From patchwork Thu Sep 23 11:15:32 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Aldy Hernandez X-Patchwork-Id: 45349 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 63EEC3858D39 for ; Thu, 23 Sep 2021 11:21:15 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 63EEC3858D39 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1632396075; bh=xoTZBmCD8QH8UihY6Ki2wkhqcTgeItxgmnlLwwnBHtc=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=m2ZUNHFqVn0PH6aJ7AbKCLW06O/cxodvq4rttaltsLNJ7lLA/qFRtbgGxAqMnK45W rDX1Y1FyJ8AlcgMt/izMCOe6oSA1IAA4O3euFSjn5A8GtamWYn+B/7ac5Ibw2da7VW 76K6AjRJ98H1fM9yiOn6F4VZ77PnrAbz/0RtUUTw= X-Original-To: gcc-patches@gcc.gnu.org Delivered-To: gcc-patches@gcc.gnu.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTP id 1DA1A3858D39 for ; Thu, 23 Sep 2021 11:20:45 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 1DA1A3858D39 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-356-zDSixJgcMMeJR9FwQBtn6w-1; Thu, 23 Sep 2021 07:20:43 -0400 X-MC-Unique: zDSixJgcMMeJR9FwQBtn6w-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A9AFA802C94; Thu, 23 Sep 2021 11:20:42 +0000 (UTC) Received: from abulafia.quesejoda.com (unknown [10.39.192.195]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CBD1760BF1; Thu, 23 Sep 2021 11:20:36 +0000 (UTC) Received: from abulafia.quesejoda.com (localhost [127.0.0.1]) by abulafia.quesejoda.com (8.16.1/8.15.2) with ESMTPS id 18NBKYYJ964767 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Thu, 23 Sep 2021 13:20:34 +0200 Received: (from aldyh@localhost) by abulafia.quesejoda.com (8.16.1/8.16.1/Submit) id 18NBKXeY964766; Thu, 23 Sep 2021 13:20:33 +0200 To: Jeff Law Subject: [PATCH] Avoid invalid loop transformations in jump threading registry. Date: Thu, 23 Sep 2021 13:15:32 +0200 Message-Id: <20210923111531.964654-1-aldyh@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-13.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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-Patchwork-Original-From: Aldy Hernandez via Gcc-patches From: Aldy Hernandez Reply-To: Aldy Hernandez Cc: Michael Matz , GCC patches Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Sender: "Gcc-patches" My upcoming improvements to the forward jump threader make it thread more aggressively. In investigating some "regressions", I noticed that it has always allowed threading through empty latches and across loop boundaries. As we have discussed recently, this should be avoided until after loop optimizations have run their course. Note that this wasn't much of a problem before because DOM/VRP couldn't find these opportunities, but with a smarter solver, we trip over them more easily. Because the forward threader doesn't have an independent localized cost model like the new threader (profitable_path_p), it is difficult to catch these things at discovery. However, we can catch them at registration time, with the added benefit that all the threaders (forward and backward) can share the handcuffs. This patch is an adaptation of what we do in the backward threader, but it is not meant to catch everything we do there, as some of the restrictions there are due to limitations of the different block copiers (for example, the generic copier does not re-use existing threading paths). We could ideally remove the now redundant bits in profitable_path_p, but I would prefer not to for two reasons. First, the backward threader uses profitable_path_p as it discovers paths to avoid discovering paths in unprofitable directions. Second, I would like to merge all the forward cost restrictions into the profitability class in the backward threader, not the other way around. Alas, that reshuffling will have to wait for the next release. As usual, there are quite a few tests that needed adjustments. It seems we were quite happily threading improper scenarios. With most of them, as can be seen in pr77445-2.c, we're merely shifting the threading to after loop optimizations. Tested on x86-64 Linux. OK for trunk? p.s. "Sure, sounds like fun... how hard can improving the threaders be?" gcc/ChangeLog: * tree-ssa-threadupdate.c (jt_path_registry::cancel_invalid_paths): New. (jt_path_registry::register_jump_thread): Call cancel_invalid_paths. * tree-ssa-threadupdate.h (class jt_path_registry): Add cancel_invalid_paths. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/20030714-2.c: Adjust. * gcc.dg/tree-ssa/pr66752-3.c: Adjust. * gcc.dg/tree-ssa/pr77445-2.c: Adjust. * gcc.dg/tree-ssa/ssa-dom-thread-18.c: Adjust. * gcc.dg/tree-ssa/ssa-dom-thread-7.c: Adjust. * gcc.dg/vect/bb-slp-16.c: Adjust. --- gcc/testsuite/gcc.dg/tree-ssa/20030714-2.c | 7 +- gcc/testsuite/gcc.dg/tree-ssa/pr66752-3.c | 19 ++++-- gcc/testsuite/gcc.dg/tree-ssa/pr77445-2.c | 4 +- .../gcc.dg/tree-ssa/ssa-dom-thread-18.c | 4 +- .../gcc.dg/tree-ssa/ssa-dom-thread-7.c | 4 +- gcc/testsuite/gcc.dg/vect/bb-slp-16.c | 7 -- gcc/tree-ssa-threadupdate.c | 67 +++++++++++++++---- gcc/tree-ssa-threadupdate.h | 1 + 8 files changed, 78 insertions(+), 35 deletions(-) diff --git a/gcc/testsuite/gcc.dg/tree-ssa/20030714-2.c b/gcc/testsuite/gcc.dg/tree-ssa/20030714-2.c index eb663f2ff5b..9585ff11307 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/20030714-2.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/20030714-2.c @@ -32,7 +32,8 @@ get_alias_set (t) } } -/* There should be exactly three IF conditionals if we thread jumps - properly. */ -/* { dg-final { scan-tree-dump-times "if " 3 "dom2"} } */ +/* There should be exactly 4 IF conditionals if we thread jumps + properly. There used to be 3, but one thread was crossing + loops. */ +/* { dg-final { scan-tree-dump-times "if " 4 "dom2"} } */ diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr66752-3.c b/gcc/testsuite/gcc.dg/tree-ssa/pr66752-3.c index e1464e21170..922a331b217 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/pr66752-3.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr66752-3.c @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-O2 -fdump-tree-thread1-details -fdump-tree-dce2" } */ +/* { dg-options "-O2 -fdump-tree-thread1-details -fdump-tree-thread3" } */ extern int status, pt; extern int count; @@ -32,10 +32,15 @@ foo (int N, int c, int b, int *a) pt--; } -/* There are 4 jump threading opportunities, all of which will be - realized, which will eliminate testing of FLAG, completely. */ -/* { dg-final { scan-tree-dump-times "Registering jump" 4 "thread1"} } */ +/* There are 2 jump threading opportunities (which don't cross loops), + all of which will be realized, which will eliminate testing of + FLAG, completely. */ +/* { dg-final { scan-tree-dump-times "Registering jump" 2 "thread1"} } */ -/* There should be no assignments or references to FLAG, verify they're - eliminated as early as possible. */ -/* { dg-final { scan-tree-dump-not "if .flag" "dce2"} } */ +/* We used to remove references to FLAG by DCE2, but this was + depending on early threaders threading through loop boundaries + (which we shouldn't do). However, the late threading passes, which + run after loop optimizations , can successfully eliminate the + references to FLAG. Verify that ther are no references by the late + threading passes. */ +/* { dg-final { scan-tree-dump-not "if .flag" "thread3"} } */ diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr77445-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr77445-2.c index f9fc212f49e..01a0f1f197d 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/pr77445-2.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr77445-2.c @@ -123,8 +123,8 @@ enum STATES FMS( u8 **in , u32 *transitions) { aarch64 has the highest CASE_VALUES_THRESHOLD in GCC. It's high enough to change decisions in switch expansion which in turn can expose new jump threading opportunities. Skip the later tests on aarch64. */ -/* { dg-final { scan-tree-dump "Jumps threaded: 1\[1-9\]" "thread1" } } */ -/* { dg-final { scan-tree-dump-times "Invalid sum" 4 "thread1" } } */ +/* { dg-final { scan-tree-dump "Jumps threaded: 9" "thread1" } } */ +/* { dg-final { scan-tree-dump-times "Invalid sum" 1 "thread1" } } */ /* { dg-final { scan-tree-dump-not "optimizing for size" "thread1" } } */ /* { dg-final { scan-tree-dump-not "optimizing for size" "thread2" } } */ /* { dg-final { scan-tree-dump-not "optimizing for size" "thread3" { target { ! aarch64*-*-* } } } } */ diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-18.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-18.c index 60d4f76f076..2d78d045516 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-18.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-18.c @@ -21,5 +21,7 @@ condition. All the cases are picked up by VRP1 as jump threads. */ -/* { dg-final { scan-tree-dump-times "Registering jump" 6 "thread1" } } */ + +/* There used to be 6 jump threads found by thread1, but they all + depended on threading through distinct loops in ethread. */ /* { dg-final { scan-tree-dump-times "Threaded" 2 "vrp1" } } */ diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-7.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-7.c index e3d4b311c03..16abcde5053 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-7.