/* Dead code elimination pass for the GNU compiler.
- Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+ Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
Contributed by Ben Elliston <bje@redhat.com>
and Andrew MacLeod <amacleod@redhat.com>
Adapted to use control dependence by Steven Bosscher, SUSE Labs.
to be recomputed. */
static bool cfg_altered;
-/* Execute CODE for each edge (given number EDGE_NUMBER within the CODE)
- for which the block with index N is control dependent. */
-#define EXECUTE_IF_CONTROL_DEPENDENT(N, EDGE_NUMBER, CODE) \
- { \
- bitmap_iterator bi; \
- \
- EXECUTE_IF_SET_IN_BITMAP (control_dependence_map[N], 0, EDGE_NUMBER, bi) \
- { \
- CODE; \
- } \
- }
+/* Execute code that follows the macro for each edge (given number
+ EDGE_NUMBER within the CODE) for which the block with index N is
+ control dependent. */
+#define EXECUTE_IF_CONTROL_DEPENDENT(BI, N, EDGE_NUMBER) \
+ EXECUTE_IF_SET_IN_BITMAP (control_dependence_map[(N)], 0, \
+ (EDGE_NUMBER), (BI))
/* Local function prototypes. */
static inline void set_control_dependence_map_bit (basic_block, int);
}
/* Clear all control dependences for block BB. */
-static inline
-void clear_control_dependence_bitmap (basic_block bb)
+static inline void
+clear_control_dependence_bitmap (basic_block bb)
{
bitmap_clear (control_dependence_map[bb->index]);
}
static void
mark_control_dependent_edges_necessary (basic_block bb, struct edge_list *el)
{
+ bitmap_iterator bi;
unsigned edge_number;
gcc_assert (bb != EXIT_BLOCK_PTR);
if (bb == ENTRY_BLOCK_PTR)
return;
- EXECUTE_IF_CONTROL_DEPENDENT (bb->index, edge_number,
+ EXECUTE_IF_CONTROL_DEPENDENT (bi, bb->index, edge_number)
{
tree t;
basic_block cd_bb = INDEX_EDGE_PRED_BB (el, edge_number);
t = last_stmt (cd_bb);
if (t && is_ctrl_stmt (t))
mark_stmt_necessary (t, true);
- });
+ }
}
\f
/* Propagate necessity using the operands of necessary statements. Process
nothing to the program, then we not only remove it, but we also change
the flow graph so that the current block will simply fall-thru to its
immediate post-dominator. The blocks we are circumventing will be
- removed by cleaup_tree_cfg if this change in the flow graph makes them
+ removed by cleanup_tree_cfg if this change in the flow graph makes them
unreachable. */
if (is_ctrl_stmt (t))
{
gcc_assert (dom_computed[CDI_POST_DOMINATORS] == DOM_OK);
/* Get the immediate post dominator of bb. */
post_dom_bb = get_immediate_dominator (CDI_POST_DOMINATORS, bb);
- /* Some blocks don't have an immediate post dominator. This can happen
- for example with infinite loops. Removing an infinite loop is an
- inappropriate transformation anyway... */
- if (! post_dom_bb)
- {
- bsi_next (i);
- return;
- }
- /* If the post dominator block has PHI nodes, we might be unable
- to compute the right PHI args for them. Since the control
- statement is unnecessary, all edges can be regarded as
- equivalent, but we have to get rid of the condition, since it
- might reference a variable that was determined to be
- unnecessary and thus removed. */
- if (phi_nodes (post_dom_bb))
- post_dom_bb = EDGE_SUCC (bb, 0)->dest;
+ /* There are three particularly problematical cases.
+
+ 1. Blocks that do not have an immediate post dominator. This
+ can happen with infinite loops.
+
+ 2. Blocks that are only post dominated by the exit block. These
+ can also happen for infinite loops as we create fake edges
+ in the dominator tree.
+
+ 3. If the post dominator has PHI nodes we may be able to compute
+ the right PHI args for them.
+
+
+ In each of these cases we must remove the control statement
+ as it may reference SSA_NAMEs which are going to be removed and
+ we remove all but one outgoing edge from the block. */
+ if (! post_dom_bb
+ || post_dom_bb == EXIT_BLOCK_PTR
+ || phi_nodes (post_dom_bb))
+ ;
else
{
/* Redirect the first edge out of BB to reach POST_DOM_BB. */
not have TRUE/FALSE flags. */
EDGE_SUCC (bb, 0)->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
- /* If the edge reaches any block other than the exit, then it is a
- fallthru edge; if it reaches the exit, then it is not a fallthru
- edge. */
- if (post_dom_bb != EXIT_BLOCK_PTR)
- EDGE_SUCC (bb, 0)->flags |= EDGE_FALLTHRU;
- else
- EDGE_SUCC (bb, 0)->flags &= ~EDGE_FALLTHRU;
+ /* The lone outgoing edge from BB will be a fallthru edge. */
+ EDGE_SUCC (bb, 0)->flags |= EDGE_FALLTHRU;
/* Remove the remaining the outgoing edges. */
while (!single_succ_p (bb))
}
/* Pass entry points. */
-static void
+static unsigned int
tree_ssa_dce (void)
{
perform_tree_ssa_dce (/*aggressive=*/false);
+ return 0;
}
-static void
+static unsigned int
tree_ssa_dce_loop (void)
{
perform_tree_ssa_dce (/*aggressive=*/false);
free_numbers_of_iterations_estimates (current_loops);
scev_reset ();
+ return 0;
}
-static void
+static unsigned int
tree_ssa_cd_dce (void)
{
perform_tree_ssa_dce (/*aggressive=*/optimize >= 2);
+ return 0;
}
static bool
OSDN Git Service
