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

/* Generic dominator tree walker
   Copyright (C) 2003-2024 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.  */

static int
cmp_bb_postorder (const void *a, const void *b, void *data)
{
  basic_block bb1 = *(const basic_block *)(a);
  basic_block bb2 = *(const basic_block *)(b);
  int *bb_postorder = (int *)data;
  /* 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, int *bb_postorder)
{
  if (LIKELY (n == 2))
    {
      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 (LIKELY (n == 3))
    {
      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
    gcc_sort_r (bbs, n, sizeof *bbs, cmp_bb_postorder, 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_reachability (reachability),
    m_user_bb_to_rpo (bb_index_to_rpo != NULL),
    m_unreachable_dom (NULL),
    m_bb_to_rpo (bb_index_to_rpo == (int *)(uintptr_t)-1
		 ? NULL : bb_index_to_rpo)
{
}

/* 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_reachability == ALL_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)
{
  /* Compute the basic-block index to RPO mapping lazily.  */
  if (!m_user_bb_to_rpo
      && !m_bb_to_rpo
      && m_dom_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.  */
  if (m_reachability == REACHABLE_BLOCKS)
    set_all_edges_as_executable (cfun);

  basic_block dest;
  basic_block *worklist = XNEWVEC (basic_block,
				   n_basic_blocks_for_fn (cfun) * 2);
  int sp = 0;

