arch/mips/math-emu/dp_tint.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 int ieee754dp_tint(union ieee754dp x)
  13 {
  14         u64 residue;
  15         int round;
  16         int sticky;
  17         int odd;
  18
  19         COMPXDP;
  20
  21         ieee754_clearcx();
  22
  23         EXPLODEXDP;
  24         FLUSHXDP;
  25
  26         switch (xc) {
  27         case IEEE754_CLASS_SNAN:
  28         case IEEE754_CLASS_QNAN:
  29                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  30                 return ieee754si_indef();
  31
  32         case IEEE754_CLASS_INF:
  33                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  34                 return ieee754si_overflow(xs);
  35
  36         case IEEE754_CLASS_ZERO:
  37                 return 0;
  38
  39         case IEEE754_CLASS_DNORM:
  40         case IEEE754_CLASS_NORM:
  41                 break;
  42         }
  43         if (xe > 31) {
  44                 /* Set invalid. We will only use overflow for floating
  45                    point overflow */
  46                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  47                 return ieee754si_overflow(xs);
  48         }
  49         /* oh gawd */
  50         if (xe > DP_FBITS) {
  51                 xm <<= xe - DP_FBITS;
  52         } else if (xe < DP_FBITS) {
  53                 if (xe < -1) {
  54                         residue = xm;
  55                         round = 0;
  56                         sticky = residue != 0;
  57                         xm = 0;
  58                 } else {
  59                         residue = xm << (64 - DP_FBITS + xe);
  60                         round = (residue >> 63) != 0;
  61                         sticky = (residue << 1) != 0;
  62                         xm >>= DP_FBITS - xe;
  63                 }
  64                 /* Note: At this point upper 32 bits of xm are guaranteed
  65                    to be zero */
  66                 odd = (xm & 0x1) != 0x0;
  67                 switch (ieee754_csr.rm) {
  68                 case FPU_CSR_RN:
  69                         if (round && (sticky || odd))
  70                                 xm++;
  71                         break;
  72                 case FPU_CSR_RZ:
  73                         break;
  74                 case FPU_CSR_RU:        /* toward +Infinity */
  75                         if ((round || sticky) && !xs)
  76                                 xm++;
  77                         break;
  78                 case FPU_CSR_RD:        /* toward -Infinity */
  79                         if ((round || sticky) && xs)
  80                                 xm++;
  81                         break;
  82                 }
  83                 /* look for valid corner case 0x80000000 */
  84                 if ((xm >> 31) != 0 && (xs == 0 || xm != 0x80000000)) {
  85                         /* This can happen after rounding */
  86                         ieee754_setcx(IEEE754_INVALID_OPERATION);
  87                         return ieee754si_overflow(xs);
  88                 }
  89                 if (round || sticky)
  90                         ieee754_setcx(IEEE754_INEXACT);
  91         }
  92         if (xs)
  93                 return -xm;
  94         else
  95                 return xm;
  96 }