tc-tahoe.c

基于4个mips核的noc设计

	  titP->tit_error = _("Unknown operator");
	  count = 0;
	  titP->tit_opcode = 0;
	}
      else
	{
	  /*
       * We found a match! So let's pick up as many operands as the
       * instruction wants, and even gripe if there are too many.
       * We expect comma to seperate each operand.
       * We let instring track the text, while p tracks a part of the
       * struct tot.
       */

	  count = 0;		/* no operands seen yet */
	  instring = p + (*p != '\0');	/* point past the operation code */
	  /* tip_op() screws with the input_line_pointer, so save it before
	 I jump in */
	  save_input_line_pointer = input_line_pointer;
	  for (p = twP->args, operandp = titP->tit_operand;
	       !*alloperr && *p;
	       operandp++, p += 2)
	    {
	      /*
	 * Here to parse one operand. Leave instring pointing just
	 * past any one ',' that marks the end of this operand.
	 */
	      if (!p[1])
		as_fatal (_("Compiler bug: ODD number of bytes in arg structure %s."),
			  twP->args);
	      else if (*instring)
		{
		  for (q = instring; (*q != ',' && *q != '\0'); q++)
		    {
		      if (*q == '\'' && q[1] != '\0')	/* Jump quoted characters */
			q++;
		    }
		  c = *q;
		  /*
	   * Q points to ',' or '\0' that ends argument. C is that
	   * character.
	   */
		  *q = '\0';
		  operandp->top_access = p[0];
		  operandp->top_width = p[1];
		  tip_op (instring - 1, operandp);
		  *q = c;	/* Restore input text.  */
		  if (*(operandp->top_error))
		    {
		      alloperr = operandp->top_error;
		    }
		  instring = q + (c ? 1 : 0);	/* next operand (if any) */
		  count++;	/*  won another argument, may have an operr */
		}
	      else
		alloperr = _("Not enough operands");
	    }
	  /* Restore the pointer.  */
	  input_line_pointer = save_input_line_pointer;

	  if (!*alloperr)
	    {
	      if (*instring == ' ')
		instring++;	/* Skip whitespace.  */
	      if (*instring)
		alloperr = _("Too many operands");
	    }
	  titP->tit_error = alloperr;
	}
    }

  titP->tit_opcode = twP->code;	/* The op-code.  */
  titP->tit_operands = count;
}				/* tip */

/* md_assemble() emit frags for 1 instruction */
void
md_assemble (instruction_string)
     char *instruction_string;	/* A string: assemble 1 instruction.  */
{
  char *p;
  register struct top *operandP;/* An operand. Scans all operands.  */
  /*  char c_save;	fixme: remove this line *//* What used to live after an expression.  */
  /*  struct frag *fragP;	fixme: remove this line *//* Fragment of code we just made.  */
  /*  register struct top *end_operandP; fixme: remove this line *//* -> slot just after last operand
					Limit of the for (each operand).  */
  register expressionS *expP;	/* -> expression values for this operand */

  /* These refer to an instruction operand expression.  */
  segT to_seg;			/* Target segment of the address.	 */

  register valueT this_add_number;
  register symbolS *this_add_symbol;	/* +ve (minuend) symbol.  */

  /*  tahoe_opcodeT opcode_as_number; fixme: remove this line *//* The opcode as a number.  */
  char *opcodeP;		/* Where it is in a frag.  */
  /*  char *opmodeP;	fixme: remove this line *//* Where opcode type is, in a frag.  */

  int dispsize;			/* From top_dispsize: tahoe_operand_width
				   (in bytes) */
  int is_undefined;		/* 1 if operand expression's
				   segment not known yet.  */
  int pc_rel;			/* Is this operand pc relative? */

  /* Decode the operand.  */
  tip (&t, instruction_string);

  /*
   * Check to see if this operand decode properly.
   * Notice that we haven't made any frags yet.
   * If it goofed, then this instruction will wedge in any pass,
   * and we can safely flush it, without causing interpass symbol phase
   * errors. That is, without changing label values in different passes.
   */
  if (*t.tit_error)
    {
      as_warn (_("Ignoring statement due to \"%s\""), t.tit_error);
    }
  else
    {
      /* We saw no errors in any operands - try to make frag(s) */
      /* Emit op-code.  */
      /* Remember where it is, in case we want to modify the op-code later.  */
      opcodeP = frag_more (1);
      *opcodeP = t.tit_opcode;
      /* Now do each operand.  */
      for (operandP = t.tit_operand;
	   operandP < t.tit_operand + t.tit_operands;
	   operandP++)
	{			/* for each operand */
	  expP = &(operandP->exp_of_operand);
	  if (operandP->top_ndx >= 0)
	    {
	      /* Indexed addressing byte
	   Legality of indexed mode already checked: it is OK */
	      FRAG_APPEND_1_CHAR (0x40 + operandP->top_ndx);
	    }			/* if(top_ndx>=0) */

