/* Calculate (post)dominators in slightly super-linear time.
- Copyright (C) 2000, 2003, 2004, 2005 Free Software Foundation, Inc.
+ Copyright (C) 2000, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
+ Free Software Foundation, Inc.
Contributed by Michael Matz (matz@ifh.de).
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 2, or (at your option)
+ 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
License for more details.
You should have received a copy of the GNU General Public License
- along with GCC; see the file COPYING. If not, write to the Free
- Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
- 02110-1301, USA. */
+ along with GCC; see the file COPYING3. If not see
+ <http://www.gnu.org/licenses/>. */
/* This file implements the well known algorithm from Lengauer and Tarjan
to compute the dominators in a control flow graph. A basic block D is said
#include "hard-reg-set.h"
#include "obstack.h"
#include "basic-block.h"
-#include "toplev.h"
+#include "diagnostic-core.h"
#include "et-forest.h"
-
-/* Whether the dominators and the postdominators are available. */
-enum dom_state dom_computed[2];
+#include "timevar.h"
+#include "vecprim.h"
+#include "pointer-set.h"
+#include "graphds.h"
+#include "bitmap.h"
/* We name our nodes with integers, beginning with 1. Zero is reserved for
'undefined' or 'end of list'. The name of each node is given by the dfs
/* The following few fields implement the structures needed for disjoint
sets. */
- /* set_chain[x] is the next node on the path from x to the representant
+ /* set_chain[x] is the next node on the path from x to the representative
of the set containing x. If set_chain[x]==0 then x is a root. */
TBB *set_chain;
/* set_size[x] is the number of elements in the set named by x. */
static void init_dom_info (struct dom_info *, enum cdi_direction);
static void free_dom_info (struct dom_info *);
-static void calc_dfs_tree_nonrec (struct dom_info *, basic_block,
- enum cdi_direction);
-static void calc_dfs_tree (struct dom_info *, enum cdi_direction);
+static void calc_dfs_tree_nonrec (struct dom_info *, basic_block, bool);
+static void calc_dfs_tree (struct dom_info *, bool);
static void compress (struct dom_info *, TBB);
static TBB eval (struct dom_info *, TBB);
static void link_roots (struct dom_info *, TBB, TBB);
-static void calc_idoms (struct dom_info *, enum cdi_direction);
+static void calc_idoms (struct dom_info *, bool);
void debug_dominance_info (enum cdi_direction);
-
-/* Keeps track of the*/
-static unsigned n_bbs_in_dom_tree[2];
+void debug_dominance_tree (enum cdi_direction, basic_block);
/* Helper macro for allocating and initializing an array,
for aesthetic reasons. */
{ \
unsigned int i = 1; /* Catch content == i. */ \
if (! (content)) \
- (var) = xcalloc ((num), sizeof (type)); \
+ (var) = XCNEWVEC (type, num); \
else \
{ \
- (var) = xmalloc ((num) * sizeof (type)); \
+ (var) = XNEWVEC (type, (num)); \
for (i = 0; i < num; i++) \
(var)[i] = (content); \
} \
static void
init_dom_info (struct dom_info *di, enum cdi_direction dir)
{
+ /* We need memory for n_basic_blocks nodes. */
unsigned int num = n_basic_blocks;
init_ar (di->dfs_parent, TBB, num, 0);
init_ar (di->path_min, TBB, num, i);
di->dfsnum = 1;
di->nodes = 0;
- di->fake_exit_edge = dir ? BITMAP_ALLOC (NULL) : NULL;
+ switch (dir)
+ {
+ case CDI_DOMINATORS:
+ di->fake_exit_edge = NULL;
+ break;
+ case CDI_POST_DOMINATORS:
+ di->fake_exit_edge = BITMAP_ALLOC (NULL);
+ break;
+ default:
+ gcc_unreachable ();
+ break;
+ }
}
#undef init_ar
+/* Map dominance calculation type to array index used for various
+ dominance information arrays. This version is simple -- it will need
+ to be modified, obviously, if additional values are added to
+ cdi_direction. */
+
+static unsigned int
+dom_convert_dir_to_idx (enum cdi_direction dir)
+{
+ gcc_assert (dir == CDI_DOMINATORS || dir == CDI_POST_DOMINATORS);
+ return dir - 1;
+}
+
/* Free all allocated memory in DI, but not DI itself. */
static void
assigned their dfs number and are linked together to form a tree. */
static void
-calc_dfs_tree_nonrec (struct dom_info *di, basic_block bb,
- enum cdi_direction reverse)
+calc_dfs_tree_nonrec (struct dom_info *di, basic_block bb, bool reverse)
{
/* We call this _only_ if bb is not already visited. */
edge e;
/* Ending block. */
basic_block ex_block;
- stack = xmalloc ((n_basic_blocks + 1) * sizeof (edge_iterator));
+ stack = XNEWVEC (edge_iterator, n_basic_blocks + 1);
sp = 0;
/* Initialize our border blocks, and the first edge. */
because there may be nodes from which the EXIT_BLOCK is unreachable. */
