[thirdparty/gcc.git] / gcc / domwalk.c

/* Generic dominator tree walker
   Copyright (C) 2003-2019 Free Software Foundation, Inc.
   Contributed by Diego Novillo <dnovillo@redhat.com>

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 "backend.h"
#include "cfganal.h"
#include "domwalk.h"
#include "dumpfile.h"

/* This file implements a generic walker for dominator trees.

  To understand the dominator walker one must first have a grasp of dominators,
  immediate dominators and the dominator tree.

  Dominators
    A block B1 is said to dominate B2 if every path from the entry to B2 must
    pass through B1.  Given the dominance relationship, we can proceed to
    compute immediate dominators.  Note it is not important whether or not
    our definition allows a block to dominate itself.

  Immediate Dominators:
    Every block in the CFG has no more than one immediate dominator.  The
    immediate dominator of block BB must dominate BB and must not dominate
    any other dominator of BB and must not be BB itself.

  Dominator tree:
    If we then construct a tree where each node is a basic block and there
    is an edge from each block's immediate dominator to the block itself, then
    we have a dominator tree.


  [ Note this walker can also walk the post-dominator tree, which is
    defined in a similar manner.  i.e., block B1 is said to post-dominate
    block B2 if all paths from B2 to the exit block must pass through
    B1.  ]

  For example, given the CFG

                   1
                   |
                   2
                  / \
                 3   4
                    / \
       +---------->5   6
       |          / \ /
       |    +--->8   7
       |    |   /    |
       |    +--9    11
       |      /      |
       +--- 10 ---> 12


  We have a dominator tree which looks like

                   1
                   |
                   2
                  / \
                 /   \
                3     4
                   / / \ \
                   | | | |
                   5 6 7 12
                   |   |
                   8   11
                   |
                   9
                   |
                  10


  The dominator tree is the basis for a number of analysis, transformation
  and optimization algorithms that operate on a semi-global basis.

  The dominator walker is a generic routine which visits blocks in the CFG
  via a depth first search of the dominator tree.  In the example above
  the dominator walker might visit blocks in the following order
  1, 2, 3, 4, 5, 8, 9, 10, 6, 7, 11, 12.

  The dominator walker has a number of callbacks to perform actions
  during the walk of the dominator tree.  There are two callbacks
  which walk statements, one before visiting the dominator children,
  one after visiting the dominator children.  There is a callback
  before and after each statement walk callback.  In addition, the
  dominator walker manages allocation/deallocation of data structures
  which are local to each block visited.

  The dominator walker is meant to provide a generic means to build a pass
  which can analyze or transform/optimize a function based on walking
  the dominator tree.  One simply fills in the dominator walker data
  structure with the appropriate callbacks and calls the walker.

  We currently use the dominator walker to prune the set of variables
  which might need PHI nodes (which can greatly improve compile-time
  performance in some cases).

  We also use the dominator walker to rewrite the function into SSA form
  which reduces code duplication since the rewriting phase is inherently
  a walk of the dominator tree.

  And (of course), we use the dominator walker to drive our dominator
  optimizer, which is a semi-global optimizer.

  TODO:

    Walking statements is based on the block statement iterator abstraction,
    which is currently an abstraction over walking tree statements.  Thus
    the dominator walker is currently only useful for trees.  */

/* Reverse postorder index of each basic block.  */
static int *bb_postorder;

static int
cmp_bb_postorder (const void *a, const void *b)
{
  basic_block bb1 = *(const basic_block *)(a);
  basic_block bb2 = *(const basic_block *)(b);
  /* Place higher completion number first (pop off lower number first).  */
  return bb_postorder[bb2->index] - bb_postorder[bb1->index];
}

