calls.c

早期freebsd实现

#endif

      actparms
	= tree_cons (error_mark_node,
		     make_tree (build_pointer_type (TREE_TYPE (funtype)),
				temp),
		     actparms);
      structure_value_addr_parm = 1;
    }

  /* Count the arguments and set NUM_ACTUALS.  */
  for (p = actparms, i = 0; p; p = TREE_CHAIN (p)) i++;
  num_actuals = i;

  /* Compute number of named args.
     Normally, don't include the last named arg if anonymous args follow.
     (If no anonymous args follow, the result of list_length
     is actually one too large.)

     If SETUP_INCOMING_VARARGS is defined, this machine will be able to
     place unnamed args that were passed in registers into the stack.  So
     treat all args as named.  This allows the insns emitting for a specific
     argument list to be independent of the function declaration.

     If SETUP_INCOMING_VARARGS is not defined, we do not have any reliable
     way to pass unnamed args in registers, so we must force them into
     memory.  */
#ifndef SETUP_INCOMING_VARARGS
  if (TYPE_ARG_TYPES (funtype) != 0)
    n_named_args
      = list_length (TYPE_ARG_TYPES (funtype)) - 1
	/* Count the struct value address, if it is passed as a parm.  */
	+ structure_value_addr_parm;
  else
#endif
    /* If we know nothing, treat all args as named.  */
    n_named_args = num_actuals;

  /* Make a vector to hold all the information about each arg.  */
  args = (struct arg_data *) alloca (num_actuals * sizeof (struct arg_data));
  bzero (args, num_actuals * sizeof (struct arg_data));

  args_size.constant = 0;
  args_size.var = 0;

  /* In this loop, we consider args in the order they are written.
     We fill up ARGS from the front of from the back if necessary
     so that in any case the first arg to be pushed ends up at the front.  */

#ifdef PUSH_ARGS_REVERSED
  i = num_actuals - 1, inc = -1;
  /* In this case, must reverse order of args
     so that we compute and push the last arg first.  */
#else
  i = 0, inc = 1;
#endif

  /* I counts args in order (to be) pushed; ARGPOS counts in order written.  */
  for (p = actparms, argpos = 0; p; p = TREE_CHAIN (p), i += inc, argpos++)
    {
      tree type = TREE_TYPE (TREE_VALUE (p));
      enum machine_mode mode;

      args[i].tree_value = TREE_VALUE (p);

      /* Replace erroneous argument with constant zero.  */
      if (type == error_mark_node || TYPE_SIZE (type) == 0)
	args[i].tree_value = integer_zero_node, type = integer_type_node;

      /* Decide where to pass this arg.

	 args[i].reg is nonzero if all or part is passed in registers.

	 args[i].partial is nonzero if part but not all is passed in registers,
	 and the exact value says how many words are passed in registers.

	 args[i].pass_on_stack is nonzero if the argument must at least be
	 computed on the stack.  It may then be loaded back into registers
	 if args[i].reg is nonzero.

	 These decisions are driven by the FUNCTION_... macros and must agree
	 with those made by function.c.  */

#ifdef FUNCTION_ARG_PASS_BY_REFERENCE
      /* See if this argument should be passed by invisible reference.  */
      if (FUNCTION_ARG_PASS_BY_REFERENCE (args_so_far, TYPE_MODE (type), type,
					  argpos < n_named_args))
	{
	  /* We make a copy of the object and pass the address to the function
	     being called.  */
	  int size = int_size_in_bytes (type);
	  rtx copy;

	  if (size < 0)
	    {
	      /* This is a variable-sized object.  Make space on the stack
		 for it.  */
	      rtx size_rtx = expand_expr (size_in_bytes (type), NULL_RTX,
					  VOIDmode, 0);

	      if (old_stack_level == 0)
		{
		  emit_stack_save (SAVE_BLOCK, &old_stack_level, NULL_RTX);
		  old_pending_adj = pending_stack_adjust;
		  pending_stack_adjust = 0;
		}

	      copy = gen_rtx (MEM, BLKmode,
			      allocate_dynamic_stack_space (size_rtx, NULL_RTX,
							    TYPE_ALIGN (type)));
	    }
	  else
	    copy = assign_stack_temp (TYPE_MODE (type), size, 1);

	  store_expr (args[i].tree_value, copy, 0);

	  args[i].tree_value = build1 (ADDR_EXPR, build_pointer_type (type),
				       make_tree (type, copy));
	  type = build_pointer_type (type);
	}
#endif

      mode = TYPE_MODE (type);

