stmt.c

早期freebsd实现

  /* The outermost stack level that should be restored for this jump.
     Each time a binding contour that resets the stack is exited,
     if the target label is *not* yet defined, this slot is updated.  */
  rtx stack_level;
  /* List of lists of cleanup expressions to be run by this goto.
     There is one element for each block that this goto is within.
     The tail of this list can be 0 (was empty_cleanup_list),
     if all remaining elements would be empty.
     The TREE_VALUE contains the cleanup list of that block as of the
     time this goto was seen.
     The TREE_ADDRESSABLE flag is 1 for a block that has been exited.  */
  tree cleanup_list_list;
};

static struct goto_fixup *goto_fixup_chain;

/* Within any binding contour that must restore a stack level,
   all labels are recorded with a chain of these structures.  */

struct label_chain
{
  /* Points to following fixup.  */
  struct label_chain *next;
  tree label;
};

void
init_stmt ()
{
  gcc_obstack_init (&stmt_obstack);
#if 0
  empty_cleanup_list = build_tree_list (NULL_TREE, NULL_TREE);
#endif
}

void
init_stmt_for_function ()
{
  /* We are not currently within any block, conditional, loop or case.  */
  block_stack = 0;
  loop_stack = 0;
  case_stack = 0;
  cond_stack = 0;
  nesting_stack = 0;
  nesting_depth = 0;

  block_start_count = 0;

  /* No gotos have been expanded yet.  */
  goto_fixup_chain = 0;

  /* We are not processing a ({...}) grouping.  */
  expr_stmts_for_value = 0;
  last_expr_type = 0;
}

void
save_stmt_status (p)
     struct function *p;
{
  p->block_stack = block_stack;
  p->stack_block_stack = stack_block_stack;
  p->cond_stack = cond_stack;
  p->loop_stack = loop_stack;
  p->case_stack = case_stack;
  p->nesting_stack = nesting_stack;
  p->nesting_depth = nesting_depth;
  p->block_start_count = block_start_count;
  p->last_expr_type = last_expr_type;
  p->last_expr_value = last_expr_value;
  p->expr_stmts_for_value = expr_stmts_for_value;
  p->emit_filename = emit_filename;
  p->emit_lineno = emit_lineno;
  p->goto_fixup_chain = goto_fixup_chain;
}

void
restore_stmt_status (p)
     struct function *p;
{
  block_stack = p->block_stack;
  stack_block_stack = p->stack_block_stack;
  cond_stack = p->cond_stack;
  loop_stack = p->loop_stack;
  case_stack = p->case_stack;
  nesting_stack = p->nesting_stack;
  nesting_depth = p->nesting_depth;
  block_start_count = p->block_start_count;
  last_expr_type = p->last_expr_type;
  last_expr_value = p->last_expr_value;
  expr_stmts_for_value = p->expr_stmts_for_value;
  emit_filename = p->emit_filename;
  emit_lineno = p->emit_lineno;
  goto_fixup_chain = p->goto_fixup_chain;
}

/* Emit a no-op instruction.  */

void
emit_nop ()
{
  rtx last_insn = get_last_insn ();
  if (!optimize
      && (GET_CODE (last_insn) == CODE_LABEL
	  || prev_real_insn (last_insn) == 0))
    emit_insn (gen_nop ());
}

/* Return the rtx-label that corresponds to a LABEL_DECL,
   creating it if necessary.  */

rtx
label_rtx (label)
     tree label;
{
  if (TREE_CODE (label) != LABEL_DECL)
    abort ();

  if (DECL_RTL (label))
    return DECL_RTL (label);

  return DECL_RTL (label) = gen_label_rtx ();
}

/* Add an unconditional jump to LABEL as the next sequential instruction.  */

void
emit_jump (label)
     rtx label;
{
  do_pending_stack_adjust ();
  emit_jump_insn (gen_jump (label));
  emit_barrier ();
}

/* Emit code to jump to the address
   specified by the pointer expression EXP.  */

void
expand_computed_goto (exp)
     tree exp;
{
  rtx x = expand_expr (exp, NULL_RTX, VOIDmode, 0);
  emit_queue ();
  emit_indirect_jump (x);
}

/* Handle goto statements and the labels that they can go to.  */

/* Specify the location in the RTL code of a label LABEL,
   which is a LABEL_DECL tree node.

   This is used for the kind of label that the user can jump to with a
   goto statement, and for alternatives of a switch or case statement.
   RTL labels generated for loops and conditionals don't go through here;
   they are generated directly at the RTL level, by other functions below.

