explow.c

来自「GCC编译器源代码」· C语言 代码 · 共 1,396 行 · 第 1/3 页

	 then we generate that address in a register
	 and index off of it.  We do this because it often makes
	 shorter code, and because the addresses thus generated
	 in registers often become common subexpressions.  */
      if (GET_CODE (x) == PLUS)
	{
	  rtx constant_term = const0_rtx;
	  rtx y = eliminate_constant_term (x, &constant_term);
	  if (constant_term == const0_rtx
	      || ! memory_address_p (mode, y))
	    x = force_operand (x, NULL_RTX);
	  else
	    {
	      y = gen_rtx (PLUS, GET_MODE (x), copy_to_reg (y), constant_term);
	      if (! memory_address_p (mode, y))
		x = force_operand (x, NULL_RTX);
	      else
		x = y;
	    }
	}

      else if (GET_CODE (x) == MULT || GET_CODE (x) == MINUS)
	x = force_operand (x, NULL_RTX);

      /* If we have a register that's an invalid address,
	 it must be a hard reg of the wrong class.  Copy it to a pseudo.  */
      else if (GET_CODE (x) == REG)
	x = copy_to_reg (x);

      /* Last resort: copy the value to a register, since
	 the register is a valid address.  */
      else
	x = force_reg (Pmode, x);

      goto done;

    win2:
      x = oldx;
    win:
      if (flag_force_addr && ! cse_not_expected && GET_CODE (x) != REG
	  /* Don't copy an addr via a reg if it is one of our stack slots.  */
	  && ! (GET_CODE (x) == PLUS
		&& (XEXP (x, 0) == virtual_stack_vars_rtx
		    || XEXP (x, 0) == virtual_incoming_args_rtx)))
	{
	  if (general_operand (x, Pmode))
	    x = force_reg (Pmode, x);
	  else
	    x = force_operand (x, NULL_RTX);
	}
    }

 done:

  /* If we didn't change the address, we are done.  Otherwise, mark
     a reg as a pointer if we have REG or REG + CONST_INT.  */
  if (oldx == x)
    return x;
  else if (GET_CODE (x) == REG)
    mark_reg_pointer (x, 1);
  else if (GET_CODE (x) == PLUS
	   && GET_CODE (XEXP (x, 0)) == REG
	   && GET_CODE (XEXP (x, 1)) == CONST_INT)
    mark_reg_pointer (XEXP (x, 0), 1);

  /* OLDX may have been the address on a temporary.  Update the address
     to indicate that X is now used.  */
  update_temp_slot_address (oldx, x);

  return x;
}

/* Like `memory_address' but pretend `flag_force_addr' is 0.  */

rtx
memory_address_noforce (mode, x)
     enum machine_mode mode;
     rtx x;
{
  int ambient_force_addr = flag_force_addr;
  rtx val;

  flag_force_addr = 0;
  val = memory_address (mode, x);
  flag_force_addr = ambient_force_addr;
  return val;
}

/* Convert a mem ref into one with a valid memory address.
   Pass through anything else unchanged.  */

rtx
validize_mem (ref)
     rtx ref;
{
  if (GET_CODE (ref) != MEM)
    return ref;
  if (memory_address_p (GET_MODE (ref), XEXP (ref, 0)))
    return ref;
  /* Don't alter REF itself, since that is probably a stack slot.  */
  return change_address (ref, GET_MODE (ref), XEXP (ref, 0));
}

/* Return a modified copy of X with its memory address copied
   into a temporary register to protect it from side effects.
   If X is not a MEM, it is returned unchanged (and not copied).
   Perhaps even if it is a MEM, if there is no need to change it.  */

rtx
stabilize (x)
     rtx x;
{
  register rtx addr;
  if (GET_CODE (x) != MEM)
    return x;
  addr = XEXP (x, 0);
  if (rtx_unstable_p (addr))
    {
      rtx temp = copy_all_regs (addr);
      rtx mem;
      if (GET_CODE (temp) != REG)
	temp = copy_to_reg (temp);
      mem = gen_rtx (MEM, GET_MODE (x), temp);

      /* Mark returned memref with in_struct if it's in an array or
	 structure.  Copy const and volatile from original memref.  */

      MEM_IN_STRUCT_P (mem) = MEM_IN_STRUCT_P (x) || GET_CODE (addr) == PLUS;
      RTX_UNCHANGING_P (mem) = RTX_UNCHANGING_P (x);
      MEM_VOLATILE_P (mem) = MEM_VOLATILE_P (x);
      return mem;
    }
  return x;
}

/* Copy the value or contents of X to a new temp reg and return that reg.  */

rtx
copy_to_reg (x)
     rtx x;
{
  register rtx temp = gen_reg_rtx (GET_MODE (x));
 
