arch/mips/math-emu/dp_div.c

   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
  12 union 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 }