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
  12s64 ieee754dp_tlong(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 ieee754di_indef();
  31
  32        case IEEE754_CLASS_INF:
  33                ieee754_setcx(IEEE754_INVALID_OPERATION);
  34                return ieee754di_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 >= 63) {
  44                /* look for valid corner case */
  45                if (xe == 63 && xs && xm == DP_HIDDEN_BIT)
  46                        return -0x8000000000000000LL;
  47                /* Set invalid. We will only use overflow for floating
  48                   point overflow */
  49                ieee754_setcx(IEEE754_INVALID_OPERATION);
  50                return ieee754di_overflow(xs);
  51        }
  52        /* oh gawd */
  53        if (xe > DP_FBITS) {
  54                xm <<= xe - DP_FBITS;
  55        } else if (xe < DP_FBITS) {
  56                if (xe < -1) {
  57                        residue = xm;
  58                        round = 0;
  59                        sticky = residue != 0;
  60                        xm = 0;
  61                } else {
  62                        /* Shifting a u64 64 times does not work,
  63                        * so we do it in two steps. Be aware that xe
  64                        * may be -1 */
  65                        residue = xm << (xe + 1);
  66                        residue <<= 63 - DP_FBITS;
  67                        round = (residue >> 63) != 0;
  68                        sticky = (residue << 1) != 0;
  69                        xm >>= DP_FBITS - xe;
  70                }
  71                odd = (xm & 0x1) != 0x0;
  72                switch (ieee754_csr.rm) {
  73                case FPU_CSR_RN:
  74                        if (round && (sticky || odd))
  75                                xm++;
  76                        break;
  77                case FPU_CSR_RZ:
  78                        break;
  79                case FPU_CSR_RU:        /* toward +Infinity */
  80                        if ((round || sticky) && !xs)
  81                                xm++;
  82                        break;
  83                case FPU_CSR_RD:        /* toward -Infinity */
  84                        if ((round || sticky) && xs)
  85                                xm++;
  86                        break;
  87                }
  88                if ((xm >> 63) != 0) {
  89                        /* This can happen after rounding */
  90                        ieee754_setcx(IEEE754_INVALID_OPERATION);
  91                        return ieee754di_overflow(xs);
  92                }
  93                if (round || sticky)
  94                        ieee754_setcx(IEEE754_INEXACT);
  95        }
  96        if (xs)
  97                return -xm;
  98        else
  99                return xm;
 100}
 101