	  /* Here to make main operand frag(s).  */
	  this_add_number = expP->X_add_number;
	  this_add_symbol = expP->X_add_symbol;
	  to_seg = operandP->seg_of_operand;
	  know (to_seg == SEG_UNKNOWN || \
		to_seg == SEG_ABSOLUTE || \
		to_seg == SEG_DATA || \
		to_seg == SEG_TEXT || \
		to_seg == SEG_BSS);
	  is_undefined = (to_seg == SEG_UNKNOWN);
	  /* Do we know how big this opperand is? */
	  dispsize = operandP->top_dispsize;
	  pc_rel = 0;
	  /* Deal with the branch possabilities. (Note, this doesn't include
	 jumps.)*/
	  if (operandP->top_access == 'b')
	    {
	      /* Branches must be expressions. A psuedo branch can also jump to
	   an absolute address.  */
	      if (to_seg == now_seg || is_undefined)
		{
		  /* If is_undefined, then it might BECOME now_seg by relax time.  */
		  if (dispsize)
		    {
		      /* I know how big the branch is supposed to be (it's a normal
	       branch), so I set up the frag, and let GAS do the rest.  */
		      p = frag_more (dispsize);
		      fix_new (frag_now, p - frag_now->fr_literal,
			       this_add_symbol, this_add_number,
			       size_to_fx (dispsize, 1),
			       NULL);
		    }
		  else
		    {
		      /* (to_seg==now_seg || to_seg == SEG_UNKNOWN) && dispsize==0 */
		      /* If we don't know how big it is, then its a synthetic branch,
	       so we set up a simple relax state.  */
		      switch (operandP->top_width)
			{
			case TAHOE_WIDTH_CONDITIONAL_JUMP:
			  /* Simple (conditional) jump. I may have to reverse the
		 condition of opcodeP, and then jump to my destination.
		 I set 1 byte aside for the branch off set, and could need 6
		 more bytes for the pc_rel jump */
			  frag_var (rs_machine_dependent, 7, 1,
				    ENCODE_RELAX (STATE_CONDITIONAL_BRANCH,
				    is_undefined ? STATE_UNDF : STATE_BYTE),
				 this_add_symbol, this_add_number, opcodeP);
			  break;
			case TAHOE_WIDTH_ALWAYS_JUMP:
			  /* Simple (unconditional) jump. I may have to convert this to
		 a word branch, or an absolute jump.  */
			  frag_var (rs_machine_dependent, 5, 1,
				    ENCODE_RELAX (STATE_ALWAYS_BRANCH,
				    is_undefined ? STATE_UNDF : STATE_BYTE),
				 this_add_symbol, this_add_number, opcodeP);
			  break;
			  /* The smallest size for the next 2 cases is word.  */
			case TAHOE_WIDTH_BIG_REV_JUMP:
			  frag_var (rs_machine_dependent, 8, 2,
				    ENCODE_RELAX (STATE_BIG_REV_BRANCH,
				    is_undefined ? STATE_UNDF : STATE_WORD),
				    this_add_symbol, this_add_number,
				    opcodeP);
			  break;
			case TAHOE_WIDTH_BIG_NON_REV_JUMP:
			  frag_var (rs_machine_dependent, 10, 2,
				    ENCODE_RELAX (STATE_BIG_NON_REV_BRANCH,
				    is_undefined ? STATE_UNDF : STATE_WORD),
				    this_add_symbol, this_add_number,
				    opcodeP);
			  break;
			default:
			  as_fatal (_("Compliler bug: Got a case (%d) I wasn't expecting."),
				    operandP->top_width);
			}
		    }
		}
	      else
		{
		  /* to_seg != now_seg && to_seg != seg_unknown (still in branch)
	     In other words, I'm jumping out of my segment so extend the
	     branches to jumps, and let GAS fix them.  */

		  /* These are "branches" what will always be branches around a jump
	     to the correct addresss in real life.
	     If to_seg is SEG_ABSOLUTE, just encode the branch in,
	     else let GAS fix the address.  */

