src/m68000/cpuextra.c

   1 //
   2 // Stuff that's neither inline or generated by gencpu.c, but depended upon by
   3 // cpuemu.c.
   4 //
   5 // Originally part of UAE by Bernd Schmidt
   6 // and released under the GPL v2 or later
   7 //
   8
   9 #include "cpuextra.h"
  10 #include "cpudefs.h"
  11 #include "inlines.h"
  12
  13
  14 uint16_t last_op_for_exception_3;               // Opcode of faulting instruction
  15 uint32_t last_addr_for_exception_3;             // PC at fault time
  16 uint32_t last_fault_for_exception_3;    // Address that generated the exception
  17
  18 int OpcodeFamily;                                               // Used by cpuemu.c...
  19 int BusCyclePenalty = 0;                                // Used by cpuemu.c...
  20 int CurrentInstrCycles;
  21
  22 struct regstruct regs;
  23
  24
  25 //
  26 // Make displacement effective address for 68000
  27 //
  28 uint32_t get_disp_ea_000(uint32_t base, uint32_t dp)
  29 {
  30         int reg = (dp >> 12) & 0x0F;
  31         int32_t regd = regs.regs[reg];
  32
  33 #if 1
  34         if ((dp & 0x800) == 0)
  35                 regd = (int32_t)(int16_t)regd;
  36
  37         return base + (int8_t)dp + regd;
  38 #else
  39         /* Branch-free code... benchmark this again now that
  40          * things are no longer inline.
  41          */
  42         int32_t regd16;
  43         uint32_t mask;
  44         mask = ((dp & 0x800) >> 11) - 1;
  45         regd16 = (int32_t)(int16_t)regd;
  46         regd16 &= mask;
  47         mask = ~mask;
  48         base += (int8_t)dp;
  49         regd &= mask;
  50         regd |= regd16;
  51         return base + regd;
  52 #endif
  53 }
  54
  55
  56 //
  57 // Create the Status Register from the flags
  58 //
  59 void MakeSR(void)
  60 {
  61         regs.sr = ((regs.s << 13) | (regs.intmask << 8) | (GET_XFLG << 4)
  62                 | (GET_NFLG << 3) | (GET_ZFLG << 2) | (GET_VFLG << 1) | GET_CFLG);
  63 }
  64
  65
  66 //
  67 // Set up the flags from Status Register
  68 //
  69 void MakeFromSR(void)
  70 {
  71         int olds = regs.s;
  72
  73         regs.s = (regs.sr >> 13) & 1;
  74         regs.intmask = (regs.sr >> 8) & 7;
  75         SET_XFLG((regs.sr >> 4) & 1);
  76         SET_NFLG((regs.sr >> 3) & 1);
  77         SET_ZFLG((regs.sr >> 2) & 1);
  78         SET_VFLG((regs.sr >> 1) & 1);
  79         SET_CFLG(regs.sr & 1);
  80
  81         if (olds != regs.s)
  82         {
  83                 if (olds)
  84                 {
  85                         regs.isp = m68k_areg(regs, 7);
  86                         m68k_areg(regs, 7) = regs.usp;
  87                 }
  88                 else
  89                 {
  90                         regs.usp = m68k_areg(regs, 7);
  91                         m68k_areg(regs, 7) = regs.isp;
  92                 }
  93         }
  94
  95         /* Pending interrupts can occur again after a write to the SR: */
  96 //JLH: is this needed?
  97 //      set_special(SPCFLAG_DOINT);
  98 }
  99
 100
 101 //
 102 // Rudimentary exception handling. This is really stripped down from what
 103 // was in Hatari.
 104 /*
 105 NB: Seems that when an address exception occurs, it doesn't get handled properly
 106     as per test1.cof. Need to figure out why it keeps going when it should wedge. :-P
 107 */
 108 //
 109 // Handle exceptions. We need a special case to handle MFP exceptions
 110 // on Atari ST, because it's possible to change the MFP's vector base
 111 // and get a conflict with 'normal' cpu exceptions.
