/* Loop header copying on trees.
- Copyright (C) 2004 Free Software Foundation, Inc.
-
+ Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
+
This file is part of GCC.
-
+
GCC is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
-Free Software Foundation; either version 2, or (at your option) any
+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 COPYING. If not, write to the Free
-Software Foundation, 59 Temple Place - Suite 330, Boston, MA
-02111-1307, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
/* Duplicates headers of loops if they are small enough, so that the statements
in the loop body are always executed when the loop is entered. This
- increases effectivity of code motion optimizations, and reduces the need
+ increases effectiveness of code motion optimizations, and reduces the need
for loop preconditioning. */
/* Check whether we should duplicate HEADER of LOOP. At most *LIMIT
should_duplicate_loop_header_p (basic_block header, struct loop *loop,
int *limit)
{
- block_stmt_iterator bsi;
- tree last;
+ gimple_stmt_iterator bsi;
+ gimple last;
/* Do not copy one block more than once (we do not really want to do
loop peeling here). */
if (header->aux)
return false;
- gcc_assert (header->succ);
- if (!header->succ->succ_next)
+ /* Loop header copying usually increases size of the code. This used not to
+ be true, since quite often it is possible to verify that the condition is
+ satisfied in the first iteration and therefore to eliminate it. Jump
+ threading handles these cases now. */
+ if (optimize_loop_for_size_p (loop))
return false;
- if (header->succ->succ_next->succ_next)
+
+ gcc_assert (EDGE_COUNT (header->succs) > 0);
+ if (single_succ_p (header))
return false;
- if (flow_bb_inside_loop_p (loop, header->succ->dest)
- && flow_bb_inside_loop_p (loop, header->succ->succ_next->dest))
+ if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest)
+ && flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 1)->dest))
return false;
/* If this is not the original loop header, we want it to have just
one predecessor in order to match the && pattern. */
- if (header != loop->header
- && header->pred->pred_next)
+ if (header != loop->header && !single_pred_p (header))
return false;
last = last_stmt (header);
- if (TREE_CODE (last) != COND_EXPR)
+ if (gimple_code (last) != GIMPLE_COND)
return false;
/* Approximately copy the conditions that used to be used in jump.c --
at most 20 insns and no calls. */
- for (bsi = bsi_start (header); !bsi_end_p (bsi); bsi_next (&bsi))
+ for (bsi = gsi_start_bb (header); !gsi_end_p (bsi); gsi_next (&bsi))
{
- last = bsi_stmt (bsi);
+ last = gsi_stmt (bsi);
+
+ if (gimple_code (last) == GIMPLE_LABEL)
+ continue;
- if (TREE_CODE (last) == LABEL_EXPR)
+ if (is_gimple_debug (last))
continue;
- if (get_call_expr_in (last))
+ if (is_gimple_call (last))
return false;
- *limit -= estimate_num_insns (last);
+ *limit -= estimate_num_insns (last, &eni_size_weights);
if (*limit < 0)
return false;
}
return true;
}
-/* Duplicates destinations of edges in BBS_TO_DUPLICATE. */
-
-static void
-duplicate_blocks (varray_type bbs_to_duplicate)
-{
- unsigned i;
- edge preheader_edge, e, e1;
- basic_block header, new_header;
- tree phi, new_phi, var;
-
- /* TODO: It should be quite easy to keep the dominance information
- up-to-date. */
- free_dominance_info (CDI_DOMINATORS);
-
- for (i = 0; i < VARRAY_ACTIVE_SIZE (bbs_to_duplicate); i++)
- {