  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,
				    m_bb_to_rpo);
	    }
	}
      /* 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;
    }
  free (worklist);
}
Commit	Line	Data
6de9cd9a	1	/* Generic dominator tree walker
a945c346	2	Copyright (C) 2003-2024 Free Software Foundation, Inc.
6de9cd9a DN	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
9dcd6f09	9	the Free Software Foundation; either version 3, or (at your option)
6de9cd9a DN	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
9dcd6f09 NC	18	along with GCC; see the file COPYING3. If not see
9dcd6f09 NC	19	<http://www.gnu.org/licenses/>. */
6de9cd9a DN	20
	21	#include "config.h"
	22	#include "system.h"
	23	#include "coretypes.h"
c7131fb2	24	#include "backend.h"
60393bbc	25	#include "cfganal.h"
6de9cd9a	26	#include "domwalk.h"
3daacdcd	27	#include "dumpfile.h"
6de9cd9a	28
b8698a0f	29	/* This file implements a generic walker for dominator trees.
6de9cd9a DN	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
454ff5cb	52	defined in a similar manner. i.e., block B1 is said to post-dominate
6de9cd9a DN	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
b8698a0f L	71
b8698a0f L	72
6de9cd9a DN	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
b8698a0f L	90
	91
	92
6de9cd9a DN	93	The dominator tree is the basis for a number of analysis, transformation
6de9cd9a DN	94	and optimization algorithms that operate on a semi-global basis.
b8698a0f	95
6de9cd9a DN	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.
b8698a0f	100
6de9cd9a DN	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,
b8698a0f	104	one after visiting the dominator children. There is a callback
6de9cd9a DN	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.
b8698a0f	108
6de9cd9a DN	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.
b8698a0f	113
6de9cd9a DN	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).
b8698a0f	117
6de9cd9a DN	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
110abdbc	122	And (of course), we use the dominator walker to drive our dominator
6de9cd9a DN	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
076b4605	131	static int
51007dc1	132	cmp_bb_postorder (const void a, const void b, void *data)
076b4605	133	{
e5df270e AM	134	basic_block bb1 = (const basic_block )(a);
e5df270e AM	135	basic_block bb2 = (const basic_block )(b);
51007dc1	136	int bb_postorder = (int )data;
076b4605	137	/* Place higher completion number first (pop off lower number first). */
e5df270e AM	138	return bb_postorder[bb2->index] - bb_postorder[bb1->index];
	139	}
	140
	141	/* Permute array BBS of N basic blocks in postorder,
	142	i.e. by descending number in BB_POSTORDER array. */
	143
	144	static void
51007dc1	145	sort_bbs_postorder (basic_block bbs, int n, int bb_postorder)
e5df270e	146	{
22d9c880	147	if (LIKELY (n == 2))
e5df270e AM	148	{
	149	basic_block bb0 = bbs[0], bb1 = bbs[1];
	150	if (bb_postorder[bb0->index] < bb_postorder[bb1->index])
	151	bbs[0] = bb1, bbs[1] = bb0;
	152	}
22d9c880	153	else if (LIKELY (n == 3))
e5df270e AM	154	{
	155	basic_block bb0 = bbs[0], bb1 = bbs[1], bb2 = bbs[2];
	156	if (bb_postorder[bb0->index] < bb_postorder[bb1->index])
	157	std::swap (bb0, bb1);
	158	if (bb_postorder[bb1->index] < bb_postorder[bb2->index])
	159	{
	160	std::swap (bb1, bb2);
	161	if (bb_postorder[bb0->index] < bb_postorder[bb1->index])
	162	std::swap (bb0, bb1);
	163	}
	164	bbs[0] = bb0, bbs[1] = bb1, bbs[2] = bb2;
	165	}
	166	else
51007dc1	167	gcc_sort_r (bbs, n, sizeof *bbs, cmp_bb_postorder, bb_postorder);
076b4605 RB	168	}
076b4605 RB	169
9972bbbc DM	170	/* Set EDGE_EXECUTABLE on every edge within FN's CFG. */
	171
	172	void
	173	set_all_edges_as_executable (function *fn)
	174	{
	175	basic_block bb;
	176	FOR_ALL_BB_FN (bb, fn)
	177	{
	178	edge_iterator ei;
	179	edge e;
	180	FOR_EACH_EDGE (e, ei, bb->succs)
	181	e->flags \|= EDGE_EXECUTABLE;
	182	}
	183	}
	184
	185	/* Constructor for a dom walker. */
3daacdcd	186
3daacdcd	187	dom_walker::dom_walker (cdi_direction direction,
9972bbbc	188	enum reachability reachability,
d2552094	189	int *bb_index_to_rpo)
3daacdcd	190	: m_dom_direction (direction),
e37240b0 RB	191	m_reachability (reachability),
e37240b0 RB	192	m_user_bb_to_rpo (bb_index_to_rpo != NULL),
d2552094	193	m_unreachable_dom (NULL),
aea32943 RB	194	m_bb_to_rpo (bb_index_to_rpo == (int *)(uintptr_t)-1
aea32943 RB	195	? NULL : bb_index_to_rpo)
3daacdcd	196	{
3daacdcd JL	197	}
3daacdcd JL	198
d2552094 RB	199	/* Destructor. */
	200
	201	dom_walker::~dom_walker ()
	202	{
	203	if (! m_user_bb_to_rpo)
	204	free (m_bb_to_rpo);
	205	}
	206
3daacdcd JL	207	/* Return TRUE if BB is reachable, false otherwise. */
	208
	209	bool
	210	dom_walker::bb_reachable (struct function *fun, basic_block bb)
	211	{
	212	/* If we're not skipping unreachable blocks, then assume everything
	213	is reachable. */
e37240b0	214	if (m_reachability == ALL_BLOCKS)
3daacdcd JL	215	return true;
	216
	217	/* If any of the predecessor edges that do not come from blocks dominated
