xref: /netbsd-src/external/gpl3/gcc/dist/libquadmath/printf/flt1282mpn.c (revision 181254a7b1bdde6873432bffef2d2decc4b5c22f)
1*181254a7Smrg /* Copyright (C) 1995,1996,1997,1998,1999,2002,2003
2*181254a7Smrg 	Free Software Foundation, Inc.
3*181254a7Smrg    This file is part of the GNU C Library.
4*181254a7Smrg 
5*181254a7Smrg    The GNU C Library is free software; you can redistribute it and/or
6*181254a7Smrg    modify it under the terms of the GNU Lesser General Public
7*181254a7Smrg    License as published by the Free Software Foundation; either
8*181254a7Smrg    version 2.1 of the License, or (at your option) any later version.
9*181254a7Smrg 
10*181254a7Smrg    The GNU C Library is distributed in the hope that it will be useful,
11*181254a7Smrg    but WITHOUT ANY WARRANTY; without even the implied warranty of
12*181254a7Smrg    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13*181254a7Smrg    Lesser General Public License for more details.
14*181254a7Smrg 
15*181254a7Smrg    You should have received a copy of the GNU Lesser General Public
16*181254a7Smrg    License along with the GNU C Library; if not, write to the Free
17*181254a7Smrg    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
18*181254a7Smrg    02111-1307 USA.  */
19*181254a7Smrg 
20*181254a7Smrg #include <float.h>
21*181254a7Smrg #include <math.h>
22*181254a7Smrg #include <stdlib.h>
23*181254a7Smrg #include "gmp-impl.h"
24*181254a7Smrg 
25*181254a7Smrg /* Convert a `__float128' in IEEE854 quad-precision format to a
26*181254a7Smrg    multi-precision integer representing the significand scaled up by its
27*181254a7Smrg    number of bits (113 for long double) and an integral power of two
28*181254a7Smrg    (MPN frexpl). */
29*181254a7Smrg 
30*181254a7Smrg mp_size_t
mpn_extract_flt128(mp_ptr res_ptr,mp_size_t size,int * expt,int * is_neg,__float128 value)31*181254a7Smrg mpn_extract_flt128 (mp_ptr res_ptr, mp_size_t size,
32*181254a7Smrg 		      int *expt, int *is_neg,
33*181254a7Smrg 		      __float128 value)
34*181254a7Smrg {
35*181254a7Smrg   ieee854_float128 u;
36*181254a7Smrg   u.value = value;
37*181254a7Smrg 
38*181254a7Smrg   *is_neg = u.ieee.negative;
39*181254a7Smrg   *expt = (int) u.ieee.exponent - IEEE854_FLOAT128_BIAS;
40*181254a7Smrg 
41*181254a7Smrg #if BITS_PER_MP_LIMB == 32
42*181254a7Smrg   res_ptr[0] = u.ieee.mantissa3; /* Low-order 32 bits of fraction.  */
43*181254a7Smrg   res_ptr[1] = u.ieee.mantissa2;
44*181254a7Smrg   res_ptr[2] = u.ieee.mantissa1;
45*181254a7Smrg   res_ptr[3] = u.ieee.mantissa0; /* High-order 32 bits.  */
46*181254a7Smrg   #define N 4
47*181254a7Smrg #elif BITS_PER_MP_LIMB == 64
48*181254a7Smrg   res_ptr[0] = ((mp_limb_t) u.ieee.mantissa2 << 32) | u.ieee.mantissa3;
49*181254a7Smrg   res_ptr[1] = ((mp_limb_t) u.ieee.mantissa0 << 32) | u.ieee.mantissa1;
50*181254a7Smrg   #define N 2
51*181254a7Smrg #else
52*181254a7Smrg   #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
53*181254a7Smrg #endif
54*181254a7Smrg /* The format does not fill the last limb.  There are some zeros.  */
55*181254a7Smrg #define NUM_LEADING_ZEROS (BITS_PER_MP_LIMB \
56*181254a7Smrg 			   - (FLT128_MANT_DIG - ((N - 1) * BITS_PER_MP_LIMB)))
57*181254a7Smrg 
58*181254a7Smrg   if (u.ieee.exponent == 0)
59*181254a7Smrg     {
60*181254a7Smrg       /* A biased exponent of zero is a special case.
