thumbemu.c

来自「这是Skyeye 0.9 版本的源代码」· C语言 代码 · 共 498 行 · 第 1/2 页

	    0xE7800000,		/* STR  Rd,[Rb,Ro] */
	    0xE7C00000,		/* STRB Rd,[Rb,Ro] */
	    0xE7900000,		/* LDR  Rd,[Rb,Ro] */
	    0xE7D00000		/* LDRB Rd,[Rb,Ro] */
	  };
	  *ainstr = subset[(tinstr & 0x0C00) >> 10]	/* base */
	    | ((tinstr & 0x0007) << (12 - 0))	/* Rd */
	    | ((tinstr & 0x0038) << (16 - 3))	/* Rb */
	    | ((tinstr & 0x01C0) >> 6);	/* Ro */
	}
      else
	{
	  /* Format 8 */
	  ARMword subset[4] = {
	    0xE18000B0,		/* STRH  Rd,[Rb,Ro] */
	    0xE19000D0,		/* LDRSB Rd,[Rb,Ro] */
	    0xE19000B0,		/* LDRH  Rd,[Rb,Ro] */
	    0xE19000F0		/* LDRSH Rd,[Rb,Ro] */
	  };
	  *ainstr = subset[(tinstr & 0x0C00) >> 10]	/* base */
	    | ((tinstr & 0x0007) << (12 - 0))	/* Rd */
	    | ((tinstr & 0x0038) << (16 - 3))	/* Rb */
	    | ((tinstr & 0x01C0) >> 6);	/* Ro */
	}
      break;
    case 12:			/* STR Rd,[Rb,#imm5] */
    case 13:			/* LDR Rd,[Rb,#imm5] */
    case 14:			/* STRB Rd,[Rb,#imm5] */
    case 15:			/* LDRB Rd,[Rb,#imm5] */
      /* Format 9 */
      {
	ARMword subset[4] = {
	  0xE5800000,		/* STR  Rd,[Rb,#imm5] */
	  0xE5900000,		/* LDR  Rd,[Rb,#imm5] */
	  0xE5C00000,		/* STRB Rd,[Rb,#imm5] */
	  0xE5D00000		/* LDRB Rd,[Rb,#imm5] */
	};
	/* The offset range defends on whether we are transferring a
	   byte or word value: */
	*ainstr = subset[(tinstr & 0x1800) >> 11]	/* base */
	  | ((tinstr & 0x0007) << (12 - 0))	/* Rd */
	  | ((tinstr & 0x0038) << (16 - 3))	/* Rb */
	  | ((tinstr & 0x07C0) >> (6 - ((tinstr & (1 << 12)) ? 0 : 2)));	/* off5 */
      }
      break;
    case 16:			/* STRH Rd,[Rb,#imm5] */
    case 17:			/* LDRH Rd,[Rb,#imm5] */
      /* Format 10 */
      *ainstr = ((tinstr & (1 << 11))	/* base */
		 ? 0xE1D000B0	/* LDRH */
		 : 0xE1C000B0)	/* STRH */
	| ((tinstr & 0x0007) << (12 - 0))	/* Rd */
	| ((tinstr & 0x0038) << (16 - 3))	/* Rb */
	| ((tinstr & 0x01C0) >> (6 - 1))	/* off5, low nibble */
	| ((tinstr & 0x0600) >> (9 - 8));	/* off5, high nibble */
      break;
    case 18:			/* STR Rd,[SP,#imm8] */
    case 19:			/* LDR Rd,[SP,#imm8] */
      /* Format 11 */
      *ainstr = ((tinstr & (1 << 11))	/* base */
		 ? 0xE59D0000	/* LDR */
		 : 0xE58D0000)	/* STR */
	| ((tinstr & 0x0700) << (12 - 8))	/* Rd */
	| ((tinstr & 0x00FF) << 2);	/* off8 */
      break;
    case 20:			/* ADD Rd,PC,#imm8 */
    case 21:			/* ADD Rd,SP,#imm8 */
      /* Format 12 */
      if ((tinstr & (1 << 11)) == 0)
	{
	  /* NOTE: The PC value used here should by word aligned */
	  /* We encode shift-left-by-2 in the rotate immediate field,
	     so no shift of off8 is needed.  */
	  *ainstr = 0xE28F0F00	/* base */
	    | ((tinstr & 0x0700) << (12 - 8))	/* Rd */
	    | (tinstr & 0x00FF);	/* off8 */
	}
      else
	{
	  /* We encode shift-left-by-2 in the rotate immediate field,
	     so no shift of off8 is needed.  */
	  *ainstr = 0xE28D0F00	/* base */
	    | ((tinstr & 0x0700) << (12 - 8))	/* Rd */
	    | (tinstr & 0x00FF);	/* off8 */
	}
      break;
    case 22:
    case 23:
      if ((tinstr & 0x0F00) == 0x0000)
	{
	  /* Format 13 */
	  /* NOTE: The instruction contains a shift left of 2
	     equivalent (implemented as ROR #30): */
	  *ainstr = ((tinstr & (1 << 7))	/* base */
		     ? 0xE24DDF00	/* SUB */
		     : 0xE28DDF00)	/* ADD */
	    | (tinstr & 0x007F);	/* off7 */
	}
      else if ((tinstr & 0x0F00) == 0x0e00)
	*ainstr = 0xEF000000 | SWI_Breakpoint;
      else
	{
	  /* Format 14 */
	  ARMword subset[4] = {
	    0xE92D0000,		/* STMDB sp!,{rlist}    */
	    0xE92D4000,		/* STMDB sp!,{rlist,lr} */
	    0xE8BD0000,		/* LDMIA sp!,{rlist}    */
	    0xE8BD8000		/* LDMIA sp!,{rlist,pc} */
	  };
	  *ainstr = subset[((tinstr & (1 << 11)) >> 10) | ((tinstr & (1 << 8)) >> 8)]	/* base */
	    | (tinstr & 0x00FF);	/* mask8 */
	}
      break;
    case 24:			/* STMIA */
    case 25:			/* LDMIA */