	218	by us are still marked as possibly executable consider this block
	219	reachable. */
	220	bool reachable = false;
	221	if (!m_unreachable_dom)
	222	{
	223	reachable = bb == ENTRY_BLOCK_PTR_FOR_FN (fun);
	224	edge_iterator ei;
	225	edge e;
	226	FOR_EACH_EDGE (e, ei, bb->preds)
	227	if (!dominated_by_p (CDI_DOMINATORS, e->src, bb))
	228	reachable \|= (e->flags & EDGE_EXECUTABLE);
	229	}
	230
	231	return reachable;
	232	}
	233
	234	/* BB has been determined to be unreachable. Propagate that property
	235	to incoming and outgoing edges of BB as appropriate. */
	236
	237	void
	238	dom_walker::propagate_unreachable_to_edges (basic_block bb,
	239	FILE *dump_file,
1a817418	240	dump_flags_t dump_flags)
3daacdcd JL	241	{
	242	if (dump_file && (dump_flags & TDF_DETAILS))
	243	fprintf (dump_file, "Marking all outgoing edges of unreachable "
	244	"BB %d as not executable\n", bb->index);
	245
	246	edge_iterator ei;
	247	edge e;
	248	FOR_EACH_EDGE (e, ei, bb->succs)
	249	e->flags &= ~EDGE_EXECUTABLE;
	250
	251	FOR_EACH_EDGE (e, ei, bb->preds)
	252	{
	253	if (dominated_by_p (CDI_DOMINATORS, e->src, bb))
	254	{
	255	if (dump_file && (dump_flags & TDF_DETAILS))
	256	fprintf (dump_file, "Marking backedge from BB %d into "
	257	"unreachable BB %d as not executable\n",
	258	e->src->index, bb->index);
	259	e->flags &= ~EDGE_EXECUTABLE;
	260	}
	261	}
	262
	263	if (!m_unreachable_dom)
	264	m_unreachable_dom = bb;
	265	}
	266
d2552094 RB	267	const edge dom_walker::STOP = (edge)-1;
d2552094 RB	268
6de9cd9a	269	/* Recursively walk the dominator tree.
6de9cd9a DN	270	BB is the basic block we are currently visiting. */
	271
	272	void
4d9192b5	273	dom_walker::walk (basic_block bb)
6de9cd9a	274	{
e37240b0	275	/* Compute the basic-block index to RPO mapping lazily. */
aea32943 RB	276	if (!m_user_bb_to_rpo
aea32943 RB	277	&& !m_bb_to_rpo
e37240b0 RB	278	&& m_dom_direction == CDI_DOMINATORS)
	279	{
	280	int *postorder = XNEWVEC (int, n_basic_blocks_for_fn (cfun));
	281	int postorder_num = pre_and_rev_post_order_compute (NULL, postorder,
	282	true);
	283	m_bb_to_rpo = XNEWVEC (int, last_basic_block_for_fn (cfun));
	284	for (int i = 0; i < postorder_num; ++i)
	285	m_bb_to_rpo[postorder[i]] = i;
	286	free (postorder);
	287	}
	288
	289	/* Set up edge flags if need be. */
	290	if (m_reachability == REACHABLE_BLOCKS)
	291	set_all_edges_as_executable (cfun);
	292
6de9cd9a	293	basic_block dest;
0cae8d31 DM	294	basic_block *worklist = XNEWVEC (basic_block,
0cae8d31 DM	295	n_basic_blocks_for_fn (cfun) * 2);
df648b94	296	int sp = 0;
0bca51f0	297
df648b94	298	while (true)
6de9cd9a	299	{
df648b94	300	/* Don't worry about unreachable blocks. */
515f36eb	301	if (EDGE_COUNT (bb->preds) > 0
fefa31b5 DM	302	\|\| bb == ENTRY_BLOCK_PTR_FOR_FN (cfun)
fefa31b5 DM	303	\|\| bb == EXIT_BLOCK_PTR_FOR_FN (cfun))
6de9cd9a	304	{
d2552094	305	edge taken_edge = NULL;
3daacdcd	306
4d9192b5 TS	307	/* Callback for subclasses to do custom things before we have walked
4d9192b5 TS	308	the dominator children, but before we walk statements. */
3daacdcd JL	309	if (this->bb_reachable (cfun, bb))
3daacdcd JL	310	{
d2552094 RB	311	taken_edge = before_dom_children (bb);
d2552094 RB	312	if (taken_edge && taken_edge != STOP)
3daacdcd JL	313	{
	314	edge_iterator ei;
	315	edge e;
	316	FOR_EACH_EDGE (e, ei, bb->succs)
	317	if (e != taken_edge)
	318	e->flags &= ~EDGE_EXECUTABLE;
	319	}
	320	}
	321	else
	322	propagate_unreachable_to_edges (bb, dump_file, dump_flags);
df648b94 JH	323
df648b94 JH	324	/* Mark the current BB to be popped out of the recursion stack
fa10beec	325	once children are processed. */
df648b94 JH	326	worklist[sp++] = bb;
	327	worklist[sp++] = NULL;
	328
d2552094 RB	329	/* If the callback returned NONE then we are supposed to
	330	stop and not even propagate EDGE_EXECUTABLE further. */
	331	if (taken_edge != STOP)
	332	{
	333	int saved_sp = sp;
	334	for (dest = first_dom_son (m_dom_direction, bb);
	335	dest; dest = next_dom_son (m_dom_direction, dest))
	336	worklist[sp++] = dest;
dc3b4a20 RB	337	/* Sort worklist after RPO order if requested. */
	338	if (sp - saved_sp > 1
	339	&& m_dom_direction == CDI_DOMINATORS
	340	&& m_bb_to_rpo)
51007dc1 RB	341	sort_bbs_postorder (&worklist[saved_sp], sp - saved_sp,
51007dc1 RB	342	m_bb_to_rpo);
d2552094	343	}
6de9cd9a	344	}
ccf5c864	345	/* NULL is used to mark pop operations in the recursion stack. */
df648b94	346	while (sp > 0 && !worklist[sp - 1])
6de9cd9a	347	{
df648b94 JH	348	--sp;
df648b94 JH	349	bb = worklist[--sp];
df648b94	350
4d9192b5 TS	351	/* Callback allowing subclasses to do custom things after we have
4d9192b5 TS	352	walked dominator children, but before we walk statements. */
3daacdcd JL	353	if (bb_reachable (cfun, bb))
	354	after_dom_children (bb);
	355	else if (m_unreachable_dom == bb)
	356	m_unreachable_dom = NULL;
6de9cd9a	357	}
df648b94	358	if (sp)
076b4605	359	bb = worklist[--sp];
6de9cd9a	360	else
df648b94	361	break;
6de9cd9a	362	}
df648b94	363	free (worklist);
6de9cd9a	364	}