_fixunstfdi.c revision 1.1.1.1.4.2 
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
54UDItype_x __fixunstfdi (long double a1);
55
56/* convert double to unsigned int */
57UDItype_x
58__fixunstfdi (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, negative */
67    if (!EXPD (dl1) || SIGND(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 (plus the implied one bit on the left) the result would be
76       zero.  */
77    if (exp <= -PRECISION)
78      return 0;
79
80    /* NaN: All exponent bits set and a nonzero fraction.  */
81    if ((EXPD(dl1) == 0x7fff) && !FRACD_ZERO_P (dl1))
82      return 0x0ULL;
83
84    /* One extra bit is needed for the unit bit which is appended by
85       MANTD_HIGH_LL on the left of the matissa.  */
86    exp += HIGH_LL_FRAC_BITS + 1;
87
88    /* If the result would still need a left shift it will be too large
89       to be represented.  */
90    if (exp > 0)
91      return 0xFFFFFFFFFFFFFFFFULL;
92
93    l = MANTD_LOW_LL (dl1) >> (HIGH_LL_FRAC_BITS + 1)
94        | MANTD_HIGH_LL (dl1) << (64 - (HIGH_LL_FRAC_BITS + 1));
95
96    return l >> -exp;
97}
98