cgen.c

来自「基于4个mips核的noc设计」· C语言 代码 · 共 691 行 · 第 1/2 页

   The "result" is stored in RESULT if non-NULL.  */

void
gas_cgen_finish_insn (insn, buf, length, relax_p, result)
     const CGEN_INSN *insn;
     CGEN_INSN_BYTES_PTR buf;
     unsigned int length;
     int relax_p;
     finished_insnS *result;
{
  int i;
  int relax_operand;
  char *f;
  unsigned int byte_len = length / 8;

  /* ??? Target foo issues various warnings here, so one might want to provide
     a hook here.  However, our caller is defined in tc-foo.c so there
     shouldn't be a need for a hook.  */

  /* Write out the instruction.
     It is important to fetch enough space in one call to `frag_more'.
     We use (f - frag_now->fr_literal) to compute where we are and we
     don't want frag_now to change between calls.

     Relaxable instructions: We need to ensure we allocate enough
     space for the largest insn.  */

  if (CGEN_INSN_ATTR_VALUE (insn, CGEN_INSN_RELAX))
    /* These currently shouldn't get here.  */
    abort ();

  /* Is there a relaxable insn with the relaxable operand needing a fixup?  */

  relax_operand = -1;
  if (relax_p && CGEN_INSN_ATTR_VALUE (insn, CGEN_INSN_RELAXABLE))
    {
      /* Scan the fixups for the operand affected by relaxing
	 (i.e. the branch address).  */

      for (i = 0; i < num_fixups; ++i)
	{
	  if (CGEN_OPERAND_ATTR_VALUE (cgen_operand_lookup_by_num (gas_cgen_cpu_desc, fixups[i].opindex),
				       CGEN_OPERAND_RELAX))
	    {
	      relax_operand = i;
	      break;
	    }
	}
    }

  if (relax_operand != -1)
    {
      int max_len;
      fragS *old_frag;
      expressionS *exp;
      symbolS *sym;
      offsetT off;

#ifdef TC_CGEN_MAX_RELAX
      max_len = TC_CGEN_MAX_RELAX (insn, byte_len);
#else
      max_len = CGEN_MAX_INSN_SIZE;
#endif
      /* Ensure variable part and fixed part are in same fragment.  */
      /* FIXME: Having to do this seems like a hack.  */
      frag_grow (max_len);

      /* Allocate space for the fixed part.  */
      f = frag_more (byte_len);

      /* Create a relaxable fragment for this instruction.  */
      old_frag = frag_now;

      exp = &fixups[relax_operand].exp;
      sym = exp->X_add_symbol;
      off = exp->X_add_number;
      if (exp->X_op != O_constant && exp->X_op != O_symbol)
	{
	  /* Handle complex expressions.  */
	  sym = make_expr_symbol (exp);
	  off = 0;
	}

      frag_var (rs_machine_dependent,
		max_len - byte_len /* max chars */,
		0 /* variable part already allocated */,
		/* FIXME: When we machine generate the relax table,
		   machine generate a macro to compute subtype.  */
		1 /* subtype */,
		sym,
		off,
		f);

      /* Record the operand number with the fragment so md_convert_frag
	 can use gas_cgen_md_record_fixup to record the appropriate reloc.  */
      old_frag->fr_cgen.insn    = insn;
      old_frag->fr_cgen.opindex = fixups[relax_operand].opindex;
      old_frag->fr_cgen.opinfo  = fixups[relax_operand].opinfo;
      if (result)
	result->frag = old_frag;
    }
  else
    {
      f = frag_more (byte_len);
      if (result)
	result->frag = frag_now;
    }

  /* If we're recording insns as numbers (rather than a string of bytes),
     target byte order handling is deferred until now.  */
#if CGEN_INT_INSN_P
  cgen_put_insn_value (gas_cgen_cpu_desc, f, length, *buf);
#else
  memcpy (f, buf, byte_len);
#endif

  /* Emit DWARF2 debugging information.  */
  dwarf2_emit_insn (byte_len);

  /* Create any fixups.  */
  for (i = 0; i < num_fixups; ++i)
    {
      fixS *fixP;
      const CGEN_OPERAND *operand =
	cgen_operand_lookup_by_num (gas_cgen_cpu_desc, fixups[i].opindex);

