147 lines
3.3 KiB
C
147 lines
3.3 KiB
C
/* Half-float conversion routines.
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Copyright (C) 2008-2016 Free Software Foundation, Inc.
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Contributed by CodeSourcery.
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This file is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 3, or (at your option) any
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later version.
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This file is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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static inline unsigned short
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__gnu_f2h_internal(unsigned int a, int ieee)
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{
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unsigned short sign = (a >> 16) & 0x8000;
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int aexp = (a >> 23) & 0xff;
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unsigned int mantissa = a & 0x007fffff;
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unsigned int mask;
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unsigned int increment;
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if (aexp == 0xff)
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{
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if (!ieee)
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return sign;
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if (mantissa == 0)
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return sign | 0x7c00; /* Infinity. */
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/* Remaining cases are NaNs. Convert SNaN to QNaN. */
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return sign | 0x7e00 | (mantissa >> 13);
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}
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if (aexp == 0 && mantissa == 0)
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return sign;
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aexp -= 127;
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/* Decimal point between bits 22 and 23. */
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mantissa |= 0x00800000;
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if (aexp < -14)
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{
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mask = 0x00ffffff;
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if (aexp >= -25)
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mask >>= 25 + aexp;
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}
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else
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mask = 0x00001fff;
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/* Round. */
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if (mantissa & mask)
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{
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increment = (mask + 1) >> 1;
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if ((mantissa & mask) == increment)
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increment = mantissa & (increment << 1);
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mantissa += increment;
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if (mantissa >= 0x01000000)
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{
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mantissa >>= 1;
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aexp++;
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}
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}
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if (ieee)
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{
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if (aexp > 15)
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return sign | 0x7c00;
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}
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else
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{
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if (aexp > 16)
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return sign | 0x7fff;
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}
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if (aexp < -24)
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return sign;
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if (aexp < -14)
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{
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mantissa >>= -14 - aexp;
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aexp = -14;
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}
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/* We leave the leading 1 in the mantissa, and subtract one
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from the exponent bias to compensate. */
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return sign | (((aexp + 14) << 10) + (mantissa >> 13));
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}
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unsigned int
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__gnu_h2f_internal(unsigned short a, int ieee)
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{
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unsigned int sign = (unsigned int)(a & 0x8000) << 16;
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int aexp = (a >> 10) & 0x1f;
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unsigned int mantissa = a & 0x3ff;
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if (aexp == 0x1f && ieee)
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return sign | 0x7f800000 | (mantissa << 13);
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if (aexp == 0)
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{
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int shift;
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if (mantissa == 0)
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return sign;
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shift = __builtin_clz(mantissa) - 21;
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mantissa <<= shift;
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aexp = -shift;
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}
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return sign | (((aexp + 0x70) << 23) + (mantissa << 13));
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}
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unsigned short
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__gnu_f2h_ieee(unsigned int a)
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{
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return __gnu_f2h_internal(a, 1);
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}
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unsigned int
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__gnu_h2f_ieee(unsigned short a)
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{
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return __gnu_h2f_internal(a, 1);
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}
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unsigned short
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__gnu_f2h_alternative(unsigned int x)
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{
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return __gnu_f2h_internal(x, 0);
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}
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unsigned int
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__gnu_h2f_alternative(unsigned short a)
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{
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return __gnu_h2f_internal(a, 0);
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}
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