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floatformat.c revision 1.1
      1  1.1  christos /* IEEE floating point support routines, for GDB, the GNU Debugger.
      2  1.1  christos    Copyright 1991, 1994, 1999, 2000, 2003, 2005, 2006, 2010
      3  1.1  christos    Free Software Foundation, Inc.
      4  1.1  christos 
      5  1.1  christos This file is part of GDB.
      6  1.1  christos 
      7  1.1  christos This program is free software; you can redistribute it and/or modify
      8  1.1  christos it under the terms of the GNU General Public License as published by
      9  1.1  christos the Free Software Foundation; either version 2 of the License, or
     10  1.1  christos (at your option) any later version.
     11  1.1  christos 
     12  1.1  christos This program is distributed in the hope that it will be useful,
     13  1.1  christos but WITHOUT ANY WARRANTY; without even the implied warranty of
     14  1.1  christos MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     15  1.1  christos GNU General Public License for more details.
     16  1.1  christos 
     17  1.1  christos You should have received a copy of the GNU General Public License
     18  1.1  christos along with this program; if not, write to the Free Software
     19  1.1  christos Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
     20  1.1  christos 
     21  1.1  christos /* This is needed to pick up the NAN macro on some systems.  */
     22  1.1  christos #define _GNU_SOURCE
     23  1.1  christos 
     24  1.1  christos #ifdef HAVE_CONFIG_H
     25  1.1  christos #include "config.h"
     26  1.1  christos #endif
     27  1.1  christos 
     28  1.1  christos #include <math.h>
     29  1.1  christos 
     30  1.1  christos #ifdef HAVE_STRING_H
     31  1.1  christos #include <string.h>
     32  1.1  christos #endif
     33  1.1  christos 
     34  1.1  christos /* On some platforms, <float.h> provides DBL_QNAN.  */
     35  1.1  christos #ifdef STDC_HEADERS
     36  1.1  christos #include <float.h>
     37  1.1  christos #endif
     38  1.1  christos 
     39  1.1  christos #include "ansidecl.h"
     40  1.1  christos #include "libiberty.h"
     41  1.1  christos #include "floatformat.h"
     42  1.1  christos 
     43  1.1  christos #ifndef INFINITY
     44  1.1  christos #ifdef HUGE_VAL
     45  1.1  christos #define INFINITY HUGE_VAL
     46  1.1  christos #else
     47  1.1  christos #define INFINITY (1.0 / 0.0)
     48  1.1  christos #endif
     49  1.1  christos #endif
     50  1.1  christos 
     51  1.1  christos #ifndef NAN
     52  1.1  christos #ifdef DBL_QNAN
     53  1.1  christos #define NAN DBL_QNAN
     54  1.1  christos #else
     55  1.1  christos #define NAN (0.0 / 0.0)
     56  1.1  christos #endif
     57  1.1  christos #endif
     58  1.1  christos 
     59  1.1  christos static int mant_bits_set (const struct floatformat *, const unsigned char *);
     60  1.1  christos static unsigned long get_field (const unsigned char *,
     61  1.1  christos                                 enum floatformat_byteorders,
     62  1.1  christos                                 unsigned int,
     63  1.1  christos                                 unsigned int,
     64  1.1  christos                                 unsigned int);
     65  1.1  christos static int floatformat_always_valid (const struct floatformat *fmt,
     66  1.1  christos                                      const void *from);
     67  1.1  christos 
     68  1.1  christos static int
     69  1.1  christos floatformat_always_valid (const struct floatformat *fmt ATTRIBUTE_UNUSED,
     70  1.1  christos                           const void *from ATTRIBUTE_UNUSED)
     71  1.1  christos {
     72  1.1  christos   return 1;
     73  1.1  christos }
     74  1.1  christos 
     75  1.1  christos /* The odds that CHAR_BIT will be anything but 8 are low enough that I'm not
     76  1.1  christos    going to bother with trying to muck around with whether it is defined in
     77  1.1  christos    a system header, what we do if not, etc.  */
     78  1.1  christos #define FLOATFORMAT_CHAR_BIT 8
     79  1.1  christos 
     80  1.1  christos /* floatformats for IEEE half, single and double, big and little endian.  */
     81  1.1  christos const struct floatformat floatformat_ieee_half_big =
     82  1.1  christos {
     83  1.1  christos   floatformat_big, 16, 0, 1, 5, 15, 31, 6, 10,
     84  1.1  christos   floatformat_intbit_no,
     85  1.1  christos   "floatformat_ieee_half_big",
     86  1.1  christos   floatformat_always_valid,
     87  1.1  christos   NULL
     88  1.1  christos };
     89  1.1  christos const struct floatformat floatformat_ieee_half_little =
     90  1.1  christos {
     91  1.1  christos   floatformat_little, 16, 0, 1, 5, 15, 31, 6, 10,
     92  1.1  christos   floatformat_intbit_no,
     93  1.1  christos   "floatformat_ieee_half_little",
     94  1.1  christos   floatformat_always_valid,
     95  1.1  christos   NULL
