gdb/dfp.c

   1 /* Decimal floating point support for GDB.
   2
   3    Copyright (C) 2007-2017 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 "dfp.h"
  23
  24 /* The order of the following headers is important for making sure
  25    decNumber structure is large enough to hold decimal128 digits.  */
  26
  27 #include "dpd/decimal128.h"
  28 #include "dpd/decimal64.h"
  29 #include "dpd/decimal32.h"
  30
  31 /* When using decimal128, this is the maximum string length + 1
  32    (value comes from libdecnumber's DECIMAL128_String constant).  */
  33 #define MAX_DECIMAL_STRING  43
  34
  35 /* In GDB, we are using an array of gdb_byte to represent decimal values.
  36    They are stored in host byte order.  This routine does the conversion if
  37    the target byte order is different.  */
  38 static void
  39 match_endianness (const gdb_byte *from, int len, enum bfd_endian byte_order,
  40                   gdb_byte *to)
  41 {
  42   int i;
  43
  44 #if WORDS_BIGENDIAN
  45 #define OPPOSITE_BYTE_ORDER BFD_ENDIAN_LITTLE
  46 #else
  47 #define OPPOSITE_BYTE_ORDER BFD_ENDIAN_BIG
  48 #endif
  49
  50   if (byte_order == OPPOSITE_BYTE_ORDER)
  51     for (i = 0; i < len; i++)
  52       to[i] = from[len - i - 1];
  53   else
  54     for (i = 0; i < len; i++)
  55       to[i] = from[i];
  56
  57   return;
  58 }
  59
  60 /* Helper function to get the appropriate libdecnumber context for each size
  61    of decimal float.  */
  62 static void
  63 set_decnumber_context (decContext *ctx, int len)
  64 {
  65   switch (len)
  66     {
  67       case 4:
  68         decContextDefault (ctx, DEC_INIT_DECIMAL32);
  69         break;
  70       case 8:
  71         decContextDefault (ctx, DEC_INIT_DECIMAL64);
  72         break;
  73       case 16:
  74         decContextDefault (ctx, DEC_INIT_DECIMAL128);
  75         break;
  76     }
  77
  78   ctx->traps = 0;
  79 }
  80
  81 /* Check for errors signaled in the decimal context structure.  */
  82 static void
  83 decimal_check_errors (decContext *ctx)
  84 {
  85   /* An error here could be a division by zero, an overflow, an underflow or
  86      an invalid operation (from the DEC_Errors constant in decContext.h).
  87      Since GDB doesn't complain about division by zero, overflow or underflow
  88      errors for binary floating, we won't complain about them for decimal
  89      floating either.  */
  90   if (ctx->status & DEC_IEEE_854_Invalid_operation)
  91     {
  92       /* Leave only the error bits in the status flags.  */
  93       ctx->status &= DEC_IEEE_854_Invalid_operation;
  94       error (_("Cannot perform operation: %s"),
  95              decContextStatusToString (ctx));
  96     }
  97 }
  98
  99 /* Helper function to convert from libdecnumber's appropriate representation
 100    for computation to each size of decimal float.  */
 101 static void
 102 decimal_from_number (const decNumber *from, gdb_byte *to, int len)
 103 {
 104   decContext set;
 105
 106   set_decnumber_context (&set, len);
 107
 108   switch (len)
 109     {
 110       case 4:
 111         decimal32FromNumber ((decimal32 *) to, from, &set);
 112         break;
 113       case 8:
 114         decimal64FromNumber ((decimal64 *) to, from, &set);
 115         break;
 116       case 16:
 117         decimal128FromNumber ((decimal128 *) to, from, &set);
 118         break;
 119     }
 120 }
 121
 122 /* Helper function to convert each size of decimal float to libdecnumber's
 123    appropriate representation for computation.  */
 124 static void
 125 decimal_to_number (const gdb_byte *from, int len, decNumber *to)
 126 {
 127   switch (len)
 128     {
 129       case 4:
 130         decimal32ToNumber ((decimal32 *) from, to);
 131         break;
 132       case 8:
 133         decimal64ToNumber ((decimal64 *) from, to);
 134         break;
 135       case 16:
 136         decimal128ToNumber ((decimal128 *) from, to);
 137         break;
 138       default:
 139         error (_("Unknown decimal floating point type."));
 140         break;
 141     }
 142 }
 143
 144 /* Convert decimal type to its string representation.  LEN is the length
 145    of the decimal type, 4 bytes for decimal32, 8 bytes for decimal64 and
 146    16 bytes for decimal128.  */
 147 std::string
 148 decimal_to_string (const gdb_byte *decbytes, int len,
 149                    enum bfd_endian byte_order, const char *format)
 150 {
 151   gdb_byte dec[16];
 152
 153   match_endianness (decbytes, len, byte_order, dec);
 154
 155   if (format != nullptr)
 156     {
 157       /* We don't handle format strings (yet).  If the host printf supports
 158          decimal floating point types, just use this.  Otherwise, fall back
 159          to printing the number while ignoring the format string.  */
 160 #if defined (PRINTF_HAS_DECFLOAT)
 161       /* FIXME: This makes unwarranted assumptions about the host ABI!  */
 162       return string_printf (format, dec);
 163 #endif
 164     }
 165
 166   std::string result;
 167   result.resize (MAX_DECIMAL_STRING);
 168
 169   switch (len)
 170     {
 171       case 4:
 172         decimal32ToString ((decimal32 *) dec, &result[0]);
 173         break;
 174       case 8:
 175         decimal64ToString ((decimal64 *) dec, &result[0]);
 176         break;
 177       case 16:
 178         decimal128ToString ((decimal128 *) dec, &result[0]);
 179         break;
 180       default:
 181         error (_("Unknown decimal floating point type."));
 182         break;
 183     }
 184
 185   return result;
 186 }
 187
 188 /* Convert the string form of a decimal value to its decimal representation.