/* Permute array BBS of N basic blocks in postorder,
   i.e. by descending number in BB_POSTORDER array.  */

static void
sort_bbs_postorder (basic_block *bbs, int n)
{
  if (__builtin_expect (n == 2, true))
    {
      basic_block bb0 = bbs[0], bb1 = bbs[1];
      if (bb_postorder[bb0->index] < bb_postorder[bb1->index])
	bbs[0] = bb1, bbs[1] = bb0;
    }
  else if (__builtin_expect (n == 3, true))
    {
      basic_block bb0 = bbs[0], bb1 = bbs[1], bb2 = bbs[2];
      if (bb_postorder[bb0->index] < bb_postorder[bb1->index])
	std::swap (bb0, bb1);
      if (bb_postorder[bb1->index] < bb_postorder[bb2->index])
	{
	  std::swap (bb1, bb2);
	  if (bb_postorder[bb0->index] < bb_postorder[bb1->index])
	    std::swap (bb0, bb1);
	}
      bbs[0] = bb0, bbs[1] = bb1, bbs[2] = bb2;
    }
  else
    qsort (bbs, n, sizeof *bbs, cmp_bb_postorder);
}

/* Set EDGE_EXECUTABLE on every edge within FN's CFG.  */

void
set_all_edges_as_executable (function *fn)
{
  basic_block bb;
  FOR_ALL_BB_FN (bb, fn)
    {
      edge_iterator ei;
      edge e;
      FOR_EACH_EDGE (e, ei, bb->succs)
	e->flags |= EDGE_EXECUTABLE;
    }
}

/* Constructor for a dom walker.  */

dom_walker::dom_walker (cdi_direction direction,
			enum reachability reachability,
			int *bb_index_to_rpo)
  : m_dom_direction (direction),
    m_skip_unreachable_blocks (reachability != ALL_BLOCKS),
    m_user_bb_to_rpo (true),
    m_unreachable_dom (NULL),
    m_bb_to_rpo (bb_index_to_rpo)
{
  /* Set up edge flags if need be.  */
  switch (reachability)
    {
    default:
      gcc_unreachable ();
    case ALL_BLOCKS:
      /* No need to touch edge flags.  */
      break;

    case REACHABLE_BLOCKS:
      set_all_edges_as_executable (cfun);
      break;

    case REACHABLE_BLOCKS_PRESERVING_FLAGS:
      /* Preserve the edge flags.  */
      break;
    }
}

/* Constructor for a dom walker.  */

dom_walker::dom_walker (cdi_direction direction,
			enum reachability reachability)
  : m_dom_direction (direction),
    m_skip_unreachable_blocks (reachability != ALL_BLOCKS),
    m_user_bb_to_rpo (false),
    m_unreachable_dom (NULL),
    m_bb_to_rpo (NULL)
{
  /* Compute the basic-block index to RPO mapping.  */
  if (direction == CDI_DOMINATORS)
    {
      int *postorder = XNEWVEC (int, n_basic_blocks_for_fn (cfun));
      int postorder_num = pre_and_rev_post_order_compute (NULL, postorder,
							  true);
      m_bb_to_rpo = XNEWVEC (int, last_basic_block_for_fn (cfun));
      for (int i = 0; i < postorder_num; ++i)
	m_bb_to_rpo[postorder[i]] = i;
      free (postorder);
    }

  /* Set up edge flags if need be.  */
  switch (reachability)
    {
    default:
      gcc_unreachable ();
    case ALL_BLOCKS:
      /* No need to touch edge flags.  */
      break;

    case REACHABLE_BLOCKS:
      set_all_edges_as_executable (cfun);
      break;

    case REACHABLE_BLOCKS_PRESERVING_FLAGS:
      /* Preserve the edge flags.  */
      break;
    }
}

/* Destructor.  */

dom_walker::~dom_walker ()
{
  if (! m_user_bb_to_rpo)
    free (m_bb_to_rpo);
}

/* Return TRUE if BB is reachable, false otherwise.  */

bool
dom_walker::bb_reachable (struct function *fun, basic_block bb)
{
  /* If we're not skipping unreachable blocks, then assume everything
     is reachable.  */
  if (!m_skip_unreachable_blocks)
    return true;