     96  1.1  christos };
     97  1.1  christos const struct floatformat floatformat_ieee_single_big =
     98  1.1  christos {
     99  1.1  christos   floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23,
    100  1.1  christos   floatformat_intbit_no,
    101  1.1  christos   "floatformat_ieee_single_big",
    102  1.1  christos   floatformat_always_valid,
    103  1.1  christos   NULL
    104  1.1  christos };
    105  1.1  christos const struct floatformat floatformat_ieee_single_little =
    106  1.1  christos {
    107  1.1  christos   floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23,
    108  1.1  christos   floatformat_intbit_no,
    109  1.1  christos   "floatformat_ieee_single_little",
    110  1.1  christos   floatformat_always_valid,
    111  1.1  christos   NULL
    112  1.1  christos };
    113  1.1  christos const struct floatformat floatformat_ieee_double_big =
    114  1.1  christos {
    115  1.1  christos   floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52,
    116  1.1  christos   floatformat_intbit_no,
    117  1.1  christos   "floatformat_ieee_double_big",
    118  1.1  christos   floatformat_always_valid,
    119  1.1  christos   NULL
    120  1.1  christos };
    121  1.1  christos const struct floatformat floatformat_ieee_double_little =
    122  1.1  christos {
    123  1.1  christos   floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52,
    124  1.1  christos   floatformat_intbit_no,
    125  1.1  christos   "floatformat_ieee_double_little",
    126  1.1  christos   floatformat_always_valid,
    127  1.1  christos   NULL
    128  1.1  christos };
    129  1.1  christos 
    130  1.1  christos /* floatformat for IEEE double, little endian byte order, with big endian word
    131  1.1  christos    ordering, as on the ARM.  */
    132  1.1  christos 
    133  1.1  christos const struct floatformat floatformat_ieee_double_littlebyte_bigword =
    134  1.1  christos {
    135  1.1  christos   floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52,
    136  1.1  christos   floatformat_intbit_no,
    137  1.1  christos   "floatformat_ieee_double_littlebyte_bigword",
    138  1.1  christos   floatformat_always_valid,
    139  1.1  christos   NULL
    140  1.1  christos };
    141  1.1  christos 
    142  1.1  christos /* floatformat for VAX.  Not quite IEEE, but close enough.  */
    143  1.1  christos 
    144  1.1  christos const struct floatformat floatformat_vax_f =
    145  1.1  christos {
    146  1.1  christos   floatformat_vax, 32, 0, 1, 8, 129, 0, 9, 23,
    147  1.1  christos   floatformat_intbit_no,
    148  1.1  christos   "floatformat_vax_f",
    149  1.1  christos   floatformat_always_valid,
    150  1.1  christos   NULL
    151  1.1  christos };
    152  1.1  christos const struct floatformat floatformat_vax_d =
    153  1.1  christos {
    154  1.1  christos   floatformat_vax, 64, 0, 1, 8, 129, 0, 9, 55,
    155  1.1  christos   floatformat_intbit_no,
    156  1.1  christos   "floatformat_vax_d",
    157  1.1  christos   floatformat_always_valid,
    158  1.1  christos   NULL
    159  1.1  christos };
    160  1.1  christos const struct floatformat floatformat_vax_g =
    161  1.1  christos {
    162  1.1  christos   floatformat_vax, 64, 0, 1, 11, 1025, 0, 12, 52,
    163  1.1  christos   floatformat_intbit_no,
    164  1.1  christos   "floatformat_vax_g",
    165  1.1  christos   floatformat_always_valid,
    166  1.1  christos   NULL
    167  1.1  christos };
    168  1.1  christos 
    169  1.1  christos static int floatformat_i387_ext_is_valid (const struct floatformat *fmt,
    170  1.1  christos 					  const void *from);
    171  1.1  christos 
    172  1.1  christos static int
    173  1.1  christos floatformat_i387_ext_is_valid (const struct floatformat *fmt, const void *from)
    174  1.1  christos {
    175  1.1  christos   /* In the i387 double-extended format, if the exponent is all ones,
    176  1.1  christos      then the integer bit must be set.  If the exponent is neither 0
    177  1.1  christos      nor ~0, the intbit must also be set.  Only if the exponent is
    178  1.1  christos      zero can it be zero, and then it must be zero.  */
    179  1.1  christos   unsigned long exponent, int_bit;
    180  1.1  christos   const unsigned char *ufrom = (const unsigned char *) from;
    181  1.1  christos 
    182  1.1  christos   exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
    183  1.1  christos 			fmt->exp_start, fmt->exp_len);
    184  1.1  christos   int_bit = get_field (ufrom, fmt->byteorder, fmt->totalsize,
    185  1.1  christos 		       fmt->man_start, 1);
    186  1.1  christos 
    187  1.1  christos   if ((exponent == 0) != (int_bit == 0))
    188  1.1  christos     return 0;
    189  1.1  christos   else
    190  1.1  christos     return 1;
    191  1.1  christos }
    192  1.1  christos 
    193  1.1  christos const struct floatformat floatformat_i387_ext =
    194  1.1  christos {
    195  1.1  christos   floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