61*181254a7Smrg 	 Either it is a zero or it is a denormal number.  */
62*181254a7Smrg       if (res_ptr[0] == 0 && res_ptr[1] == 0
63*181254a7Smrg 	  && res_ptr[N - 2] == 0 && res_ptr[N - 1] == 0) /* Assumes N<=4.  */
64*181254a7Smrg 	/* It's zero.  */
65*181254a7Smrg 	*expt = 0;
66*181254a7Smrg       else
67*181254a7Smrg 	{
68*181254a7Smrg 	  /* It is a denormal number, meaning it has no implicit leading
69*181254a7Smrg   	     one bit, and its exponent is in fact the format minimum.  */
70*181254a7Smrg 	  int cnt;
71*181254a7Smrg 
72*181254a7Smrg #if N == 2
73*181254a7Smrg 	  if (res_ptr[N - 1] != 0)
74*181254a7Smrg 	    {
75*181254a7Smrg 	      count_leading_zeros (cnt, res_ptr[N - 1]);
76*181254a7Smrg 	      cnt -= NUM_LEADING_ZEROS;
77*181254a7Smrg 	      res_ptr[N - 1] = res_ptr[N - 1] << cnt
78*181254a7Smrg 			       | (res_ptr[0] >> (BITS_PER_MP_LIMB - cnt));
79*181254a7Smrg 	      res_ptr[0] <<= cnt;
80*181254a7Smrg 	      *expt = FLT128_MIN_EXP - 1 - cnt;
81*181254a7Smrg 	    }
82*181254a7Smrg 	  else
83*181254a7Smrg 	    {
84*181254a7Smrg 	      count_leading_zeros (cnt, res_ptr[0]);
85*181254a7Smrg 	      if (cnt >= NUM_LEADING_ZEROS)
86*181254a7Smrg 		{
87*181254a7Smrg 		  res_ptr[N - 1] = res_ptr[0] << (cnt - NUM_LEADING_ZEROS);
88*181254a7Smrg 		  res_ptr[0] = 0;
89*181254a7Smrg 		}
90*181254a7Smrg 	      else
91*181254a7Smrg 		{
92*181254a7Smrg 		  res_ptr[N - 1] = res_ptr[0] >> (NUM_LEADING_ZEROS - cnt);
93*181254a7Smrg 		  res_ptr[0] <<= BITS_PER_MP_LIMB - (NUM_LEADING_ZEROS - cnt);
94*181254a7Smrg 		}
95*181254a7Smrg 	      *expt = FLT128_MIN_EXP - 1
96*181254a7Smrg 		- (BITS_PER_MP_LIMB - NUM_LEADING_ZEROS) - cnt;
97*181254a7Smrg 	    }
98*181254a7Smrg #else
99*181254a7Smrg 	  int j, k, l;
100*181254a7Smrg 
101*181254a7Smrg 	  for (j = N - 1; j > 0; j--)
102*181254a7Smrg 	    if (res_ptr[j] != 0)
103*181254a7Smrg 	      break;
104*181254a7Smrg 
105*181254a7Smrg 	  count_leading_zeros (cnt, res_ptr[j]);
106*181254a7Smrg 	  cnt -= NUM_LEADING_ZEROS;
107*181254a7Smrg 	  l = N - 1 - j;
108*181254a7Smrg 	  if (cnt < 0)
109*181254a7Smrg 	    {
110*181254a7Smrg 	      cnt += BITS_PER_MP_LIMB;
111*181254a7Smrg 	      l--;
112*181254a7Smrg 	    }
113*181254a7Smrg 	  if (!cnt)
114*181254a7Smrg 	    for (k = N - 1; k >= l; k--)
115*181254a7Smrg 	      res_ptr[k] = res_ptr[k-l];
116*181254a7Smrg 	  else
117*181254a7Smrg 	    {
118*181254a7Smrg 	      for (k = N - 1; k > l; k--)
119*181254a7Smrg 		res_ptr[k] = res_ptr[k-l] << cnt
120*181254a7Smrg 			     | res_ptr[k-l-1] >> (BITS_PER_MP_LIMB - cnt);
121*181254a7Smrg 	      res_ptr[k--] = res_ptr[0] << cnt;
122*181254a7Smrg 	    }
123*181254a7Smrg 
124*181254a7Smrg 	  for (; k >= 0; k--)
125*181254a7Smrg 	    res_ptr[k] = 0;
126*181254a7Smrg 	  *expt = FLT128_MIN_EXP - 1 - l * BITS_PER_MP_LIMB - cnt;
127*181254a7Smrg #endif
128*181254a7Smrg 	}
129*181254a7Smrg     }
130*181254a7Smrg   else
131*181254a7Smrg     /* Add the implicit leading one bit for a normalized number.  */
132*181254a7Smrg     res_ptr[N - 1] |= (mp_limb_t) 1 << (FLT128_MANT_DIG - 1
133*181254a7Smrg 					- ((N - 1) * BITS_PER_MP_LIMB));
134*181254a7Smrg 
135*181254a7Smrg   return N;
136*181254a7Smrg }
137