/* CFG cleanup for trees.
- Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+ Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
+ 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)
+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,
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, 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/>. */
#include "config.h"
#include "system.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "output.h"
-#include "errors.h"
+#include "toplev.h"
#include "flags.h"
#include "function.h"
#include "expr.h"
#include "tree-ssa-propagate.h"
#include "tree-scalar-evolution.h"
+/* The set of blocks in that at least one of the following changes happened:
+ -- the statement at the end of the block was changed
+ -- the block was newly created
+ -- the set of the predecessors of the block changed
+ -- the set of the successors of the block changed
+ ??? Maybe we could track these changes separately, since they determine
+ what cleanups it makes sense to try on the block. */
+bitmap cfgcleanup_altered_bbs;
+
/* Remove any fallthru edge from EV. Return true if an edge was removed. */
static bool
FOR_EACH_EDGE (e, ei, ev)
if ((e->flags & EDGE_FALLTHRU) != 0)
{
- remove_edge (e);
+ remove_edge_and_dominated_blocks (e);
return true;
}
return false;
{
edge e;
edge_iterator ei;
+ bool warned;
+
+ fold_defer_overflow_warnings ();
switch (TREE_CODE (expr))
{
case SWITCH_EXPR:
val = fold (SWITCH_COND (expr));
if (TREE_CODE (val) != INTEGER_CST)
- return false;
+ {
+ fold_undefer_and_ignore_overflow_warnings ();
+ return false;
+ }
break;
default:
taken_edge = find_taken_edge (bb, val);
if (!taken_edge)
- return false;
+ {
+ fold_undefer_and_ignore_overflow_warnings ();
+ return false;
+ }
/* Remove all the edges except the one that is always executed. */
+ warned = false;
for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
{
if (e != taken_edge)
{
+ if (!warned)
+ {
+ fold_undefer_overflow_warnings
+ (true, expr, WARN_STRICT_OVERFLOW_CONDITIONAL);
+ warned = true;
+ }
+
taken_edge->probability += e->probability;
taken_edge->count += e->count;
- remove_edge (e);
+ remove_edge_and_dominated_blocks (e);
retval = true;
}
else
ei_next (&ei);
}
+ if (!warned)
+ fold_undefer_and_ignore_overflow_warnings ();
if (taken_edge->probability > REG_BR_PROB_BASE)
taken_edge->probability = REG_BR_PROB_BASE;
}
else
taken_edge = single_succ_edge (bb);
+ bitmap_set_bit (cfgcleanup_altered_bbs, bb->index);
bsi_remove (&bsi, true);
taken_edge->flags = EDGE_FALLTHRU;
- /* We removed some paths from the cfg. */
- free_dominance_info (CDI_DOMINATORS);
-
return retval;
}
-/* Try to remove superfluous control structures. */
+/* Try to remove superfluous control structures in basic block BB. Returns
+ true if anything changes. */
static bool
-cleanup_control_flow (void)
+cleanup_control_flow_bb (basic_block bb)
{
- basic_block bb;
block_stmt_iterator bsi;
bool retval = false;
tree stmt;
- /* Detect cases where a mid-block call is now known not to return. */
- if (cfun->gimple_df)
- while (VEC_length (tree, MODIFIED_NORETURN_CALLS (cfun)))
- {
- stmt = VEC_pop (tree, MODIFIED_NORETURN_CALLS (cfun));
- bb = bb_for_stmt (stmt);
- if (bb != NULL && last_stmt (bb) != stmt && noreturn_call_p (stmt))
- split_block (bb, stmt);
- }
-
- FOR_EACH_BB (bb)
+ /* If the last statement of the block could throw and now cannot,
+ we need to prune cfg. */
+ retval |= tree_purge_dead_eh_edges (bb);
+
+ bsi = bsi_last (bb);
+ if (bsi_end_p (bsi))
+ return retval;
+
+ stmt = bsi_stmt (bsi);
+
+ if (TREE_CODE (stmt) == COND_EXPR
+ || TREE_CODE (stmt) == SWITCH_EXPR)
+ retval |= cleanup_control_expr_graph (bb, bsi);
+ /* If we had a computed goto which has a compile-time determinable
+ destination, then we can eliminate the goto. */
+ else if (TREE_CODE (stmt) == GOTO_EXPR
+ && TREE_CODE (GOTO_DESTINATION (stmt)) == ADDR_EXPR
+ && (TREE_CODE (TREE_OPERAND (GOTO_DESTINATION (stmt), 0))
+ == LABEL_DECL))
{
- bsi = bsi_last (bb);
-
- /* If the last statement of the block could throw and now cannot,
- we need to prune cfg. */
- retval |= tree_purge_dead_eh_edges (bb);
-
- if (bsi_end_p (bsi))
- continue;
+ edge e;
+ tree label;
+ edge_iterator ei;
+ basic_block target_block;
- stmt = bsi_stmt (bsi);
-