      /* Don't create fixups for these.  That's done during relaxation.
	 We don't need to test for CGEN_INSN_RELAX as they can't get here
	 (see above).  */
      if (relax_p
	  && CGEN_INSN_ATTR_VALUE (insn, CGEN_INSN_RELAXABLE)
	  && CGEN_OPERAND_ATTR_VALUE (operand, CGEN_OPERAND_RELAX))
	continue;

#ifndef md_cgen_record_fixup_exp
#define md_cgen_record_fixup_exp gas_cgen_record_fixup_exp
#endif

      fixP = md_cgen_record_fixup_exp (frag_now, f - frag_now->fr_literal,
				       insn, length, operand,
				       fixups[i].opinfo,
				       &fixups[i].exp);
      if (result)
	result->fixups[i] = fixP;
    }

  if (result)
    {
      result->num_fixups = num_fixups;
      result->addr = f;
    }
}

/* Apply a fixup to the object code.  This is called for all the
   fixups we generated by the call to fix_new_exp, above.  In the call
   above we used a reloc code which was the largest legal reloc code
   plus the operand index.  Here we undo that to recover the operand
   index.  At this point all symbol values should be fully resolved,
   and we attempt to completely resolve the reloc.  If we can not do
   that, we determine the correct reloc code and put it back in the fixup.  */

/* FIXME: This function handles some of the fixups and bfd_install_relocation
   handles the rest.  bfd_install_relocation (or some other bfd function)
   should handle them all.  */

int
gas_cgen_md_apply_fix3 (fixP, valueP, seg)
     fixS *   fixP;
     valueT * valueP;
     segT     seg ATTRIBUTE_UNUSED;
{
  char *where = fixP->fx_frag->fr_literal + fixP->fx_where;
  valueT value;
  /* Canonical name, since used a lot.  */
  CGEN_CPU_DESC cd = gas_cgen_cpu_desc;

  /* FIXME FIXME FIXME: The value we are passed in *valuep includes
     the symbol values.  Since we are using BFD_ASSEMBLER, if we are
     doing this relocation the code in write.c is going to call
     bfd_install_relocation, which is also going to use the symbol
     value.  That means that if the reloc is fully resolved we want to
     use *valuep since bfd_install_relocation is not being used.
     However, if the reloc is not fully resolved we do not want to use
     *valuep, and must use fx_offset instead.  However, if the reloc
     is PC relative, we do want to use *valuep since it includes the
     result of md_pcrel_from.  This is confusing.  */

  if (fixP->fx_addsy == (symbolS *) NULL)
    {
      value = *valueP;
      fixP->fx_done = 1;
    }
  else if (fixP->fx_pcrel)
    value = *valueP;
  else
    {
      value = fixP->fx_offset;
      if (fixP->fx_subsy != (symbolS *) NULL)
	{
	  if (S_GET_SEGMENT (fixP->fx_subsy) == absolute_section)
	    value -= S_GET_VALUE (fixP->fx_subsy);
	  else
	    {
	      /* We don't actually support subtracting a symbol.  */
	      as_bad_where (fixP->fx_file, fixP->fx_line,
			    _("expression too complex"));
	    }
	}
    }

  if ((int) fixP->fx_r_type >= (int) BFD_RELOC_UNUSED)
    {
      int opindex = (int) fixP->fx_r_type - (int) BFD_RELOC_UNUSED;
      const CGEN_OPERAND *operand = cgen_operand_lookup_by_num (cd, opindex);
      const char *errmsg;
      bfd_reloc_code_real_type reloc_type;
      CGEN_FIELDS *fields = alloca (CGEN_CPU_SIZEOF_FIELDS (cd));
      const CGEN_INSN *insn = fixP->fx_cgen.insn;

      /* If the reloc has been fully resolved finish the operand here.  */
      /* FIXME: This duplicates the capabilities of code in BFD.  */
      if (fixP->fx_done
	  /* FIXME: If partial_inplace isn't set bfd_install_relocation won't
	     finish the job.  Testing for pcrel is a temporary hack.  */
	  || fixP->fx_pcrel)
	{
	  CGEN_CPU_SET_FIELDS_BITSIZE (cd) (fields, CGEN_INSN_BITSIZE (insn));
	  CGEN_CPU_SET_VMA_OPERAND (cd) (cd, opindex, fields, (bfd_vma) value);