- preheader_edge = VARRAY_GENERIC_PTR_NOGC (bbs_to_duplicate, i);
- header = preheader_edge->dest;
-
- gcc_assert (header->aux);
- header->aux = NULL;
-
- new_header = duplicate_block (header, preheader_edge);
-
- /* Create the phi nodes on on entry to new_header. */
- for (phi = phi_nodes (header), var = PENDING_STMT (preheader_edge);
- phi;
- phi = TREE_CHAIN (phi), var = TREE_CHAIN (var))
- {
- new_phi = create_phi_node (PHI_RESULT (phi), new_header);
- add_phi_arg (&new_phi, TREE_VALUE (var), preheader_edge);
- }
- PENDING_STMT (preheader_edge) = NULL;
-
- /* Add the phi arguments to the outgoing edges. */
- for (e = header->succ; e; e = e->succ_next)
- {
- for (e1 = new_header->succ; e1->dest != e->dest; e1 = e1->succ_next)
- continue;
-
- for (phi = phi_nodes (e->dest); phi; phi = TREE_CHAIN (phi))
- {
- tree def = PHI_ARG_DEF_FROM_EDGE (phi, e);
- add_phi_arg (&phi, def, e1);
- }
- }
- }
-
- calculate_dominance_info (CDI_DOMINATORS);
-
- rewrite_ssa_into_ssa ();
-}
-
/* Checks whether LOOP is a do-while style loop. */
static bool
do_while_loop_p (struct loop *loop)
{
- tree stmt = last_stmt (loop->latch);
+ gimple stmt = last_stmt (loop->latch);
/* If the latch of the loop is not empty, it is not a do-while loop. */
if (stmt
- && TREE_CODE (stmt) != LABEL_EXPR)
+ && gimple_code (stmt) != GIMPLE_LABEL)
return false;
/* If the header contains just a condition, it is not a do-while loop. */
stmt = last_and_only_stmt (loop->header);
if (stmt
- && TREE_CODE (stmt) == COND_EXPR)
+ && gimple_code (stmt) == GIMPLE_COND)
return false;
return true;
of the loop. This is beneficial since it increases efficiency of
code motion optimizations. It also saves one jump on entry to the loop. */
-static void
+static unsigned int
copy_loop_headers (void)
{
- struct loops *loops;
- unsigned i;
+ loop_iterator li;
struct loop *loop;
basic_block header;
- edge preheader_edge;
- varray_type bbs_to_duplicate = NULL;
-
- loops = loop_optimizer_init (dump_file);
- if (!loops)
- return;
-
- /* We do not try to keep the information about irreducible regions
- up-to-date. */
- loops->state &= ~LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS;
+ edge exit, entry;
+ basic_block *bbs, *copied_bbs;
+ unsigned n_bbs;
+ unsigned bbs_size;
+
+ loop_optimizer_init (LOOPS_HAVE_PREHEADERS
+ | LOOPS_HAVE_SIMPLE_LATCHES);
+ if (number_of_loops () <= 1)
+ {
+ loop_optimizer_finalize ();
+ return 0;
+ }
#ifdef ENABLE_CHECKING
- verify_loop_structure (loops);
+ verify_loop_structure ();
#endif
- for (i = 1; i < loops->num; i++)
+ bbs = XNEWVEC (basic_block, n_basic_blocks);
+ copied_bbs = XNEWVEC (basic_block, n_basic_blocks);
+ bbs_size = n_basic_blocks;
+
+ FOR_EACH_LOOP (li, loop, 0)
{
/* Copy at most 20 insns. */
int limit = 20;
- loop = loops->parray[i];
- preheader_edge = loop_preheader_edge (loop);
- header = preheader_edge->dest;
+ header = loop->header;
/* If the loop is already a do-while style one (either because it was
written as such, or because jump threading transformed it into one),
like while (a && b) {...}, where we want to have both of the conditions
copied. TODO -- handle while (a || b) - like cases, by not requiring
the header to have just a single successor and copying up to
- postdominator.
-
- We do not really copy the blocks immediately, so that we do not have
- to worry about updating loop structures, and also so that we do not
- have to rewrite variables out of and into ssa form for each block.
