tm.c

一个小型C语言编译器

        }
      iMem[loc].iop = op;
      iMem[loc].iarg1 = arg1;
      iMem[loc].iarg2 = arg2;
      iMem[loc].iarg3 = arg3;
    }
  }
  return TRUE;
} /* readInstructions */


/********************************************/
STEPRESULT stepTM (void)
{ INSTRUCTION currentinstruction  ;
  int pc  ;
  int r,s,t,m  ;
  int ok ;

  pc = reg[PC_REG] ;
  if ( (pc < 0) || (pc > IADDR_SIZE)  )
      return srIMEM_ERR ;
  reg[PC_REG] = pc + 1 ;
  currentinstruction = iMem[ pc ] ;
  switch (opClass(currentinstruction.iop) )
  { case opclRR :
    /***********************************/
      r = currentinstruction.iarg1 ;
      s = currentinstruction.iarg2 ;
      t = currentinstruction.iarg3 ;
      break;

    case opclRM :
    /***********************************/
      r = currentinstruction.iarg1 ;
      s = currentinstruction.iarg3 ;
      m = currentinstruction.iarg2 + reg[s] ;
      if ( (m < 0) || (m > DADDR_SIZE))
         return srDMEM_ERR ;
      break;

    case opclRA :
    /***********************************/
      r = currentinstruction.iarg1 ;
      s = currentinstruction.iarg3 ;
      m = currentinstruction.iarg2 + reg[s] ;
      break;
  } /* case */

  switch ( currentinstruction.iop)
  { /* RR instructions */
    case opHALT :
    /***********************************/
      printf("HALT: %1d,%1d,%1d\n",r,s,t);
      return srHALT ;
      /* break; */

    case opIN :
    /***********************************/
      do
      { printf("Enter value for IN instruction: ") ;
        fflush (stdin);
        fflush (stdout);
        gets(in_Line);
        lineLen = strlen(in_Line) ;
        inCol = 0;
        ok = getNum();
        if ( ! ok ) printf ("Illegal value\n");
        else reg[r] = num;
      }
      while (! ok);
      break;

    case opOUT :  
      printf ("OUT instruction prints: %d\n", reg[r] ) ;
      break;
    case opADD :  reg[r] = reg[s] + reg[t] ;  break;
    case opSUB :  reg[r] = reg[s] - reg[t] ;  break;
    case opMUL :  reg[r] = reg[s] * reg[t] ;  break;

    case opDIV :
    /***********************************/
      if ( reg[t] != 0 ) reg[r] = reg[s] / reg[t];
      else return srZERODIVIDE ;
      break;

    /*************** RM instructions ********************/
    case opLD :    reg[r] = dMem[m] ;  break;
    case opST :    dMem[m] = reg[r] ;  break;

    /*************** RA instructions ********************/
    case opLDA :    reg[r] = m ; break;
    case opLDC :    reg[r] = currentinstruction.iarg2 ;   break;
    case opJLT :    if ( reg[r] <  0 ) reg[PC_REG] = m ; break;
    case opJLE :    if ( reg[r] <=  0 ) reg[PC_REG] = m ; break;
    case opJGT :    if ( reg[r] >  0 ) reg[PC_REG] = m ; break;
    case opJGE :    if ( reg[r] >=  0 ) reg[PC_REG] = m ; break;
    case opJEQ :    if ( reg[r] == 0 ) reg[PC_REG] = m ; break;
    case opJNE :    if ( reg[r] != 0 ) reg[PC_REG] = m ; break;

    /* end of legal instructions */
  } /* case */
  return srOKAY ;
} /* stepTM */

/********************************************/
int doCommand (void)
{ char cmd;
  int stepcnt=0, i;
  int printcnt;
  int stepResult;
  int regNo, loc;
  do
  { printf ("Enter command: ");
    fflush (stdin);
    fflush (stdout);
    gets(in_Line);
    lineLen = strlen(in_Line);
    inCol = 0;
  }
  while (! getWord ());

  cmd = word[0] ;
  switch ( cmd )
  { case 't' :
    /***********************************/
      traceflag = ! traceflag ;
      printf("Tracing now ");
      if ( traceflag ) printf("on.\n"); else printf("off.\n");
      break;