#if CGEN_INT_INSN_P
	  {
	    CGEN_INSN_INT insn_value =
	      cgen_get_insn_value (cd, where, CGEN_INSN_BITSIZE (insn));

	    /* ??? 0 is passed for `pc'.  */
	    errmsg = CGEN_CPU_INSERT_OPERAND (cd) (cd, opindex, fields,
						   &insn_value, (bfd_vma) 0);
	    cgen_put_insn_value (cd, where, CGEN_INSN_BITSIZE (insn),
				 insn_value);
	  }
#else
	  /* ??? 0 is passed for `pc'.  */
	  errmsg = CGEN_CPU_INSERT_OPERAND (cd) (cd, opindex, fields, where,
						 (bfd_vma) 0);
#endif
	  if (errmsg)
	    as_bad_where (fixP->fx_file, fixP->fx_line, "%s", errmsg);
	}

      if (fixP->fx_done)
	return 1;

      /* The operand isn't fully resolved.  Determine a BFD reloc value
	 based on the operand information and leave it to
	 bfd_install_relocation.  Note that this doesn't work when
	 partial_inplace == false.  */

      reloc_type = md_cgen_lookup_reloc (insn, operand, fixP);
      if (reloc_type != BFD_RELOC_NONE)
	{
	  fixP->fx_r_type = reloc_type;
	}
      else
	{
	  as_bad_where (fixP->fx_file, fixP->fx_line,
			_("unresolved expression that must be resolved"));
	  fixP->fx_done = 1;
	  return 1;
	}
    }
  else if (fixP->fx_done)
    {
      /* We're finished with this fixup.  Install it because
	 bfd_install_relocation won't be called to do it.  */
      switch (fixP->fx_r_type)
	{
	case BFD_RELOC_8:
	  md_number_to_chars (where, value, 1);
	  break;
	case BFD_RELOC_16:
	  md_number_to_chars (where, value, 2);
	  break;
	case BFD_RELOC_32:
	  md_number_to_chars (where, value, 4);
	  break;
	case BFD_RELOC_64:
	  md_number_to_chars (where, value, 8);
	  break;
	default:
	  as_bad_where (fixP->fx_file, fixP->fx_line,
			_("internal error: can't install fix for reloc type %d (`%s')"),
			fixP->fx_r_type, bfd_get_reloc_code_name (fixP->fx_r_type));
	  break;
	}
    }
  else
    {
      /* bfd_install_relocation will be called to finish things up.  */
    }

  /* Tuck `value' away for use by tc_gen_reloc.
     See the comment describing fx_addnumber in write.h.
     This field is misnamed (or misused :-).  */
  fixP->fx_addnumber = value;

  return 1;
}

/* Translate internal representation of relocation info to BFD target format.

   FIXME: To what extent can we get all relevant targets to use this?  */

arelent *
gas_cgen_tc_gen_reloc (section, fixP)
     asection * section ATTRIBUTE_UNUSED;
     fixS *     fixP;
{
  arelent *reloc;

  reloc = (arelent *) xmalloc (sizeof (arelent));

  reloc->howto = bfd_reloc_type_lookup (stdoutput, fixP->fx_r_type);
  if (reloc->howto == (reloc_howto_type *) NULL)
    {
      as_bad_where (fixP->fx_file, fixP->fx_line,
		    _("relocation is not supported"));
      return NULL;
    }

  assert (!fixP->fx_pcrel == !reloc->howto->pc_relative);

  reloc->sym_ptr_ptr = (asymbol **) xmalloc (sizeof (asymbol *));
  *reloc->sym_ptr_ptr = symbol_get_bfdsym (fixP->fx_addsy);

  /* Use fx_offset for these cases.  */
  if (fixP->fx_r_type == BFD_RELOC_VTABLE_ENTRY
      || fixP->fx_r_type == BFD_RELOC_VTABLE_INHERIT)
    reloc->addend = fixP->fx_offset;
  else
    reloc->addend = fixP->fx_addnumber;

  reloc->address = fixP->fx_frag->fr_address + fixP->fx_where;
  return reloc;
}