static void
-calc_dfs_tree (struct dom_info *di, enum cdi_direction reverse)
+calc_dfs_tree (struct dom_info *di, bool reverse)
{
/* The first block is the ENTRY_BLOCK (or EXIT_BLOCK if REVERSE). */
basic_block begin = reverse ? EXIT_BLOCK_PTR : ENTRY_BLOCK_PTR;
static inline TBB
eval (struct dom_info *di, TBB v)
{
- /* The representant of the set V is in, also called root (as the set
+ /* The representative of the set V is in, also called root (as the set
representation is a tree). */
TBB rep = di->set_chain[v];
On return the immediate dominator to node V is in di->dom[V]. */
static void
-calc_idoms (struct dom_info *di, enum cdi_direction reverse)
+calc_idoms (struct dom_info *di, bool reverse)
{
TBB v, w, k, par;
basic_block en_block;
{
int num = 0;
basic_block bb;
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
gcc_assert (dom_info_available_p (dir));
- if (dom_computed[dir] == DOM_OK)
+ if (dom_computed[dir_index] == DOM_OK)
return;
FOR_ALL_BB (bb)
{
- if (!bb->dom[dir]->father)
- assign_dfs_numbers (bb->dom[dir], &num);
+ if (!bb->dom[dir_index]->father)
+ assign_dfs_numbers (bb->dom[dir_index], &num);
}
- dom_computed[dir] = DOM_OK;
+ dom_computed[dir_index] = DOM_OK;
}
/* The main entry point into this module. DIR is set depending on whether
{
struct dom_info di;
basic_block b;
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+ bool reverse = (dir == CDI_POST_DOMINATORS) ? true : false;
- if (dom_computed[dir] == DOM_OK)
+ if (dom_computed[dir_index] == DOM_OK)
return;
+ timevar_push (TV_DOMINANCE);
if (!dom_info_available_p (dir))
{
- gcc_assert (!n_bbs_in_dom_tree[dir]);
+ gcc_assert (!n_bbs_in_dom_tree[dir_index]);
FOR_ALL_BB (b)
{
- b->dom[dir] = et_new_tree (b);
+ b->dom[dir_index] = et_new_tree (b);
}
- n_bbs_in_dom_tree[dir] = n_basic_blocks;
+ n_bbs_in_dom_tree[dir_index] = n_basic_blocks;
init_dom_info (&di, dir);
- calc_dfs_tree (&di, dir);
- calc_idoms (&di, dir);
+ calc_dfs_tree (&di, reverse);
+ calc_idoms (&di, reverse);
FOR_EACH_BB (b)
{
TBB d = di.dom[di.dfs_order[b->index]];
if (di.dfs_to_bb[d])
- et_set_father (b->dom[dir], di.dfs_to_bb[d]->dom[dir]);
+ et_set_father (b->dom[dir_index], di.dfs_to_bb[d]->dom[dir_index]);
}
free_dom_info (&di);
- dom_computed[dir] = DOM_NO_FAST_QUERY;
+ dom_computed[dir_index] = DOM_NO_FAST_QUERY;
}
compute_dom_fast_query (dir);
+
+ timevar_pop (TV_DOMINANCE);
}
/* Free dominance information for direction DIR. */
free_dominance_info (enum cdi_direction dir)
{
basic_block bb;
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
if (!dom_info_available_p (dir))
return;
FOR_ALL_BB (bb)
{
- et_free_tree_force (bb->dom[dir]);
- bb->dom[dir] = NULL;
+ et_free_tree_force (bb->dom[dir_index]);
+ bb->dom[dir_index] = NULL;
}
+ et_free_pools ();
- n_bbs_in_dom_tree[dir] = 0;
+ n_bbs_in_dom_tree[dir_index] = 0;
- dom_computed[dir] = DOM_NONE;
+ dom_computed[dir_index] = DOM_NONE;
}
/* Return the immediate dominator of basic block BB. */
basic_block
get_immediate_dominator (enum cdi_direction dir, basic_block bb)
{
- struct et_node *node = bb->dom[dir];
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+ struct et_node *node = bb->dom[dir_index];
- gcc_assert (dom_computed[dir]);
+ gcc_assert (dom_computed[dir_index]);
if (!node->father)
return NULL;
- return node->father->data;
+ return (basic_block) node->father->data;
}
/* Set the immediate dominator of the block possibly removing
existing edge. NULL can be used to remove any edge. */
-inline void
+void
set_immediate_dominator (enum cdi_direction dir, basic_block bb,
basic_block dominated_by)
{
- struct et_node *node = bb->dom[dir];
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+ struct et_node *node = bb->dom[dir_index];
- gcc_assert (dom_computed[dir]);
+ gcc_assert (dom_computed[dir_index]);
if (node->father)
{
}
if (dominated_by)
- et_set_father (node, dominated_by->dom[dir]);
+ et_set_father (node, dominated_by->dom[dir_index]);
- if (dom_computed[dir] == DOM_OK)
- dom_computed[dir] = DOM_NO_FAST_QUERY;
+ if (dom_computed[dir_index] == DOM_OK)
+ dom_computed[dir_index] = DOM_NO_FAST_QUERY;
}
-/* Store all basic blocks immediately dominated by BB into BBS and return
- their number. */
-int
-get_dominated_by (enum cdi_direction dir, basic_block bb, basic_block **bbs)
+/* Returns the list of basic blocks immediately dominated by BB, in the
+ direction DIR. */
+VEC (basic_block, heap) *
+get_dominated_by (enum cdi_direction dir, basic_block bb)
{
- int n;
- struct et_node *node = bb->dom[dir], *son = node->son, *ason;
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+ struct et_node *node = bb->dom[dir_index], *son = node->son, *ason;
