gdb/dfp.c

   1 /* Decimal floating point support for GDB.
   2
   3    Copyright 2007, 2008, 2009 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "expression.h"
  22 #include "gdbtypes.h"
  23 #include "value.h"
  24 #include "dfp.h"
  25
  26 /* The order of the following headers is important for making sure
  27    decNumber structure is large enough to hold decimal128 digits.  */
  28
  29 #include "dpd/decimal128.h"
  30 #include "dpd/decimal64.h"
  31 #include "dpd/decimal32.h"
  32
  33 /* In GDB, we are using an array of gdb_byte to represent decimal values.
  34    They are stored in host byte order.  This routine does the conversion if
  35    the target byte order is different.  */
  36 static void
  37 match_endianness (const gdb_byte *from, int len, gdb_byte *to)
  38 {
  39   int i;
  40
  41 #if WORDS_BIGENDIAN
  42 #define OPPOSITE_BYTE_ORDER BFD_ENDIAN_LITTLE
  43 #else
  44 #define OPPOSITE_BYTE_ORDER BFD_ENDIAN_BIG
  45 #endif
  46
  47   if (gdbarch_byte_order (current_gdbarch) == OPPOSITE_BYTE_ORDER)
  48     for (i = 0; i < len; i++)
  49       to[i] = from[len - i - 1];
  50   else
  51     for (i = 0; i < len; i++)
  52       to[i] = from[i];
  53
  54   return;
  55 }
  56
  57 /* Helper function to get the appropriate libdecnumber context for each size
  58    of decimal float.  */
  59 static void
  60 set_decnumber_context (decContext *ctx, int len)
  61 {
  62   switch (len)
  63     {
  64       case 4:
  65         decContextDefault (ctx, DEC_INIT_DECIMAL32);
  66         break;
  67       case 8:
  68         decContextDefault (ctx, DEC_INIT_DECIMAL64);
  69         break;
  70       case 16:
  71         decContextDefault (ctx, DEC_INIT_DECIMAL128);
  72         break;
  73     }
  74
  75   ctx->traps = 0;
  76 }
  77
  78 /* Check for errors signaled in the decimal context structure.  */
  79 static void
  80 decimal_check_errors (decContext *ctx)
  81 {
  82   /* An error here could be a division by zero, an overflow, an underflow or
  83      an invalid operation (from the DEC_Errors constant in decContext.h).
  84      Since GDB doesn't complain about division by zero, overflow or underflow
  85      errors for binary floating, we won't complain about them for decimal
  86      floating either.  */
  87   if (ctx->status & DEC_IEEE_854_Invalid_operation)
  88     {
  89       /* Leave only the error bits in the status flags.  */
  90       ctx->status &= DEC_IEEE_854_Invalid_operation;
  91       error (_("Cannot perform operation: %s"), decContextStatusToString (ctx));
  92     }
  93 }
  94
  95 /* Helper function to convert from libdecnumber's appropriate representation
  96    for computation to each size of decimal float.  */
  97 static void
  98 decimal_from_number (const decNumber *from, gdb_byte *to, int len)
  99 {
 100   decContext set;
 101
 102   set_decnumber_context (&set, len);
 103
 104   switch (len)
 105     {
 106       case 4:
 107         decimal32FromNumber ((decimal32 *) to, from, &set);
 108         break;
 109       case 8:
 110         decimal64FromNumber ((decimal64 *) to, from, &set);
 111         break;
 112       case 16:
 113         decimal128FromNumber ((decimal128 *) to, from, &set);
 114         break;
 115     }
 116 }
 117
 118 /* Helper function to convert each size of decimal float to libdecnumber's
 119    appropriate representation for computation.  */
 120 static void
 121 decimal_to_number (const gdb_byte *from, int len, decNumber *to)
 122 {
 123   switch (len)
 124     {
 125       case 4:
 126         decimal32ToNumber ((decimal32 *) from, to);
 127         break;
 128       case 8:
 129         decimal64ToNumber ((decimal64 *) from, to);
 130         break;
 131       case 16:
 132         decimal128ToNumber ((decimal128 *) from, to);
 133         break;
 134       default:
 135         error (_("Unknown decimal floating point type.\n"));
 136         break;
 137     }
 138 }
 139
 140 /* Convert decimal type to its string representation.  LEN is the length
 141    of the decimal type, 4 bytes for decimal32, 8 bytes for decimal64 and
 142    16 bytes for decimal128.  */
 143 void
 144 decimal_to_string (const gdb_byte *decbytes, int len, char *s)
 145 {
 146   gdb_byte dec[16];
 147
 148   match_endianness (decbytes, len, dec);
 149
 150   switch (len)
 151     {
 152       case 4:
 153         decimal32ToString ((decimal32 *) dec, s);
 154         break;
 155       case 8:
 156         decimal64ToString ((decimal64 *) dec, s);
 157         break;
 158       case 16:
 159         decimal128ToString ((decimal128 *) dec, s);
 160         break;
 161       default:
 162         error (_("Unknown decimal floating point type."));
 163         break;
 164     }
 165 }
 166
 167 /* Convert the string form of a decimal value to its decimal representation.
