gcc/libgcc/config/s390/32/_fixtfdi.c

/* Definitions of target machine for GNU compiler, for IBM S/390
   Copyright (C) 1999, 2000, 2001, 2007, 2008 and 2009
   Free Software Foundation, Inc.
   Contributed by Hartmut Penner (hpenner@de.ibm.com) and
                  Ulrich Weigand (uweigand@de.ibm.com).

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#define EXPD(fp)	   (((fp.l.i[0]) >> 16) & 0x7FFF)
#define EXPONENT_BIAS	   16383
#define MANTISSA_BITS      112
#define PRECISION          (MANTISSA_BITS + 1)
#define SIGNBIT		   0x80000000
#define SIGND(fp)	   ((fp.l.i[0]) & SIGNBIT)
#define MANTD_HIGH_LL(fp)  ((fp.ll[0] & HIGH_LL_FRAC_MASK) | HIGH_LL_UNIT_BIT)
#define MANTD_LOW_LL(fp)   (fp.ll[1])
#define FRACD_ZERO_P(fp)   (!fp.ll[1] && !(fp.ll[0] & HIGH_LL_FRAC_MASK))
#define HIGH_LL_FRAC_BITS  48
#define HIGH_LL_UNIT_BIT   ((UDItype_x)1 << HIGH_LL_FRAC_BITS)
#define HIGH_LL_FRAC_MASK  (HIGH_LL_UNIT_BIT - 1)

typedef int DItype_x __attribute__ ((mode (DI)));
typedef unsigned int UDItype_x __attribute__ ((mode (DI)));
typedef int SItype_x __attribute__ ((mode (SI)));
typedef unsigned int USItype_x __attribute__ ((mode (SI)));

union double_long {
  long double d;
  struct {
      SItype_x i[4]; /* 32 bit parts: 0 upper ... 3 lowest */
    } l;
  UDItype_x ll[2];   /* 64 bit parts: 0 upper, 1 lower */
};

DItype_x __fixtfdi (long double a1);

/* convert double to unsigned int */
DItype_x
__fixtfdi (long double a1)
{
    register union double_long dl1;
    register int exp;
    register UDItype_x l;

    dl1.d = a1;

    /* +/- 0, denormalized */
    if (!EXPD (dl1))
      return 0;

    /* The exponent - considered the binary point at the right end of
       the mantissa.  */
    exp = EXPD (dl1) - EXPONENT_BIAS - MANTISSA_BITS;

    /* number < 1: If the mantissa would need to be right-shifted more bits than
       its size the result would be zero.  */
    if (exp <= -PRECISION)
      return 0;

    /* NaN: All exponent bits set and a nonzero fraction.  */
    if ((EXPD(dl1) == 0x7fff) && !FRACD_ZERO_P (dl1))
      return 0x8000000000000000ULL;

    /* One extra bit is needed for the unit bit which is appended by
       MANTD_HIGH_LL on the left of the matissa.  */
    exp += HIGH_LL_FRAC_BITS + 1;

    /* If the result would still need a left shift it will be too large
       to be represented.  Compared to the unsigned variant we have to
       take care that there is still space for the sign bit to be
       applied.  So we can only go on if there is a right-shift by one
       or more.  */
    if (exp >= 0)
      {
	l = 1ULL << 63; /* long long min */
	return SIGND (dl1) ? l : l - 1;
      }

    l = MANTD_LOW_LL (dl1) >> (HIGH_LL_FRAC_BITS + 1)
        | MANTD_HIGH_LL (dl1) << (64 - (HIGH_LL_FRAC_BITS + 1));

    return SIGND (dl1) ? -(l >> -exp) : l >> -exp;
}