  /* If any of the predecessor edges that do not come from blocks dominated
     by us are still marked as possibly executable consider this block
     reachable.  */
  bool reachable = false;
  if (!m_unreachable_dom)
    {
      reachable = bb == ENTRY_BLOCK_PTR_FOR_FN (fun);
      edge_iterator ei;
      edge e;
      FOR_EACH_EDGE (e, ei, bb->preds)
	if (!dominated_by_p (CDI_DOMINATORS, e->src, bb))
	  reachable |= (e->flags & EDGE_EXECUTABLE);
    }

  return reachable;
}

/* BB has been determined to be unreachable.  Propagate that property
   to incoming and outgoing edges of BB as appropriate.  */

void
dom_walker::propagate_unreachable_to_edges (basic_block bb,
					    FILE *dump_file,
					    dump_flags_t dump_flags)
{
  if (dump_file && (dump_flags & TDF_DETAILS))
    fprintf (dump_file, "Marking all outgoing edges of unreachable "
	     "BB %d as not executable\n", bb->index);

  edge_iterator ei;
  edge e;
  FOR_EACH_EDGE (e, ei, bb->succs)
    e->flags &= ~EDGE_EXECUTABLE;

  FOR_EACH_EDGE (e, ei, bb->preds)
    {
      if (dominated_by_p (CDI_DOMINATORS, e->src, bb))
	{
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    fprintf (dump_file, "Marking backedge from BB %d into "
		     "unreachable BB %d as not executable\n",
		     e->src->index, bb->index);
	  e->flags &= ~EDGE_EXECUTABLE;
	}
    }

  if (!m_unreachable_dom)
    m_unreachable_dom = bb;
}

const edge dom_walker::STOP = (edge)-1;

/* Recursively walk the dominator tree.
   BB is the basic block we are currently visiting.  */

void
dom_walker::walk (basic_block bb)
{
  basic_block dest;
  basic_block *worklist = XNEWVEC (basic_block,
				   n_basic_blocks_for_fn (cfun) * 2);
  int sp = 0;
  bb_postorder = m_bb_to_rpo;

  while (true)
    {
      /* Don't worry about unreachable blocks.  */
      if (EDGE_COUNT (bb->preds) > 0
	  || bb == ENTRY_BLOCK_PTR_FOR_FN (cfun)
	  || bb == EXIT_BLOCK_PTR_FOR_FN (cfun))
	{
	  edge taken_edge = NULL;

	  /* Callback for subclasses to do custom things before we have walked
	     the dominator children, but before we walk statements.  */
	  if (this->bb_reachable (cfun, bb))
	    {
	      taken_edge = before_dom_children (bb);
	      if (taken_edge && taken_edge != STOP)
		{
		  edge_iterator ei;
		  edge e;
		  FOR_EACH_EDGE (e, ei, bb->succs)
		    if (e != taken_edge)
		      e->flags &= ~EDGE_EXECUTABLE;
		}
	    }
	  else
	    propagate_unreachable_to_edges (bb, dump_file, dump_flags);

	  /* Mark the current BB to be popped out of the recursion stack
	     once children are processed.  */
	  worklist[sp++] = bb;
	  worklist[sp++] = NULL;

	  /* If the callback returned NONE then we are supposed to
	     stop and not even propagate EDGE_EXECUTABLE further.  */
	  if (taken_edge != STOP)
	    {
	      int saved_sp = sp;
	      for (dest = first_dom_son (m_dom_direction, bb);
		   dest; dest = next_dom_son (m_dom_direction, dest))
		worklist[sp++] = dest;
	      /* Sort worklist after RPO order if requested.  */
	      if (sp - saved_sp > 1
		  && m_dom_direction == CDI_DOMINATORS
		  && m_bb_to_rpo)
		sort_bbs_postorder (&worklist[saved_sp], sp - saved_sp);
	    }
	}
      /* NULL is used to mark pop operations in the recursion stack.  */
      while (sp > 0 && !worklist[sp - 1])
	{
	  --sp;
	  bb = worklist[--sp];