+ VEC (basic_block, heap) *bbs = NULL;
- gcc_assert (dom_computed[dir]);
+ gcc_assert (dom_computed[dir_index]);
if (!son)
- {
- *bbs = NULL;
- return 0;
- }
-
- for (ason = son->right, n = 1; ason != son; ason = ason->right)
- n++;
+ return NULL;
- *bbs = xmalloc (n * sizeof (basic_block));
- (*bbs)[0] = son->data;
- for (ason = son->right, n = 1; ason != son; ason = ason->right)
- (*bbs)[n++] = ason->data;
+ VEC_safe_push (basic_block, heap, bbs, (basic_block) son->data);
+ for (ason = son->right; ason != son; ason = ason->right)
+ VEC_safe_push (basic_block, heap, bbs, (basic_block) ason->data);
- return n;
+ return bbs;
}
-/* Find all basic blocks that are immediately dominated (in direction DIR)
- by some block between N_REGION ones stored in REGION, except for blocks
- in the REGION itself. The found blocks are stored to DOMS and their number
- is returned. */
+/* Returns the list of basic blocks that are immediately dominated (in
+ direction DIR) by some block between N_REGION ones stored in REGION,
+ except for blocks in the REGION itself. */
-unsigned
+VEC (basic_block, heap) *
get_dominated_by_region (enum cdi_direction dir, basic_block *region,
- unsigned n_region, basic_block *doms)
+ unsigned n_region)
{
- unsigned n_doms = 0, i;
+ unsigned i;
basic_block dom;
+ VEC (basic_block, heap) *doms = NULL;
for (i = 0; i < n_region; i++)
region[i]->flags |= BB_DUPLICATED;
dom;
dom = next_dom_son (dir, dom))
if (!(dom->flags & BB_DUPLICATED))
- doms[n_doms++] = dom;
+ VEC_safe_push (basic_block, heap, doms, dom);
for (i = 0; i < n_region; i++)
region[i]->flags &= ~BB_DUPLICATED;
- return n_doms;
+ return doms;
+}
+
+/* Returns the list of basic blocks including BB dominated by BB, in the
+ direction DIR up to DEPTH in the dominator tree. The DEPTH of zero will
+ produce a vector containing all dominated blocks. The vector will be sorted
+ in preorder. */
+
+VEC (basic_block, heap) *
+get_dominated_to_depth (enum cdi_direction dir, basic_block bb, int depth)
+{
+ VEC(basic_block, heap) *bbs = NULL;
+ unsigned i;
+ unsigned next_level_start;
+
+ i = 0;
+ VEC_safe_push (basic_block, heap, bbs, bb);
+ next_level_start = 1; /* = VEC_length (basic_block, bbs); */
+
+ do
+ {
+ basic_block son;
+
+ bb = VEC_index (basic_block, bbs, i++);
+ for (son = first_dom_son (dir, bb);
+ son;
+ son = next_dom_son (dir, son))
+ VEC_safe_push (basic_block, heap, bbs, son);
+
+ if (i == next_level_start && --depth)
+ next_level_start = VEC_length (basic_block, bbs);
+ }
+ while (i < next_level_start);
+
+ return bbs;
+}
+
+/* Returns the list of basic blocks including BB dominated by BB, in the
+ direction DIR. The vector will be sorted in preorder. */
+
+VEC (basic_block, heap) *
+get_all_dominated_blocks (enum cdi_direction dir, basic_block bb)
+{
+ return get_dominated_to_depth (dir, bb, 0);
}
/* Redirect all edges pointing to BB to TO. */
redirect_immediate_dominators (enum cdi_direction dir, basic_block bb,
basic_block to)
{
- struct et_node *bb_node = bb->dom[dir], *to_node = to->dom[dir], *son;
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+ struct et_node *bb_node, *to_node, *son;
+
+ bb_node = bb->dom[dir_index];
+ to_node = to->dom[dir_index];
- gcc_assert (dom_computed[dir]);
+ gcc_assert (dom_computed[dir_index]);
if (!bb_node->son)
return;
et_set_father (son, to_node);
}
- if (dom_computed[dir] == DOM_OK)
- dom_computed[dir] = DOM_NO_FAST_QUERY;
+ if (dom_computed[dir_index] == DOM_OK)
+ dom_computed[dir_index] = DOM_NO_FAST_QUERY;
}
/* Find first basic block in the tree dominating both BB1 and BB2. */
basic_block
nearest_common_dominator (enum cdi_direction dir, basic_block bb1, basic_block bb2)
{
- gcc_assert (dom_computed[dir]);
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+
+ gcc_assert (dom_computed[dir_index]);
if (!bb1)
return bb2;
if (!bb2)
return bb1;
- return et_nca (bb1->dom[dir], bb2->dom[dir])->data;
+ return (basic_block) et_nca (bb1->dom[dir_index], bb2->dom[dir_index])->data;
}
unsigned i, first;
bitmap_iterator bi;
basic_block dom;
-
+
first = bitmap_first_set_bit (blocks);
dom = BASIC_BLOCK (first);
EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi)
return dom;
}
+/* Given a dominator tree, we can determine whether one thing
+ dominates another in constant time by using two DFS numbers:
+
+ 1. The number for when we visit a node on the way down the tree
+ 2. The number for when we visit a node on the way back up the tree
+
+ You can view these as bounds for the range of dfs numbers the
+ nodes in the subtree of the dominator tree rooted at that node
+ will contain.
