8252292: 8240795 may cause anti-dependence to be missed

Reviewed-by: thartmann, kvn

src/hotspot/share/opto/loopnode.cpp

@@ -4209,17 +4209,26 @@ Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
           }
         } else {
           Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
-          const TypePtr* adr_type = s->adr_type();
-          if (s->is_ArrayCopy()) {
-            // Copy to known instance needs destination type to test for aliasing
-            const TypePtr* dest_type = s->as_ArrayCopy()->_dest_type;
-            if (dest_type != TypeOopPtr::BOTTOM) {
-              adr_type = dest_type;
-            }
-          }
           assert(sctrl != NULL || !s->is_reachable_from_root(), "must have control");
-          if (sctrl != NULL && !sctrl->is_top() && C->can_alias(adr_type, load_alias_idx) && is_dominator(early, sctrl)) {
-            LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
+          if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
+            const TypePtr* adr_type = s->adr_type();
+            if (s->is_ArrayCopy()) {
+              // Copy to known instance needs destination type to test for aliasing
+              const TypePtr* dest_type = s->as_ArrayCopy()->_dest_type;
+              if (dest_type != TypeOopPtr::BOTTOM) {
+                adr_type = dest_type;
+              }
+            }
+            if (C->can_alias(adr_type, load_alias_idx)) {
+              LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
+            } else if (s->is_CFG()) {
+              for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
+                Node* s1 = s->fast_out(i);
+                if (_igvn.type(s1) == Type::MEMORY) {
+                  worklist.push(s1);
+                }
+              }
+            }
           }
         }
       }

test/hotspot/jtreg/compiler/escapeAnalysis/TestMissingAntiDependency.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2020, 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 8252292
+ * @summary 8240795 may cause anti-dependency to be missed
+ * @requires vm.gc.Parallel
+ *
+ * @run main/othervm -XX:-BackgroundCompilation -XX:+UseParallelGC TestMissingAntiDependency
+ *
+ */
+
+public class TestMissingAntiDependency {
+    public static void main(String[] args) {
+        int[] src = new int[10];
+        for (int i = 0; i < 20_000; i++) {
+            test(src, true, true, 10);
+            test(src, true, false, 10);
+            test(src, false, false, 10);
+        }
+        src[9] = 42;
+        final int v = test(src, true, true, 1);
+        if (v != 42) {
+            throw new RuntimeException("Incorrect return value " + v);
+        }
+    }
+
+    private static int test(int[] src, boolean flag1, boolean flag2, int stop) {
+        int v = 0;
+        int j = 1;
+        for (; j < 10; j++) {
+            for (int i = 0; i < 2; i++) {
+
+            }
+        }
+        int[] dst = new int[10];
+        for (int i = 0; i < stop; i ++) {
+            if (flag1) {
+                System.arraycopy(src, 0, dst, 0, j);
+                v = dst[9];
+                if (flag2) {
+                    src[9] = 0x42;
+                }
+            }
+        }
+        return v;
+    }
+}