#ifdef PROMOTE_FUNCTION_ARGS
      /* Compute the mode in which the arg is actually to be extended to.  */
      if (TREE_CODE (type) == INTEGER_TYPE || TREE_CODE (type) == ENUMERAL_TYPE
	  || TREE_CODE (type) == BOOLEAN_TYPE || TREE_CODE (type) == CHAR_TYPE
	  || TREE_CODE (type) == REAL_TYPE || TREE_CODE (type) == POINTER_TYPE
	  || TREE_CODE (type) == OFFSET_TYPE)
	{
	  int unsignedp = TREE_UNSIGNED (type);
	  PROMOTE_MODE (mode, unsignedp, type);
	  args[i].unsignedp = unsignedp;
	}
#endif

      args[i].reg = FUNCTION_ARG (args_so_far, mode, type,
				  argpos < n_named_args);
#ifdef FUNCTION_ARG_PARTIAL_NREGS
      if (args[i].reg)
	args[i].partial
	  = FUNCTION_ARG_PARTIAL_NREGS (args_so_far, mode, type,
					argpos < n_named_args);
#endif

      args[i].pass_on_stack = MUST_PASS_IN_STACK (mode, type);

      /* If FUNCTION_ARG returned an (expr_list (nil) FOO), it means that
	 we are to pass this arg in the register(s) designated by FOO, but
	 also to pass it in the stack.  */
      if (args[i].reg && GET_CODE (args[i].reg) == EXPR_LIST
	  && XEXP (args[i].reg, 0) == 0)
	args[i].pass_on_stack = 1, args[i].reg = XEXP (args[i].reg, 1);

      /* If this is an addressable type, we must preallocate the stack
	 since we must evaluate the object into its final location.

	 If this is to be passed in both registers and the stack, it is simpler
	 to preallocate.  */
      if (TREE_ADDRESSABLE (type)
	  || (args[i].pass_on_stack && args[i].reg != 0))
	must_preallocate = 1;

      /* If this is an addressable type, we cannot pre-evaluate it.  Thus,
	 we cannot consider this function call constant.  */
      if (TREE_ADDRESSABLE (type))
	is_const = 0;

      /* Compute the stack-size of this argument.  */
      if (args[i].reg == 0 || args[i].partial != 0
#ifdef REG_PARM_STACK_SPACE
	  || reg_parm_stack_space > 0
#endif
	  || args[i].pass_on_stack)
	locate_and_pad_parm (TYPE_MODE (type), type,
#ifdef STACK_PARMS_IN_REG_PARM_AREA
			     1,
#else
			     args[i].reg != 0,
#endif
			     fndecl, &args_size, &args[i].offset,
			     &args[i].size);

#ifndef ARGS_GROW_DOWNWARD
      args[i].slot_offset = args_size;
#endif

#ifndef REG_PARM_STACK_SPACE
      /* If a part of the arg was put into registers,
	 don't include that part in the amount pushed.  */
      if (! args[i].pass_on_stack)
	args[i].size.constant -= ((args[i].partial * UNITS_PER_WORD)
				  / (PARM_BOUNDARY / BITS_PER_UNIT)
				  * (PARM_BOUNDARY / BITS_PER_UNIT));
#endif
      
      /* Update ARGS_SIZE, the total stack space for args so far.  */

      args_size.constant += args[i].size.constant;
      if (args[i].size.var)
	{
	  ADD_PARM_SIZE (args_size, args[i].size.var);
	}

      /* Since the slot offset points to the bottom of the slot,
	 we must record it after incrementing if the args grow down.  */
#ifdef ARGS_GROW_DOWNWARD
      args[i].slot_offset = args_size;

      args[i].slot_offset.constant = -args_size.constant;
      if (args_size.var)
	{
	  SUB_PARM_SIZE (args[i].slot_offset, args_size.var);
	}
#endif

      /* Increment ARGS_SO_FAR, which has info about which arg-registers
	 have been used, etc.  */

      FUNCTION_ARG_ADVANCE (args_so_far, TYPE_MODE (type), type,
			    argpos < n_named_args);
    }

#ifdef FINAL_REG_PARM_STACK_SPACE
  reg_parm_stack_space = FINAL_REG_PARM_STACK_SPACE (args_size.constant,
						     args_size.var);
#endif
      
  /* Compute the actual size of the argument block required.  The variable
     and constant sizes must be combined, the size may have to be rounded,
     and there may be a minimum required size.  */

  original_args_size = args_size;
  if (args_size.var)
    {
      /* If this function requires a variable-sized argument list, don't try to
	 make a cse'able block for this call.  We may be able to do this
	 eventually, but it is too complicated to keep track of what insns go
	 in the cse'able block and which don't.  */

      is_const = 0;
      must_preallocate = 1;

      args_size.var = ARGS_SIZE_TREE (args_size);
      args_size.constant = 0;

#ifdef STACK_BOUNDARY
      if (STACK_BOUNDARY != BITS_PER_UNIT)
	args_size.var = round_up (args_size.var, STACK_BYTES);
#endif

#ifdef REG_PARM_STACK_SPACE
      if (reg_parm_stack_space > 0)
	{
	  args_size.var
	    = size_binop (MAX_EXPR, args_size.var,
			  size_int (REG_PARM_STACK_SPACE (fndecl)));

#ifndef OUTGOING_REG_PARM_STACK_SPACE
	  /* The area corresponding to register parameters is not to count in
	     the size of the block we need.  So make the adjustment.  */
	  args_size.var
	    = size_binop (MINUS_EXPR, args_size.var,
			  size_int (reg_parm_stack_space));
#endif
	}
#endif
    }
  else
    {
#ifdef STACK_BOUNDARY
      args_size.constant = (((args_size.constant + (STACK_BYTES - 1))
			     / STACK_BYTES) * STACK_BYTES);
#endif

#ifdef REG_PARM_STACK_SPACE
      args_size.constant = MAX (args_size.constant,
				reg_parm_stack_space);
#ifndef OUTGOING_REG_PARM_STACK_SPACE
      args_size.constant -= reg_parm_stack_space;
#endif
#endif
    }

  /* See if we have or want to preallocate stack space.