    196  1.1  christos   floatformat_intbit_yes,
    197  1.1  christos   "floatformat_i387_ext",
    198  1.1  christos   floatformat_i387_ext_is_valid,
    199  1.1  christos   NULL
    200  1.1  christos };
    201  1.1  christos const struct floatformat floatformat_m68881_ext =
    202  1.1  christos {
    203  1.1  christos   /* Note that the bits from 16 to 31 are unused.  */
    204  1.1  christos   floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64,
    205  1.1  christos   floatformat_intbit_yes,
    206  1.1  christos   "floatformat_m68881_ext",
    207  1.1  christos   floatformat_always_valid,
    208  1.1  christos   NULL
    209  1.1  christos };
    210  1.1  christos const struct floatformat floatformat_i960_ext =
    211  1.1  christos {
    212  1.1  christos   /* Note that the bits from 0 to 15 are unused.  */
    213  1.1  christos   floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64,
    214  1.1  christos   floatformat_intbit_yes,
    215  1.1  christos   "floatformat_i960_ext",
    216  1.1  christos   floatformat_always_valid,
    217  1.1  christos   NULL
    218  1.1  christos };
    219  1.1  christos const struct floatformat floatformat_m88110_ext =
    220  1.1  christos {
    221  1.1  christos   floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
    222  1.1  christos   floatformat_intbit_yes,
    223  1.1  christos   "floatformat_m88110_ext",
    224  1.1  christos   floatformat_always_valid,
    225  1.1  christos   NULL
    226  1.1  christos };
    227  1.1  christos const struct floatformat floatformat_m88110_harris_ext =
    228  1.1  christos {
    229  1.1  christos   /* Harris uses raw format 128 bytes long, but the number is just an ieee
    230  1.1  christos      double, and the last 64 bits are wasted. */
    231  1.1  christos   floatformat_big,128, 0, 1, 11,  0x3ff,  0x7ff, 12, 52,
    232  1.1  christos   floatformat_intbit_no,
    233  1.1  christos   "floatformat_m88110_ext_harris",
    234  1.1  christos   floatformat_always_valid,
    235  1.1  christos   NULL
    236  1.1  christos };
    237  1.1  christos const struct floatformat floatformat_arm_ext_big =
    238  1.1  christos {
    239  1.1  christos   /* Bits 1 to 16 are unused.  */
    240  1.1  christos   floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
    241  1.1  christos   floatformat_intbit_yes,
    242  1.1  christos   "floatformat_arm_ext_big",
    243  1.1  christos   floatformat_always_valid,
    244  1.1  christos   NULL
    245  1.1  christos };
    246  1.1  christos const struct floatformat floatformat_arm_ext_littlebyte_bigword =
    247  1.1  christos {
    248  1.1  christos   /* Bits 1 to 16 are unused.  */
    249  1.1  christos   floatformat_littlebyte_bigword, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
    250  1.1  christos   floatformat_intbit_yes,
    251  1.1  christos   "floatformat_arm_ext_littlebyte_bigword",
    252  1.1  christos   floatformat_always_valid,
    253  1.1  christos   NULL
    254  1.1  christos };
    255  1.1  christos const struct floatformat floatformat_ia64_spill_big =
    256  1.1  christos {
    257  1.1  christos   floatformat_big, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
    258  1.1  christos   floatformat_intbit_yes,
    259  1.1  christos   "floatformat_ia64_spill_big",
    260  1.1  christos   floatformat_always_valid,
    261  1.1  christos   NULL
    262  1.1  christos };
    263  1.1  christos const struct floatformat floatformat_ia64_spill_little =
    264  1.1  christos {
    265  1.1  christos   floatformat_little, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
    266  1.1  christos   floatformat_intbit_yes,
    267  1.1  christos   "floatformat_ia64_spill_little",
    268  1.1  christos   floatformat_always_valid,
    269  1.1  christos   NULL
    270  1.1  christos };
    271  1.1  christos const struct floatformat floatformat_ia64_quad_big =
    272  1.1  christos {
    273  1.1  christos   floatformat_big, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
    274  1.1  christos   floatformat_intbit_no,
    275  1.1  christos   "floatformat_ia64_quad_big",
    276  1.1  christos   floatformat_always_valid,
    277  1.1  christos   NULL
    278  1.1  christos };
    279  1.1  christos const struct floatformat floatformat_ia64_quad_little =
    280  1.1  christos {
    281  1.1  christos   floatformat_little, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
    282  1.1  christos   floatformat_intbit_no,
    283  1.1  christos   "floatformat_ia64_quad_little",
    284  1.1  christos   floatformat_always_valid,
    285  1.1  christos   NULL
    286  1.1  christos };
    287  1.1  christos 
    288  1.1  christos static int
    289  1.1  christos floatformat_ibm_long_double_is_valid (const struct floatformat *fmt,
    290  1.1  christos 				      const void *from)
    291  1.1  christos {
    292  1.1  christos   const unsigned char *ufrom = (const unsigned char *) from;