		  switch (operandP->top_width)
		    {
		      /* The theory:
	       For SEG_ABSOLUTE, then mode is ABSOLUTE_ADDR, jump
	       to that addresss (not pc_rel).
	       For other segs, address is a long word PC rel jump.  */
		    case TAHOE_WIDTH_CONDITIONAL_JUMP:
		      /* b<cond> */
		      /* To reverse the condition in a TAHOE branch,
	       complement bit 4 */
		      *opcodeP ^= 0x10;
		      p = frag_more (7);
		      *p++ = 6;
		      *p++ = TAHOE_JMP;
		      *p++ = (operandP->top_mode ==
			      TAHOE_ABSOLUTE_ADDR ? TAHOE_ABSOLUTE_ADDR :
			      TAHOE_PC_REL_LONG);
		      fix_new (frag_now, p - frag_now->fr_literal,
			       this_add_symbol, this_add_number,
		       (to_seg != SEG_ABSOLUTE) ? FX_PCREL32 : FX_32, NULL);
		      /*
	     * Now (eg)	BLEQ	1f
	     *		JMP	foo
	     *	1:
	     */
		      break;
		    case TAHOE_WIDTH_ALWAYS_JUMP:
		      /* br, just turn it into a jump */
		      *opcodeP = TAHOE_JMP;
		      p = frag_more (5);
		      *p++ = (operandP->top_mode ==
			      TAHOE_ABSOLUTE_ADDR ? TAHOE_ABSOLUTE_ADDR :
			      TAHOE_PC_REL_LONG);
		      fix_new (frag_now, p - frag_now->fr_literal,
			       this_add_symbol, this_add_number,
		       (to_seg != SEG_ABSOLUTE) ? FX_PCREL32 : FX_32, NULL);
		      /* Now (eg) JMP foo */
		      break;
		    case TAHOE_WIDTH_BIG_REV_JUMP:
		      p = frag_more (8);
		      *opcodeP ^= 0x10;
		      *p++ = 0;
		      *p++ = 6;
		      *p++ = TAHOE_JMP;
		      *p++ = (operandP->top_mode ==
			      TAHOE_ABSOLUTE_ADDR ? TAHOE_ABSOLUTE_ADDR :
			      TAHOE_PC_REL_LONG);
		      fix_new (frag_now, p - frag_now->fr_literal,
			       this_add_symbol, this_add_number,
		       (to_seg != SEG_ABSOLUTE) ? FX_PCREL32 : FX_32, NULL);
		      /*
	     * Now (eg)	ACBx	1f
	     *		JMP     foo
	     *	1:
	     */
		      break;
		    case TAHOE_WIDTH_BIG_NON_REV_JUMP:
		      p = frag_more (10);
		      *p++ = 0;
		      *p++ = 2;
		      *p++ = TAHOE_BRB;
		      *p++ = 6;
		      *p++ = TAHOE_JMP;
		      *p++ = (operandP->top_mode ==
			      TAHOE_ABSOLUTE_ADDR ? TAHOE_ABSOLUTE_ADDR :
			      TAHOE_PC_REL_LONG);
		      fix_new (frag_now, p - frag_now->fr_literal,
			       this_add_symbol, this_add_number,
		       (to_seg != SEG_ABSOLUTE) ? FX_PCREL32 : FX_32, NULL);
		      /*
	     * Now (eg)	xOBxxx	1f
	     *		BRB	2f
	     *	1:	JMP	@#foo
	     *	2:
	     */
		      break;
		    case 'b':
		    case 'w':
		      as_warn (_("Real branch displacements must be expressions."));
		      break;
		    default:
		      as_fatal (_("Complier error: I got an unknown synthetic branch :%c"),
				operandP->top_width);
		      break;
		    }
		}
	    }
	  else
	    {
	      /* It ain't a branch operand.  */
	      switch (operandP->top_mode)
		{
		  /* Auto-foo access, only works for one reg (SP)
	     so the only thing needed is the mode.  */
		case TAHOE_AUTO_DEC:
		case TAHOE_AUTO_INC:
		case TAHOE_AUTO_INC_DEFERRED:
		  FRAG_APPEND_1_CHAR (operandP->top_mode);
		  break;

		  /* Numbered Register only access. Only thing needed is the
	     mode + Register number */
		case TAHOE_DIRECT_REG:
		case TAHOE_REG_DEFERRED:
		  FRAG_APPEND_1_CHAR (operandP->top_mode + operandP->top_reg);
		  break;

		  /* An absolute address. It's size is always 5 bytes.
	     (mode_type + 4 byte address).  */
		case TAHOE_ABSOLUTE_ADDR:
		  know ((this_add_symbol == NULL));
		  p = frag_more (5);
		  *p = TAHOE_ABSOLUTE_ADDR;
		  md_number_to_chars (p + 1, this_add_number, 4);
		  break;

		  /* Immediate data. If the size isn't known, then it's an address
	     + and offset, which is 4 bytes big.  */
		case TAHOE_IMMEDIATE:
		  if (this_add_symbol != NULL)
		    {
		      p = frag_more (5);
		      *p++ = TAHOE_IMMEDIATE_LONGWORD;
		      fix_new (frag_now, p - frag_now->fr_literal,
			       this_add_symbol, this_add_number,
			       FX_32, NULL);
		    }
		  else
		    {
		      /* It's a integer, and I know it's size.  */
		      if ((unsigned) this_add_number < 0x40)
			{
			  /* Will it fit in a literal? */
			  FRAG_APPEND_1_CHAR ((byte) this_add_number);
			}
		      else
			{
			  p = frag_more (dispsize + 1);
			  switch (dispsize)
			    {
			    case 1:
			      *p++ = TAHOE_IMMEDIATE_BYTE;
			      *p = (byte) this_add_number;
			      break;
			    case 2:
			      *p++ = TAHOE_IMMEDIATE_WORD;
			      md_number_to_chars (p, this_add_number, 2);
			      break;
			    case 4:
			      *p++ = TAHOE_IMMEDIATE_LONGWORD;
			      md_number_to_chars (p, this_add_number, 4);
			      break;
			    }
			}
		    }
		  break;