+
+ The dominator tree is always a simple acyclic tree, so there are
+ only three possible relations two nodes in the dominator tree have
+ to each other:
+
+ 1. Node A is above Node B (and thus, Node A dominates node B)
+
+ A
+ |
+ C
+ / \
+ B D
+
+
+ In the above case, DFS_Number_In of A will be <= DFS_Number_In of
+ B, and DFS_Number_Out of A will be >= DFS_Number_Out of B. This is
+ because we must hit A in the dominator tree *before* B on the walk
+ down, and we will hit A *after* B on the walk back up
+
+ 2. Node A is below node B (and thus, node B dominates node A)
+
+
+ B
+ |
+ A
+ / \
+ C D
+
+ In the above case, DFS_Number_In of A will be >= DFS_Number_In of
+ B, and DFS_Number_Out of A will be <= DFS_Number_Out of B.
+
+ This is because we must hit A in the dominator tree *after* B on
+ the walk down, and we will hit A *before* B on the walk back up
+
+ 3. Node A and B are siblings (and thus, neither dominates the other)
+
+ C
+ |
+ D
+ / \
+ A B
+
+ In the above case, DFS_Number_In of A will *always* be <=
+ DFS_Number_In of B, and DFS_Number_Out of A will *always* be <=
+ DFS_Number_Out of B. This is because we will always finish the dfs
+ walk of one of the subtrees before the other, and thus, the dfs
+ numbers for one subtree can't intersect with the range of dfs
+ numbers for the other subtree. If you swap A and B's position in
+ the dominator tree, the comparison changes direction, but the point
+ is that both comparisons will always go the same way if there is no
+ dominance relationship.
+
+ Thus, it is sufficient to write
+
+ A_Dominates_B (node A, node B)
+ {
+ return DFS_Number_In(A) <= DFS_Number_In(B)
+ && DFS_Number_Out (A) >= DFS_Number_Out(B);
+ }
+
+ A_Dominated_by_B (node A, node B)
+ {
+ return DFS_Number_In(A) >= DFS_Number_In(A)
+ && DFS_Number_Out (A) <= DFS_Number_Out(B);
+ } */
/* Return TRUE in case BB1 is dominated by BB2. */
bool
-dominated_by_p (enum cdi_direction dir, basic_block bb1, basic_block bb2)
-{
- struct et_node *n1 = bb1->dom[dir], *n2 = bb2->dom[dir];
+dominated_by_p (enum cdi_direction dir, const_basic_block bb1, const_basic_block bb2)
+{
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+ struct et_node *n1 = bb1->dom[dir_index], *n2 = bb2->dom[dir_index];
- gcc_assert (dom_computed[dir]);
+ gcc_assert (dom_computed[dir_index]);
- if (dom_computed[dir] == DOM_OK)
+ if (dom_computed[dir_index] == DOM_OK)
return (n1->dfs_num_in >= n2->dfs_num_in
&& n1->dfs_num_out <= n2->dfs_num_out);
return et_below (n1, n2);
}
+/* Returns the entry dfs number for basic block BB, in the direction DIR. */
+
+unsigned
+bb_dom_dfs_in (enum cdi_direction dir, basic_block bb)
+{
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+ struct et_node *n = bb->dom[dir_index];
+
+ gcc_assert (dom_computed[dir_index] == DOM_OK);
+ return n->dfs_num_in;
+}
+
+/* Returns the exit dfs number for basic block BB, in the direction DIR. */
+
+unsigned
+bb_dom_dfs_out (enum cdi_direction dir, basic_block bb)
+{
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+ struct et_node *n = bb->dom[dir_index];
+
+ gcc_assert (dom_computed[dir_index] == DOM_OK);
+ return n->dfs_num_out;
+}
+
/* Verify invariants of dominator structure. */
-void
+DEBUG_FUNCTION void
verify_dominators (enum cdi_direction dir)
{
int err = 0;
- basic_block bb;
+ basic_block bb, imm_bb, imm_bb_correct;
+ struct dom_info di;
+ bool reverse = (dir == CDI_POST_DOMINATORS) ? true : false;
gcc_assert (dom_info_available_p (dir));
+ init_dom_info (&di, dir);
+ calc_dfs_tree (&di, reverse);
+ calc_idoms (&di, reverse);
+
FOR_EACH_BB (bb)
{
- basic_block dom_bb;
- basic_block imm_bb;
-
- dom_bb = recount_dominator (dir, bb);
imm_bb = get_immediate_dominator (dir, bb);
- if (dom_bb != imm_bb)
+ if (!imm_bb)
{
- if ((dom_bb == NULL) || (imm_bb == NULL))
- error ("dominator of %d status unknown", bb->index);
- else
- error ("dominator of %d should be %d, not %d",
- bb->index, dom_bb->index, imm_bb->index);