    293  1.1  christos   const struct floatformat *hfmt = fmt->split_half;
    294  1.1  christos   long top_exp, bot_exp;
    295  1.1  christos   int top_nan = 0;
    296  1.1  christos 
    297  1.1  christos   top_exp = get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
    298  1.1  christos 		       hfmt->exp_start, hfmt->exp_len);
    299  1.1  christos   bot_exp = get_field (ufrom + 8, hfmt->byteorder, hfmt->totalsize,
    300  1.1  christos 		       hfmt->exp_start, hfmt->exp_len);
    301  1.1  christos 
    302  1.1  christos   if ((unsigned long) top_exp == hfmt->exp_nan)
    303  1.1  christos     top_nan = mant_bits_set (hfmt, ufrom);
    304  1.1  christos 
    305  1.1  christos   /* A NaN is valid with any low part.  */
    306  1.1  christos   if (top_nan)
    307  1.1  christos     return 1;
    308  1.1  christos 
    309  1.1  christos   /* An infinity, zero or denormal requires low part 0 (positive or
    310  1.1  christos      negative).  */
    311  1.1  christos   if ((unsigned long) top_exp == hfmt->exp_nan || top_exp == 0)
    312  1.1  christos     {
    313  1.1  christos       if (bot_exp != 0)
    314  1.1  christos 	return 0;
    315  1.1  christos 
    316  1.1  christos       return !mant_bits_set (hfmt, ufrom + 8);
    317  1.1  christos     }
    318  1.1  christos 
    319  1.1  christos   /* The top part is now a finite normal value.  The long double value
    320  1.1  christos      is the sum of the two parts, and the top part must equal the
    321  1.1  christos      result of rounding the long double value to nearest double.  Thus
    322  1.1  christos      the bottom part must be <= 0.5ulp of the top part in absolute
    323  1.1  christos      value, and if it is < 0.5ulp then the long double is definitely
    324  1.1  christos      valid.  */
    325  1.1  christos   if (bot_exp < top_exp - 53)
    326  1.1  christos     return 1;
    327  1.1  christos   if (bot_exp > top_exp - 53 && bot_exp != 0)
    328  1.1  christos     return 0;
    329  1.1  christos   if (bot_exp == 0)
    330  1.1  christos     {
    331  1.1  christos       /* The bottom part is 0 or denormal.  Determine which, and if
    332  1.1  christos 	 denormal the first two set bits.  */
    333  1.1  christos       int first_bit = -1, second_bit = -1, cur_bit;
    334  1.1  christos       for (cur_bit = 0; (unsigned int) cur_bit < hfmt->man_len; cur_bit++)
    335  1.1  christos 	if (get_field (ufrom + 8, hfmt->byteorder, hfmt->totalsize,
    336  1.1  christos 		       hfmt->man_start + cur_bit, 1))
    337  1.1  christos 	  {
    338  1.1  christos 	    if (first_bit == -1)
    339  1.1  christos 	      first_bit = cur_bit;
    340  1.1  christos 	    else
    341  1.1  christos 	      {
    342  1.1  christos 		second_bit = cur_bit;
    343  1.1  christos 		break;
    344  1.1  christos 	      }
    345  1.1  christos 	  }
    346  1.1  christos       /* Bottom part 0 is OK.  */
    347  1.1  christos       if (first_bit == -1)
    348  1.1  christos 	return 1;
    349  1.1  christos       /* The real exponent of the bottom part is -first_bit.  */
    350  1.1  christos       if (-first_bit < top_exp - 53)
    351  1.1  christos 	return 1;
    352  1.1  christos       if (-first_bit > top_exp - 53)
    353  1.1  christos 	return 0;
    354  1.1  christos       /* The bottom part is at least 0.5ulp of the top part.  For this
    355  1.1  christos 	 to be OK, the bottom part must be exactly 0.5ulp (i.e. no
    356  1.1  christos 	 more bits set) and the top part must have last bit 0.  */
    357  1.1  christos       if (second_bit != -1)
    358  1.1  christos 	return 0;
    359  1.1  christos       return !get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
    360  1.1  christos 			 hfmt->man_start + hfmt->man_len - 1, 1);
    361  1.1  christos     }
    362  1.1  christos   else
    363  1.1  christos     {
    364  1.1  christos       /* The bottom part is at least 0.5ulp of the top part.  For this
    365  1.1  christos 	 to be OK, it must be exactly 0.5ulp (i.e. no explicit bits
    366  1.1  christos 	 set) and the top part must have last bit 0.  */
    367  1.1  christos       if (get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
    368  1.1  christos 		     hfmt->man_start + hfmt->man_len - 1, 1))
    369  1.1  christos 	return 0;
    370  1.1  christos       return !mant_bits_set (hfmt, ufrom + 8);
    371  1.1  christos     }
    372  1.1  christos }
    373  1.1  christos 
    374  1.1  christos const struct floatformat floatformat_ibm_long_double =
    375  1.1  christos {
    376  1.1  christos   floatformat_big, 128, 0, 1, 11, 1023, 2047, 12, 52,
    377  1.1  christos   floatformat_intbit_no,
    378  1.1  christos   "floatformat_ibm_long_double",
    379  1.1  christos   floatformat_ibm_long_double_is_valid,
    380  1.1  christos   &floatformat_ieee_double_big
    381  1.1  christos };
    382  1.1  christos 
    383  1.1  christos 
    385  1.1  christos #ifndef min