   Note that this has nothing to do with defining label *names*.
   Languages vary in how they do that and what that even means.  */

void
expand_label (label)
     tree label;
{
  struct label_chain *p;

  do_pending_stack_adjust ();
  emit_label (label_rtx (label));
  if (DECL_NAME (label))
    LABEL_NAME (DECL_RTL (label)) = IDENTIFIER_POINTER (DECL_NAME (label));

  if (stack_block_stack != 0)
    {
      p = (struct label_chain *) oballoc (sizeof (struct label_chain));
      p->next = stack_block_stack->data.block.label_chain;
      stack_block_stack->data.block.label_chain = p;
      p->label = label;
    }
}

/* Declare that LABEL (a LABEL_DECL) may be used for nonlocal gotos
   from nested functions.  */

void
declare_nonlocal_label (label)
     tree label;
{
  nonlocal_labels = tree_cons (NULL_TREE, label, nonlocal_labels);
  LABEL_PRESERVE_P (label_rtx (label)) = 1;
  if (nonlocal_goto_handler_slot == 0)
    {
      nonlocal_goto_handler_slot
	= assign_stack_local (Pmode, GET_MODE_SIZE (Pmode), 0);
      emit_stack_save (SAVE_NONLOCAL,
		       &nonlocal_goto_stack_level,
		       PREV_INSN (tail_recursion_reentry));
    }
}

/* Generate RTL code for a `goto' statement with target label LABEL.
   LABEL should be a LABEL_DECL tree node that was or will later be
   defined with `expand_label'.  */

void
expand_goto (label)
     tree label;
{
  /* Check for a nonlocal goto to a containing function.  */
  tree context = decl_function_context (label);
  if (context != 0 && context != current_function_decl)
    {
      struct function *p = find_function_data (context);
      rtx label_ref = gen_rtx (LABEL_REF, Pmode, label_rtx (label));
      rtx temp;

      p->has_nonlocal_label = 1;
      LABEL_REF_NONLOCAL_P (label_ref) = 1;

      /* Copy the rtl for the slots so that they won't be shared in
	 case the virtual stack vars register gets instantiated differently
	 in the parent than in the child.  */

#if HAVE_nonlocal_goto
      if (HAVE_nonlocal_goto)
	emit_insn (gen_nonlocal_goto (lookup_static_chain (label),
				      copy_rtx (p->nonlocal_goto_handler_slot),
				      copy_rtx (p->nonlocal_goto_stack_level),
				      label_ref));
      else
#endif
	{
	  rtx addr;

	  /* Restore frame pointer for containing function.
	     This sets the actual hard register used for the frame pointer
	     to the location of the function's incoming static chain info.
	     The non-local goto handler will then adjust it to contain the
	     proper value and reload the argument pointer, if needed.  */
	  emit_move_insn (frame_pointer_rtx, lookup_static_chain (label));

	  /* We have now loaded the frame pointer hardware register with
	     the address of that corresponds to the start of the virtual
	     stack vars.  So replace virtual_stack_vars_rtx in all
	     addresses we use with stack_pointer_rtx.  */

	  /* Get addr of containing function's current nonlocal goto handler,
	     which will do any cleanups and then jump to the label.  */
	  addr = copy_rtx (p->nonlocal_goto_handler_slot);
	  temp = copy_to_reg (replace_rtx (addr, virtual_stack_vars_rtx,
					   frame_pointer_rtx));
	  
	  /* Restore the stack pointer.  Note this uses fp just restored.  */
	  addr = p->nonlocal_goto_stack_level;
	  if (addr)
	    addr = replace_rtx (copy_rtx (addr),
				virtual_stack_vars_rtx, frame_pointer_rtx);

	  emit_stack_restore (SAVE_NONLOCAL, addr, NULL_RTX);

	  /* Put in the static chain register the nonlocal label address.  */
	  emit_move_insn (static_chain_rtx, label_ref);
	  /* USE of frame_pointer_rtx added for consistency; not clear if
	     really needed.  */
	  emit_insn (gen_rtx (USE, VOIDmode, frame_pointer_rtx));
	  emit_insn (gen_rtx (USE, VOIDmode, stack_pointer_rtx));
	  emit_insn (gen_rtx (USE, VOIDmode, static_chain_rtx));
	  emit_indirect_jump (temp);
	}
     }
  else
    expand_goto_internal (label, label_rtx (label), NULL_RTX);
}