	  /* Callback allowing subclasses to do custom things after we have
	     walked dominator children, but before we walk statements.  */
	  if (bb_reachable (cfun, bb))
	    after_dom_children (bb);
	  else if (m_unreachable_dom == bb)
	    m_unreachable_dom = NULL;
	}
      if (sp)
	bb = worklist[--sp];
      else
	break;
    }
  bb_postorder = NULL;
  free (worklist);
}
Commit	Line	Data
4ee9c684	1	/* Generic dominator tree walker
fbd26352	2	Copyright (C) 2003-2019 Free Software Foundation, Inc.
4ee9c684	3	Contributed by Diego Novillo <dnovillo@redhat.com>
	4
	5	This file is part of GCC.
	6
	7	GCC is free software; you can redistribute it and/or modify
	8	it under the terms of the GNU General Public License as published by
8c4c00c1	9	the Free Software Foundation; either version 3, or (at your option)
4ee9c684	10	any later version.
	11
	12	GCC is distributed in the hope that it will be useful,
	13	but WITHOUT ANY WARRANTY; without even the implied warranty of
	14	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	15	GNU General Public License for more details.
	16
	17	You should have received a copy of the GNU General Public License
8c4c00c1	18	along with GCC; see the file COPYING3. If not see
8c4c00c1	19	<http://www.gnu.org/licenses/>. */
4ee9c684	20
	21	#include "config.h"
	22	#include "system.h"
	23	#include "coretypes.h"
9ef16211	24	#include "backend.h"
94ea8568	25	#include "cfganal.h"
4ee9c684	26	#include "domwalk.h"
96752458	27	#include "dumpfile.h"
4ee9c684	28
48e1416a	29	/* This file implements a generic walker for dominator trees.
4ee9c684	30
	31	To understand the dominator walker one must first have a grasp of dominators,
	32	immediate dominators and the dominator tree.
	33
	34	Dominators
	35	A block B1 is said to dominate B2 if every path from the entry to B2 must
	36	pass through B1. Given the dominance relationship, we can proceed to
	37	compute immediate dominators. Note it is not important whether or not
	38	our definition allows a block to dominate itself.
	39
	40	Immediate Dominators:
	41	Every block in the CFG has no more than one immediate dominator. The
	42	immediate dominator of block BB must dominate BB and must not dominate
	43	any other dominator of BB and must not be BB itself.
	44
	45	Dominator tree:
	46	If we then construct a tree where each node is a basic block and there
	47	is an edge from each block's immediate dominator to the block itself, then
	48	we have a dominator tree.
	49
	50
	51	[ Note this walker can also walk the post-dominator tree, which is
0c6d8c36	52	defined in a similar manner. i.e., block B1 is said to post-dominate
4ee9c684	53	block B2 if all paths from B2 to the exit block must pass through
	54	B1. ]
	55
	56	For example, given the CFG
	57
	58	1
	59	\|
	60	2
	61	/ \
	62	3 4
	63	/ \
	64	+---------->5 6
	65	\| / \ /
	66	\| +--->8 7
	67	\| \| / \|
	68	\| +--9 11
	69	\| / \|
	70	+--- 10 ---> 12
48e1416a	71
48e1416a	72
4ee9c684	73	We have a dominator tree which looks like
	74
	75	1
	76	\|
	77	2
	78	/ \
	79	/ \
	80	3 4
	81	/ / \ \
	82	\| \| \| \|
	83	5 6 7 12
	84	\| \|
	85	8 11
	86	\|
	87	9
	88	\|
	89	10
48e1416a	90
	91
	92
4ee9c684	93	The dominator tree is the basis for a number of analysis, transformation
4ee9c684	94	and optimization algorithms that operate on a semi-global basis.
48e1416a	95
4ee9c684	96	The dominator walker is a generic routine which visits blocks in the CFG
	97	via a depth first search of the dominator tree. In the example above