    386  1.1  christos #define min(a, b) ((a) < (b) ? (a) : (b))
    387  1.1  christos #endif
    388  1.1  christos 
    389  1.1  christos /* Return 1 if any bits are explicitly set in the mantissa of UFROM,
    390  1.1  christos    format FMT, 0 otherwise.  */
    391  1.1  christos static int
    392  1.1  christos mant_bits_set (const struct floatformat *fmt, const unsigned char *ufrom)
    393  1.1  christos {
    394  1.1  christos   unsigned int mant_bits, mant_off;
    395  1.1  christos   int mant_bits_left;
    396  1.1  christos 
    397  1.1  christos   mant_off = fmt->man_start;
    398  1.1  christos   mant_bits_left = fmt->man_len;
    399  1.1  christos   while (mant_bits_left > 0)
    400  1.1  christos     {
    401  1.1  christos       mant_bits = min (mant_bits_left, 32);
    402  1.1  christos 
    403  1.1  christos       if (get_field (ufrom, fmt->byteorder, fmt->totalsize,
    404  1.1  christos 		     mant_off, mant_bits) != 0)
    405  1.1  christos 	return 1;
    406  1.1  christos 
    407  1.1  christos       mant_off += mant_bits;
    408  1.1  christos       mant_bits_left -= mant_bits;
    409  1.1  christos     }
    410  1.1  christos   return 0;
    411  1.1  christos }
    412  1.1  christos 
    413  1.1  christos /* Extract a field which starts at START and is LEN bits long.  DATA and
    414  1.1  christos    TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */
    415  1.1  christos static unsigned long
    416  1.1  christos get_field (const unsigned char *data, enum floatformat_byteorders order,
    417  1.1  christos            unsigned int total_len, unsigned int start, unsigned int len)
    418  1.1  christos {
    419  1.1  christos   unsigned long result = 0;
    420  1.1  christos   unsigned int cur_byte;
    421  1.1  christos   int lo_bit, hi_bit, cur_bitshift = 0;
    422  1.1  christos   int nextbyte = (order == floatformat_little) ? 1 : -1;
    423  1.1  christos 
    424  1.1  christos   /* Start is in big-endian bit order!  Fix that first.  */
    425  1.1  christos   start = total_len - (start + len);
    426  1.1  christos 
    427  1.1  christos   /* Start at the least significant part of the field.  */
    428  1.1  christos   if (order == floatformat_little)
    429  1.1  christos     cur_byte = start / FLOATFORMAT_CHAR_BIT;
    430  1.1  christos   else
    431  1.1  christos     cur_byte = (total_len - start - 1) / FLOATFORMAT_CHAR_BIT;
    432  1.1  christos 
    433  1.1  christos   lo_bit = start % FLOATFORMAT_CHAR_BIT;
    434  1.1  christos   hi_bit = min (lo_bit + len, FLOATFORMAT_CHAR_BIT);
    435  1.1  christos 
    436  1.1  christos   do
    437  1.1  christos     {
    438  1.1  christos       unsigned int shifted = *(data + cur_byte) >> lo_bit;
    439  1.1  christos       unsigned int bits = hi_bit - lo_bit;
    440  1.1  christos       unsigned int mask = (1 << bits) - 1;
    441  1.1  christos       result |= (shifted & mask) << cur_bitshift;
    442  1.1  christos       len -= bits;
    443  1.1  christos       cur_bitshift += bits;
    444  1.1  christos       cur_byte += nextbyte;
    445  1.1  christos       lo_bit = 0;
    446  1.1  christos       hi_bit = min (len, FLOATFORMAT_CHAR_BIT);
    447  1.1  christos     }
    448  1.1  christos   while (len != 0);
    449  1.1  christos 
    450  1.1  christos   return result;
    451  1.1  christos }
    452  1.1  christos 
    453  1.1  christos /* Convert from FMT to a double.
    454  1.1  christos    FROM is the address of the extended float.
    455  1.1  christos    Store the double in *TO.  */
    456  1.1  christos 
    457  1.1  christos void
    458  1.1  christos floatformat_to_double (const struct floatformat *fmt,
    459  1.1  christos                        const void *from, double *to)
    460  1.1  christos {
    461  1.1  christos   const unsigned char *ufrom = (const unsigned char *) from;
    462  1.1  christos   double dto;
    463  1.1  christos   long exponent;
    464  1.1  christos   unsigned long mant;
    465  1.1  christos   unsigned int mant_bits, mant_off;
    466  1.1  christos   int mant_bits_left;
    467  1.1  christos   int special_exponent;		/* It's a NaN, denorm or zero */
    468  1.1  christos 
    469  1.1  christos   /* Split values are not handled specially, since the top half has
    470  1.1  christos      the correctly rounded double value (in the only supported case of
    471  1.1  christos      split values).  */
    472  1.1  christos 
    473  1.1  christos   exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
    474  1.1  christos 			fmt->exp_start, fmt->exp_len);
    475  1.1  christos 
    476  1.1  christos   /* If the exponent indicates a NaN, we don't have information to
    477  1.1  christos      decide what to do.  So we handle it like IEEE, except that we
    478  1.1  christos      don't try to preserve the type of NaN.  FIXME.  */
    479  1.1  christos   if ((unsigned long) exponent == fmt->exp_nan)