 189    LEN is the length of the decimal type, 4 bytes for decimal32, 8 bytes for
 190    decimal64 and 16 bytes for decimal128.  */
 191 bool
 192 decimal_from_string (gdb_byte *decbytes, int len, enum bfd_endian byte_order,
 193                      const std::string &string)
 194 {
 195   decContext set;
 196   gdb_byte dec[16];
 197
 198   set_decnumber_context (&set, len);
 199
 200   switch (len)
 201     {
 202       case 4:
 203         decimal32FromString ((decimal32 *) dec, string.c_str (), &set);
 204         break;
 205       case 8:
 206         decimal64FromString ((decimal64 *) dec, string.c_str (), &set);
 207         break;
 208       case 16:
 209         decimal128FromString ((decimal128 *) dec, string.c_str (), &set);
 210         break;
 211       default:
 212         error (_("Unknown decimal floating point type."));
 213         break;
 214     }
 215
 216   match_endianness (dec, len, byte_order, decbytes);
 217
 218   /* Check for errors in the DFP operation.  */
 219   decimal_check_errors (&set);
 220
 221   return true;
 222 }
 223
 224 /* Converts a LONGEST to a decimal float of specified LEN bytes.  */
 225 void
 226 decimal_from_longest (LONGEST from,
 227                       gdb_byte *to, int len, enum bfd_endian byte_order)
 228 {
 229   gdb_byte dec[16];
 230   decNumber number;
 231   if ((int32_t) from != from)
 232     /* libdecnumber can convert only 32-bit integers.  */
 233     error (_("Conversion of large integer to a "
 234              "decimal floating type is not supported."));
 235
 236   decNumberFromInt32 (&number, (int32_t) from);
 237
 238   decimal_from_number (&number, dec, len);
 239   match_endianness (dec, len, byte_order, to);
 240 }
 241
 242 /* Converts a ULONGEST to a decimal float of specified LEN bytes.  */
 243 void
 244 decimal_from_ulongest (ULONGEST from,
 245                        gdb_byte *to, int len, enum bfd_endian byte_order)
 246 {
 247   gdb_byte dec[16];
 248   decNumber number;
 249
 250   if ((uint32_t) from != from)
 251     /* libdecnumber can convert only 32-bit integers.  */
 252     error (_("Conversion of large integer to a "
 253              "decimal floating type is not supported."));
 254
 255   decNumberFromUInt32 (&number, (uint32_t) from);
 256
 257   decimal_from_number (&number, dec, len);
 258   match_endianness (dec, len, byte_order, to);
 259 }
 260
 261 /* Converts a decimal float of LEN bytes to a LONGEST.  */
 262 LONGEST
 263 decimal_to_longest (const gdb_byte *from, int len, enum bfd_endian byte_order)
 264 {
 265   /* libdecnumber has a function to convert from decimal to integer, but
 266      it doesn't work when the decimal number has a fractional part.  */
 267   std::string str = decimal_to_string (from, len, byte_order);
 268   return strtoll (str.c_str (), NULL, 10);
 269 }
 270
 271 /* Perform operation OP with operands X and Y with sizes LEN_X and LEN_Y
 272    and byte orders BYTE_ORDER_X and BYTE_ORDER_Y, and store value in
 273    RESULT with size LEN_RESULT and byte order BYTE_ORDER_RESULT.  */
 274 void
 275 decimal_binop (enum exp_opcode op,
 276                const gdb_byte *x, int len_x, enum bfd_endian byte_order_x,
 277                const gdb_byte *y, int len_y, enum bfd_endian byte_order_y,
 278                gdb_byte *result, int len_result,
 279                enum bfd_endian byte_order_result)
 280 {
 281   decContext set;
 282   decNumber number1, number2, number3;
 283   gdb_byte dec1[16], dec2[16], dec3[16];
 284
 285   match_endianness (x, len_x, byte_order_x, dec1);
