From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by sourceware.org (Postfix) with ESMTPS id 6A7483856DDD for ; Mon, 22 Aug 2022 13:38:20 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 6A7483856DDD Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 3CD9234ACA for ; Mon, 22 Aug 2022 13:38:19 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 1D5F813523 for ; Mon, 22 Aug 2022 13:38:19 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id Lz0eBsuGA2OOZwAAMHmgww (envelope-from ) for ; Mon, 22 Aug 2022 13:38:19 +0000 Date: Mon, 22 Aug 2022 15:38:18 +0200 (CEST) From: Richard Biener To: gcc-patches@gcc.gnu.org Subject: [PATCH] Refactor is_non_loop_exit_postdominating MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Message-Id: <20220822133819.1D5F813523@imap2.suse-dmz.suse.de> X-Spam-Status: No, score=-11.9 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 22 Aug 2022 13:38:21 -0000 That's a weird function in predicate analysis that currently looks like /* Return true if BB1 is postdominating BB2 and BB1 is not a loop exit bb. The loop exit bb check is simple and does not cover all cases. */ static bool is_non_loop_exit_postdominating (basic_block bb1, basic_block bb2) { if (!dominated_by_p (CDI_POST_DOMINATORS, bb2, bb1)) return false; if (single_pred_p (bb1) && !single_succ_p (bb2)) return false; return true; } One can refactor this to return (dominated_by_p (CDI_POST_DOMINATORS, bb2, bb1) && !(single_pred_p (bb1) && !single_succ_p (bb2))); Notable is that the comment refers to BB1 with respect to a loop exit but the test seems to be written with an exit edge bb1 -> bb2 in mind. From the three callers only a single one is guaranteed to have bb1 and bb2 connected directly with an edge. The patch now introduces a is_loop_exit function and inlines the post-dominance check which makes the find_control_equiv_block case simpler because the post-dominance check can be elided. It also avoids the double negation in compute_control_dep_chain and makes it obvious this is the case where we do look at an edge. For the main is_use_guarded API I chose to elide the loop exit test, if the use block post-dominates the definition block of the PHI node the use is always unconditional. I don't quite understand the loop exit special-casing of the remaining two uses though. Bootstrap and regtest running on x86_64-unknown-linux-gnu. The code is this way since the original r0-99656-g34f97b9407c6a3 so I'm not hoping for any insights ... :/ * gimple-predicate-analysis.cc (is_loop_exit): Split out from ... (is_non_loop_exit_postdominating): ... here. Remove after inlining ... (find_control_equiv_block): ... here. (compute_control_dep_chain): ... and here. (predicate::is_use_guarded): Do not excempt loop exits from short-cutting the case of the use post-dominating the PHI definition. --- gcc/gimple-predicate-analysis.cc | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-) diff --git a/gcc/gimple-predicate-analysis.cc b/gcc/gimple-predicate-analysis.cc index d1b0d1283dc..4cf05951ec7 100644 --- a/gcc/gimple-predicate-analysis.cc +++ b/gcc/gimple-predicate-analysis.cc @@ -46,19 +46,12 @@ #define DEBUG_PREDICATE_ANALYZER 1 -/* Return true if BB1 is postdominating BB2 and BB1 is not a loop exit - bb. The loop exit bb check is simple and does not cover all cases. */ +/* Return true if, when BB1 is postdominating BB2, BB1 is a loop exit. */ static bool -is_non_loop_exit_postdominating (basic_block bb1, basic_block bb2) +is_loop_exit (basic_block bb2, basic_block bb1) { - if (!dominated_by_p (CDI_POST_DOMINATORS, bb2, bb1)) - return false; - - if (single_pred_p (bb1) && !single_succ_p (bb2)) - return false; - - return true; + return single_pred_p (bb1) && !single_succ_p (bb2); } /* Find BB's closest postdominator that is its control equivalent (i.e., @@ -70,7 +63,7 @@ find_control_equiv_block (basic_block bb) basic_block pdom = get_immediate_dominator (CDI_POST_DOMINATORS, bb); /* Skip the postdominating bb that is also a loop exit. */ - if (!is_non_loop_exit_postdominating (pdom, bb)) + if (is_loop_exit (bb, pdom)) return NULL; /* If the postdominator is dominated by BB, return it. */ @@ -1112,10 +1105,11 @@ compute_control_dep_chain (basic_block dom_bb, const_basic_block dep_bb, if (e->flags & (EDGE_FAKE | EDGE_ABNORMAL)) continue; - basic_block cd_bb = e->dest; cur_cd_chain.safe_push (e); - while (!is_non_loop_exit_postdominating (cd_bb, dom_bb)) + while (!dominated_by_p (CDI_POST_DOMINATORS, e->src, e->dest) + || is_loop_exit (e->src, e->dest)) { + basic_block cd_bb = e->dest; if (cd_bb == dep_bb) { /* Found a direct control dependence. */ @@ -1885,7 +1879,7 @@ predicate::is_use_guarded (gimple *use_stmt, basic_block use_bb, in the same bb. */ predicate use_preds (def_bb, use_bb, m_eval); - if (is_non_loop_exit_postdominating (use_bb, def_bb)) + if (dominated_by_p (CDI_POST_DOMINATORS, def_bb, use_bb)) { if (is_empty ()) { -- 2.35.3