--- /dev/null	2017-11-16 08:17:56.803999947 +0100
+++ new/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.hotspot.jdk9.test/src/org/graalvm/compiler/hotspot/jdk9/test/StringUTF16ToBytesGetCharsTest.java	2019-03-12 08:10:35.091958693 +0100
@@ -0,0 +1,142 @@
+/*
+ * Copyright (c) 2018, 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.
+ */
+
+
+package org.graalvm.compiler.hotspot.jdk9.test;
+
+import static org.junit.Assume.assumeFalse;
+
+import jdk.vm.ci.code.InstalledCode;
+import jdk.vm.ci.meta.ResolvedJavaMethod;
+import org.graalvm.compiler.core.common.CompilationIdentifier;
+import org.graalvm.compiler.hotspot.replacements.StringUTF16Substitutions;
+import org.graalvm.compiler.nodes.StructuredGraph;
+import org.graalvm.compiler.nodes.java.NewArrayNode;
+import org.graalvm.compiler.replacements.arraycopy.ArrayCopyCallNode;
+import org.graalvm.compiler.replacements.test.MethodSubstitutionTest;
+import org.graalvm.compiler.test.AddExports;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Test substitutions for (innate) methods StringUTF16.toBytes and StringUTF16.getChars provided by
+ * {@link StringUTF16Substitutions}.
+ */
+@AddExports({"java.base/java.lang"})
+public final class StringUTF16ToBytesGetCharsTest extends MethodSubstitutionTest {
+
+    private static final int N = 1000;
+    private static final int N_OVERFLOW = 10;
+
+    @Before
+    public void checkAMD64() {
+        assumeFalse(Java8OrEarlier);
+    }
+
+    @Test
+    public void testStringUTF16ToBytes() throws ClassNotFoundException {
+        Class<?> javaclass = Class.forName("java.lang.StringUTF16");
+
+        ResolvedJavaMethod caller = getResolvedJavaMethod(javaclass, "toBytes", char[].class, int.class, int.class);
+        StructuredGraph graph = getReplacements().getIntrinsicGraph(caller, CompilationIdentifier.INVALID_COMPILATION_ID, getDebugContext());
+        assertInGraph(graph, NewArrayNode.class);
+        assertInGraph(graph, ArrayCopyCallNode.class);
+
+        InstalledCode code = getCode(caller, graph);
+
+        for (int srcOffset = 0; srcOffset < 2; srcOffset++) {
+            for (int i = 0; i < N; i++) {
+                int length = i2sz(i);
+                char[] src = fillUTF16Chars(new char[length]);
+                int copiedLength = Math.max(0, length - srcOffset);
+                int srcDelta = Math.min(srcOffset, copiedLength);
+                byte[] dst = (byte[]) invokeSafe(caller, null, src, srcDelta, copiedLength);
+                assert dst.length == copiedLength * 2;
+                byte[] dst2 = (byte[]) executeVarargsSafe(code, src, srcDelta, copiedLength);
+                assertDeepEquals(dst, dst2);
+            }
+        }
+        for (int srcOff = 0; srcOff < N_OVERFLOW; ++srcOff) {
+            for (int len = 0; len < N_OVERFLOW; ++len) {
+                char[] src = fillUTF16Chars(new char[N_OVERFLOW]);
+                test(caller, null, src, srcOff, len);
+            }
+        }
+    }
+
+    @Test
+    public void testStringUTF16getChars() throws ClassNotFoundException {
+        Class<?> javaclass = Class.forName("java.lang.StringUTF16");
+
+        ResolvedJavaMethod caller = getResolvedJavaMethod(javaclass, "getChars", byte[].class, int.class, int.class, char[].class, int.class);
+        StructuredGraph graph = getReplacements().getIntrinsicGraph(caller, CompilationIdentifier.INVALID_COMPILATION_ID, getDebugContext());
+        assertInGraph(graph, ArrayCopyCallNode.class);
+
+        InstalledCode code = getCode(caller, graph);
+
+        for (int dstOffset = 0; dstOffset < 2; dstOffset++) {
+            for (int srcOffset = 0; srcOffset < 2; srcOffset++) {
+                for (int i = 0; i < N; i++) {
+                    int length = i2sz(i);
+                    byte[] src = fillUTF16Bytes(new byte[length * 2]);
+                    char[] dst = new char[length];
+                    int copiedLength = Math.max(0, length - Math.max(dstOffset, srcOffset));
+                    int dstDelta = Math.min(dstOffset, copiedLength);
+                    int srcDelta = Math.min(srcOffset, copiedLength);
+                    invokeSafe(caller, null, src, srcDelta, srcDelta + copiedLength, dst, dstDelta);
+                    char[] dst2 = new char[length];
+                    executeVarargsSafe(code, src, srcDelta, srcDelta + copiedLength, dst2, dstDelta);
+                    assertDeepEquals(dst, dst2);
+                }
+            }
+        }
+        for (int srcOff = 0; srcOff < N_OVERFLOW; ++srcOff) {
+            for (int dstOff = 0; dstOff < N_OVERFLOW; ++dstOff) {
+                for (int len = 0; len < N_OVERFLOW; ++len) {
+                    byte[] src = fillUTF16Bytes(new byte[N_OVERFLOW]);
+                    char[] dst = new char[N_OVERFLOW];
+                    test(caller, null, src, srcOff, len, dst, dstOff);
+                }
+            }
+        }
+    }
+
+    private static char[] fillUTF16Chars(char[] v) {
+        for (int ch = 0, i = 0; i < v.length; i++, ch += 0x101) {
+            v[i] = (char) ch;
+        }
+        return v;
+    }
+
+    private static byte[] fillUTF16Bytes(byte[] v) {
+        for (int ch = 1, i = 0; i < v.length; i += 2, ch++) {
+            v[i] = (byte) (ch - 1);
+            v[i + 1] = (byte) ch;
+        }
+        return v;
+    }
+
+    private static int i2sz(int i) {
+        return i * 3;
+    }
+}