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re PR middle-end/28071 (A file that can not be compiled in reasonable time/space)

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PR rtl-optimization/28071
	* basic-block.h (bb_dom_dfs_in, bb_dom_dfs_out): Declare.
	* dominance.c (bb_dom_dfs_in, bb_dom_dfs_out): New functions.
	* tree-into-ssa.c (struct dom_dfsnum): New.
	(cmp_dfsnum, find_dfsnum_interval, prune_unused_phi_nodes): New
	functions.
	(insert_phi_nodes_for): Use prune_unused_phi_nodes instead of
	compute_global_livein.
	(prepare_block_for_update, prepare_use_sites_for): Mark the uses
	in phi nodes in the correct blocks.

From-SVN: r116190
This commit is contained in:
Zdenek Dvorak 2006-08-16 23:25:39 +02:00 committed by Zdenek Dvorak
parent b43a2366d6
commit f074ff6cc0
4 changed files with 268 additions and 40 deletions
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13
gcc/ChangeLog
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@ -1,3 +1,16 @@
2006-08-16 Zdenek Dvorak <dvorakz@suse.cz>
PR rtl-optimization/28071
* basic-block.h (bb_dom_dfs_in, bb_dom_dfs_out): Declare.
* dominance.c (bb_dom_dfs_in, bb_dom_dfs_out): New functions.
* tree-into-ssa.c (struct dom_dfsnum): New.
(cmp_dfsnum, find_dfsnum_interval, prune_unused_phi_nodes): New
functions.
(insert_phi_nodes_for): Use prune_unused_phi_nodes instead of
compute_global_livein.
(prepare_block_for_update, prepare_use_sites_for): Mark the uses
in phi nodes in the correct blocks.
2006-08-16 Zdenek Dvorak <dvorakz@suse.cz>
PR tree-optimization/28364

3
gcc/basic-block.h
View File

@ -988,6 +988,9 @@ extern void iterate_fix_dominators (enum cdi_direction, basic_block *, int);
extern void verify_dominators (enum cdi_direction);
extern basic_block first_dom_son (enum cdi_direction, basic_block);
extern basic_block next_dom_son (enum cdi_direction, basic_block);
unsigned bb_dom_dfs_in (enum cdi_direction, basic_block);
unsigned bb_dom_dfs_out (enum cdi_direction, basic_block);
extern edge try_redirect_by_replacing_jump (edge, basic_block, bool);
extern void break_superblocks (void);
extern void check_bb_profile (basic_block, FILE *);

22
gcc/dominance.c
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@ -909,6 +909,28 @@ dominated_by_p (enum cdi_direction dir, basic_block bb1, basic_block bb2)
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)
{
struct et_node *n = bb->dom[dir];
gcc_assert (dom_computed[dir] == 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)
{
struct et_node *n = bb->dom[dir];
gcc_assert (dom_computed[dir] == DOM_OK);
return n->dfs_num_out;
}
/* Verify invariants of dominator structure. */
void
verify_dominators (enum cdi_direction dir)