	98	the dominator walker might visit blocks in the following order
	99	1, 2, 3, 4, 5, 8, 9, 10, 6, 7, 11, 12.
48e1416a	100
4ee9c684	101	The dominator walker has a number of callbacks to perform actions
	102	during the walk of the dominator tree. There are two callbacks
	103	which walk statements, one before visiting the dominator children,
48e1416a	104	one after visiting the dominator children. There is a callback
4ee9c684	105	before and after each statement walk callback. In addition, the
	106	dominator walker manages allocation/deallocation of data structures
	107	which are local to each block visited.
48e1416a	108
4ee9c684	109	The dominator walker is meant to provide a generic means to build a pass
	110	which can analyze or transform/optimize a function based on walking
	111	the dominator tree. One simply fills in the dominator walker data
	112	structure with the appropriate callbacks and calls the walker.
48e1416a	113
4ee9c684	114	We currently use the dominator walker to prune the set of variables
	115	which might need PHI nodes (which can greatly improve compile-time
	116	performance in some cases).
48e1416a	117
4ee9c684	118	We also use the dominator walker to rewrite the function into SSA form
	119	which reduces code duplication since the rewriting phase is inherently
	120	a walk of the dominator tree.
	121
80777cd8	122	And (of course), we use the dominator walker to drive our dominator
4ee9c684	123	optimizer, which is a semi-global optimizer.
	124
	125	TODO:
	126
	127	Walking statements is based on the block statement iterator abstraction,
	128	which is currently an abstraction over walking tree statements. Thus
	129	the dominator walker is currently only useful for trees. */
	130
f4203922	131	/* Reverse postorder index of each basic block. */
0da53361	132	static int *bb_postorder;
	133
	134	static int
	135	cmp_bb_postorder (const void a, const void b)
	136	{
f4203922	137	basic_block bb1 = (const basic_block )(a);
f4203922	138	basic_block bb2 = (const basic_block )(b);
0da53361	139	/* Place higher completion number first (pop off lower number first). */
f4203922	140	return bb_postorder[bb2->index] - bb_postorder[bb1->index];
	141	}
	142
	143	/* Permute array BBS of N basic blocks in postorder,
	144	i.e. by descending number in BB_POSTORDER array. */
	145
	146	static void
	147	sort_bbs_postorder (basic_block *bbs, int n)
	148	{
	149	if (__builtin_expect (n == 2, true))
	150	{
	151	basic_block bb0 = bbs[0], bb1 = bbs[1];
	152	if (bb_postorder[bb0->index] < bb_postorder[bb1->index])
	153	bbs[0] = bb1, bbs[1] = bb0;
	154	}
	155	else if (__builtin_expect (n == 3, true))
	156	{
	157	basic_block bb0 = bbs[0], bb1 = bbs[1], bb2 = bbs[2];
	158	if (bb_postorder[bb0->index] < bb_postorder[bb1->index])
	159	std::swap (bb0, bb1);
	160	if (bb_postorder[bb1->index] < bb_postorder[bb2->index])
	161	{
	162	std::swap (bb1, bb2);
	163	if (bb_postorder[bb0->index] < bb_postorder[bb1->index])
	164	std::swap (bb0, bb1);
	165	}
	166	bbs[0] = bb0, bbs[1] = bb1, bbs[2] = bb2;
	167	}
	168	else
	169	qsort (bbs, n, sizeof *bbs, cmp_bb_postorder);
0da53361	170	}
0da53361	171
c9d75619	172	/* Set EDGE_EXECUTABLE on every edge within FN's CFG. */
	173
	174	void
	175	set_all_edges_as_executable (function *fn)
	176	{
	177	basic_block bb;
	178	FOR_ALL_BB_FN (bb, fn)
	179	{
	180	edge_iterator ei;
	181	edge e;
	182	FOR_EACH_EDGE (e, ei, bb->succs)
	183	e->flags \|= EDGE_EXECUTABLE;
