arch/parisc/math-emu/decode_exc.c

   1 /*
   2  * Linux/PA-RISC Project (http://www.parisc-linux.org/)
   3  *
   4  * Floating-point emulation code
   5  *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
   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 2, or (at your option)
  10  *    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, write to the Free Software
  19  *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21 /*
  22  * BEGIN_DESC
  23  *
  24  *  File:
  25  *      @(#)    pa/fp/decode_exc.c              $ Revision: $
  26  *
  27  *  Purpose:
  28  *      <<please update with a synopsis of the functionality provided by this file>>
  29  *
  30  *  External Interfaces:
  31  *      <<the following list was autogenerated, please review>>
  32  *      decode_fpu(Fpu_register, trap_counts)
  33  *
  34  *  Internal Interfaces:
  35  *      <<please update>>
  36  *
  37  *  Theory:
  38  *      <<please update with a overview of the operation of this file>>
  39  *
  40  * END_DESC
  41 */
  42
  43 #include <linux/kernel.h>
  44 #include "float.h"
  45 #include "sgl_float.h"
  46 #include "dbl_float.h"
  47 #include "cnv_float.h"
  48 /* #include "types.h" */
  49 #include <asm/signal.h>
  50 #include <asm/siginfo.h>
  51 /* #include <machine/sys/mdep_private.h> */
  52
  53 #undef Fpustatus_register
  54 #define Fpustatus_register Fpu_register[0]
  55
  56 /* General definitions */
  57 #define DOESTRAP 1
  58 #define NOTRAP 0
  59 #define SIGNALCODE(signal, code) ((signal) << 24 | (code));
  60 #define copropbit       1<<31-2 /* bit position 2 */
  61 #define opclass         9       /* bits 21 & 22 */
  62 #define fmt             11      /* bits 19 & 20 */
  63 #define df              13      /* bits 17 & 18 */
  64 #define twobits         3       /* mask low-order 2 bits */
  65 #define fivebits        31      /* mask low-order 5 bits */
  66 #define MAX_EXCP_REG    7       /* number of excpeption registers to check */
  67
  68 /* Exception register definitions */
  69 #define Excp_type(index) Exceptiontype(Fpu_register[index])
  70 #define Excp_instr(index) Instructionfield(Fpu_register[index])
  71 #define Clear_excp_register(index) Allexception(Fpu_register[index]) = 0
  72 #define Excp_format() \
  73     (current_ir >> ((current_ir>>opclass & twobits)==1 ? df : fmt) & twobits)
  74
  75 /* Miscellaneous definitions */
  76 #define Fpu_sgl(index) Fpu_register[index*2]
  77
  78 #define Fpu_dblp1(index) Fpu_register[index*2]
  79 #define Fpu_dblp2(index) Fpu_register[(index*2)+1]
  80
  81 #define Fpu_quadp1(index) Fpu_register[index*2]
  82 #define Fpu_quadp2(index) Fpu_register[(index*2)+1]
  83 #define Fpu_quadp3(index) Fpu_register[(index*2)+2]
  84 #define Fpu_quadp4(index) Fpu_register[(index*2)+3]
  85
  86 /* Single precision floating-point definitions */
  87 #ifndef Sgl_decrement
  88 # define Sgl_decrement(sgl_value) Sall(sgl_value)--
  89 #endif
  90
  91 /* Double precision floating-point definitions */
  92 #ifndef Dbl_decrement
  93 # define Dbl_decrement(dbl_valuep1,dbl_valuep2) \
  94     if ((Dallp2(dbl_valuep2)--) == 0) Dallp1(dbl_valuep1)--
  95 #endif
  96
  97
  98 #define update_trap_counts(Fpu_register, aflags, bflags, trap_counts) { \
  99         aflags=(Fpu_register[0])>>27;   /* assumes zero fill. 32 bit */ \
 100         Fpu_register[0] |= bflags;                                      \
 101 }
 102
 103 u_int
 104 decode_fpu(unsigned int Fpu_register[], unsigned int trap_counts[])
 105 {
 106     unsigned int current_ir, excp;
 107     int target, exception_index = 1;
 108     boolean inexact;
 109     unsigned int aflags;
 110     unsigned int bflags;
 111     unsigned int excptype;
 112
 113
 114     /* Keep stats on how many floating point exceptions (based on type)
 115      * that happen.  Want to keep this overhead low, but still provide
 116      * some information to the customer.  All exits from this routine
 117      * need to restore Fpu_register[0]
 118     */
 119
 120     bflags=(Fpu_register[0] & 0xf8000000);
 121     Fpu_register[0] &= 0x07ffffff;
 122
 123     /* exception_index is used to index the exception register queue.  It
 124      *   always points at the last register that contains a valid exception.  A
 125      *   zero value implies no exceptions (also the initialized value).  Setting
 126      *   the T-bit resets the exception_index to zero.
