8290705: StringConcat::validate_mem_flow asserts with "unexpected user: StoreI"

Reviewed-by: kvn, xliu

src/hotspot/share/opto/stringopts.cpp

@@ -1022,6 +1022,21 @@ bool StringConcat::validate_control_flow() {
       fail = true;
       break;
     } else if (ptr->is_Proj() && ptr->in(0)->is_Initialize()) {
+      // Check for side effect between Initialize and the constructor
+      for (SimpleDUIterator iter(ptr); iter.has_next(); iter.next()) {
+        Node* use = iter.get();
+        if (!use->is_CFG() && !use->is_CheckCastPP() && !use->is_Load()) {
+#ifndef PRODUCT
+          if (PrintOptimizeStringConcat) {
+            tty->print_cr("unexpected control use of Initialize");
+            ptr->in(0)->dump(); // Initialize node
+            use->dump(1);
+          }
+#endif
+          fail = true;
+          break;
+        }
+      }
       ptr = ptr->in(0)->in(0);
     } else if (ptr->is_Region()) {
       Node* copy = ptr->as_Region()->is_copy();

test/hotspot/jtreg/compiler/stringopts/SideEffectBeforeConstructor.jasm

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2022, 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.
+ */
+
+super public class compiler/stringopts/SideEffectBeforeConstructor
+	version 51:0
+{
+  public static Field result:I;
+
+  static Method "<clinit>":"()V"
+	stack 2 locals 0
+  {
+		iconst_0;
+		putstatic	Field result:"I";
+		return;
+  }
+  public Method "<init>":"()V"
+	stack 1 locals 1
+  {
+		aload_0;
+		invokespecial	Method java/lang/Object."<init>":"()V";
+		return;
+  }
+
+  public static Method test:"(Ljava/lang/String;)V"
+	stack 4 locals 1
+  {
+		new	class java/lang/StringBuffer;
+		dup;
+		getstatic	Field result:"I";
+		iconst_1;
+		iadd;
+		putstatic	Field result:"I";
+		aload_0;
+		invokespecial	Method java/lang/StringBuffer."<init>":"(Ljava/lang/String;)V";
+		invokevirtual	Method java/lang/StringBuffer.toString:"()Ljava/lang/String;";
+		return;
+  }
+}

test/hotspot/jtreg/compiler/stringopts/TestSideEffectBeforeConstructor.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2022, 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 8290705
+ * @summary Test correctness of the string concatenation optimization with
+ *          a store between StringBuffer allocation and constructor invocation.
+ * @compile SideEffectBeforeConstructor.jasm
+ * @run main/othervm -Xbatch compiler.stringopts.TestSideEffectBeforeConstructor
+ */
+
+package compiler.stringopts;
+
+public class TestSideEffectBeforeConstructor {
+
+    public static void main(String[] args) {
+        for (int i = 0; i < 100_000; ++i) {
+            try {
+                SideEffectBeforeConstructor.test(null);
+            } catch (NullPointerException npe) {
+                // Expected
+            }
+        }
+        if (SideEffectBeforeConstructor.result != 100_000) {
+            throw new RuntimeException("Unexpected result: " + SideEffectBeforeConstructor.result);
+        }
+    }
+}