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From: Richard Biener <rguenth@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-2342] Remove cycle checking from compute_control_dep_chain Date: Thu, 1 Sep 2022 13:07:44 +0000 (GMT) [thread overview] Message-ID: <20220901130744.4A4F2385828D@sourceware.org> (raw) https://gcc.gnu.org/g:47e15513c9e581ef04ad25fb0d561a45d345edd1 commit r13-2342-g47e15513c9e581ef04ad25fb0d561a45d345edd1 Author: Richard Biener <rguenther@suse.de> Date: Thu Sep 1 13:28:08 2022 +0200 Remove cycle checking from compute_control_dep_chain 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. * gimple-predicate-analysis.cc (compute_control_dep_chain): Remove cycle detection, instead avoid walking backedges. Diff: --- 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)
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