 168    LEN is the length of the decimal type, 4 bytes for decimal32, 8 bytes for
 169    decimal64 and 16 bytes for decimal128.  */
 170 int
 171 decimal_from_string (gdb_byte *decbytes, int len, const char *string)
 172 {
 173   decContext set;
 174   gdb_byte dec[16];
 175
 176   set_decnumber_context (&set, len);
 177
 178   switch (len)
 179     {
 180       case 4:
 181         decimal32FromString ((decimal32 *) dec, string, &set);
 182         break;
 183       case 8:
 184         decimal64FromString ((decimal64 *) dec, string, &set);
 185         break;
 186       case 16:
 187         decimal128FromString ((decimal128 *) dec, string, &set);
 188         break;
 189       default:
 190         error (_("Unknown decimal floating point type."));
 191         break;
 192     }
 193
 194   match_endianness (dec, len, decbytes);
 195
 196   /* Check for errors in the DFP operation.  */
 197   decimal_check_errors (&set);
 198
 199   return 1;
 200 }
 201
 202 /* Converts a value of an integral type to a decimal float of
 203    specified LEN bytes.  */
 204 void
 205 decimal_from_integral (struct value *from, gdb_byte *to, int len)
 206 {
 207   LONGEST l;
 208   gdb_byte dec[16];
 209   decNumber number;
 210   struct type *type;
 211
 212   type = check_typedef (value_type (from));
 213
 214   if (TYPE_LENGTH (type) > 4)
 215     /* libdecnumber can convert only 32-bit integers.  */
 216     error (_("Conversion of large integer to a decimal floating type is not supported."));
 217
 218   l = value_as_long (from);
 219
 220   if (TYPE_UNSIGNED (type))
 221     decNumberFromUInt32 (&number, (unsigned int) l);
 222   else
 223     decNumberFromInt32 (&number, (int) l);
 224
 225   decimal_from_number (&number, dec, len);
 226   match_endianness (dec, len, to);
 227 }
 228
 229 /* Converts a value of a float type to a decimal float of
 230    specified LEN bytes.
 231
 232    This is an ugly way to do the conversion, but libdecnumber does
 233    not offer a direct way to do it.  */
 234 void
 235 decimal_from_floating (struct value *from, gdb_byte *to, int len)
 236 {
 237   char *buffer;
 238
 239   buffer = xstrprintf ("%.30" DOUBLEST_PRINT_FORMAT, value_as_double (from));
 240
 241   decimal_from_string (to, len, buffer);
 242
 243   xfree (buffer);
 244 }
 245
 246 /* Converts a decimal float of LEN bytes to a double value.  */
 247 DOUBLEST
 248 decimal_to_doublest (const gdb_byte *from, int len)
 249 {
 250   char buffer[MAX_DECIMAL_STRING];
 251
 252   /* This is an ugly way to do the conversion, but libdecnumber does
 253      not offer a direct way to do it.  */
 254   decimal_to_string (from, len, buffer);
 255   return strtod (buffer, NULL);
 256 }
 257
 258 /* Check if operands have the same size and convert them to the
 259    biggest of the two if necessary.  */
 260 static int
 261 promote_decimal (gdb_byte *x, int len_x, gdb_byte *y, int len_y)
 262 {
 263   int len_result;
 264   decNumber number;
 265
 266   if (len_x < len_y)
 267     {
 268       decimal_to_number (x, len_x, &number);
 269       decimal_from_number (&number, x, len_y);
 270       len_result = len_y;
 271     }
 272   else if (len_x > len_y)
 273     {
 274       decimal_to_number (y, len_y, &number);
 275       decimal_from_number (&number, y, len_x);
 276       len_result = len_x;
 277     }
 278   else
 279     len_result = len_x;
 280
 281   return len_result;
 282 }
 283
 284 /* Perform operation OP with operands X and Y and store value in RESULT.