	184	}
	185	}
	186
	187	/* Constructor for a dom walker. */
96752458	188
96752458	189	dom_walker::dom_walker (cdi_direction direction,
c9d75619	190	enum reachability reachability,
0fcd2c46	191	int *bb_index_to_rpo)
96752458	192	: m_dom_direction (direction),
c9d75619	193	m_skip_unreachable_blocks (reachability != ALL_BLOCKS),
11b3ff74	194	m_user_bb_to_rpo (true),
0fcd2c46	195	m_unreachable_dom (NULL),
0fcd2c46	196	m_bb_to_rpo (bb_index_to_rpo)
96752458	197	{
11b3ff74	198	/* Set up edge flags if need be. */
	199	switch (reachability)
	200	{
	201	default:
	202	gcc_unreachable ();
	203	case ALL_BLOCKS:
	204	/* No need to touch edge flags. */
	205	break;
	206
	207	case REACHABLE_BLOCKS:
	208	set_all_edges_as_executable (cfun);
	209	break;
	210
	211	case REACHABLE_BLOCKS_PRESERVING_FLAGS:
	212	/* Preserve the edge flags. */
	213	break;
	214	}
	215	}
	216
	217	/* Constructor for a dom walker. */
	218
	219	dom_walker::dom_walker (cdi_direction direction,
	220	enum reachability reachability)
	221	: m_dom_direction (direction),
	222	m_skip_unreachable_blocks (reachability != ALL_BLOCKS),
	223	m_user_bb_to_rpo (false),
	224	m_unreachable_dom (NULL),
	225	m_bb_to_rpo (NULL)
	226	{
	227	/* Compute the basic-block index to RPO mapping. */
	228	if (direction == CDI_DOMINATORS)
0fcd2c46	229	{
	230	int *postorder = XNEWVEC (int, n_basic_blocks_for_fn (cfun));
	231	int postorder_num = pre_and_rev_post_order_compute (NULL, postorder,
	232	true);
	233	m_bb_to_rpo = XNEWVEC (int, last_basic_block_for_fn (cfun));
	234	for (int i = 0; i < postorder_num; ++i)
	235	m_bb_to_rpo[postorder[i]] = i;
	236	free (postorder);
	237	}
	238
c9d75619	239	/* Set up edge flags if need be. */
c9d75619	240	switch (reachability)
96752458	241	{
c9d75619	242	default:
	243	gcc_unreachable ();
	244	case ALL_BLOCKS:
	245	/* No need to touch edge flags. */
	246	break;
	247
	248	case REACHABLE_BLOCKS:
	249	set_all_edges_as_executable (cfun);
	250	break;
	251
	252	case REACHABLE_BLOCKS_PRESERVING_FLAGS:
	253	/* Preserve the edge flags. */
	254	break;
96752458	255	}
	256	}
	257
0fcd2c46	258	/* Destructor. */
	259
	260	dom_walker::~dom_walker ()
	261	{
	262	if (! m_user_bb_to_rpo)
	263	free (m_bb_to_rpo);
	264	}
	265
96752458	266	/* Return TRUE if BB is reachable, false otherwise. */
	267
	268	bool
	269	dom_walker::bb_reachable (struct function *fun, basic_block bb)
	270	{
	271	/* If we're not skipping unreachable blocks, then assume everything
	272	is reachable. */
	273	if (!m_skip_unreachable_blocks)
	274	return true;
	275
	276	/* If any of the predecessor edges that do not come from blocks dominated
	277	by us are still marked as possibly executable consider this block
	278	reachable. */
	279	bool reachable = false;
	280	if (!m_unreachable_dom)
	281	{
	282	reachable = bb == ENTRY_BLOCK_PTR_FOR_FN (fun);
	283	edge_iterator ei;
	284	edge e;
	285	FOR_EACH_EDGE (e, ei, bb->preds)
	286	if (!dominated_by_p (CDI_DOMINATORS, e->src, bb))
	287	reachable \|= (e->flags & EDGE_EXECUTABLE);
	288	}
	289
	290	return reachable;
	291	}
	292
	293	/* BB has been determined to be unreachable. Propagate that property
	294	to incoming and outgoing edges of BB as appropriate. */
	295
	296	void
	297	dom_walker::propagate_unreachable_to_edges (basic_block bb,
	298	FILE *dump_file,
3f6e5ced	299	dump_flags_t dump_flags)
96752458	300	{
	301	if (dump_file && (dump_flags & TDF_DETAILS))
	302	fprintf (dump_file, "Marking all outgoing edges of unreachable "