+ error ("dominator of %d status unknown", bb->index);
err = 1;
}
- }
- if (dir == CDI_DOMINATORS)
- {
- FOR_EACH_BB (bb)
+ imm_bb_correct = di.dfs_to_bb[di.dom[di.dfs_order[bb->index]]];
+ if (imm_bb != imm_bb_correct)
{
- if (!dominated_by_p (dir, bb, ENTRY_BLOCK_PTR))
- {
- error ("ENTRY does not dominate bb %d", bb->index);
- err = 1;
- }
+ error ("dominator of %d should be %d, not %d",
+ bb->index, imm_bb_correct->index, imm_bb->index);
+ err = 1;
}
}
+ free_dom_info (&di);
gcc_assert (!err);
}
reaches a fixed point. */
basic_block
-recount_dominator (enum cdi_direction dir, basic_block bb)
+recompute_dominator (enum cdi_direction dir, basic_block bb)
{
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
basic_block dom_bb = NULL;
edge e;
edge_iterator ei;
- gcc_assert (dom_computed[dir]);
+ gcc_assert (dom_computed[dir_index]);
if (dir == CDI_DOMINATORS)
{
FOR_EACH_EDGE (e, ei, bb->preds)
{
- /* Ignore the predecessors that either are not reachable from
- the entry block, or whose dominator was not determined yet. */
- if (!dominated_by_p (dir, e->src, ENTRY_BLOCK_PTR))
- continue;
-
if (!dominated_by_p (dir, e->src, bb))
dom_bb = nearest_common_dominator (dir, dom_bb, e->src);
}
return dom_bb;
}
-/* Iteratively recount dominators of BBS. The change is supposed to be local
- and not to grow further. */
-void
-iterate_fix_dominators (enum cdi_direction dir, basic_block *bbs, int n)
+/* Use simple heuristics (see iterate_fix_dominators) to determine dominators
+ of BBS. We assume that all the immediate dominators except for those of the
+ blocks in BBS are correct. If CONSERVATIVE is true, we also assume that the
+ currently recorded immediate dominators of blocks in BBS really dominate the
+ blocks. The basic blocks for that we determine the dominator are removed
+ from BBS. */
+
+static void
+prune_bbs_to_update_dominators (VEC (basic_block, heap) *bbs,
+ bool conservative)
{
- int i, changed = 1;
- basic_block old_dom, new_dom;
+ unsigned i;
+ bool single;
+ basic_block bb, dom = NULL;
+ edge_iterator ei;
+ edge e;
+
+ for (i = 0; VEC_iterate (basic_block, bbs, i, bb);)
+ {
+ if (bb == ENTRY_BLOCK_PTR)
+ goto succeed;
+
+ if (single_pred_p (bb))
+ {
+ set_immediate_dominator (CDI_DOMINATORS, bb, single_pred (bb));
+ goto succeed;
+ }
+
+ if (!conservative)
+ goto fail;
- gcc_assert (dom_computed[dir]);
+ single = true;
+ dom = NULL;
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ {
+ if (dominated_by_p (CDI_DOMINATORS, e->src, bb))
+ continue;
- for (i = 0; i < n; i++)
- set_immediate_dominator (dir, bbs[i], NULL);
+ if (!dom)
+ dom = e->src;
+ else
+ {
+ single = false;
+ dom = nearest_common_dominator (CDI_DOMINATORS, dom, e->src);
+ }
+ }
- while (changed)
+ gcc_assert (dom != NULL);
+ if (single
+ || find_edge (dom, bb))
+ {
+ set_immediate_dominator (CDI_DOMINATORS, bb, dom);
+ goto succeed;
+ }
+
+fail:
+ i++;
+ continue;
+
+succeed:
+ VEC_unordered_remove (basic_block, bbs, i);
+ }
+}
+
+/* Returns root of the dominance tree in the direction DIR that contains
+ BB. */
+
+static basic_block
+root_of_dom_tree (enum cdi_direction dir, basic_block bb)
+{
+ return (basic_block) et_root (bb->dom[dom_convert_dir_to_idx (dir)])->data;
+}
+
+/* See the comment in iterate_fix_dominators. Finds the immediate dominators
+ for the sons of Y, found using the SON and BROTHER arrays representing
+ the dominance tree of graph G. BBS maps the vertices of G to the basic
+ blocks. */
+
+static void
+determine_dominators_for_sons (struct graph *g, VEC (basic_block, heap) *bbs,
+ int y, int *son, int *brother)
+{
+ bitmap gprime;
+ int i, a, nc;
+ VEC (int, heap) **sccs;
+ basic_block bb, dom, ybb;
+ unsigned si;
+ edge e;
+ edge_iterator ei;
+
+ if (son[y] == -1)
+ return;
+ if (y == (int) VEC_length (basic_block, bbs))
+ ybb = ENTRY_BLOCK_PTR;
+ else
+ ybb = VEC_index (basic_block, bbs, y);
+
+ if (brother[son[y]] == -1)
{
- changed = 0;
- for (i = 0; i < n; i++)
+ /* Handle the common case Y has just one son specially. */
