/* List management for the GCC expander.
   Copyright (C) 1987-2020 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "rtl.h"

static void free_list (rtx *, rtx *);

/* Functions for maintaining cache-able lists of EXPR_LIST and INSN_LISTs.  */

/* An INSN_LIST containing all INSN_LISTs allocated but currently unused.  */
static GTY ((deletable)) rtx unused_insn_list;

/* An EXPR_LIST containing all EXPR_LISTs allocated but currently unused.  */
static GTY ((deletable)) rtx unused_expr_list;

/* This function will free an entire list of either EXPR_LIST, INSN_LIST
   or DEPS_LIST nodes.  This is to be used only on lists that consist
   exclusively of nodes of one type only.  This is only called by
   free_EXPR_LIST_list, free_INSN_LIST_list and free_DEPS_LIST_list.  */
static void
free_list (rtx *listp, rtx *unused_listp)
{
  rtx link, prev_link;

  prev_link = *listp;
  link = XEXP (prev_link, 1);

  gcc_assert (unused_listp != &unused_insn_list
	      || GET_CODE (prev_link) == INSN_LIST);

  while (link)
    {
      gcc_assert (unused_listp != &unused_insn_list
		  || GET_CODE (prev_link) == INSN_LIST);

      prev_link = link;
      link = XEXP (link, 1);
    }

  XEXP (prev_link, 1) = *unused_listp;
  *unused_listp = *listp;
  *listp = 0;
}

/* Find corresponding to ELEM node in the list pointed to by LISTP.
   This node must exist in the list.  Returns pointer to that node.  */
static rtx *
find_list_elem (rtx elem, rtx *listp)
{
  while (XEXP (*listp, 0) != elem)
    listp = &XEXP (*listp, 1);
  return listp;
}

/* Remove the node pointed to by LISTP from the list.  */
static void
remove_list_node (rtx *listp)
{
  rtx node;

  node = *listp;
  *listp = XEXP (node, 1);
  XEXP (node, 1) = 0;
}

/* Removes corresponding to ELEM node from the list pointed to by LISTP.
   Returns that node.  */
rtx
remove_list_elem (rtx elem, rtx *listp)
{
  rtx node;

  listp = find_list_elem (elem, listp);
  node = *listp;
  remove_list_node (listp);
  return node;
}

/* This call is used in place of a gen_rtx_INSN_LIST. If there is a cached
   node available, we'll use it, otherwise a call to gen_rtx_INSN_LIST
   is made.  */
rtx_insn_list *
alloc_INSN_LIST (rtx val, rtx next)
{
  rtx_insn_list *r;

  if (unused_insn_list)
    {
      r = as_a <rtx_insn_list *> (unused_insn_list);
      unused_insn_list = r->next ();
      XEXP (r, 0) = val;
      XEXP (r, 1) = next;
      PUT_REG_NOTE_KIND (r, VOIDmode);

      gcc_assert (GET_CODE (r) == INSN_LIST);
    }
  else
    r = gen_rtx_INSN_LIST (VOIDmode, val, next);

  return r;
}

/* This call is used in place of a gen_rtx_EXPR_LIST. If there is a cached
   node available, we'll use it, otherwise a call to gen_rtx_EXPR_LIST
   is made.  */
rtx_expr_list *
alloc_EXPR_LIST (int kind, rtx val, rtx next)
{
  rtx_expr_list *r;

  if (unused_expr_list)
    {
      r = as_a <rtx_expr_list *> (unused_expr_list);
      unused_expr_list = XEXP (r, 1);
      XEXP (r, 0) = val;
      XEXP (r, 1) = next;
      PUT_REG_NOTE_KIND (r, kind);
    }
  else
    r = gen_rtx_EXPR_LIST ((machine_mode) kind, val, next);

  return r;
}

/* This function will free up an entire list of EXPR_LIST nodes.  */
void
free_EXPR_LIST_list (rtx_expr_list **listp)
{
  if (*listp == 0)
    return;
  free_list ((rtx *)listp, &unused_expr_list);
}

/* This function will free up an entire list of INSN_LIST nodes.  */
void
free_INSN_LIST_list (rtx_insn_list **listp)
{
  if (*listp == 0)
    return;
  free_list ((rtx *)listp, &unused_insn_list);
}

/* Make a copy of the INSN_LIST list LINK and return it.  */
rtx_insn_list *
copy_INSN_LIST (rtx_insn_list *link)
{
  rtx_insn_list *new_queue;
  rtx_insn_list **pqueue = &new_queue;

  for (; link; link = link->next ())
    {
      rtx_insn *x = link->insn ();
      rtx_insn_list *newlink = alloc_INSN_LIST (x, NULL);
      *pqueue = newlink;
      pqueue = (rtx_insn_list **)&XEXP (newlink, 1);
    }
  *pqueue = NULL;
  return new_queue;
}

/* Duplicate the INSN_LIST elements of COPY and prepend them to OLD.  */
rtx_insn_list *
concat_INSN_LIST (rtx_insn_list *copy, rtx_insn_list *old)
{
  rtx_insn_list *new_rtx = old;
  for (; copy ; copy = copy->next ())
    {
      new_rtx = alloc_INSN_LIST (copy->insn (), new_rtx);
      PUT_REG_NOTE_KIND (new_rtx, REG_NOTE_KIND (copy));
    }
  return new_rtx;
}

/* This function will free up an individual EXPR_LIST node.  */
void
free_EXPR_LIST_node (rtx ptr)
{
  XEXP (ptr, 1) = unused_expr_list;
  unused_expr_list = ptr;
}

/* This function will free up an individual INSN_LIST node.  */
void
free_INSN_LIST_node (rtx ptr)
{
  gcc_assert (GET_CODE (ptr) == INSN_LIST);
  XEXP (ptr, 1) = unused_insn_list;
  unused_insn_list = ptr;
}

/* Remove and free corresponding to ELEM node in the INSN_LIST pointed to
   by LISTP.  */
void
remove_free_INSN_LIST_elem (rtx_insn *elem, rtx_insn_list **listp)
{
  free_INSN_LIST_node (remove_list_elem (elem, (rtx *)listp));
}

/* Remove and free the first node in the INSN_LIST pointed to by LISTP.  */
rtx_insn *
remove_free_INSN_LIST_node (rtx_insn_list **listp)
{
  rtx_insn_list *node = *listp;
  rtx_insn *elem = node->insn ();

  remove_list_node ((rtx *)listp);
  free_INSN_LIST_node (node);

  return elem;
}

/* Remove and free the first node in the EXPR_LIST pointed to by LISTP.  */
rtx
remove_free_EXPR_LIST_node (rtx_expr_list **listp)
{
  rtx_expr_list *node = *listp;
  rtx elem = XEXP (node, 0);

  remove_list_node ((rtx *)listp);
  free_EXPR_LIST_node (node);

  return elem;
}

#include "gt-lists.h"