Now that we have DFS_BACK_EDGE marks we can simply avoid walking
those instead of repeatedly looking for a cycle on the current chain.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
* gimple-predicate-analysis.cc (compute_control_dep_chain):
Remove cycle detection, instead avoid walking backedges.
---
gcc/gimple-predicate-analysis.cc | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)
diff --git a/gcc/gimple-predicate-analysis.cc b/gcc/gimple-predicate-analysis.cc
index 2982268fdfd..a754ff0a029 100644
--- a/gcc/gimple-predicate-analysis.cc
+++ b/gcc/gimple-predicate-analysis.cc
@@ -1035,18 +1035,6 @@ compute_control_dep_chain (basic_block dom_bb,
const_basic_block dep_bb,
fprintf (dump_file, "chain length exceeds 5: %u\n", cur_chain_len);
}
- for (unsigned i = 0; i < cur_chain_len; i++)
- {
- edge e = cur_cd_chain[i];
- /* Cycle detected. */
- if (e->src == dom_bb)
- {
- if (dump_file)
- fprintf (dump_file, "cycle detected\n");
- return false;
- }
- }
-
if (DEBUG_PREDICATE_ANALYZER && dump_file)
fprintf (dump_file,
"%*s%s (dom_bb = %u, dep_bb = %u, cd_chains = { %s }, ...)\n",
@@ -1061,7 +1049,7 @@ compute_control_dep_chain (basic_block dom_bb,
const_basic_block dep_bb,
FOR_EACH_EDGE (e, ei, dom_bb->succs)
{
int post_dom_check = 0;
- if (e->flags & (EDGE_FAKE | EDGE_ABNORMAL))
+ if (e->flags & (EDGE_FAKE | EDGE_ABNORMAL | EDGE_DFS_BACK))
continue;
basic_block cd_bb = e->dest;
@@ -1110,6 +1098,12 @@ compute_control_dep_chain (basic_block dom_bb,
const_basic_block dep_bb,
break;
}
+ /* The post-dominator walk will reach a backedge only
+ from a forwarder, otherwise it should choose to exit
+ the SCC. */
+ if (single_succ_p (cd_bb)
+ && single_succ_edge (cd_bb)->flags & EDGE_DFS_BACK)
+ break;
cd_bb = get_immediate_dominator (CDI_POST_DOMINATORS, cd_bb);
post_dom_check++;
if (cd_bb == EXIT_BLOCK_PTR_FOR_FN (cfun)
--
2.35.3