 112 //
 113 #if 0
 114 /*
 115 This is the STOP # function. Dunno if exception handling occurs when it hits here or not, because don't know if the regs.s bit is set or not!
 116 Seems to be...
 117
 118 SR-----------------
 119 1111 11
 120 5432 1098 7654 3210
 121 ---- ---- ---- ----
 122   1    1
 123
 124
 125 */
 126 unsigned long CPUFUNC(op_4e72_5)(uint32_t opcode) /* STOP */
 127 {
 128         OpcodeFamily = 44;
 129         CurrentInstrCycles = 4;
 130
 131         if (!regs.s)
 132         {
 133                 Exception(8, 0, M68000_EXC_SRC_CPU);
 134         }
 135         else
 136         {
 137                 int16_t src = get_iword_prefetch(2);
 138                 regs.sr = src;
 139                 MakeFromSR();
 140                 m68k_setstopped(1);
 141                 m68k_incpc(4);
 142                 fill_prefetch_0();
 143         }
 144
 145         return 4;
 146 }
 147 #endif
 148 //tmp...
 149 void WriteLog(const char * text, ...);
 150 void Exception(int nr, uint32_t oldpc, int ExceptionSource)
 151 {
 152         uint32_t currpc = m68k_getpc(), newpc;
 153
 154 // Need to figure out how to report this stuff without using printf on stdout :-/
 155 #if 0
 156 char excNames[33][64] = {
 157         "???", "???", "Bus Error", "Address Error",
 158         "Illegal Instruction", "Zero Divide", "CHK", "TrapV",
 159         "Privilege Violation", "Trace", "Line A", "Line F",
 160         "???", "???", "Format Error", "Uninitialized Interrupt",
 161         "???", "???", "???", "???",
 162         "???", "???", "???", "???",
 163         "Spurious/Autovector", "???", "???", "???",
 164         "???", "???", "???", "???",
 165         "Trap #"
 166 };
 167
 168 WriteLog("Exception #%i occurred! (%s)\n", nr, (nr < 32 ? excNames[nr] : (nr < 48 ? "Trap #" : "????")));
 169 WriteLog("Vector @ #%i = %08X\n", nr, m68k_read_memory_32(nr * 4));
 170 //abort();
 171 WriteLog("PC = $%08X\n", currpc);
 172 WriteLog("A0 = $%08X A1 = $%08X A2 = $%08X A3 = $%08X\n", m68k_areg(regs, 0), m68k_areg(regs, 1), m68k_areg(regs, 2), m68k_areg(regs, 3));
 173 WriteLog("A4 = $%08X A5 = $%08X A6 = $%08X A7 = $%08X\n", m68k_areg(regs, 4), m68k_areg(regs, 5), m68k_areg(regs, 6), m68k_areg(regs, 7));
 174 WriteLog("D0 = $%08X D1 = $%08X D2 = $%08X D3 = $%08X\n", m68k_dreg(regs, 0), m68k_dreg(regs, 1), m68k_dreg(regs, 2), m68k_dreg(regs, 3));
 175 WriteLog("D4 = $%08X D5 = $%08X D6 = $%08X D7 = $%08X\n", m68k_dreg(regs, 4), m68k_dreg(regs, 5), m68k_dreg(regs, 6), m68k_dreg(regs, 7));
 176 WriteLog("\n");
 177
 178 uint32_t disPC = currpc - 10;
 179 char buffer[128];
 180
 181 do
 182 {
 183         uint32_t oldpc = disPC;
 184         disPC += m68k_disassemble(buffer, disPC, 0);
 185         WriteLog("%s%08X: %s\n", (oldpc == currpc ? ">" : " "), oldpc, buffer);
 186 }
 187 while (disPC < (currpc + 10));
 188 #endif
 189
 190 /*if( nr>=2 && nr<10 )  fprintf(stderr,"Exception (-> %i bombs)!\n",nr);*/
 191
 192         MakeSR();
 193
 194         // Change to supervisor mode if necessary
 195         if (!regs.s)
 196         {
 197                 regs.usp = m68k_areg(regs, 7);
 198                 m68k_areg(regs, 7) = regs.isp;
 199                 regs.s = 1;
 200         }
 201
 202         // Create 68000 style stack frame
 203         m68k_areg(regs, 7) -= 4;                                // Push PC on stack
 204         m68k_write_memory_32(m68k_areg(regs, 7), currpc);
 205         m68k_areg(regs, 7) -= 2;                                // Push SR on stack
 206         m68k_write_memory_16(m68k_areg(regs, 7), regs.sr);
 207
 208 //      LOG_TRACE(TRACE_CPU_EXCEPTION, "cpu exception %d currpc %x buspc %x newpc %x fault_e3 %x op_e3 %hx addr_e3 %x\n",
 209 //      nr, currpc, BusErrorPC, get_long(4 * nr), last_fault_for_exception_3, last_op_for_exception_3, last_addr_for_exception_3);