    480  1.1  christos     {
    481  1.1  christos       int nan = mant_bits_set (fmt, ufrom);
    482  1.1  christos 
    483  1.1  christos       /* On certain systems (such as GNU/Linux), the use of the
    484  1.1  christos 	 INFINITY macro below may generate a warning that can not be
    485  1.1  christos 	 silenced due to a bug in GCC (PR preprocessor/11931).  The
    486  1.1  christos 	 preprocessor fails to recognise the __extension__ keyword in
    487  1.1  christos 	 conjunction with the GNU/C99 extension for hexadecimal
    488  1.1  christos 	 floating point constants and will issue a warning when
    489  1.1  christos 	 compiling with -pedantic.  */
    490  1.1  christos       if (nan)
    491  1.1  christos 	dto = NAN;
    492  1.1  christos       else
    493  1.1  christos #ifdef __vax__
    494  1.1  christos 	dto = HUGE_VAL;
    495  1.1  christos #else
    496  1.1  christos 	dto = INFINITY;
    497  1.1  christos #endif
    498  1.1  christos 
    499  1.1  christos       if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
    500  1.1  christos 	dto = -dto;
    501  1.1  christos 
    502  1.1  christos       *to = dto;
    503  1.1  christos 
    504  1.1  christos       return;
    505  1.1  christos     }
    506  1.1  christos 
    507  1.1  christos   mant_bits_left = fmt->man_len;
    508  1.1  christos   mant_off = fmt->man_start;
    509  1.1  christos   dto = 0.0;
    510  1.1  christos 
    511  1.1  christos   special_exponent = exponent == 0 || (unsigned long) exponent == fmt->exp_nan;
    512  1.1  christos 
    513  1.1  christos   /* Don't bias zero's, denorms or NaNs.  */
    514  1.1  christos   if (!special_exponent)
    515  1.1  christos     exponent -= fmt->exp_bias;
    516  1.1  christos 
    517  1.1  christos   /* Build the result algebraically.  Might go infinite, underflow, etc;
    518  1.1  christos      who cares. */
    519  1.1  christos 
    520  1.1  christos   /* If this format uses a hidden bit, explicitly add it in now.  Otherwise,
    521  1.1  christos      increment the exponent by one to account for the integer bit.  */
    522  1.1  christos 
    523  1.1  christos   if (!special_exponent)
    524  1.1  christos     {
    525  1.1  christos       if (fmt->intbit == floatformat_intbit_no)
    526  1.1  christos 	dto = ldexp (1.0, exponent);
    527  1.1  christos       else
    528  1.1  christos 	exponent++;
    529  1.1  christos     }
    530  1.1  christos 
    531  1.1  christos   while (mant_bits_left > 0)
    532  1.1  christos     {
    533  1.1  christos       mant_bits = min (mant_bits_left, 32);
    534  1.1  christos 
    535  1.1  christos       mant = get_field (ufrom, fmt->byteorder, fmt->totalsize,
    536  1.1  christos 			 mant_off, mant_bits);
    537  1.1  christos 
    538  1.1  christos       /* Handle denormalized numbers.  FIXME: What should we do for
    539  1.1  christos 	 non-IEEE formats?  */
    540  1.1  christos       if (special_exponent && exponent == 0 && mant != 0)
    541  1.1  christos 	dto += ldexp ((double)mant,
    542  1.1  christos 		      (- fmt->exp_bias
    543  1.1  christos 		       - mant_bits
    544  1.1  christos 		       - (mant_off - fmt->man_start)
    545  1.1  christos 		       + 1));
    546  1.1  christos       else
    547  1.1  christos 	dto += ldexp ((double)mant, exponent - mant_bits);
    548  1.1  christos       if (exponent != 0)
    549  1.1  christos 	exponent -= mant_bits;
    550  1.1  christos       mant_off += mant_bits;
    551  1.1  christos       mant_bits_left -= mant_bits;
    552  1.1  christos     }
    553  1.1  christos 
    554  1.1  christos   /* Negate it if negative.  */
    555  1.1  christos   if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
    556  1.1  christos     dto = -dto;
    557  1.1  christos   *to = dto;
    558  1.1  christos }
    559  1.1  christos 
    560  1.1  christos static void put_field (unsigned char *, enum floatformat_byteorders,
    562  1.1  christos                        unsigned int,
    563  1.1  christos                        unsigned int,
    564  1.1  christos                        unsigned int,
    565  1.1  christos                        unsigned long);
    566  1.1  christos 
    567  1.1  christos /* Set a field which starts at START and is LEN bits long.  DATA and
    568  1.1  christos    TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */
    569  1.1  christos static void
    570  1.1  christos put_field (unsigned char *data, enum floatformat_byteorders order,
    571  1.1  christos            unsigned int total_len, unsigned int start, unsigned int len,
    572  1.1  christos            unsigned long stuff_to_put)
    573  1.1  christos {
    574  1.1  christos   unsigned int cur_byte;
    575  1.1  christos   int lo_bit, hi_bit;
    576  1.1  christos   int nextbyte = (order == floatformat_little) ? 1 : -1;
    577  1.1  christos 
    578  1.1  christos   /* Start is in big-endian bit order!  Fix that first.  */
