+2006-02-08 Jeff Law <law@redhat.com>
+
+ * tree-ssa-dce.c (remove_dead_statement): When removing a dead
+ control statement, handle all three special cases in the same
+ manner as they all have the same desired solution. No longer
+ special case edge flag updating when the post dominator is
+ the exit block.
+
2006-02-08 Roger Sayle <roger@eyesopen.com>
* tree.def (CHAR_TYPE): Remove.
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))