+ bb = VEC_index (basic_block, bbs, son[y]);
+ set_immediate_dominator (CDI_DOMINATORS, bb,
+ recompute_dominator (CDI_DOMINATORS, bb));
+ identify_vertices (g, y, son[y]);
+ return;
+ }
+
+ gprime = BITMAP_ALLOC (NULL);
+ for (a = son[y]; a != -1; a = brother[a])
+ bitmap_set_bit (gprime, a);
+
+ nc = graphds_scc (g, gprime);
+ BITMAP_FREE (gprime);
+
+ sccs = XCNEWVEC (VEC (int, heap) *, nc);
+ for (a = son[y]; a != -1; a = brother[a])
+ VEC_safe_push (int, heap, sccs[g->vertices[a].component], a);
+
+ for (i = nc - 1; i >= 0; i--)
+ {
+ dom = NULL;
+ FOR_EACH_VEC_ELT (int, sccs[i], si, a)
{
- old_dom = get_immediate_dominator (dir, bbs[i]);
- new_dom = recount_dominator (dir, bbs[i]);
- if (old_dom != new_dom)
+ bb = VEC_index (basic_block, bbs, a);
+ FOR_EACH_EDGE (e, ei, bb->preds)
{
- changed = 1;
- set_immediate_dominator (dir, bbs[i], new_dom);
+ if (root_of_dom_tree (CDI_DOMINATORS, e->src) != ybb)
+ continue;
+
+ dom = nearest_common_dominator (CDI_DOMINATORS, dom, e->src);
}
}
+
+ gcc_assert (dom != NULL);
+ FOR_EACH_VEC_ELT (int, sccs[i], si, a)
+ {
+ bb = VEC_index (basic_block, bbs, a);
+ set_immediate_dominator (CDI_DOMINATORS, bb, dom);
+ }
+ }
+
+ for (i = 0; i < nc; i++)
+ VEC_free (int, heap, sccs[i]);
+ free (sccs);
+
+ for (a = son[y]; a != -1; a = brother[a])
+ identify_vertices (g, y, a);
+}
+
+/* Recompute dominance information for basic blocks in the set BBS. The
+ function assumes that the immediate dominators of all the other blocks
+ in CFG are correct, and that there are no unreachable blocks.
+
+ If CONSERVATIVE is true, we additionally assume that all the ancestors of
+ a block of BBS in the current dominance tree dominate it. */
+
+void
+iterate_fix_dominators (enum cdi_direction dir, VEC (basic_block, heap) *bbs,
+ bool conservative)
+{
+ unsigned i;
+ basic_block bb, dom;
+ struct graph *g;
+ int n, y;
+ size_t dom_i;
+ edge e;
+ edge_iterator ei;
+ struct pointer_map_t *map;
+ int *parent, *son, *brother;
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+
+ /* We only support updating dominators. There are some problems with
+ updating postdominators (need to add fake edges from infinite loops
+ and noreturn functions), and since we do not currently use
+ iterate_fix_dominators for postdominators, any attempt to handle these
+ problems would be unused, untested, and almost surely buggy. We keep
+ the DIR argument for consistency with the rest of the dominator analysis
+ interface. */
+ gcc_assert (dir == CDI_DOMINATORS);
+ gcc_assert (dom_computed[dir_index]);
+
+ /* The algorithm we use takes inspiration from the following papers, although
+ the details are quite different from any of them:
+
+ [1] G. Ramalingam, T. Reps, An Incremental Algorithm for Maintaining the
+ Dominator Tree of a Reducible Flowgraph
+ [2] V. C. Sreedhar, G. R. Gao, Y.-F. Lee: Incremental computation of
+ dominator trees
+ [3] K. D. Cooper, T. J. Harvey and K. Kennedy: A Simple, Fast Dominance
+ Algorithm
+
+ First, we use the following heuristics to decrease the size of the BBS
+ set:
+ a) if BB has a single predecessor, then its immediate dominator is this
+ predecessor
+ additionally, if CONSERVATIVE is true:
+ b) if all the predecessors of BB except for one (X) are dominated by BB,
+ then X is the immediate dominator of BB
+ c) if the nearest common ancestor of the predecessors of BB is X and
+ X -> BB is an edge in CFG, then X is the immediate dominator of BB
+
+ Then, we need to establish the dominance relation among the basic blocks
+ in BBS. We split the dominance tree by removing the immediate dominator
+ edges from BBS, creating a forest F. We form a graph G whose vertices
+ are BBS and ENTRY and X -> Y is an edge of G if there exists an edge
+ X' -> Y in CFG such that X' belongs to the tree of the dominance forest
+ whose root is X. We then determine dominance tree of G. Note that
+ for X, Y in BBS, X dominates Y in CFG if and only if X dominates Y in G.