    579  1.1  christos   start = total_len - (start + len);
    580  1.1  christos 
    581  1.1  christos   /* Start at the least significant part of the field.  */
    582  1.1  christos   if (order == floatformat_little)
    583  1.1  christos     cur_byte = start / FLOATFORMAT_CHAR_BIT;
    584  1.1  christos   else
    585  1.1  christos     cur_byte = (total_len - start - 1) / FLOATFORMAT_CHAR_BIT;
    586  1.1  christos 
    587  1.1  christos   lo_bit = start % FLOATFORMAT_CHAR_BIT;
    588  1.1  christos   hi_bit = min (lo_bit + len, FLOATFORMAT_CHAR_BIT);
    589  1.1  christos 
    590  1.1  christos   do
    591  1.1  christos     {
    592  1.1  christos       unsigned char *byte_ptr = data + cur_byte;
    593  1.1  christos       unsigned int bits = hi_bit - lo_bit;
    594  1.1  christos       unsigned int mask = ((1 << bits) - 1) << lo_bit;
    595  1.1  christos       *byte_ptr = (*byte_ptr & ~mask) | ((stuff_to_put << lo_bit) & mask);
    596  1.1  christos       stuff_to_put >>= bits;
    597  1.1  christos       len -= bits;
    598  1.1  christos       cur_byte += nextbyte;
    599  1.1  christos       lo_bit = 0;
    600  1.1  christos       hi_bit = min (len, FLOATFORMAT_CHAR_BIT);
    601  1.1  christos     }
    602  1.1  christos   while (len != 0);
    603  1.1  christos }
    604  1.1  christos 
    605  1.1  christos /* The converse: convert the double *FROM to an extended float
    606  1.1  christos    and store where TO points.  Neither FROM nor TO have any alignment
    607  1.1  christos    restrictions.  */
    608  1.1  christos 
    609  1.1  christos void
    610  1.1  christos floatformat_from_double (const struct floatformat *fmt,
    611  1.1  christos                          const double *from, void *to)
    612  1.1  christos {
    613  1.1  christos   double dfrom;
    614  1.1  christos   int exponent;
    615  1.1  christos   double mant;
    616  1.1  christos   unsigned int mant_bits, mant_off;
    617  1.1  christos   int mant_bits_left;
    618  1.1  christos   unsigned char *uto = (unsigned char *) to;
    619  1.1  christos 
    620  1.1  christos   dfrom = *from;
    621  1.1  christos   memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT);
    622  1.1  christos 
    623  1.1  christos   /* Split values are not handled specially, since a bottom half of
    624  1.1  christos      zero is correct for any value representable as double (in the
    625  1.1  christos      only supported case of split values).  */
    626  1.1  christos 
    627  1.1  christos   /* If negative, set the sign bit.  */
    628  1.1  christos   if (dfrom < 0)
    629  1.1  christos     {
    630  1.1  christos       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1);
    631  1.1  christos       dfrom = -dfrom;
    632  1.1  christos     }
    633  1.1  christos 
    634  1.1  christos   if (dfrom == 0)
    635  1.1  christos     {
    636  1.1  christos       /* 0.0.  */
    637  1.1  christos       return;
    638  1.1  christos     }
    639  1.1  christos 
    640  1.1  christos   if (dfrom != dfrom)
    641  1.1  christos     {
    642  1.1  christos       /* NaN.  */
    643  1.1  christos       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
    644  1.1  christos 		 fmt->exp_len, fmt->exp_nan);
    645  1.1  christos       /* Be sure it's not infinity, but NaN value is irrelevant.  */
    646  1.1  christos       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start,
    647  1.1  christos 		 32, 1);
    648  1.1  christos       return;
    649  1.1  christos     }
    650  1.1  christos 
    651  1.1  christos   if (dfrom + dfrom == dfrom)
    652  1.1  christos     {
    653  1.1  christos       /* This can only happen for an infinite value (or zero, which we
    654  1.1  christos 	 already handled above).  */
    655  1.1  christos       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
    656  1.1  christos 		 fmt->exp_len, fmt->exp_nan);
    657  1.1  christos       return;
    658  1.1  christos     }
    659  1.1  christos 
    660  1.1  christos   mant = frexp (dfrom, &exponent);
    661  1.1  christos   if (exponent + fmt->exp_bias - 1 > 0)
    662  1.1  christos     put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
    663  1.1  christos 	       fmt->exp_len, exponent + fmt->exp_bias - 1);
    664  1.1  christos   else
    665  1.1  christos     {
    666  1.1  christos       /* Handle a denormalized number.  FIXME: What should we do for
    667  1.1  christos 	 non-IEEE formats?  */
    668  1.1  christos       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
    669  1.1  christos 		 fmt->exp_len, 0);
    670  1.1  christos       mant = ldexp (mant, exponent + fmt->exp_bias - 1);
    671  1.1  christos     }
    672  1.1  christos 
    673  1.1  christos   mant_bits_left = fmt->man_len;
    674  1.1  christos   mant_off = fmt->man_start;
    675  1.1  christos   while (mant_bits_left > 0)
    676  1.1  christos     {
    677  1.1  christos       unsigned long mant_long;
