From d2a63f259e0708cc87058cb8053e65c536adc0a2 Mon Sep 17 00:00:00 2001
From: Roland Westrelin <roland@openjdk.org>
Date: Tue, 30 Mar 2021 07:58:49 +0000
Subject: [PATCH] 8264360: Loop strip mining verification fails with "should be
 on the backedge"

Reviewed-by: kvn, thartmann
---
 src/hotspot/share/opto/loopnode.cpp           |  2 +-
 .../TestLoadOnBackedgeWithPrec.java           | 71 +++++++++++++++++++
 2 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 test/hotspot/jtreg/compiler/loopstripmining/TestLoadOnBackedgeWithPrec.java

diff --git a/src/hotspot/share/opto/loopnode.cpp b/src/hotspot/share/opto/loopnode.cpp
index be986f26052..304b6385b3d 100644
--- a/src/hotspot/share/opto/loopnode.cpp
+++ b/src/hotspot/share/opto/loopnode.cpp
@@ -1807,7 +1807,7 @@ void LoopNode::verify_strip_mined(int expect_skeleton) const {
           for (DUIterator_Fast jmax, j = be->fast_outs(jmax); j < jmax; j++) {
             Node* n = be->fast_out(j);
             if (n->is_Load()) {
-              assert(n->in(0) == be, "should be on the backedge");
+              assert(n->in(0) == be || n->find_prec_edge(be) > 0, "should be on the backedge");
               do {
                 n = n->raw_out(0);
               } while (!n->is_Phi());
diff --git a/test/hotspot/jtreg/compiler/loopstripmining/TestLoadOnBackedgeWithPrec.java b/test/hotspot/jtreg/compiler/loopstripmining/TestLoadOnBackedgeWithPrec.java
new file mode 100644
index 00000000000..e998e984558
--- /dev/null
+++ b/test/hotspot/jtreg/compiler/loopstripmining/TestLoadOnBackedgeWithPrec.java
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2021, Red Hat, Inc. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8264360
+ * @summary Loop strip mining verification fails with "should be on the backedge"
+ *
+ * @run main/othervm -XX:-TieredCompilation -XX:-BackgroundCompilation TestLoadOnBackedgeWithPrec
+ *
+ */
+
+
+class a {
+    int g = 20;
+    float h = 2;
+    long b = 6;
+}
+
+public class TestLoadOnBackedgeWithPrec {
+    int c ;
+    a[] i = {new a()};
+    float j() {
+        a k = new a();
+        float l = 5;
+        for (int d = 0; d < 8; ++d) {
+            for (int e = 0; e < 9; ++e) {
+                k = k;
+                l *= k.g;
+            }
+            for (int f = 0; f < 9; ++f) {
+                new a();
+            }
+            {
+                a[] m = {
+                    new a(), new a(), new a(),
+                    new a(), new a(), new a(),
+                    new a(), new a(), new a()};
+                c = i[0].g + k.g;
+            }
+        }
+        return k.h;
+    }
+    public static void main(String[] args) {
+        TestLoadOnBackedgeWithPrec n = new TestLoadOnBackedgeWithPrec();
+        for (int i = 0; i < 5_000; i++) {
+            n.j();
+        }
+    }
+}
+