270
gcc/tree-into-ssa.c
View File

@ -779,6 +779,214 @@ mark_def_sites (struct dom_walk_data *walk_data,
SET_BIT (gd->interesting_blocks, bb->index);
}
/* Structure used by prune_unused_phi_nodes to record bounds of the intervals
in the dfs numbering of the dominance tree. */
struct dom_dfsnum
{
/* Basic block whose index this entry corresponds to. */
unsigned bb_index;
/* The dfs number of this node. */
unsigned dfs_num;
};
/* Compares two entries of type struct dom_dfsnum by dfs_num field. Callback
for qsort. */
static int
cmp_dfsnum (const void *a, const void *b)
{
const struct dom_dfsnum *da = a;
const struct dom_dfsnum *db = b;
return (int) da->dfs_num - (int) db->dfs_num;
}
/* Among the intervals starting at the N points specified in DEFS, find
the one that contains S, and return its bb_index. */
static unsigned
find_dfsnum_interval (struct dom_dfsnum *defs, unsigned n, unsigned s)
{
unsigned f = 0, t = n, m;
while (t > f + 1)
{
m = (f + t) / 2;
if (defs[m].dfs_num <= s)
f = m;
else
t = m;
}
return defs[f].bb_index;
}
/* Clean bits from PHIS for phi nodes whose value cannot be used in USES.
KILLS is a bitmap of blocks where the value is defined before any use. */
static void
prune_unused_phi_nodes (bitmap phis, bitmap kills, bitmap uses)
{
VEC(int, heap) *worklist;
bitmap_iterator bi;
unsigned i, b, p, u, top;
bitmap live_phis;
basic_block def_bb, use_bb;
edge e;
edge_iterator ei;
bitmap to_remove;
struct dom_dfsnum *defs;
unsigned n_defs, adef;
if (bitmap_empty_p (uses))
{
bitmap_clear (phis);
return;
}
/* The phi must dominate a use, or an argument of a live phi. Also, we
do not create any phi nodes in def blocks, unless they are also livein. */
to_remove = BITMAP_ALLOC (NULL);
bitmap_and_compl (to_remove, kills, uses);
bitmap_and_compl_into (phis, to_remove);
if (bitmap_empty_p (phis))
{
BITMAP_FREE (to_remove);
return;
}
/* We want to remove the unnecessary phi nodes, but we do not want to compute
liveness information, as that may be linear in the size of CFG, and if
there are lot of different variables to rewrite, this may lead to quadratic
behavior.
Instead, we basically emulate standard dce. We put all uses to worklist,
then for each of them find the nearest def that dominates them. If this
def is a phi node, we mark it live, and if it was not live before, we
add the predecessors of its basic block to the worklist.
To quickly locate the nearest def that dominates use, we use dfs numbering
of the dominance tree (that is already available in order to speed up
queries). For each def, we have the interval given by the dfs number on
entry to and on exit from the corresponding subtree in the dominance tree.
The nearest dominator for a given use is the smallest of these intervals
that contains entry and exit dfs numbers for the basic block with the use.
If we store the bounds for all the uses to an array and sort it, we can
locate the nearest dominating def in logarithmic time by binary search.*/
bitmap_ior (to_remove, kills, phis);
n_defs = bitmap_count_bits (to_remove);
defs = XNEWVEC (struct dom_dfsnum, 2 * n_defs + 1);
defs[0].bb_index = 1;
defs[0].dfs_num = 0;
adef = 1;
EXECUTE_IF_SET_IN_BITMAP (to_remove, 0, i, bi)
{
def_bb = BASIC_BLOCK (i);
defs[adef].bb_index = i;
defs[adef].dfs_num = bb_dom_dfs_in (CDI_DOMINATORS, def_bb);
defs[adef + 1].bb_index = i;
defs[adef + 1].dfs_num = bb_dom_dfs_out (CDI_DOMINATORS, def_bb);
adef += 2;
}
BITMAP_FREE (to_remove);
gcc_assert (adef == 2 * n_defs + 1);
qsort (defs, adef, sizeof (struct dom_dfsnum), cmp_dfsnum);
gcc_assert (defs[0].bb_index == 1);
/* Now each DEFS entry contains the number of the basic block to that the
dfs number corresponds. Change them to the number of basic block that
corresponds to the interval following the dfs number. Also, for the
dfs_out numbers, increase the dfs number by one (so that it corresponds
to the start of the following interval, not to the end of the current
one). We use WORKLIST as a stack. */
worklist = VEC_alloc (int, heap, n_defs + 1);
VEC_quick_push (int, worklist, 1);
top = 1;
n_defs = 1;
for (i = 1; i < adef; i++)
{
b = defs[i].bb_index;
if (b == top)
{
/* This is a closing element. Interval corresponding to the top
of the stack after removing it follows. */
VEC_pop (int, worklist);
top = VEC_index (int, worklist, VEC_length (int, worklist) - 1);
defs[n_defs].bb_index = top;
defs[n_defs].dfs_num = defs[i].dfs_num + 1;
}
else
{
/* Opening element. Nothing to do, just push it to the stack and move
it to the correct position. */
defs[n_defs].bb_index = defs[i].bb_index;
defs[n_defs].dfs_num = defs[i].dfs_num;
VEC_quick_push (int, worklist, b);
top = b;
}
/* If this interval starts at the same point as the previous one, cancel
the previous one. */
if (defs[n_defs].dfs_num == defs[n_defs - 1].dfs_num)