+ In this step, we can use arbitrary algorithm to determine dominators.
+ We decided to prefer the algorithm [3] to the algorithm of
+ Lengauer and Tarjan, since the set BBS is usually small (rarely exceeding
+ 10 during gcc bootstrap), and [3] should perform better in this case.
+
+ Finally, we need to determine the immediate dominators for the basic
+ blocks of BBS. If the immediate dominator of X in G is Y, then
+ the immediate dominator of X in CFG belongs to the tree of F rooted in
+ Y. We process the dominator tree T of G recursively, starting from leaves.
+ Suppose that X_1, X_2, ..., X_k are the sons of Y in T, and that the
+ subtrees of the dominance tree of CFG rooted in X_i are already correct.
+ Let G' be the subgraph of G induced by {X_1, X_2, ..., X_k}. We make
+ the following observations:
+ (i) the immediate dominator of all blocks in a strongly connected
+ component of G' is the same
+ (ii) if X has no predecessors in G', then the immediate dominator of X
+ is the nearest common ancestor of the predecessors of X in the
+ subtree of F rooted in Y
+ Therefore, it suffices to find the topological ordering of G', and
+ process the nodes X_i in this order using the rules (i) and (ii).
+ Then, we contract all the nodes X_i with Y in G, so that the further
+ steps work correctly. */
+
+ if (!conservative)
+ {
+ /* Split the tree now. If the idoms of blocks in BBS are not
+ conservatively correct, setting the dominators using the
+ heuristics in prune_bbs_to_update_dominators could
+ create cycles in the dominance "tree", and cause ICE. */
+ FOR_EACH_VEC_ELT (basic_block, bbs, i, bb)
+ set_immediate_dominator (CDI_DOMINATORS, bb, NULL);
+ }
+
+ prune_bbs_to_update_dominators (bbs, conservative);
+ n = VEC_length (basic_block, bbs);
+
+ if (n == 0)
+ return;
+
+ if (n == 1)
+ {
+ bb = VEC_index (basic_block, bbs, 0);
+ set_immediate_dominator (CDI_DOMINATORS, bb,
+ recompute_dominator (CDI_DOMINATORS, bb));
+ return;
+ }
+
+ /* Construct the graph G. */
+ map = pointer_map_create ();
+ FOR_EACH_VEC_ELT (basic_block, bbs, i, bb)
+ {
+ /* If the dominance tree is conservatively correct, split it now. */
+ if (conservative)
+ set_immediate_dominator (CDI_DOMINATORS, bb, NULL);
+ *pointer_map_insert (map, bb) = (void *) (size_t) i;
+ }
+ *pointer_map_insert (map, ENTRY_BLOCK_PTR) = (void *) (size_t) n;
+
+ g = new_graph (n + 1);
+ for (y = 0; y < g->n_vertices; y++)
+ g->vertices[y].data = BITMAP_ALLOC (NULL);
+ FOR_EACH_VEC_ELT (basic_block, bbs, i, bb)
+ {
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ {
+ dom = root_of_dom_tree (CDI_DOMINATORS, e->src);
+ if (dom == bb)
+ continue;
+
+ dom_i = (size_t) *pointer_map_contains (map, dom);
+
+ /* Do not include parallel edges to G. */
+ if (!bitmap_set_bit ((bitmap) g->vertices[dom_i].data, i))
+ continue;
+
+ add_edge (g, dom_i, i);
+ }
+ }
+ for (y = 0; y < g->n_vertices; y++)
+ BITMAP_FREE (g->vertices[y].data);
+ pointer_map_destroy (map);
+
+ /* Find the dominator tree of G. */
+ son = XNEWVEC (int, n + 1);
+ brother = XNEWVEC (int, n + 1);
+ parent = XNEWVEC (int, n + 1);
+ graphds_domtree (g, n, parent, son, brother);
+
+ /* Finally, traverse the tree and find the immediate dominators. */
+ for (y = n; son[y] != -1; y = son[y])
+ continue;
+ while (y != -1)
+ {
+ determine_dominators_for_sons (g, bbs, y, son, brother);
+
+ if (brother[y] != -1)
+ {
+ y = brother[y];
+ while (son[y] != -1)
+ y = son[y];
+ }
+ else
+ y = parent[y];
}
- for (i = 0; i < n; i++)
- gcc_assert (get_immediate_dominator (dir, bbs[i]));
+ free (son);
+ free (brother);
+ free (parent);
+
+ free_graph (g);
}
void
add_to_dominance_info (enum cdi_direction dir, basic_block bb)
{
- gcc_assert (dom_computed[dir]);
- gcc_assert (!bb->dom[dir]);