     If we would have to push a partially-in-regs parm
     before other stack parms, preallocate stack space instead.

     If the size of some parm is not a multiple of the required stack
     alignment, we must preallocate.

     If the total size of arguments that would otherwise create a copy in
     a temporary (such as a CALL) is more than half the total argument list
     size, preallocation is faster.

     Another reason to preallocate is if we have a machine (like the m88k)
     where stack alignment is required to be maintained between every
     pair of insns, not just when the call is made.  However, we assume here
     that such machines either do not have push insns (and hence preallocation
     would occur anyway) or the problem is taken care of with
     PUSH_ROUNDING.  */

  if (! must_preallocate)
    {
      int partial_seen = 0;
      int copy_to_evaluate_size = 0;

      for (i = 0; i < num_actuals && ! must_preallocate; i++)
	{
	  if (args[i].partial > 0 && ! args[i].pass_on_stack)
	    partial_seen = 1;
	  else if (partial_seen && args[i].reg == 0)
	    must_preallocate = 1;

	  if (TYPE_MODE (TREE_TYPE (args[i].tree_value)) == BLKmode
	      && (TREE_CODE (args[i].tree_value) == CALL_EXPR
		  || TREE_CODE (args[i].tree_value) == TARGET_EXPR
		  || TREE_CODE (args[i].tree_value) == COND_EXPR
		  || TREE_ADDRESSABLE (TREE_TYPE (args[i].tree_value))))
	    copy_to_evaluate_size
	      += int_size_in_bytes (TREE_TYPE (args[i].tree_value));
	}

      if (copy_to_evaluate_size * 2 >= args_size.constant
	  && args_size.constant > 0)
	must_preallocate = 1;
    }

  /* If the structure value address will reference the stack pointer, we must
     stabilize it.  We don't need to do this if we know that we are not going
     to adjust the stack pointer in processing this call.  */

  if (structure_value_addr
      && (reg_mentioned_p (virtual_stack_dynamic_rtx, structure_value_addr)
       || reg_mentioned_p (virtual_outgoing_args_rtx, structure_value_addr))
      && (args_size.var
#ifndef ACCUMULATE_OUTGOING_ARGS
	  || args_size.constant
#endif
	  ))
    structure_value_addr = copy_to_reg (structure_value_addr);

  /* If this function call is cse'able, precompute all the parameters.
     Note that if the parameter is constructed into a temporary, this will
     cause an additional copy because the parameter will be constructed
     into a temporary location and then copied into the outgoing arguments.
     If a parameter contains a call to alloca and this function uses the
     stack, precompute the parameter.  */

  for (i = 0; i < num_actuals; i++)
    if (is_const
	|| ((args_size.var != 0 || args_size.constant != 0)
	    && calls_alloca (args[i].tree_value)))
      {
	args[i].initial_value = args[i].value
	  = expand_expr (args[i].tree_value, NULL_RTX, VOIDmode, 0);
	preserve_temp_slots (args[i].value);
	free_temp_slots ();

	/* ANSI doesn't require a sequence point here,
	   but PCC has one, so this will avoid some problems.  */
	emit_queue ();
      }

  /* Now we are about to start emitting insns that can be deleted
     if a libcall is deleted.  */
  if (is_const)
    start_sequence ();

  /* If we have no actual push instructions, or shouldn't use them,
     make space for all args right now.  */

  if (args_size.var != 0)
    {
      if (old_stack_level == 0)
	{
	  emit_stack_save (SAVE_BLOCK, &old_stack_level, NULL_RTX);
	  old_pending_adj = pending_stack_adjust;
	  pending_stack_adjust = 0;
#ifdef ACCUMULATE_OUTGOING_ARGS
	  /* stack_arg_under_construction says whether a stack arg is
	     being constructed at the old stack level.  Pushing the stack
	     gets a clean outgoing argument block.  */
	  old_stack_arg_under_construction = stack_arg_under_construction;
	  stack_arg_under_construction = 0;
#endif
	}
      argblock = push_block (ARGS_SIZE_RTX (args_size), 0, 0);
    }
  else if (must_preallocate)
    {
      /* Note that we must go through the motions of allocating an argument
	 block even if the size is zero because we may be storing args
	 in the area reserved for register arguments, which may be part of
	 the stack frame.  */
      int needed = args_size.constant;