 285    If LEN_X and LEN_Y are not equal, RESULT will have the size of the biggest
 286    of the two, and LEN_RESULT will be set accordingly.  */
 287 void
 288 decimal_binop (enum exp_opcode op, const gdb_byte *x, int len_x,
 289                const gdb_byte *y, int len_y, gdb_byte *result, int *len_result)
 290 {
 291   decContext set;
 292   decNumber number1, number2, number3;
 293   gdb_byte dec1[16], dec2[16], dec3[16];
 294
 295   match_endianness (x, len_x, dec1);
 296   match_endianness (y, len_y, dec2);
 297
 298   *len_result = promote_decimal (dec1, len_x, dec2, len_y);
 299
 300   /* Both operands are of size *len_result from now on.  */
 301
 302   decimal_to_number (dec1, *len_result, &number1);
 303   decimal_to_number (dec2, *len_result, &number2);
 304
 305   set_decnumber_context (&set, *len_result);
 306
 307   switch (op)
 308     {
 309       case BINOP_ADD:
 310         decNumberAdd (&number3, &number1, &number2, &set);
 311         break;
 312       case BINOP_SUB:
 313         decNumberSubtract (&number3, &number1, &number2, &set);
 314         break;
 315       case BINOP_MUL:
 316         decNumberMultiply (&number3, &number1, &number2, &set);
 317         break;
 318       case BINOP_DIV:
 319         decNumberDivide (&number3, &number1, &number2, &set);
 320         break;
 321       case BINOP_EXP:
 322         decNumberPower (&number3, &number1, &number2, &set);
 323         break;
 324       default:
 325         internal_error (__FILE__, __LINE__,
 326                         _("Unknown decimal floating point operation."));
 327         break;
 328     }
 329
 330   /* Check for errors in the DFP operation.  */
 331   decimal_check_errors (&set);
 332
 333   decimal_from_number (&number3, dec3, *len_result);
 334
 335   match_endianness (dec3, *len_result, result);
 336 }
 337
 338 /* Returns true if X (which is LEN bytes wide) is the number zero.  */
 339 int
 340 decimal_is_zero (const gdb_byte *x, int len)
 341 {
 342   decNumber number;
 343   gdb_byte dec[16];
 344
 345   match_endianness (x, len, dec);
 346   decimal_to_number (dec, len, &number);
 347
 348   return decNumberIsZero (&number);
 349 }
 350
 351 /* Compares two numbers numerically.  If X is less than Y then the return value
 352    will be -1.  If they are equal, then the return value will be 0.  If X is
 353    greater than the Y then the return value will be 1.  */
 354 int
 355 decimal_compare (const gdb_byte *x, int len_x, const gdb_byte *y, int len_y)
 356 {
 357   decNumber number1, number2, result;
 358   decContext set;
 359   gdb_byte dec1[16], dec2[16];
 360   int len_result;
 361
 362   match_endianness (x, len_x, dec1);
 363   match_endianness (y, len_y, dec2);
 364
 365   len_result = promote_decimal (dec1, len_x, dec2, len_y);
 366
 367   decimal_to_number (dec1, len_result, &number1);
 368   decimal_to_number (dec2, len_result, &number2);
 369
 370   set_decnumber_context (&set, len_result);
 371
 372   decNumberCompare (&result, &number1, &number2, &set);
 373
 374   /* Check for errors in the DFP operation.  */
 375   decimal_check_errors (&set);
 376
 377   if (decNumberIsNaN (&result))
 378     error (_("Comparison with an invalid number (NaN)."));
 379   else if (decNumberIsZero (&result))
 380     return 0;
 381   else if (decNumberIsNegative (&result))
 382     return -1;
 383   else
 384     return 1;
 385 }
 386
 387 /* Convert a decimal value from a decimal type with LEN_FROM bytes to a
 388    decimal type with LEN_TO bytes.  */
 389 void
 390 decimal_convert (const gdb_byte *from, int len_from, gdb_byte *to,
 391                  int len_to)
 392 {
 393   decNumber number;
 394   gdb_byte dec[16];
 395
 396   match_endianness (from, len_from, dec);
 397
 398   decimal_to_number (dec, len_from, &number);
 399   decimal_from_number (&number, dec, len_to);
 400
 401   match_endianness (dec, len_to, to);
 402 }