 127      */
 128
 129     /*
 130      * Check for reserved-op exception.  A reserved-op exception does not
 131      * set any exception registers nor does it set the T-bit.  If the T-bit
 132      * is not set then a reserved-op exception occurred.
 133      *
 134      * At some point, we may want to report reserved op exceptions as
 135      * illegal instructions.
 136      */
 137
 138     if (!Is_tbit_set()) {
 139         update_trap_counts(Fpu_register, aflags, bflags, trap_counts);
 140         return SIGNALCODE(SIGILL, ILL_COPROC);
 141     }
 142
 143     /*
 144      * Is a coprocessor op.
 145      *
 146      * Now we need to determine what type of exception occurred.
 147      */
 148     for (exception_index=1; exception_index<=MAX_EXCP_REG; exception_index++) {
 149         current_ir = Excp_instr(exception_index);
 150           /*
 151            * On PA89: there are 5 different unimplemented exception
 152            * codes: 0x1, 0x9, 0xb, 0x3, and 0x23.  PA-RISC 2.0 adds
 153            * another, 0x2b.  Only these have the low order bit set.
 154            */
 155         excptype = Excp_type(exception_index);
 156         if (excptype & UNIMPLEMENTEDEXCEPTION) {
 157                 /*
 158                  * Clear T-bit and exception register so that
 159                  * we can tell if a trap really occurs while
 160                  * emulating the instruction.
 161                  */
 162                 Clear_tbit();
 163                 Clear_excp_register(exception_index);
 164                 /*
 165                  * Now emulate this instruction.  If a trap occurs,
 166                  * fpudispatch will return a non-zero number
 167                  */
 168                 excp = fpudispatch(current_ir,excptype,0,Fpu_register);
 169                 /* accumulate the status flags, don't lose them as in hpux */
 170                 if (excp) {
 171                         /*
 172                          * We now need to make sure that the T-bit and the
 173                          * exception register contain the correct values
 174                          * before continuing.
 175                          */
 176                         /*
 177                          * Set t-bit since it might still be needed for a
 178                          * subsequent real trap (I don't understand fully -PB)
 179                          */
 180                         Set_tbit();
 181                         /* some of the following code uses
 182                          * Excp_type(exception_index) so fix that up */
 183                         Set_exceptiontype_and_instr_field(excp,current_ir,
 184                          Fpu_register[exception_index]);
 185                         if (excp == UNIMPLEMENTEDEXCEPTION) {
 186                                 /*
 187                                  * it is really unimplemented, so restore the
 188                                  * TIMEX extended unimplemented exception code
 189                                  */
 190                                 excp = excptype;
 191                                 update_trap_counts(Fpu_register, aflags, bflags,
 192                                            trap_counts);
 193                                 return SIGNALCODE(SIGILL, ILL_COPROC);
 194                         }
 195                         /* some of the following code uses excptype, so
 196                          * fix that up too */
 197                         excptype = excp;
 198                 }
 199                 /* handle exceptions other than the real UNIMPLIMENTED the
 200                  * same way as if the hardware had caused them */
 201                 if (excp == NOEXCEPTION)
 202                         /* For now use 'break', should technically be 'continue' */
 203                         break;
 204         }
 205
 206           /*
 207            * In PA89, the underflow exception has been extended to encode
 208            * additional information.  The exception looks like pp01x0,
 209            * where x is 1 if inexact and pp represent the inexact bit (I)
 210            * and the round away bit (RA)
 211            */
 212         if (excptype & UNDERFLOWEXCEPTION) {
 213                 /* check for underflow trap enabled */
 214                 if (Is_underflowtrap_enabled()) {
 215                         update_trap_counts(Fpu_register, aflags, bflags,
 216                                            trap_counts);
 217                         return SIGNALCODE(SIGFPE, FPE_FLTUND);
 218                 } else {
 219                     /*
 220                      * Isn't a real trap; we need to
 221                      * return the default value.
 222                      */
 223                     target = current_ir & fivebits;
 224 #ifndef lint
 225                     if (Ibit(Fpu_register[exception_index])) inexact = TRUE;
 226                     else inexact = FALSE;
 227 #endif
 228                     switch (Excp_format()) {
 229                       case SGL:
 230                         /*
 231                          * If ra (round-away) is set, will
 232                          * want to undo the rounding done
 233                          * by the hardware.
 234                          */
 235                         if (Rabit(Fpu_register[exception_index]))
 236                                 Sgl_decrement(Fpu_sgl(target));
 237
 238                         /* now denormalize */
 239                         sgl_denormalize(&Fpu_sgl(target),&inexact,Rounding_mode());
 240                         break;
 241                       case DBL:
 242                         /*
 243                          * If ra (round-away) is set, will
 244                          * want to undo the rounding done
 245                          * by the hardware.