    case 'h' :
    /***********************************/
      printf("Commands are:\n");
      printf("   s(tep <n>      "\
             "Execute n (default 1) TM instructions\n");
      printf("   g(o            "\
             "Execute TM instructions until HALT\n");
      printf("   r(egs          "\
             "Print the contents of the registers\n");
      printf("   i(Mem <b <n>>  "\
             "Print n iMem locations starting at b\n");
      printf("   d(Mem <b <n>>  "\
             "Print n dMem locations starting at b\n");
      printf("   t(race         "\
             "Toggle instruction trace\n");
      printf("   p(rint         "\
             "Toggle print of total instructions executed"\
             " ('go' only)\n");
      printf("   c(lear         "\
             "Reset simulator for new execution of program\n");
      printf("   h(elp          "\
             "Cause this list of commands to be printed\n");
      printf("   q(uit          "\
             "Terminate the simulation\n");
      break;

    case 'p' :
    /***********************************/
      icountflag = ! icountflag ;
      printf("Printing instruction count now ");
      if ( icountflag ) printf("on.\n"); else printf("off.\n");
      break;

    case 's' :
    /***********************************/
      if ( atEOL ())  stepcnt = 1;
      else if ( getNum ())  stepcnt = abs(num);
      else   printf("Step count?\n");
      break;

    case 'g' :   stepcnt = 1 ;     break;

    case 'r' :
    /***********************************/
      for (i = 0; i < NO_REGS; i++)
      { printf("%1d: %4d    ", i,reg[i]);
        if ( (i % 4) == 3 ) printf ("\n");
      }
      break;

    case 'i' :
    /***********************************/
      printcnt = 1 ;
      if ( getNum ())
      { iloc = num ;
        if ( getNum ()) printcnt = num ;
      }
      if ( ! atEOL ())
        printf ("Instruction locations?\n");
      else
      { while ((iloc >= 0) && (iloc < IADDR_SIZE)
                && (printcnt > 0) )
        { writeInstruction(iloc);
          iloc++ ;
          printcnt-- ;
        }
      }
      break;

    case 'd' :
    /***********************************/
      printcnt = 1 ;
      if ( getNum  ())
      { dloc = num ;
        if ( getNum ()) printcnt = num ;
      }
      if ( ! atEOL ())
        printf("Data locations?\n");
      else
      { while ((dloc >= 0) && (dloc < DADDR_SIZE)
                  && (printcnt > 0))
        { printf("%5d: %5d\n",dloc,dMem[dloc]);
          dloc++;
          printcnt--;
        }
      }
      break;

    case 'c' :
    /***********************************/
      iloc = 0;
      dloc = 0;
      stepcnt = 0;
      for (regNo = 0;  regNo < NO_REGS ; regNo++)
            reg[regNo] = 0 ;
      dMem[0] = DADDR_SIZE - 1 ;
      for (loc = 1 ; loc < DADDR_SIZE ; loc++)
            dMem[loc] = 0 ;
      break;

    case 'q' : return FALSE;  /* break; */

    default : printf("Command %c unknown.\n", cmd); break;
  }  /* case */
  stepResult = srOKAY;
  if ( stepcnt > 0 )
  { if ( cmd == 'g' )
    { stepcnt = 0;
      while (stepResult == srOKAY)
      { iloc = reg[PC_REG] ;
        if ( traceflag ) writeInstruction( iloc ) ;
        stepResult = stepTM ();
        stepcnt++;
      }
      if ( icountflag )
        printf("Number of instructions executed = %d\n",stepcnt);
    }
    else
    { while ((stepcnt > 0) && (stepResult == srOKAY))
      { iloc = reg[PC_REG] ;
        if ( traceflag ) writeInstruction( iloc ) ;
        stepResult = stepTM ();
        stepcnt-- ;
      }
    }
    printf( "%s\n",stepResultTab[stepResult] );
  }
  return TRUE;
} /* doCommand */


/********************************************/
/* E X E C U T I O N   B E G I N S   H E R E */
/********************************************/

main( int argc, char * argv[] )
{ if (argc != 2)
  { printf("usage: %s <filename>\n",argv[0]);
    exit(1);
  }
  strcpy(pgmName,argv[1]) ;
  if (strchr (pgmName, '.') == NULL)
     strcat(pgmName,".tm");
  pgm = fopen(pgmName,"r");
  if (pgm == NULL)
  { printf("file '%s' not found\n",pgmName);
    exit(1);
  }

  /* read the program */
  if ( ! readInstructions ())
         exit(1) ;
  /* switch input file to terminal */
  /* reset( input ); */
  /* read-eval-print */
  printf("TM  simulation (enter h for help)...\n");
  do
     done = ! doCommand ();
  while (! done );
  printf("Simulation done.\n");
  return 0;
}