- if (TREE_CODE (stmt) == COND_EXPR
- || TREE_CODE (stmt) == SWITCH_EXPR)
- retval |= cleanup_control_expr_graph (bb, bsi);
- /* If we had a computed goto which has a compile-time determinable
- destination, then we can eliminate the goto. */
- else if (TREE_CODE (stmt) == GOTO_EXPR
- && TREE_CODE (GOTO_DESTINATION (stmt)) == ADDR_EXPR
- && (TREE_CODE (TREE_OPERAND (GOTO_DESTINATION (stmt), 0))
- == LABEL_DECL))
+ /* First look at all the outgoing edges. Delete any outgoing
+ edges which do not go to the right block. For the one
+ edge which goes to the right block, fix up its flags. */
+ label = TREE_OPERAND (GOTO_DESTINATION (stmt), 0);
+ target_block = label_to_block (label);
+ for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
{
- edge e;
- tree label;
- edge_iterator ei;
- basic_block target_block;
- bool removed_edge = false;
-
- /* First look at all the outgoing edges. Delete any outgoing
- edges which do not go to the right block. For the one
- edge which goes to the right block, fix up its flags. */
- label = TREE_OPERAND (GOTO_DESTINATION (stmt), 0);
- target_block = label_to_block (label);
- for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
+ if (e->dest != target_block)
+ remove_edge_and_dominated_blocks (e);
+ else
{
- if (e->dest != target_block)
- {
- removed_edge = true;
- remove_edge (e);
- }
- else
- {
- /* Turn off the EDGE_ABNORMAL flag. */
- e->flags &= ~EDGE_ABNORMAL;
-
- /* And set EDGE_FALLTHRU. */
- e->flags |= EDGE_FALLTHRU;
- ei_next (&ei);
- }
- }
-
- /* If we removed one or more edges, then we will need to fix the
- dominators. It may be possible to incrementally update them. */
- if (removed_edge)
- free_dominance_info (CDI_DOMINATORS);
+ /* Turn off the EDGE_ABNORMAL flag. */
+ e->flags &= ~EDGE_ABNORMAL;
- /* Remove the GOTO_EXPR as it is not needed. The CFG has all the
- relevant information we need. */
- bsi_remove (&bsi, true);
- retval = true;
+ /* And set EDGE_FALLTHRU. */
+ e->flags |= EDGE_FALLTHRU;
+ ei_next (&ei);
+ }
}
- /* Check for indirect calls that have been turned into
- noreturn calls. */
- else if (noreturn_call_p (stmt) && remove_fallthru_edge (bb->succs))
- {
- free_dominance_info (CDI_DOMINATORS);
- retval = true;
- }
+ bitmap_set_bit (cfgcleanup_altered_bbs, bb->index);
+ bitmap_set_bit (cfgcleanup_altered_bbs, target_block->index);
+
+ /* Remove the GOTO_EXPR as it is not needed. The CFG has all the
+ relevant information we need. */
+ bsi_remove (&bsi, true);
+ retval = true;
}
+
+ /* Check for indirect calls that have been turned into
+ noreturn calls. */
+ else if (noreturn_call_p (stmt) && remove_fallthru_edge (bb->succs))
+ retval = true;
+
return retval;
}
return true;
}
-/* Removes forwarder block BB. Returns false if this failed. If a new
- forwarder block is created due to redirection of edges, it is
- stored to worklist. */
+/* Removes forwarder block BB. Returns false if this failed. */
static bool
-remove_forwarder_block (basic_block bb, basic_block **worklist)
+remove_forwarder_block (basic_block bb)
{
edge succ = single_succ_edge (bb), e, s;
basic_block dest = succ->dest;
/* Redirect the edges. */
for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); )
{
+ bitmap_set_bit (cfgcleanup_altered_bbs, e->src->index);
+
if (e->flags & EDGE_ABNORMAL)
{
/* If there is an abnormal edge, redirect it anyway, and
for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
add_phi_arg (phi, PHI_ARG_DEF (phi, succ->dest_idx), s);
}
- else
- {
- /* The source basic block might become a forwarder. We know
- that it was not a forwarder before, since it used to have
- at least two outgoing edges, so we may just add it to
- worklist. */
- if (tree_forwarder_block_p (s->src, false))
- *(*worklist)++ = s->src;
- }
}
if (seen_abnormal_edge)
}
}
+ bitmap_set_bit (cfgcleanup_altered_bbs, dest->index);
+
/* Update the dominators. */
if (dom_info_available_p (CDI_DOMINATORS))
{
return true;
}
-/* Removes forwarder blocks. */
+/* Split basic blocks on calls in the middle of a basic block that are now
+ known not to return, and remove the unreachable code. */
static bool
-cleanup_forwarder_blocks (void)
+split_bbs_on_noreturn_calls (void)
{
- basic_block bb;
bool changed = false;
- basic_block *worklist = XNEWVEC (basic_block, n_basic_blocks);