  /* If not an operand, must be an address with PLUS and MULT so
     do the computation.  */ 
  if (! general_operand (x, VOIDmode))
    x = force_operand (x, temp);
  
  if (x != temp)
    emit_move_insn (temp, x);

  return temp;
}

/* Like copy_to_reg but always give the new register mode Pmode
   in case X is a constant.  */

rtx
copy_addr_to_reg (x)
     rtx x;
{
  return copy_to_mode_reg (Pmode, x);
}

/* Like copy_to_reg but always give the new register mode MODE
   in case X is a constant.  */

rtx
copy_to_mode_reg (mode, x)
     enum machine_mode mode;
     rtx x;
{
  register rtx temp = gen_reg_rtx (mode);
  
  /* If not an operand, must be an address with PLUS and MULT so
     do the computation.  */ 
  if (! general_operand (x, VOIDmode))
    x = force_operand (x, temp);

  if (GET_MODE (x) != mode && GET_MODE (x) != VOIDmode)
    abort ();
  if (x != temp)
    emit_move_insn (temp, x);
  return temp;
}

/* Load X into a register if it is not already one.
   Use mode MODE for the register.
   X should be valid for mode MODE, but it may be a constant which
   is valid for all integer modes; that's why caller must specify MODE.

   The caller must not alter the value in the register we return,
   since we mark it as a "constant" register.  */

rtx
force_reg (mode, x)
     enum machine_mode mode;
     rtx x;
{
  register rtx temp, insn, set;

  if (GET_CODE (x) == REG)
    return x;
  temp = gen_reg_rtx (mode);
  insn = emit_move_insn (temp, x);

  /* Let optimizers know that TEMP's value never changes
     and that X can be substituted for it.  Don't get confused
     if INSN set something else (such as a SUBREG of TEMP).  */
  if (CONSTANT_P (x)
      && (set = single_set (insn)) != 0
      && SET_DEST (set) == temp)
    {
      rtx note = find_reg_note (insn, REG_EQUAL, NULL_RTX);

      if (note)
	XEXP (note, 0) = x;
      else
	REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_EQUAL, x, REG_NOTES (insn));
    }
  return temp;
}

/* If X is a memory ref, copy its contents to a new temp reg and return
   that reg.  Otherwise, return X.  */

rtx
force_not_mem (x)
     rtx x;
{
  register rtx temp;
  if (GET_CODE (x) != MEM || GET_MODE (x) == BLKmode)
    return x;
  temp = gen_reg_rtx (GET_MODE (x));
  emit_move_insn (temp, x);
  return temp;
}

/* Copy X to TARGET (if it's nonzero and a reg)
   or to a new temp reg and return that reg.
   MODE is the mode to use for X in case it is a constant.  */

rtx
copy_to_suggested_reg (x, target, mode)
     rtx x, target;
     enum machine_mode mode;
{
  register rtx temp;

  if (target && GET_CODE (target) == REG)
    temp = target;
  else
    temp = gen_reg_rtx (mode);

  emit_move_insn (temp, x);
  return temp;
}

/* Return the mode to use to store a scalar of TYPE and MODE.
   PUNSIGNEDP points to the signedness of the type and may be adjusted
   to show what signedness to use on extension operations.

   FOR_CALL is non-zero if this call is promoting args for a call.  */

enum machine_mode
promote_mode (type, mode, punsignedp, for_call)
     tree type;
     enum machine_mode mode;
     int *punsignedp;
     int for_call;
{
  enum tree_code code = TREE_CODE (type);
  int unsignedp = *punsignedp;

#ifdef PROMOTE_FOR_CALL_ONLY
  if (! for_call)
    return mode;
#endif

  switch (code)
    {
#ifdef PROMOTE_MODE
    case INTEGER_TYPE:   case ENUMERAL_TYPE:   case BOOLEAN_TYPE:
    case CHAR_TYPE:      case REAL_TYPE:       case OFFSET_TYPE:
      PROMOTE_MODE (mode, unsignedp, type);
      break;
#endif