defs[n_defs - 1].bb_index = defs[n_defs].bb_index;
else
n_defs++;
}
VEC_pop (int, worklist);
gcc_assert (VEC_empty (int, worklist));
/* Now process the uses. */
live_phis = BITMAP_ALLOC (NULL);
EXECUTE_IF_SET_IN_BITMAP (uses, 0, i, bi)
{
VEC_safe_push (int, heap, worklist, i);
}
while (!VEC_empty (int, worklist))
{
b = VEC_pop (int, worklist);
if (b == ENTRY_BLOCK)
continue;
/* If there is a phi node in USE_BB, it is made live. Otherwise,
find the def that dominates the immediate dominator of USE_BB
(the kill in USE_BB does not dominate the use). */
if (bitmap_bit_p (phis, b))
p = b;
else
{
use_bb = get_immediate_dominator (CDI_DOMINATORS, BASIC_BLOCK (b));
p = find_dfsnum_interval (defs, n_defs,
bb_dom_dfs_in (CDI_DOMINATORS, use_bb));
if (!bitmap_bit_p (phis, p))
continue;
}
/* If the phi node is already live, there is nothing to do. */
if (bitmap_bit_p (live_phis, p))
continue;
/* Mark the phi as live, and add the new uses to the worklist. */
bitmap_set_bit (live_phis, p);
def_bb = BASIC_BLOCK (p);
FOR_EACH_EDGE (e, ei, def_bb->preds)
{
u = e->src->index;
if (bitmap_bit_p (uses, u))
continue;
bitmap_set_bit (uses, u);
VEC_safe_push (int, heap, worklist, u);
}
}
VEC_free (int, heap, worklist);
bitmap_copy (phis, live_phis);
BITMAP_FREE (live_phis);
free (defs);
}
/* Given a set of blocks with variable definitions (DEF_BLOCKS),
return a bitmap with all the blocks in the iterated dominance
@ -926,13 +1134,12 @@ insert_phi_nodes_for (tree var, bitmap phi_insertion_points, bool update_p)
/* Remove the blocks where we already have PHI nodes for VAR. */
bitmap_and_compl_into (phi_insertion_points, def_map->phi_blocks);
/* Now compute global livein for this variable. Note this modifies
def_map->livein_blocks. */
compute_global_livein (def_map->livein_blocks, def_map->def_blocks);
/* Remove obviously useless phi nodes. */
prune_unused_phi_nodes (phi_insertion_points, def_map->def_blocks,
def_map->livein_blocks);
/* And insert the PHI nodes. */
EXECUTE_IF_AND_IN_BITMAP (phi_insertion_points, def_map->livein_blocks,
0, bb_index, bi)
EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points, 0, bb_index, bi)
{
bb = BASIC_BLOCK (bb_index);
if (update_p)
@ -2009,6 +2216,8 @@ prepare_block_for_update (basic_block bb, bool insert_phi_p)
basic_block son;
block_stmt_iterator si;
tree phi;
edge e;
edge_iterator ei;
mark_block_for_update (bb);
@ -2020,10 +2229,20 @@ prepare_block_for_update (basic_block bb, bool insert_phi_p)
lhs_sym = DECL_P (lhs) ? lhs : SSA_NAME_VAR (lhs);
if (symbol_marked_for_renaming (lhs_sym))
if (!symbol_marked_for_renaming (lhs_sym))
continue;
mark_def_interesting (lhs_sym, phi, bb, insert_phi_p);
/* Mark the uses in phi nodes as interesting. It would be more correct
to process the arguments of the phi nodes of the successor edges of
BB at the end of prepare_block_for_update, however, that turns out
to be significantly more expensive. Doing it here is conservatively
correct -- it may only cause us to believe a value to be live in a
block that also contains its definition, and thus insert a few more
phi nodes for it. */
FOR_EACH_EDGE (e, ei, bb->preds)
{
mark_use_interesting (lhs_sym, phi, bb, insert_phi_p);
mark_def_interesting (lhs_sym, phi, bb, insert_phi_p);
mark_use_interesting (lhs_sym, phi, e->src, insert_phi_p);
}
}
@ -2101,38 +2320,9 @@ prepare_use_sites_for (tree name, bool insert_phi_p)
if (TREE_CODE (stmt) == PHI_NODE)
{
/* Mark this use of NAME interesting for the renamer.
Notice that we explicitly call mark_use_interesting with
INSERT_PHI_P == false.
This is to avoid marking NAME as live-in in this block
BB. If we were to mark NAME live-in to BB, then NAME
would be considered live-in through ALL incoming edges to
BB which is not what we want. Since we are updating the
SSA form for NAME, we don't really know what other names
of NAME are coming in through other edges into BB.
If we considered NAME live-in at BB, then the PHI
placement algorithm may try to insert PHI nodes in blocks
that are not only unnecessary but also the renamer would
not know how to fill in. */
mark_use_interesting (name, stmt, bb, false);
/* As discussed above, we only want to mark NAME live-in
through the edge corresponding to its slot inside the PHI
argument list. So, we look for the block BB1 where NAME
is flowing through. If BB1 does not contain a definition
of NAME, then consider NAME live-in at BB1. */
if (insert_phi_p)
{
int ix = PHI_ARG_INDEX_FROM_USE (use_p);
edge e = PHI_ARG_EDGE (stmt, ix);
basic_block bb1 = e->src;
struct def_blocks_d *db = get_def_blocks_for (name);
if (!bitmap_bit_p (db->def_blocks, bb1->index))
set_livein_block (name, bb1);
}
int ix = PHI_ARG_INDEX_FROM_USE (use_p);
edge e = PHI_ARG_EDGE (stmt, ix);
mark_use_interesting (name, stmt, e->src, insert_phi_p);
}
else
{