    678  1.1  christos       mant_bits = mant_bits_left < 32 ? mant_bits_left : 32;
    679  1.1  christos 
    680  1.1  christos       mant *= 4294967296.0;
    681  1.1  christos       mant_long = (unsigned long)mant;
    682  1.1  christos       mant -= mant_long;
    683  1.1  christos 
    684  1.1  christos       /* If the integer bit is implicit, and we are not creating a
    685  1.1  christos 	 denormalized number, then we need to discard it.  */
    686  1.1  christos       if ((unsigned int) mant_bits_left == fmt->man_len
    687  1.1  christos 	  && fmt->intbit == floatformat_intbit_no
    688  1.1  christos 	  && exponent + fmt->exp_bias - 1 > 0)
    689  1.1  christos 	{
    690  1.1  christos 	  mant_long &= 0x7fffffff;
    691  1.1  christos 	  mant_bits -= 1;
    692  1.1  christos 	}
    693  1.1  christos       else if (mant_bits < 32)
    694  1.1  christos 	{
    695  1.1  christos 	  /* The bits we want are in the most significant MANT_BITS bits of
    696  1.1  christos 	     mant_long.  Move them to the least significant.  */
    697  1.1  christos 	  mant_long >>= 32 - mant_bits;
    698  1.1  christos 	}
    699  1.1  christos 
    700  1.1  christos       put_field (uto, fmt->byteorder, fmt->totalsize,
    701  1.1  christos 		 mant_off, mant_bits, mant_long);
    702  1.1  christos       mant_off += mant_bits;
    703  1.1  christos       mant_bits_left -= mant_bits;
    704  1.1  christos     }
    705  1.1  christos }
    706  1.1  christos 
    707  1.1  christos /* Return non-zero iff the data at FROM is a valid number in format FMT.  */
    708  1.1  christos 
    709  1.1  christos int
    710  1.1  christos floatformat_is_valid (const struct floatformat *fmt, const void *from)
    711  1.1  christos {
    712  1.1  christos   return fmt->is_valid (fmt, from);
    713  1.1  christos }
    714  1.1  christos 
    715  1.1  christos 
    716  1.1  christos #ifdef IEEE_DEBUG
    717  1.1  christos 
    718  1.1  christos #include <stdio.h>
    719  1.1  christos 
    720  1.1  christos /* This is to be run on a host which uses IEEE floating point.  */
    721  1.1  christos 
    722  1.1  christos void
    723  1.1  christos ieee_test (double n)
    724  1.1  christos {
    725  1.1  christos   double result;
    726  1.1  christos 
    727  1.1  christos   floatformat_to_double (&floatformat_ieee_double_little, &n, &result);
    728  1.1  christos   if ((n != result && (! isnan (n) || ! isnan (result)))
    729  1.1  christos       || (n < 0 && result >= 0)
    730  1.1  christos       || (n >= 0 && result < 0))
    731  1.1  christos     printf ("Differ(to): %.20g -> %.20g\n", n, result);
    732  1.1  christos 
    733  1.1  christos   floatformat_from_double (&floatformat_ieee_double_little, &n, &result);
    734  1.1  christos   if ((n != result && (! isnan (n) || ! isnan (result)))
    735  1.1  christos       || (n < 0 && result >= 0)
    736  1.1  christos       || (n >= 0 && result < 0))
    737  1.1  christos     printf ("Differ(from): %.20g -> %.20g\n", n, result);
    738  1.1  christos 
    739  1.1  christos #if 0
    740  1.1  christos   {
    741  1.1  christos     char exten[16];
    742  1.1  christos 
    743  1.1  christos     floatformat_from_double (&floatformat_m68881_ext, &n, exten);
    744  1.1  christos     floatformat_to_double (&floatformat_m68881_ext, exten, &result);
    745  1.1  christos     if (n != result)
    746  1.1  christos       printf ("Differ(to+from): %.20g -> %.20g\n", n, result);
    747  1.1  christos   }
    748  1.1  christos #endif
    749  1.1  christos 
    750  1.1  christos #if IEEE_DEBUG > 1
    751  1.1  christos   /* This is to be run on a host which uses 68881 format.  */
    752  1.1  christos   {
    753  1.1  christos     long double ex = *(long double *)exten;
    754  1.1  christos     if (ex != n)
    755  1.1  christos       printf ("Differ(from vs. extended): %.20g\n", n);
    756  1.1  christos   }
    757  1.1  christos #endif
    758  1.1  christos }
    759  1.1  christos 
    760  1.1  christos int
    761  1.1  christos main (void)
    762  1.1  christos {
    763  1.1  christos   ieee_test (0.0);
    764  1.1  christos   ieee_test (0.5);
    765  1.1  christos   ieee_test (256.0);
    766  1.1  christos   ieee_test (0.12345);
    767  1.1  christos   ieee_test (234235.78907234);
    768  1.1  christos   ieee_test (-512.0);
    769  1.1  christos   ieee_test (-0.004321);
    770  1.1  christos   ieee_test (1.2E-70);
    771  1.1  christos   ieee_test (1.2E-316);
    772  1.1  christos   ieee_test (4.9406564584124654E-324);
    773  1.1  christos   ieee_test (- 4.9406564584124654E-324);
    774  1.1  christos   ieee_test (- 0.0);
    775  1.1  christos   ieee_test (- INFINITY);
    776  1.1  christos   ieee_test (- NAN);
    777  1.1  christos   ieee_test (INFINITY);
    778  1.1  christos   ieee_test (NAN);
    779  1.1  christos   return 0;
    780                }
    781                #endif
    782