 210
 211 #if 0
 212         /* 68000 bus/address errors: */
 213         if ((nr == 2 || nr == 3) && ExceptionSource == M68000_EXC_SRC_CPU)
 214         {
 215                 uint16_t specialstatus = 1;
 216
 217                 /* Special status word emulation isn't perfect yet... :-( */
 218                 if (regs.sr & 0x2000)
 219                         specialstatus |= 0x4;
 220
 221                 m68k_areg(regs, 7) -= 8;
 222
 223                 if (nr == 3)     /* Address error */
 224                 {
 225                         specialstatus |= (last_op_for_exception_3 & (~0x1F));   /* [NP] unused bits of specialstatus are those of the last opcode ! */
 226                         put_word(m68k_areg(regs, 7), specialstatus);
 227                         put_long(m68k_areg(regs, 7) + 2, last_fault_for_exception_3);
 228                         put_word(m68k_areg(regs, 7) + 6, last_op_for_exception_3);
 229                         put_long(m68k_areg(regs, 7) + 10, last_addr_for_exception_3);
 230
 231 //JLH: Not now...
 232 #if 0
 233                         if (bExceptionDebugging)
 234                         {
 235                                 fprintf(stderr,"Address Error at address $%x, PC=$%x\n", last_fault_for_exception_3, currpc);
 236                                 DebugUI();
 237                         }
 238 #endif
 239                 }
 240                 else     /* Bus error */
 241                 {
 242                         specialstatus |= (get_word(BusErrorPC) & (~0x1F));      /* [NP] unused bits of special status are those of the last opcode ! */
 243
 244                         if (bBusErrorReadWrite)
 245                                 specialstatus |= 0x10;
 246
 247                         put_word(m68k_areg(regs, 7), specialstatus);
 248                         put_long(m68k_areg(regs, 7) + 2, BusErrorAddress);
 249                         put_word(m68k_areg(regs, 7) + 6, get_word(BusErrorPC)); /* Opcode */
 250
 251                         /* [NP] PC stored in the stack frame is not necessarily pointing to the next instruction ! */
 252                         /* FIXME : we should have a proper model for this, in the meantime we handle specific cases */
 253                         if (get_word(BusErrorPC) == 0x21F8)                     /* move.l $0.w,$24.w (Transbeauce 2 loader) */
 254                                 put_long(m68k_areg(regs, 7) + 10, currpc - 2);          /* correct PC is 2 bytes less than usual value */
 255
 256                         /* Check for double bus errors: */
 257                         if (regs.spcflags & SPCFLAG_BUSERROR)
 258                         {
 259                                 fprintf(stderr, "Detected double bus error at address $%x, PC=$%lx => CPU halted!\n",
 260                                 BusErrorAddress, (long)currpc);
 261                                 unset_special(SPCFLAG_BUSERROR);
 262
 263                                 if (bExceptionDebugging)
 264                                         DebugUI();
 265                                 else
 266                                         DlgAlert_Notice("Detected double bus error => CPU halted!\nEmulation needs to be reset.\n");
 267
 268                                 regs.intmask = 7;
 269                                 m68k_setstopped(true);
 270                                 return;
 271                         }
 272
 273                         if (bExceptionDebugging && BusErrorAddress != 0xFF8A00)
 274                         {
 275                                 fprintf(stderr,"Bus Error at address $%x, PC=$%lx\n", BusErrorAddress, (long)currpc);
 276                                 DebugUI();
 277                         }
 278                 }
 279         }
 280
 281 //Not now...