- basic_block *current = worklist;
-
- FOR_EACH_BB (bb)
- {
- if (tree_forwarder_block_p (bb, false))
- *current++ = bb;
- }
+ tree stmt;
+ basic_block bb;
- while (current != worklist)
- {
- bb = *--current;
- changed |= remove_forwarder_block (bb, ¤t);
- }
+ /* Detect cases where a mid-block call is now known not to return. */
+ if (cfun->gimple_df)
+ while (VEC_length (tree, MODIFIED_NORETURN_CALLS (cfun)))
+ {
+ stmt = VEC_pop (tree, MODIFIED_NORETURN_CALLS (cfun));
+ bb = bb_for_stmt (stmt);
+ if (bb == NULL
+ || last_stmt (bb) == stmt
+ || !noreturn_call_p (stmt))
+ continue;
+
+ changed = true;
+ split_block (bb, stmt);
+ remove_fallthru_edge (bb->succs);
+ }
- free (worklist);
return changed;
}
-/* Do one round of CFG cleanup. */
+/* If OMP_RETURN in basic block BB is unreachable, remove it. */
static bool
-cleanup_tree_cfg_1 (void)
+cleanup_omp_return (basic_block bb)
{
- bool retval;
+ tree stmt = last_stmt (bb);
+ basic_block control_bb;
+
+ if (stmt == NULL_TREE
+ || TREE_CODE (stmt) != OMP_RETURN
+ || !single_pred_p (bb))
+ return false;
- retval = cleanup_control_flow ();
- retval |= delete_unreachable_blocks ();
+ control_bb = single_pred (bb);
+ stmt = last_stmt (control_bb);
+ if (TREE_CODE (stmt) != OMP_SECTIONS_SWITCH)
+ return false;
+
+ /* The block with the control statement normally has two entry edges -- one
+ from entry, one from continue. If continue is removed, return is
+ unreachable, so we remove it here as well. */
+ if (EDGE_COUNT (control_bb->preds) == 2)
+ return false;
+
+ gcc_assert (EDGE_COUNT (control_bb->preds) == 1);
+ remove_edge_and_dominated_blocks (single_pred_edge (bb));
+ return true;
+}
+
+/* Tries to cleanup cfg in basic block BB. Returns true if anything
+ changes. */
+
+static bool
+cleanup_tree_cfg_bb (basic_block bb)
+{
+ bool retval = false;
+
+ if (cleanup_omp_return (bb))
+ return true;
+
+ retval = cleanup_control_flow_bb (bb);
+
/* Forwarder blocks can carry line number information which is
useful when debugging, so we only clean them up when
optimizing. */
- if (optimize > 0)
- {
- /* cleanup_forwarder_blocks can redirect edges out of
- SWITCH_EXPRs, which can get expensive. So we want to enable
- recording of edge to CASE_LABEL_EXPR mappings around the call
- to cleanup_forwarder_blocks. */
- start_recording_case_labels ();
- retval |= cleanup_forwarder_blocks ();
- end_recording_case_labels ();
- }
+ if (optimize > 0
+ && tree_forwarder_block_p (bb, false)
+ && remove_forwarder_block (bb))
+ return true;
/* Merging the blocks may create new opportunities for folding
conditional branches (due to the elimination of single-valued PHI
nodes). */
- retval |= merge_seq_blocks ();
+ if (single_succ_p (bb)
+ && can_merge_blocks_p (bb, single_succ (bb)))
+ {
+ merge_blocks (bb, single_succ (bb));
+ return true;
+ }
+
+ return retval;
+}
+
+/* Iterate the cfg cleanups, while anything changes. */
+
+static bool
+cleanup_tree_cfg_1 (void)
+{
+ bool retval = false;
+ basic_block bb;
+ unsigned i, n;
+
+ retval |= split_bbs_on_noreturn_calls ();
+
+ /* Prepare the worklists of altered blocks. */
+ cfgcleanup_altered_bbs = BITMAP_ALLOC (NULL);
+
+ /* During forwarder block cleanup, we may redirect edges out of
+ SWITCH_EXPRs, which can get expensive. So we want to enable
+ recording of edge to CASE_LABEL_EXPR. */
+ start_recording_case_labels ();
+
+ /* Start by iterating over all basic blocks. We cannot use FOR_EACH_BB,
+ since the basic blocks may get removed. */
+ n = last_basic_block;
+ for (i = NUM_FIXED_BLOCKS; i < n; i++)
+ {
+ bb = BASIC_BLOCK (i);
+ if (bb)
+ retval |= cleanup_tree_cfg_bb (bb);
+ }
+
+ /* Now process the altered blocks, as long as any are available. */
+ while (!bitmap_empty_p (cfgcleanup_altered_bbs))
+ {
+ i = bitmap_first_set_bit (cfgcleanup_altered_bbs);
+ bitmap_clear_bit (cfgcleanup_altered_bbs, i);
+ if (i < NUM_FIXED_BLOCKS)
+ continue;
+
+ bb = BASIC_BLOCK (i);
+ if (!bb)
+ continue;
+
+ retval |= cleanup_tree_cfg_bb (bb);
+ /* Rerun split_bbs_on_noreturn_calls, in case we have altered any noreturn
+ calls. */
+ retval |= split_bbs_on_noreturn_calls ();
+ }
+
+ end_recording_case_labels ();
+ BITMAP_FREE (cfgcleanup_altered_bbs);
return retval;
}
/* Remove unreachable blocks and other miscellaneous clean up work.