- Instead we just record the block into worklist and duplicate all of
- them at once. */
+ postdominator. */
+
+ exit = NULL;
+ n_bbs = 0;
while (should_duplicate_loop_header_p (header, loop, &limit))
{
- if (!bbs_to_duplicate)
- VARRAY_GENERIC_PTR_NOGC_INIT (bbs_to_duplicate, 10,
- "bbs_to_duplicate");
- VARRAY_PUSH_GENERIC_PTR_NOGC (bbs_to_duplicate, preheader_edge);
- header->aux = &header->aux;
-
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file,
- "Scheduled basic block %d for duplication.\n",
- header->index);
-
/* Find a successor of header that is inside a loop; i.e. the new
header after the condition is copied. */
- if (flow_bb_inside_loop_p (loop, header->succ->dest))
- preheader_edge = header->succ;
+ if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest))
+ exit = EDGE_SUCC (header, 0);
else
- preheader_edge = header->succ->succ_next;
- header = preheader_edge->dest;
+ exit = EDGE_SUCC (header, 1);
+ bbs[n_bbs++] = header;
+ gcc_assert (bbs_size > n_bbs);
+ header = exit->dest;
}
- }
- loop_optimizer_finalize (loops, NULL);
+ if (!exit)
+ continue;
- if (bbs_to_duplicate)
- {
- duplicate_blocks (bbs_to_duplicate);
- VARRAY_FREE (bbs_to_duplicate);
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ "Duplicating header of the loop %d up to edge %d->%d.\n",
+ loop->num, exit->src->index, exit->dest->index);
+
+ /* Ensure that the header will have just the latch as a predecessor
+ inside the loop. */
+ if (!single_pred_p (exit->dest))
+ exit = single_pred_edge (split_edge (exit));
+
+ entry = loop_preheader_edge (loop);
+
+ if (!gimple_duplicate_sese_region (entry, exit, bbs, n_bbs, copied_bbs))
+ {
+ fprintf (dump_file, "Duplication failed.\n");
+ continue;
+ }
+
+ /* If the loop has the form "for (i = j; i < j + 10; i++)" then
+ this copying can introduce a case where we rely on undefined
+ signed overflow to eliminate the preheader condition, because
+ we assume that "j < j + 10" is true. We don't want to warn
+ about that case for -Wstrict-overflow, because in general we
+ don't warn about overflow involving loops. Prevent the
+ warning by setting the no_warning flag in the condition. */
+ if (warn_strict_overflow > 0)
+ {
+ unsigned int i;
+
+ for (i = 0; i < n_bbs; ++i)
+ {
+ gimple_stmt_iterator bsi;
+
+ for (bsi = gsi_start_bb (copied_bbs[i]);
+ !gsi_end_p (bsi);
+ gsi_next (&bsi))
+ {
+ gimple stmt = gsi_stmt (bsi);
+ if (gimple_code (stmt) == GIMPLE_COND)
+ gimple_set_no_warning (stmt, true);
+ else if (is_gimple_assign (stmt))
+ {
+ enum tree_code rhs_code = gimple_assign_rhs_code (stmt);
+ if (TREE_CODE_CLASS (rhs_code) == tcc_comparison)
+ gimple_set_no_warning (stmt, true);
+ }
+ }
+ }
+ }
+
+ /* Ensure that the latch and the preheader is simple (we know that they
+ are not now, since there was the loop exit condition. */
+ split_edge (loop_preheader_edge (loop));
+ split_edge (loop_latch_edge (loop));
}
- /* Run cleanup_tree_cfg here regardless of whether we have done anything, so
- that we cleanup the blocks created in order to get the loops into a
- canonical shape. */
- cleanup_tree_cfg ();
+ free (bbs);
+ free (copied_bbs);
+
+ loop_optimizer_finalize ();
+ return 0;
}
static bool
return flag_tree_ch != 0;
}
-struct tree_opt_pass pass_ch =
+struct gimple_opt_pass pass_ch =
{
+ {
+ GIMPLE_PASS,
"ch", /* name */
gate_ch, /* gate */
copy_loop_headers, /* execute */
NULL, /* next */
0, /* static_pass_number */
TV_TREE_CH, /* tv_id */
- PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
+ PROP_cfg | PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- (TODO_dump_func
- | TODO_verify_ssa), /* todo_flags_finish */
- 0 /* letter */
+ TODO_cleanup_cfg | TODO_dump_func
+ | TODO_verify_ssa /* todo_flags_finish */
+ }
};
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