/* Generate RTL code for a `goto' statement with target label BODY.
   LABEL should be a LABEL_REF.
   LAST_INSN, if non-0, is the rtx we should consider as the last
   insn emitted (for the purposes of cleaning up a return).  */

static void
expand_goto_internal (body, label, last_insn)
     tree body;
     rtx label;
     rtx last_insn;
{
  struct nesting *block;
  rtx stack_level = 0;

  if (GET_CODE (label) != CODE_LABEL)
    abort ();

  /* If label has already been defined, we can tell now
     whether and how we must alter the stack level.  */

  if (PREV_INSN (label) != 0)
    {
      /* Find the innermost pending block that contains the label.
	 (Check containment by comparing insn-uids.)
	 Then restore the outermost stack level within that block,
	 and do cleanups of all blocks contained in it.  */
      for (block = block_stack; block; block = block->next)
	{
	  if (INSN_UID (block->data.block.first_insn) < INSN_UID (label))
	    break;
	  if (block->data.block.stack_level != 0)
	    stack_level = block->data.block.stack_level;
	  /* Execute the cleanups for blocks we are exiting.  */
	  if (block->data.block.cleanups != 0)
	    {
	      expand_cleanups (block->data.block.cleanups, NULL_TREE);
	      do_pending_stack_adjust ();
	    }
	}

      if (stack_level)
	{
	  /* Ensure stack adjust isn't done by emit_jump, as this would clobber
	     the stack pointer.  This one should be deleted as dead by flow. */
	  clear_pending_stack_adjust ();
	  do_pending_stack_adjust ();
	  emit_stack_restore (SAVE_BLOCK, stack_level, NULL_RTX);
	}

      if (body != 0 && DECL_TOO_LATE (body))
	error ("jump to `%s' invalidly jumps into binding contour",
	       IDENTIFIER_POINTER (DECL_NAME (body)));
    }
  /* Label not yet defined: may need to put this goto
     on the fixup list.  */
  else if (! expand_fixup (body, label, last_insn))
    {
      /* No fixup needed.  Record that the label is the target
	 of at least one goto that has no fixup.  */
      if (body != 0)
	TREE_ADDRESSABLE (body) = 1;
    }

  emit_jump (label);
}

/* Generate if necessary a fixup for a goto
   whose target label in tree structure (if any) is TREE_LABEL
   and whose target in rtl is RTL_LABEL.

   If LAST_INSN is nonzero, we pretend that the jump appears
   after insn LAST_INSN instead of at the current point in the insn stream.

   The fixup will be used later to insert insns just before the goto.
   Those insns will restore the stack level as appropriate for the
   target label, and will (in the case of C++) also invoke any object
   destructors which have to be invoked when we exit the scopes which
   are exited by the goto.

   Value is nonzero if a fixup is made.  */

static int
expand_fixup (tree_label, rtl_label, last_insn)
     tree tree_label;
     rtx rtl_label;
     rtx last_insn;
{
  struct nesting *block, *end_block;

  /* See if we can recognize which block the label will be output in.
     This is possible in some very common cases.
     If we succeed, set END_BLOCK to that block.
     Otherwise, set it to 0.  */

  if (cond_stack
      && (rtl_label == cond_stack->data.cond.endif_label
	  || rtl_label == cond_stack->data.cond.next_label))
    end_block = cond_stack;
  /* If we are in a loop, recognize certain labels which
     are likely targets.  This reduces the number of fixups
     we need to create.  */
  else if (loop_stack
      && (rtl_label == loop_stack->data.loop.start_label
	  || rtl_label == loop_stack->data.loop.end_label
	  || rtl_label == loop_stack->data.loop.continue_label))
    end_block = loop_stack;
  else
    end_block = 0;

  /* Now set END_BLOCK to the binding level to which we will return.  */

  if (end_block)
    {
      struct nesting *next_block = end_block->all;
      block = block_stack;

      /* First see if the END_BLOCK is inside the innermost binding level.
	 If so, then no cleanups or stack levels are relevant.  */
      while (next_block && next_block != block)
	next_block = next_block->all;

      if (next_block)
	return 0;

      /* Otherwise, set END_BLOCK to the innermost binding level
	 which is outside the relevant control-structure nesting.  */
      next_block = block_stack->next;
      for (block = block_stack; block != end_block; block = block->all)
	if (block == next_block)
	  next_block = next_block->next;
      end_block = next_block;
    }

  /* Does any containing block have a stack level or cleanups?
     If not, no fixup is needed, and that is the normal case
     (the only case, for standard C).  */
  for (block = block_stack; block != end_block; block = block->next)
    if (block->data.block.stack_level != 0
	|| block->data.block.cleanups != 0)
      break;

  if (block != end_block)