      /* Format 15 */
      *ainstr = ((tinstr & (1 << 11))	/* base */
		 ? 0xE8B00000	/* LDMIA */
		 : 0xE8A00000)	/* STMIA */
	| ((tinstr & 0x0700) << (16 - 8))	/* Rb */
	| (tinstr & 0x00FF);	/* mask8 */
      break;
    case 26:			/* Bcc */
    case 27:			/* Bcc/SWI */
      if ((tinstr & 0x0F00) == 0x0F00)
	{
	  /* Format 17 : SWI */
	  *ainstr = 0xEF000000;
	  /* Breakpoint must be handled specially.  */
	  if ((tinstr & 0x00FF) == 0x18)
	    *ainstr |= ((tinstr & 0x00FF) << 16);
	  /* New breakpoint value.  See gdb/arm-tdep.c  */
	  else if ((tinstr & 0x00FF) == 0xFE)
	    *ainstr |= SWI_Breakpoint;
	  else
	    *ainstr |= (tinstr & 0x00FF);
	}
      else if ((tinstr & 0x0F00) != 0x0E00)
	{
	  /* Format 16 */
	  int doit = FALSE;
	  /* TODO: Since we are doing a switch here, we could just add
	     the SWI and undefined instruction checks into this
	     switch to same on a couple of conditionals: */
	  switch ((tinstr & 0x0F00) >> 8)
	    {
	    case EQ:
	      doit = ZFLAG;
	      break;
	    case NE:
	      doit = !ZFLAG;
	      break;
	    case VS:
	      doit = VFLAG;
	      break;
	    case VC:
	      doit = !VFLAG;
	      break;
	    case MI:
	      doit = NFLAG;
	      break;
	    case PL:
	      doit = !NFLAG;
	      break;
	    case CS:
	      doit = CFLAG;
	      break;
	    case CC:
	      doit = !CFLAG;
	      break;
	    case HI:
	      doit = (CFLAG && !ZFLAG);
	      break;
	    case LS:
	      doit = (!CFLAG || ZFLAG);
	      break;
	    case GE:
	      doit = ((!NFLAG && !VFLAG) || (NFLAG && VFLAG));
	      break;
	    case LT:
	      doit = ((NFLAG && !VFLAG) || (!NFLAG && VFLAG));
	      break;
	    case GT:
	      doit = ((!NFLAG && !VFLAG && !ZFLAG)
		      || (NFLAG && VFLAG && !ZFLAG));
	      break;
	    case LE:
	      doit = ((NFLAG && !VFLAG) || (!NFLAG && VFLAG)) || ZFLAG;
	      break;
	    }
	  if (doit)
	    {
	      state->Reg[15] = (pc + 4
				+ (((tinstr & 0x7F) << 1)
				   | ((tinstr & (1 << 7)) ? 0xFFFFFF00 : 0)));
	      FLUSHPIPE;
	    }
	  valid = t_branch;
	}
      else			/* UNDEFINED : cc=1110(AL) uses different format */
	valid = t_undefined;
      break;
    case 28:			/* B */
      /* Format 18 */
      state->Reg[15] = (pc + 4
			+ (((tinstr & 0x3FF) << 1)
			   | ((tinstr & (1 << 10)) ? 0xFFFFF800 : 0)));
      FLUSHPIPE;
      valid = t_branch;
      break;
    case 29:			/* UNDEFINED */
      valid = t_undefined;
      break;
    case 30:			/* BL instruction 1 */
      /* Format 19 */
      /* There is no single ARM instruction equivalent for this Thumb
         instruction. To keep the simulation simple (from the user
         perspective) we check if the following instruction is the
         second half of this BL, and if it is we simulate it
         immediately.  */
      state->Reg[14] = state->Reg[15]
	+ (((tinstr & 0x07FF) << 12)
	   | ((tinstr & (1 << 10)) ? 0xFF800000 : 0));
      valid = t_branch;		/* in-case we don't have the 2nd half */
      tinstr = next_instr;	/* move the instruction down */
      if (((tinstr & 0xF800) >> 11) != 31)
	break;			/* exit, since not correct instruction */
      /* else we fall through to process the second half of the BL */
      pc += 2;			/* point the pc at the 2nd half */
    case 31:			/* BL instruction 2 */
      /* Format 19 */
      /* There is no single ARM instruction equivalent for this
         instruction. Also, it should only ever be matched with the
         fmt19 "BL instruction 1" instruction. However, we do allow
         the simulation of it on its own, with undefined results if
         r14 is not suitably initialised.  */
      {
	ARMword tmp = (pc + 2);
	state->Reg[15] = (state->Reg[14] + ((tinstr & 0x07FF) << 1));
	state->Reg[14] = (tmp | 1);
	valid = t_branch;
	FLUSHPIPE;
      }
      break;
    }

  return valid;
}