Return true if the flowgraph was modified, false otherwise. */
-bool
-cleanup_tree_cfg (void)
+static bool
+cleanup_tree_cfg_noloop (void)
{
- bool retval, changed;
+ bool changed;
timevar_push (TV_TREE_CLEANUP_CFG);
/* Iterate until there are no more cleanups left to do. If any
- iteration changed the flowgraph, set CHANGED to true. */
- changed = false;
- do
+ iteration changed the flowgraph, set CHANGED to true.
+
+ If dominance information is available, there cannot be any unreachable
+ blocks. */
+ if (!dom_info_available_p (CDI_DOMINATORS))
{
- retval = cleanup_tree_cfg_1 ();
- changed |= retval;
+ changed = delete_unreachable_blocks ();
+ calculate_dominance_info (CDI_DOMINATORS);
+ }
+ else
+ {
+#ifdef ENABLE_CHECKING
+ verify_dominators (CDI_DOMINATORS);
+#endif
+ changed = false;
}
- while (retval);
+ changed |= cleanup_tree_cfg_1 ();
+
+ gcc_assert (dom_info_available_p (CDI_DOMINATORS));
compact_blocks ();
#ifdef ENABLE_CHECKING
timevar_pop (TV_TREE_CLEANUP_CFG);
+ if (changed && current_loops)
+ loops_state_set (LOOPS_NEED_FIXUP);
+
return changed;
}
-/* Cleanup cfg and repair loop structures. */
+/* Repairs loop structures. */
-bool
-cleanup_tree_cfg_loop (void)
+static void
+repair_loop_structures (void)
{
- bool changed = cleanup_tree_cfg ();
+ bitmap changed_bbs = BITMAP_ALLOC (NULL);
+ fix_loop_structure (changed_bbs);
- if (changed)
- {
- bitmap changed_bbs = BITMAP_ALLOC (NULL);
- calculate_dominance_info (CDI_DOMINATORS);
- fix_loop_structure (changed_bbs);
+ /* This usually does nothing. But sometimes parts of cfg that originally
+ were inside a loop get out of it due to edge removal (since they
+ become unreachable by back edges from latch). */
+ if (loops_state_satisfies_p (LOOP_CLOSED_SSA))
+ rewrite_into_loop_closed_ssa (changed_bbs, TODO_update_ssa);
- /* This usually does nothing. But sometimes parts of cfg that originally
- were inside a loop get out of it due to edge removal (since they
- become unreachable by back edges from latch). */
- rewrite_into_loop_closed_ssa (changed_bbs, TODO_update_ssa);
-
- BITMAP_FREE (changed_bbs);
+ BITMAP_FREE (changed_bbs);
#ifdef ENABLE_CHECKING
- verify_loop_structure ();
+ verify_loop_structure ();
#endif
- scev_reset ();
- }
+ scev_reset ();
+
+ loops_state_clear (LOOPS_NEED_FIXUP);
+}
+
+/* Cleanup cfg and repair loop structures. */
+
+bool
+cleanup_tree_cfg (void)
+{
+ bool changed = cleanup_tree_cfg_noloop ();
+
+ if (current_loops != NULL
+ && loops_state_satisfies_p (LOOPS_NEED_FIXUP))
+ repair_loop_structures ();
+
return changed;
}
OSDN Git Service
