_fixtfdi.c revision 1.1.1.1.8.2 
1/* Definitions of target machine for GNU compiler, for IBM S/390
2   Copyright (C) 1999, 2000, 2001, 2007, 2008 and 2009
3   Free Software Foundation, Inc.
4   Contributed by Hartmut Penner (hpenner@de.ibm.com) and
5                  Ulrich Weigand (uweigand@de.ibm.com).
6
7This file is part of GCC.
8
9GCC is free software; you can redistribute it and/or modify it under
10the terms of the GNU General Public License as published by the Free
11Software Foundation; either version 3, or (at your option) any later
12version.
13
14GCC is distributed in the hope that it will be useful, but WITHOUT ANY
15WARRANTY; without even the implied warranty of MERCHANTABILITY or
16FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
17for more details.
18
19Under Section 7 of GPL version 3, you are granted additional
20permissions described in the GCC Runtime Library Exception, version
213.1, as published by the Free Software Foundation.
22
23You should have received a copy of the GNU General Public License and
24a copy of the GCC Runtime Library Exception along with this program;
25see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
26<http://www.gnu.org/licenses/>.  */
27
28#define EXPD(fp)	   (((fp.l.i[0]) >> 16) & 0x7FFF)
29#define EXPONENT_BIAS	   16383
30#define MANTISSA_BITS      112
31#define PRECISION          (MANTISSA_BITS + 1)
32#define SIGNBIT		   0x80000000
33#define SIGND(fp)	   ((fp.l.i[0]) & SIGNBIT)
34#define MANTD_HIGH_LL(fp)  ((fp.ll[0] & HIGH_LL_FRAC_MASK) | HIGH_LL_UNIT_BIT)
35#define MANTD_LOW_LL(fp)   (fp.ll[1])
36#define FRACD_ZERO_P(fp)   (!fp.ll[1] && !(fp.ll[0] & HIGH_LL_FRAC_MASK))
37#define HIGH_LL_FRAC_BITS  48
38#define HIGH_LL_UNIT_BIT   ((UDItype_x)1 << HIGH_LL_FRAC_BITS)
39#define HIGH_LL_FRAC_MASK  (HIGH_LL_UNIT_BIT - 1)
40
41typedef int DItype_x __attribute__ ((mode (DI)));
42typedef unsigned int UDItype_x __attribute__ ((mode (DI)));
43typedef int SItype_x __attribute__ ((mode (SI)));
44typedef unsigned int USItype_x __attribute__ ((mode (SI)));
45
46union double_long {
47  long double d;
48  struct {
49      SItype_x i[4]; /* 32 bit parts: 0 upper ... 3 lowest */
50    } l;
51  UDItype_x ll[2];   /* 64 bit parts: 0 upper, 1 lower */
52};
53
54DItype_x __fixtfdi (long double a1);
55
56/* convert double to unsigned int */
57DItype_x
58__fixtfdi (long double a1)
59{
60    register union double_long dl1;
61    register int exp;
62    register UDItype_x l;
63
64    dl1.d = a1;
65
66    /* +/- 0, denormalized */
67    if (!EXPD (dl1))
68      return 0;
69
70    /* The exponent - considered the binary point at the right end of
71       the mantissa.  */
72    exp = EXPD (dl1) - EXPONENT_BIAS - MANTISSA_BITS;
73
74    /* number < 1: If the mantissa would need to be right-shifted more bits than
75       its size the result would be zero.  */
76    if (exp <= -PRECISION)
77      return 0;
78
79    /* NaN: All exponent bits set and a nonzero fraction.  */
80    if ((EXPD(dl1) == 0x7fff) && !FRACD_ZERO_P (dl1))
81      return 0x8000000000000000ULL;
82
83    /* One extra bit is needed for the unit bit which is appended by
84       MANTD_HIGH_LL on the left of the matissa.  */
85    exp += HIGH_LL_FRAC_BITS + 1;
86
87    /* If the result would still need a left shift it will be too large
88       to be represented.  Compared to the unsigned variant we have to
89       take care that there is still space for the sign bit to be
90       applied.  So we can only go on if there is a right-shift by one
91       or more.  */
92    if (exp >= 0)
93      {
94	l = 1ULL << 63; /* long long min */
95	return SIGND (dl1) ? l : l - 1;
96      }
97
98    l = MANTD_LOW_LL (dl1) >> (HIGH_LL_FRAC_BITS + 1)
99        | MANTD_HIGH_LL (dl1) << (64 - (HIGH_LL_FRAC_BITS + 1));
100
101    return SIGND (dl1) ? -(l >> -exp) : l >> -exp;
102}
103