 286   match_endianness (y, len_y, byte_order_y, dec2);
 287
 288   decimal_to_number (dec1, len_x, &number1);
 289   decimal_to_number (dec2, len_y, &number2);
 290
 291   set_decnumber_context (&set, len_result);
 292
 293   switch (op)
 294     {
 295       case BINOP_ADD:
 296         decNumberAdd (&number3, &number1, &number2, &set);
 297         break;
 298       case BINOP_SUB:
 299         decNumberSubtract (&number3, &number1, &number2, &set);
 300         break;
 301       case BINOP_MUL:
 302         decNumberMultiply (&number3, &number1, &number2, &set);
 303         break;
 304       case BINOP_DIV:
 305         decNumberDivide (&number3, &number1, &number2, &set);
 306         break;
 307       case BINOP_EXP:
 308         decNumberPower (&number3, &number1, &number2, &set);
 309         break;
 310      default:
 311         error (_("Operation not valid for decimal floating point number."));
 312         break;
 313     }
 314
 315   /* Check for errors in the DFP operation.  */
 316   decimal_check_errors (&set);
 317
 318   decimal_from_number (&number3, dec3, len_result);
 319
 320   match_endianness (dec3, len_result, byte_order_result, result);
 321 }
 322
 323 /* Returns true if X (which is LEN bytes wide) is the number zero.  */
 324 int
 325 decimal_is_zero (const gdb_byte *x, int len, enum bfd_endian byte_order)
 326 {
 327   decNumber number;
 328   gdb_byte dec[16];
 329
 330   match_endianness (x, len, byte_order, dec);
 331   decimal_to_number (dec, len, &number);
 332
 333   return decNumberIsZero (&number);
 334 }
 335
 336 /* Compares two numbers numerically.  If X is less than Y then the return value
 337    will be -1.  If they are equal, then the return value will be 0.  If X is
 338    greater than the Y then the return value will be 1.  */
 339 int
 340 decimal_compare (const gdb_byte *x, int len_x, enum bfd_endian byte_order_x,
 341                  const gdb_byte *y, int len_y, enum bfd_endian byte_order_y)
 342 {
 343   decNumber number1, number2, result;
 344   decContext set;
 345   gdb_byte dec1[16], dec2[16];
 346   int len_result;
 347
 348   match_endianness (x, len_x, byte_order_x, dec1);
 349   match_endianness (y, len_y, byte_order_y, dec2);
 350
 351   decimal_to_number (dec1, len_x, &number1);
 352   decimal_to_number (dec2, len_y, &number2);
 353
 354   /* Perform the comparison in the larger of the two sizes.  */
 355   len_result = len_x > len_y ? len_x : len_y;
 356   set_decnumber_context (&set, len_result);
 357
 358   decNumberCompare (&result, &number1, &number2, &set);
 359
 360   /* Check for errors in the DFP operation.  */
 361   decimal_check_errors (&set);
 362
 363   if (decNumberIsNaN (&result))
 364     error (_("Comparison with an invalid number (NaN)."));
 365   else if (decNumberIsZero (&result))
 366     return 0;
 367   else if (decNumberIsNegative (&result))
 368     return -1;
 369   else
 370     return 1;
 371 }
 372
 373 /* Convert a decimal value from a decimal type with LEN_FROM bytes to a
 374    decimal type with LEN_TO bytes.  */
 375 void
 376 decimal_convert (const gdb_byte *from, int len_from,
 377                  enum bfd_endian byte_order_from, gdb_byte *to, int len_to,
 378                  enum bfd_endian byte_order_to)
 379 {
 380   decNumber number;
 381   gdb_byte dec[16];
 382
 383   match_endianness (from, len_from, byte_order_from, dec);
 384
 385   decimal_to_number (dec, len_from, &number);
 386   decimal_from_number (&number, dec, len_to);
 387
 388   match_endianness (dec, len_to, byte_order_to, to);
 389 }