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-7.c @@ -1,8 +1,8 @@ /* { dg-do compile } */ /* { dg-options "-O2 -fdump-tree-thread1-stats -fdump-tree-thread2-stats -fdump-tree-dom2-stats -fdump-tree-thread3-stats -fdump-tree-dom3-stats -fdump-tree-vrp2-stats -fno-guess-branch-probability" } */ -/* { dg-final { scan-tree-dump "Jumps threaded: 18" "thread1" } } */ -/* { dg-final { scan-tree-dump "Jumps threaded: 8" "thread3" { target { ! aarch64*-*-* } } } } */ +/* { dg-final { scan-tree-dump "Jumps threaded: 12" "thread1" } } */ +/* { dg-final { scan-tree-dump "Jumps threaded: 5" "thread3" { target { ! aarch64*-*-* } } } } */ /* { dg-final { scan-tree-dump-not "Jumps threaded" "dom2" } } */ /* aarch64 has the highest CASE_VALUES_THRESHOLD in GCC. It's high enough diff --git a/gcc/testsuite/gcc.dg/vect/bb-slp-16.c b/gcc/testsuite/gcc.dg/vect/bb-slp-16.c index 664e93e9b60..e68a9b62535 100644 --- a/gcc/testsuite/gcc.dg/vect/bb-slp-16.c +++ b/gcc/testsuite/gcc.dg/vect/bb-slp-16.c @@ -1,8 +1,5 @@ /* { dg-require-effective-target vect_int } */ -/* See note below as to why we disable threading. */ -/* { dg-additional-options "-fdisable-tree-thread1" } */ - #include #include "tree-vect.h" @@ -30,10 +27,6 @@ main1 (int dummy) *pout++ = *pin++ + a; *pout++ = *pin++ + a; *pout++ = *pin++ + a; - /* In some architectures like ppc64, jump threading may thread - the iteration where i==0 such that we no longer optimize the - BB. Another alternative to disable jump threading would be - to wrap the read from `i' into a function returning i. */ if (arr[i] = i) a = i; else diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c index baac11280fa..2b9b8f81274 100644 --- a/gcc/tree-ssa-threadupdate.c +++ b/gcc/tree-ssa-threadupdate.c @@ -2757,6 +2757,58 @@ fwd_jt_path_registry::update_cfg (bool may_peel_loop_headers) return retval; } +bool +jt_path_registry::cancel_invalid_paths (vec &path) +{ + gcc_checking_assert (!path.is_empty ()); + edge taken_edge = path[path.length () - 1]->e; + loop_p loop = taken_edge->src->loop_father; + bool seen_latch = false; + bool path_crosses_loops = false; + + for (unsigned int i = 0; i < path.length (); i++) + { + edge e = path[i]->e; + + if (e == NULL) + { + // NULL outgoing edges on a path can happen for jumping to a + // constant address. + cancel_thread (&path, "Found NULL edge in jump threading path"); + return true; + } + + if (loop->latch == e->src || loop->latch == e->dest) + seen_latch = true; + + // The first entry represents the block with an outgoing edge + // that we will redirect to the jump threading path. Thus we + // don't care about that block's loop father. + if ((i > 0 && e->src->loop_father != loop) + || e->dest->loop_father != loop) + path_crosses_loops = true; + + if (flag_checking && !m_backedge_threads) + gcc_assert ((path[i]->e->flags & EDGE_DFS_BACK) == 0); + } + + if (cfun->curr_properties & PROP_loop_opts_done) + return false; + + if (seen_latch && empty_block_p (loop->latch)) + { + cancel_thread (&path, "Threading through latch before loop opts " + "would create non-empty latch"); + return true; + } + if (path_crosses_loops) + { + cancel_thread (&path, "Path crosses loops"); + return true; + } + return false; +} + /* Register a jump threading opportunity. We queue up all the jump threading opportunities discovered by a pass and update the CFG and SSA form all at once. @@ -2776,19 +2828,8 @@ jt_path_registry::register_jump_thread (vec *path) return false; } - /* First make sure there are no NULL outgoing edges on the jump threading - path. That can happen for jumping to a constant address. */ - for (unsigned int i = 0; i < path->length (); i++) - { - if ((*path)[i]->e == NULL) - { - cancel_thread (path, "Found NULL edge in jump threading path"); - return false; - } - - if (flag_checking && !m_backedge_threads) - gcc_assert (((*path)[i]->e->flags & EDGE_DFS_BACK) == 0); - } + if (cancel_invalid_paths (*path)) + return false; if (dump_file && (dump_flags & TDF_DETAILS)) dump_jump_thread_path (dump_file, *path, true); diff --git a/gcc/tree-ssa-threadupdate.h b/gcc/tree-ssa-threadupdate.h index 8b48a671212..d68795c9f27 100644 --- a/gcc/tree-ssa-threadupdate.h +++ b/gcc/tree-ssa-threadupdate.h @@ -75,6 +75,7 @@ protected: unsigned long m_num_threaded_edges; private: virtual bool update_cfg (bool peel_loop_headers) = 0; + bool cancel_invalid_paths (vec &path); jump_thread_path_allocator m_allocator; // True if threading through back edges is allowed. This is only // allowed in the generic copier in the backward threader.