		  /* Distance from the PC. If the size isn't known, we have to relax
	     into it. The difference between this and disp(sp) is that
	     this offset is pc_rel, and disp(sp) isn't.
	     Note the drop through code.  */

		case TAHOE_DISPLACED_RELATIVE:
		case TAHOE_DISP_REL_DEFERRED:
		  operandP->top_reg = PC_REG;
		  pc_rel = 1;

		  /* Register, plus a displacement mode. Save the register number,
	     and weather its deffered or not, and relax the size if it isn't
	     known.  */
		case TAHOE_REG_DISP:
		case TAHOE_REG_DISP_DEFERRED:
		  if (operandP->top_mode == TAHOE_DISP_REL_DEFERRED ||
		      operandP->top_mode == TAHOE_REG_DISP_DEFERRED)
		    operandP->top_reg += 0x10;	/* deffered mode is always 0x10 higher
					  than it's non-deffered sibling.  */

		  /* Is this a value out of this segment?
	     The first part of this conditional is a cludge to make gas
	     produce the same output as 'as' when there is a lable, in
	     the current segment, displaceing a register. It's strange,
	     and no one in their right mind would do it, but it's easy
	     to cludge.  */
		  if ((dispsize == 0 && !pc_rel) ||
		      (to_seg != now_seg && !is_undefined && to_seg != SEG_ABSOLUTE))
		    dispsize = 4;

		  if (dispsize == 0)
		    {
		      /*
	     * We have a SEG_UNKNOWN symbol, or the size isn't cast.
	     * It might turn out to be in the same segment as
	     * the instruction, permitting relaxation.
	     */
		      p = frag_var (rs_machine_dependent, 5, 2,
				    ENCODE_RELAX (STATE_PC_RELATIVE,
				    is_undefined ? STATE_UNDF : STATE_BYTE),
				    this_add_symbol, this_add_number, 0);
		      *p = operandP->top_reg;
		    }
		  else
		    {
		      /* Either this is an abs, or a cast.  */
		      p = frag_more (dispsize + 1);
		      switch (dispsize)
			{
			case 1:
			  *p = TAHOE_PC_OR_BYTE + operandP->top_reg;
			  break;
			case 2:
			  *p = TAHOE_PC_OR_WORD + operandP->top_reg;
			  break;
			case 4:
			  *p = TAHOE_PC_OR_LONG + operandP->top_reg;
			  break;
			};
		      fix_new (frag_now, p + 1 - frag_now->fr_literal,
			       this_add_symbol, this_add_number,
			       size_to_fx (dispsize, pc_rel), NULL);
		    }
		  break;
		default:
		  as_fatal (_("Barf, bad mode %x\n"), operandP->top_mode);
		}
	    }
	}			/* for(operandP) */
    }				/* if(!need_pass_2 && !goofed) */
}				/* tahoe_assemble() */

/* We have no need to default values of symbols.  */

symbolS *
md_undefined_symbol (name)
     char *name;
{
  return 0;
}				/* md_undefined_symbol() */

/* Round up a section size to the appropriate boundary.  */
valueT
md_section_align (segment, size)
     segT segment;
     valueT size;
{
  return ((size + 7) & ~7);	/* Round all sects to multiple of 8 */
}				/* md_section_align() */

/* Exactly what point is a PC-relative offset relative TO?
   On the sparc, they're relative to the address of the offset, plus
   its size.  This gets us to the following instruction.
   (??? Is this right?  FIXME-SOON) */
long
md_pcrel_from (fixP)
     fixS *fixP;
{
  return (((fixP->fx_type == FX_8
	    || fixP->fx_type == FX_PCREL8)
	   ? 1
	   : ((fixP->fx_type == FX_16
	       || fixP->fx_type == FX_PCREL16)
	      ? 2
	      : ((fixP->fx_type == FX_32
		  || fixP->fx_type == FX_PCREL32)
		 ? 4
		 : 0))) + fixP->fx_where + fixP->fx_frag->fr_address);
}				/* md_pcrel_from() */

int
tc_is_pcrel (fixP)
     fixS *fixP;
{
  /* should never be called */
  know (0);
  return (0);
}				/* tc_is_pcrel() */