8229450: C2 compilation fails with assert(found_sfpt) failed

Reviewed-by: roland, thartmann

Author: Xin Liu

src/hotspot/share/opto/loopopts.cpp

@@ -1191,6 +1191,22 @@ bool PhaseIdealLoop::can_split_if(Node* n_ctrl) {
   return true;
 }
 
+// Detect if the node is the inner strip-mined loop
+// Return: NULL if it's not the case, or the exit of outer strip-mined loop
+static Node* is_inner_of_stripmined_loop(const Node* out) {
+  Node* out_le = NULL;
+
+  if (out->is_CountedLoopEnd()) {
+      const CountedLoopNode* loop = out->as_CountedLoopEnd()->loopnode();
+
+      if (loop != NULL && loop->is_strip_mined()) {
+        out_le = loop->in(LoopNode::EntryControl)->as_OuterStripMinedLoop()->outer_loop_exit();
+      }
+  }
+
+  return out_le;
+}
+
 //------------------------------split_if_with_blocks_post----------------------
 // Do the real work in a non-recursive function.  CFG hackery wants to be
 // in the post-order, so it can dirty the I-DOM info and not use the dirtied
@@ -1324,6 +1340,15 @@ void PhaseIdealLoop::split_if_with_blocks_post(Node *n) {
       Node *dom = idom(prevdom);
       while (dom != cutoff) {
         if (dom->req() > 1 && dom->in(1) == bol && prevdom->in(0) == dom) {
+          // It's invalid to move control dependent data nodes in the inner
+          // strip-mined loop, because:
+          //  1) break validation of LoopNode::verify_strip_mined()
+          //  2) move code with side-effect in strip-mined loop
+          // Move to the exit of outer strip-mined loop in that case.
+          Node* out_le = is_inner_of_stripmined_loop(dom);
+          if (out_le != NULL) {
+            prevdom = out_le;
+          }
           // Replace the dominated test with an obvious true or false.
           // Place it on the IGVN worklist for later cleanup.
           C->set_major_progress();

test/hotspot/jtreg/compiler/loopstripmining/LoadDependsOnIfIdenticalToLoopExit.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2019, 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 8229450
+ * @summary shared an identical bool node with a strip-mined loop
+ *
+ * @run main/othervm -XX:-TieredCompilation -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:LoopMaxUnroll=0 -XX:CompileCommand=dontinline,LoadDependsOnIfIdenticalToLoopExit::not_inlined -XX:CompileCommand=compileonly,LoadDependsOnIfIdenticalToLoopExit::test1 LoadDependsOnIfIdenticalToLoopExit
+ *
+ */
+
+public class LoadDependsOnIfIdenticalToLoopExit {
+    public static void main(String[] args) {
+        for (int i = 0; i < 20_000; i++) {
+            test1(false, false);
+            test1(true, true);
+        }
+    }
+
+    private static int test1(boolean flag1, boolean flag2) {
+        int res = 1;
+        int[] array = new int[10];
+        not_inlined(array);
+        int i;
+        for (i = 0; i < 2000; i++) {
+            res *= i;
+        }
+
+        if (flag1) {
+            if (flag2) {
+                res++;
+            }
+        }
+
+        if (i >= 2000) {
+            res *= array[0];
+        }
+        return res;
+    }
+
+    private static void not_inlined(int[] array) {
+    }
+}