	303	"BB %d as not executable\n", bb->index);
	304
	305	edge_iterator ei;
	306	edge e;
	307	FOR_EACH_EDGE (e, ei, bb->succs)
	308	e->flags &= ~EDGE_EXECUTABLE;
	309
	310	FOR_EACH_EDGE (e, ei, bb->preds)
	311	{
	312	if (dominated_by_p (CDI_DOMINATORS, e->src, bb))
	313	{
	314	if (dump_file && (dump_flags & TDF_DETAILS))
	315	fprintf (dump_file, "Marking backedge from BB %d into "
	316	"unreachable BB %d as not executable\n",
	317	e->src->index, bb->index);
	318	e->flags &= ~EDGE_EXECUTABLE;
	319	}
	320	}
	321
	322	if (!m_unreachable_dom)
	323	m_unreachable_dom = bb;
	324	}
	325
0fcd2c46	326	const edge dom_walker::STOP = (edge)-1;
0fcd2c46	327
4ee9c684	328	/* Recursively walk the dominator tree.
4ee9c684	329	BB is the basic block we are currently visiting. */
	330
	331	void
54c91640	332	dom_walker::walk (basic_block bb)
4ee9c684	333	{
4ee9c684	334	basic_block dest;
a28770e1	335	basic_block *worklist = XNEWVEC (basic_block,
a28770e1	336	n_basic_blocks_for_fn (cfun) * 2);
3100c298	337	int sp = 0;
0fcd2c46	338	bb_postorder = m_bb_to_rpo;
88dbf20f	339
3100c298	340	while (true)
4ee9c684	341	{
3100c298	342	/* Don't worry about unreachable blocks. */
a490a493	343	if (EDGE_COUNT (bb->preds) > 0
34154e27	344	\|\| bb == ENTRY_BLOCK_PTR_FOR_FN (cfun)
34154e27	345	\|\| bb == EXIT_BLOCK_PTR_FOR_FN (cfun))
4ee9c684	346	{
0fcd2c46	347	edge taken_edge = NULL;
96752458	348
54c91640	349	/* Callback for subclasses to do custom things before we have walked
54c91640	350	the dominator children, but before we walk statements. */
96752458	351	if (this->bb_reachable (cfun, bb))
96752458	352	{
0fcd2c46	353	taken_edge = before_dom_children (bb);
0fcd2c46	354	if (taken_edge && taken_edge != STOP)
96752458	355	{
	356	edge_iterator ei;
	357	edge e;
	358	FOR_EACH_EDGE (e, ei, bb->succs)
	359	if (e != taken_edge)
	360	e->flags &= ~EDGE_EXECUTABLE;
	361	}
	362	}
	363	else
	364	propagate_unreachable_to_edges (bb, dump_file, dump_flags);
3100c298	365
3100c298	366	/* Mark the current BB to be popped out of the recursion stack
f0b5f617	367	once children are processed. */
3100c298	368	worklist[sp++] = bb;
	369	worklist[sp++] = NULL;
	370
0fcd2c46	371	/* If the callback returned NONE then we are supposed to
	372	stop and not even propagate EDGE_EXECUTABLE further. */
	373	if (taken_edge != STOP)
	374	{
	375	int saved_sp = sp;
	376	for (dest = first_dom_son (m_dom_direction, bb);
	377	dest; dest = next_dom_son (m_dom_direction, dest))
	378	worklist[sp++] = dest;
11b3ff74	379	/* Sort worklist after RPO order if requested. */
	380	if (sp - saved_sp > 1
	381	&& m_dom_direction == CDI_DOMINATORS
	382	&& m_bb_to_rpo)
0fcd2c46	383	sort_bbs_postorder (&worklist[saved_sp], sp - saved_sp);
0fcd2c46	384	}
4ee9c684	385	}
6bf320fb	386	/* NULL is used to mark pop operations in the recursion stack. */
3100c298	387	while (sp > 0 && !worklist[sp - 1])
4ee9c684	388	{
3100c298	389	--sp;
3100c298	390	bb = worklist[--sp];
3100c298	391
54c91640	392	/* Callback allowing subclasses to do custom things after we have
54c91640	393	walked dominator children, but before we walk statements. */
96752458	394	if (bb_reachable (cfun, bb))
	395	after_dom_children (bb);
	396	else if (m_unreachable_dom == bb)
	397	m_unreachable_dom = NULL;
4ee9c684	398	}
3100c298	399	if (sp)
0da53361	400	bb = worklist[--sp];
4ee9c684	401	else
3100c298	402	break;
4ee9c684	403	}
0fcd2c46	404	bb_postorder = NULL;
3100c298	405	free (worklist);
4ee9c684	406	}