 246                          */
 247                         if (Rabit(Fpu_register[exception_index]))
 248                                 Dbl_decrement(Fpu_dblp1(target),Fpu_dblp2(target));
 249
 250                         /* now denormalize */
 251                         dbl_denormalize(&Fpu_dblp1(target),&Fpu_dblp2(target),
 252                           &inexact,Rounding_mode());
 253                         break;
 254                     }
 255                     if (inexact) Set_underflowflag();
 256                     /*
 257                      * Underflow can generate an inexact
 258                      * exception.  If inexact trap is enabled,
 259                      * want to do an inexact trap, otherwise
 260                      * set inexact flag.
 261                      */
 262                     if (inexact && Is_inexacttrap_enabled()) {
 263                         /*
 264                          * Set exception field of exception register
 265                          * to inexact, parm field to zero.
 266                          * Underflow bit should be cleared.
 267                          */
 268                         Set_exceptiontype(Fpu_register[exception_index],
 269                          INEXACTEXCEPTION);
 270                         Set_parmfield(Fpu_register[exception_index],0);
 271                         update_trap_counts(Fpu_register, aflags, bflags,
 272                                            trap_counts);
 273                         return SIGNALCODE(SIGFPE, FPE_FLTRES);
 274                     }
 275                     else {
 276                         /*
 277                          * Exception register needs to be cleared.
 278                          * Inexact flag needs to be set if inexact.
 279                          */
 280                         Clear_excp_register(exception_index);
 281                         if (inexact) Set_inexactflag();
 282                     }
 283                 }
 284                 continue;
 285         }
 286         switch(Excp_type(exception_index)) {
 287           case OVERFLOWEXCEPTION:
 288           case OVERFLOWEXCEPTION | INEXACTEXCEPTION:
 289                 /* check for overflow trap enabled */
 290                         update_trap_counts(Fpu_register, aflags, bflags,
 291                                            trap_counts);
 292                 if (Is_overflowtrap_enabled()) {
 293                         update_trap_counts(Fpu_register, aflags, bflags,
 294                                            trap_counts);
 295                         return SIGNALCODE(SIGFPE, FPE_FLTOVF);
 296                 } else {
 297                         /*
 298                          * Isn't a real trap; we need to
 299                          * return the default value.
 300                          */
 301                         target = current_ir & fivebits;
 302                         switch (Excp_format()) {
 303                           case SGL:
 304                                 Sgl_setoverflow(Fpu_sgl(target));
 305                                 break;
 306                           case DBL:
 307                                 Dbl_setoverflow(Fpu_dblp1(target),Fpu_dblp2(target));
 308                                 break;
 309                         }
 310                         Set_overflowflag();
 311                         /*
 312                          * Overflow always generates an inexact
 313                          * exception.  If inexact trap is enabled,
 314                          * want to do an inexact trap, otherwise
 315                          * set inexact flag.
 316                          */
 317                         if (Is_inexacttrap_enabled()) {
 318                                 /*
 319                                  * Set exception field of exception
 320                                  * register to inexact.  Overflow
 321                                  * bit should be cleared.
 322                                  */
 323                                 Set_exceptiontype(Fpu_register[exception_index],
 324                                  INEXACTEXCEPTION);
 325                                 update_trap_counts(Fpu_register, aflags, bflags,
 326                                            trap_counts);
 327                                 return SIGNALCODE(SIGFPE, FPE_FLTRES);
 328                         }
 329                         else {
 330                                 /*
 331                                  * Exception register needs to be cleared.
 332                                  * Inexact flag needs to be set.
 333                                  */
 334                                 Clear_excp_register(exception_index);
 335                                 Set_inexactflag();
 336                         }
 337                 }
 338                 break;
 339           case INVALIDEXCEPTION:
 340           case OPC_2E_INVALIDEXCEPTION:
 341                 update_trap_counts(Fpu_register, aflags, bflags, trap_counts);
 342                 return SIGNALCODE(SIGFPE, FPE_FLTINV);
 343           case DIVISIONBYZEROEXCEPTION:
 344                 update_trap_counts(Fpu_register, aflags, bflags, trap_counts);
 345                 Clear_excp_register(exception_index);
 346                 return SIGNALCODE(SIGFPE, FPE_FLTDIV);
 347           case INEXACTEXCEPTION:
 348                 update_trap_counts(Fpu_register, aflags, bflags, trap_counts);
 349                 return SIGNALCODE(SIGFPE, FPE_FLTRES);
 350           default:
 351                 update_trap_counts(Fpu_register, aflags, bflags, trap_counts);
 352                 printk("%s(%d) Unknown FPU exception 0x%x\n", __FILE__,
 353                         __LINE__, Excp_type(exception_index));
 354                 return SIGNALCODE(SIGILL, ILL_COPROC);
 355           case NOEXCEPTION:     /* no exception */
 356                 /*
 357                  * Clear exception register in case
 358                  * other fields are non-zero.
 359                  */
 360                 Clear_excp_register(exception_index);
 361                 break;
 362         }
 363     }
 364     /*
 365      * No real exceptions occurred.
 366      */
 367     Clear_tbit();
 368     update_trap_counts(Fpu_register, aflags, bflags, trap_counts);
 369     return(NOTRAP);
 370 }