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+
+ gcc_assert (dom_computed[dir_index]);
+ gcc_assert (!bb->dom[dir_index]);
- n_bbs_in_dom_tree[dir]++;
-
- bb->dom[dir] = et_new_tree (bb);
+ n_bbs_in_dom_tree[dir_index]++;
- if (dom_computed[dir] == DOM_OK)
- dom_computed[dir] = DOM_NO_FAST_QUERY;
+ bb->dom[dir_index] = et_new_tree (bb);
+
+ if (dom_computed[dir_index] == DOM_OK)
+ dom_computed[dir_index] = DOM_NO_FAST_QUERY;
}
void
delete_from_dominance_info (enum cdi_direction dir, basic_block bb)
{
- gcc_assert (dom_computed[dir]);
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+
+ gcc_assert (dom_computed[dir_index]);
- et_free_tree (bb->dom[dir]);
- bb->dom[dir] = NULL;
- n_bbs_in_dom_tree[dir]--;
+ et_free_tree (bb->dom[dir_index]);
+ bb->dom[dir_index] = NULL;
+ n_bbs_in_dom_tree[dir_index]--;
- if (dom_computed[dir] == DOM_OK)
- dom_computed[dir] = DOM_NO_FAST_QUERY;
+ if (dom_computed[dir_index] == DOM_OK)
+ dom_computed[dir_index] = DOM_NO_FAST_QUERY;
}
/* Returns the first son of BB in the dominator or postdominator tree
basic_block
first_dom_son (enum cdi_direction dir, basic_block bb)
{
- struct et_node *son = bb->dom[dir]->son;
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+ struct et_node *son = bb->dom[dir_index]->son;
- return son ? son->data : NULL;
+ return (basic_block) (son ? son->data : NULL);
}
/* Returns the next dominance son after BB in the dominator or postdominator
basic_block
next_dom_son (enum cdi_direction dir, basic_block bb)
{
- struct et_node *next = bb->dom[dir]->right;
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+ struct et_node *next = bb->dom[dir_index]->right;
- return next->father->son == next ? NULL : next->data;
+ return (basic_block) (next->father->son == next ? NULL : next->data);
+}
+
+/* Return dominance availability for dominance info DIR. */
+
+enum dom_state
+dom_info_state (enum cdi_direction dir)
+{
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+
+ return dom_computed[dir_index];
+}
+
+/* Set the dominance availability for dominance info DIR to NEW_STATE. */
+
+void
+set_dom_info_availability (enum cdi_direction dir, enum dom_state new_state)
+{
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+
+ dom_computed[dir_index] = new_state;
}
/* Returns true if dominance information for direction DIR is available. */
bool
dom_info_available_p (enum cdi_direction dir)
{
- return dom_computed[dir] != DOM_NONE;
+ unsigned int dir_index = dom_convert_dir_to_idx (dir);
+
+ return dom_computed[dir_index] != DOM_NONE;
}
-void
+DEBUG_FUNCTION void
debug_dominance_info (enum cdi_direction dir)
{
basic_block bb, bb2;
if ((bb2 = get_immediate_dominator (dir, bb)))
fprintf (stderr, "%i %i\n", bb->index, bb2->index);
}
+
+/* Prints to stderr representation of the dominance tree (for direction DIR)
+ rooted in ROOT, indented by INDENT tabulators. If INDENT_FIRST is false,
+ the first line of the output is not indented. */
+
+static void
+debug_dominance_tree_1 (enum cdi_direction dir, basic_block root,
+ unsigned indent, bool indent_first)
+{
+ basic_block son;
+ unsigned i;
+ bool first = true;
+
+ if (indent_first)
+ for (i = 0; i < indent; i++)
+ fprintf (stderr, "\t");
+ fprintf (stderr, "%d\t", root->index);
+
+ for (son = first_dom_son (dir, root);
+ son;
+ son = next_dom_son (dir, son))
+ {
+ debug_dominance_tree_1 (dir, son, indent + 1, !first);
+ first = false;
+ }
+
+ if (first)
+ fprintf (stderr, "\n");
+}
+
+/* Prints to stderr representation of the dominance tree (for direction DIR)
+ rooted in ROOT. */
+
+DEBUG_FUNCTION void
+debug_dominance_tree (enum cdi_direction dir, basic_block root)
+{
+ debug_dominance_tree_1 (dir, root, 0, false);
+}
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