP;
  21
  22        ieee754_clearcx();
  23
  24        FLUSHXDP;
  25        FLUSHYDP;
  26
  27        switch (CLPAIR(xc, yc)) {
  28        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  29        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  30        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  31        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  32        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  33                return ieee754dp_nanxcpt(y);
  34
  35        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  36        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  37        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  38        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  39        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  40        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  41                return ieee754dp_nanxcpt(x);
  42
  43        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  44        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  45        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  46        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  47                return y;
  48
  49        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  50        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  51        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  52        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  53        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  54                return x;
  55
  56
  57        /*
  58         * Infinity handling
  59         */
  60        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  61                if (xs == ys)
  62                        return x;
  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 y;
  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 x;
  75
  76        /*
  77         * Zero handling
  78         */
  79        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  80                if (xs == ys)
  81                        return x;
  82                else
  83                        return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
  84
  85        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  86        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  87                return x;
  88
  89        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
  90        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
  91                return y;
  92
  93        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
  94                DPDNORMX;
  95                fallthrough;
  96        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
  97                DPDNORMY;
  98                break;
  99
 100        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 101                DPDNORMX;
 102                break;
 103
 104        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 105                break;
 106        }
 107        assert(xm & DP_HIDDEN_BIT);
 108        assert(ym & DP_HIDDEN_BIT);
 109
 110        /*
 111         * Provide guard,round and stick bit space.
 112         */
 113        xm <<= 3;
 114        ym <<= 3;
 115
 116        if (xe > ye) {
 117                /*
 118                 * Have to shift y fraction right to align.
 119                 */
 120                s = xe - ye;
 121                ym = XDPSRS(ym, s);
 122                ye += s;
 123        } else if (ye > xe) {
 124                /*
 125                 * Have to shift x fraction right to align.
 126                 */
 127                s = ye - xe;
 128                xm = XDPSRS(xm, s);
 129                xe += s;
 130        }
 131        assert(xe == ye);
 132        assert(xe <= DP_EMAX);
 133
 134        if (xs == ys) {
 135                /*
 136                 * Generate 28 bit result of adding two 27 bit numbers
 137                 * leaving result in xm, xs and xe.
 138                 */
 139                xm = xm + ym;
 140
 141                if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */
 142                        xm = XDPSRS1(xm);
 143                        xe++;
 144                }
 145        } else {
 146                if (xm >= ym) {
 147                        xm = xm - ym;
 148                } else {
 149                        xm = ym - xm;
 150                        xs = ys;
 151                }
 152                if (xm == 0)
 153                        return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
 154
 155                /*
 156                 * Normalize to rounding precision.
 157                 */
 158                while ((xm >> (DP_FBITS + 3)) == 0) {
 159                        xm <<= 1;
 160                        xe--;
 161                }
 162        }
 163
 164        return ieee754dp_format(xs, xe, xm);
 165}
 166