 282 #if 0
 283         /* Set PC and flags */
 284         if (bExceptionDebugging && get_long(4 * nr) == 0)
 285         {
 286                 write_log("Uninitialized exception handler #%i!\n", nr);
 287                 DebugUI();
 288         }
 289 #endif
 290
 291         newpc = get_long(4 * nr);
 292
 293         if (newpc & 1)                          /* check new pc is odd */
 294         {
 295                 if (nr == 2 || nr == 3)                 /* address error during bus/address error -> stop emulation */
 296                 {
 297                         fprintf(stderr,"Address Error during exception 2/3, aborting new PC=$%x\n", newpc);
 298                         DebugUI();
 299                 }
 300                 else
 301                 {
 302                         fprintf(stderr,"Address Error during exception, new PC=$%x\n", newpc);
 303                         Exception(3, m68k_getpc(), M68000_EXC_SRC_CPU);
 304                 }
 305
 306                 return;
 307         }
 308 #endif
 309
 310         m68k_setpc(m68k_read_memory_32(4 * nr));
 311         fill_prefetch_0();
 312         /* Handle trace flags depending on current state */
 313 //JLH:no        exception_trace(nr);
 314
 315 #if 0
 316         /* Handle exception cycles (special case for MFP) */
 317 //      if (ExceptionSource == M68000_EXC_SRC_INT_MFP)
 318 //      {
 319 //              M68000_AddCycles(44 + 12);                      /* MFP interrupt, 'nr' can be in a different range depending on $fffa17 */
 320 //      }
 321 //      else
 322         if (nr >= 24 && nr <= 31)
 323         {
 324 #if 0
 325                 if (nr == 26)                           /* HBL */
 326                 {
 327                         /* store current cycle pos when then interrupt was received (see video.c) */
 328                         LastCycleHblException = Cycles_GetCounter(CYCLES_COUNTER_VIDEO);
 329                         M68000_AddCycles(44 + 12);              /* Video Interrupt */
 330                 }
 331                 else if (nr == 28)                      /* VBL */
 332                         M68000_AddCycles(44 + 12);              /* Video Interrupt */
 333                 else
 334 #endif
 335                         M68000_AddCycles(44 + 4);                       /* Other Interrupts */
 336         }
 337         else if (nr >= 32 && nr <= 47)
 338         {
 339                 M68000_AddCycles(34 - 4);                       /* Trap (total is 34, but cpuemu.c already adds 4) */
 340         }
 341         else switch(nr)
 342         {
 343                 case 2: M68000_AddCycles(50); break;    /* Bus error */
 344                 case 3: M68000_AddCycles(50); break;    /* Address error */
 345                 case 4: M68000_AddCycles(34); break;    /* Illegal instruction */
 346                 case 5: M68000_AddCycles(38); break;    /* Div by zero */
 347                 case 6: M68000_AddCycles(40); break;    /* CHK */
 348                 case 7: M68000_AddCycles(34); break;    /* TRAPV */
 349                 case 8: M68000_AddCycles(34); break;    /* Privilege violation */
 350                 case 9: M68000_AddCycles(34); break;    /* Trace */
 351                 case 10: M68000_AddCycles(34); break;   /* Line-A - probably wrong */
 352                 case 11: M68000_AddCycles(34); break;   /* Line-F - probably wrong */
 353                 default:
 354                 /* FIXME: Add right cycles value for MFP interrupts and copro exceptions ... */
 355                 if (nr < 64)
 356                         M68000_AddCycles(4);                    /* Coprocessor and unassigned exceptions (???) */
 357                 else
 358                         M68000_AddCycles(44 + 12);              /* Must be a MFP or DSP interrupt */
 359
 360                 break;
 361         }
 362 #endif
 363 }
 364
 365
 366 /*
 367  The routines below take dividend and divisor as parameters.
 368  They return 0 if division by zero, or exact number of cycles otherwise.
 369
 370  The number of cycles returned assumes a register operand.
 371  Effective address time must be added if memory operand.
 372
 373  For 68000 only (not 68010, 68012, 68020, etc).
 374  Probably valid for 68008 after adding the extra prefetch cycle.
 375
 376
 377  Best and worst cases are for register operand:
 378  (Note the difference with the documented range.)
