8237945: CTW: C2 compilation fails with assert(just_allocated_object(alloc_ctl) == ptr) failed: most recent allo

Removing too strong assertion about array allocation in LibraryCallKit::tightly_coupled_allocation().

Reviewed-by: thartmann, neliasso

src/hotspot/share/opto/library_call.cpp

@@ -4852,8 +4852,6 @@ LibraryCallKit::tightly_coupled_allocation(Node* ptr,
 
   // This arraycopy must unconditionally follow the allocation of the ptr.
   Node* alloc_ctl = ptr->in(0);
-  assert(just_allocated_object(alloc_ctl) == ptr, "most recent allo");
-
   Node* ctl = control();
   while (ctl != alloc_ctl) {
     // There may be guards which feed into the slow_region.

test/hotspot/jtreg/compiler/arraycopy/TestTightlyCoupledAllocationAssert.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2020, Oracle and/or its affiliates. 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 8237945
+ * @summary Test that triggers the too strong assertion "just_allocated_object(alloc_ctl) == ptr" in LibraryCallKit::tightly_coupled_allocation()
+ *
+ * @run main/othervm -Xbatch compiler.arraycopy.TestTightlyCoupledAllocationAssert
+ */
+
+package compiler.arraycopy;
+
+public class TestTightlyCoupledAllocationAssert {
+
+    static A a;
+    static byte[] bArr = new byte[8];
+
+    public static void main(String[] strArr) {
+        for (int i = 0; i < 10000; i++ ) {
+            test(i % 20);
+        }
+    }
+
+    public static void test(int i) {
+        byte [] bArrLocal = new byte[8]; // (1)
+        if (i < 16) {
+            a = new A(); // (2)
+            return;
+        }
+        // The assertion "just_allocated_object(alloc_ctl) == ptr" in LibraryCallKit::tightly_coupled_allocation() fails during parsing here since
+        // the most recent allocation is (2) and not (1). The earlier bailout checks about the memory state (involving the variable "rawmem") pass
+        // because the if branch returns and the memory state from (2) is not merged with the memory state from (1) for the array copy.
+        System.arraycopy(bArr, 0, bArrLocal, 0, 8);
+    }
+}
+
+class A { }