#ifdef POINTERS_EXTEND_UNSIGNED
    case REFERENCE_TYPE:
    case POINTER_TYPE:
      mode = Pmode;
      unsignedp = POINTERS_EXTEND_UNSIGNED;
      break;
#endif
      
    default:
      break;
    }

  *punsignedp = unsignedp;
  return mode;
}

/* Adjust the stack pointer by ADJUST (an rtx for a number of bytes).
   This pops when ADJUST is positive.  ADJUST need not be constant.  */

void
adjust_stack (adjust)
     rtx adjust;
{
  rtx temp;
  adjust = protect_from_queue (adjust, 0);

  if (adjust == const0_rtx)
    return;

  temp = expand_binop (Pmode,
#ifdef STACK_GROWS_DOWNWARD
		       add_optab,
#else
		       sub_optab,
#endif
		       stack_pointer_rtx, adjust, stack_pointer_rtx, 0,
		       OPTAB_LIB_WIDEN);

  if (temp != stack_pointer_rtx)
    emit_move_insn (stack_pointer_rtx, temp);
}

/* Adjust the stack pointer by minus ADJUST (an rtx for a number of bytes).
   This pushes when ADJUST is positive.  ADJUST need not be constant.  */

void
anti_adjust_stack (adjust)
     rtx adjust;
{
  rtx temp;
  adjust = protect_from_queue (adjust, 0);

  if (adjust == const0_rtx)
    return;

  temp = expand_binop (Pmode,
#ifdef STACK_GROWS_DOWNWARD
		       sub_optab,
#else
		       add_optab,
#endif
		       stack_pointer_rtx, adjust, stack_pointer_rtx, 0,
		       OPTAB_LIB_WIDEN);

  if (temp != stack_pointer_rtx)
    emit_move_insn (stack_pointer_rtx, temp);
}

/* Round the size of a block to be pushed up to the boundary required
   by this machine.  SIZE is the desired size, which need not be constant.  */

rtx
round_push (size)
     rtx size;
{
#ifdef STACK_BOUNDARY
  int align = STACK_BOUNDARY / BITS_PER_UNIT;
  if (align == 1)
    return size;
  if (GET_CODE (size) == CONST_INT)
    {
      int new = (INTVAL (size) + align - 1) / align * align;
      if (INTVAL (size) != new)
	size = GEN_INT (new);
    }
  else
    {
      /* CEIL_DIV_EXPR needs to worry about the addition overflowing,
	 but we know it can't.  So add ourselves and then do
	 TRUNC_DIV_EXPR.  */
      size = expand_binop (Pmode, add_optab, size, GEN_INT (align - 1),
			   NULL_RTX, 1, OPTAB_LIB_WIDEN);
      size = expand_divmod (0, TRUNC_DIV_EXPR, Pmode, size, GEN_INT (align),
			    NULL_RTX, 1);
      size = expand_mult (Pmode, size, GEN_INT (align), NULL_RTX, 1);
    }
#endif /* STACK_BOUNDARY */
  return size;
}

/* Save the stack pointer for the purpose in SAVE_LEVEL.  PSAVE is a pointer
   to a previously-created save area.  If no save area has been allocated,
   this function will allocate one.  If a save area is specified, it
   must be of the proper mode.

   The insns are emitted after insn AFTER, if nonzero, otherwise the insns
   are emitted at the current position.  */

void
emit_stack_save (save_level, psave, after)
     enum save_level save_level;
     rtx *psave;
     rtx after;
{
  rtx sa = *psave;
  /* The default is that we use a move insn and save in a Pmode object.  */
  rtx (*fcn) () = gen_move_insn;
  enum machine_mode mode = Pmode;

  /* See if this machine has anything special to do for this kind of save.  */
  switch (save_level)
    {
#ifdef HAVE_save_stack_block
    case SAVE_BLOCK:
      if (HAVE_save_stack_block)
	{
	  fcn = gen_save_stack_block;
	  mode = insn_operand_mode[CODE_FOR_save_stack_block][0];
	}
      break;
#endif
#ifdef HAVE_save_stack_function
    case SAVE_FUNCTION:
      if (HAVE_save_stack_function)
	{
	  fcn = gen_save_stack_function;
	  mode = insn_operand_mode[CODE_FOR_save_stack_function][0];
	}
      break;
#endif
#ifdef HAVE_save_stack_nonlocal
    case SAVE_NONLOCAL:
      if (HAVE_save_stack_nonlocal)
	{
	  fcn = gen_save_stack_nonlocal;
	  mode = insn_operand_mode[(int) CODE_FOR_save_stack_nonlocal][0];
	}
      break;
#endif
    default:
      break;
    }

  /* If there is no save area and we have to allocate one, do so.  Otherwise
     verify the save area is the proper mode.  */

  if (sa == 0)
    {
      if (mode != VOIDmode)
	{
	  if (save_level == SAVE_NONLOCAL)
	    *psave = sa = assign_stack_local (mode, GET_MODE_SIZE (mode), 0);
	  else
	    *psave = sa = gen_reg_rtx (mode);
	}
    }
  else
    {
      if (mode == VOIDmode || GET_MODE (sa) != mode)
	abort ();
    }

  if (after)
    {
      rtx seq;

      start_sequence ();
      /* We must validize inside the sequence, to ensure that any instructions