 379
 380
 381  DIVU:
 382
 383  Overflow (always): 10 cycles.
 384  Worst case: 136 cycles.
 385  Best case: 76 cycles.
 386
 387
 388  DIVS:
 389
 390  Absolute overflow: 16-18 cycles.
 391  Signed overflow is not detected prematurely.
 392
 393  Worst case: 156 cycles.
 394  Best case without signed overflow: 122 cycles.
 395  Best case with signed overflow: 120 cycles
 396  */
 397
 398 //
 399 // DIVU
 400 // Unsigned division
 401 //
 402 STATIC_INLINE int getDivu68kCycles_2 (uint32_t dividend, uint16_t divisor)
 403 {
 404         int mcycles;
 405         uint32_t hdivisor;
 406         int i;
 407
 408         if (divisor == 0)
 409                 return 0;
 410
 411         // Overflow
 412         if ((dividend >> 16) >= divisor)
 413                 return (mcycles = 5) * 2;
 414
 415         mcycles = 38;
 416         hdivisor = divisor << 16;
 417
 418         for(i=0; i<15; i++)
 419         {
 420                 uint32_t temp;
 421                 temp = dividend;
 422
 423                 dividend <<= 1;
 424
 425                 // If carry from shift
 426                 if ((int32_t)temp < 0)
 427                         dividend -= hdivisor;
 428                 else
 429                 {
 430                         mcycles += 2;
 431
 432                         if (dividend >= hdivisor)
 433                         {
 434                                 dividend -= hdivisor;
 435                                 mcycles--;
 436                         }
 437                 }
 438         }
 439
 440         return mcycles * 2;
 441 }
 442
 443
 444 // This is called by cpuemu.c
 445 int getDivu68kCycles(uint32_t dividend, uint16_t divisor)
 446 {
 447         int v = getDivu68kCycles_2(dividend, divisor) - 4;
 448 //      write_log ("U%d ", v);
 449         return v;
 450 }
 451
 452
 453 //
 454 // DIVS
 455 // Signed division
 456 //
 457 STATIC_INLINE int getDivs68kCycles_2(int32_t dividend, int16_t divisor)
 458 {
 459         int mcycles;
 460         uint32_t aquot;
 461         int i;
 462
 463         if (divisor == 0)
 464                 return 0;
 465
 466         mcycles = 6;
 467
 468         if (dividend < 0)
 469                 mcycles++;
 470
 471         // Check for absolute overflow
 472         if (((uint32_t)abs(dividend) >> 16) >= (uint16_t)abs(divisor))
 473                 return (mcycles + 2) * 2;
 474
 475         // Absolute quotient
 476         aquot = (uint32_t)abs(dividend) / (uint16_t)abs(divisor);
 477
 478         mcycles += 55;
 479
 480         if (divisor >= 0)
 481         {
 482                 if (dividend >= 0)
 483                         mcycles--;
 484                 else
 485                         mcycles++;
 486         }
 487
 488         // Count 15 msbits in absolute of quotient
 489
 490         for(i=0; i<15; i++)
 491         {
 492                 if ((int16_t)aquot >= 0)
 493                         mcycles++;
 494
 495                 aquot <<= 1;
 496         }
 497
 498         return mcycles * 2;
 499 }
 500
 501
 502 // This is called by cpuemu.c
 503 int getDivs68kCycles(int32_t dividend, int16_t divisor)
 504 {
 505         int v = getDivs68kCycles_2(dividend, divisor) - 4;
 506 //      write_log ("S%d ", v);
 507         return v;
 508 }
 509