--- a/src/hotspot/cpu/ppc/c1_LIRAssembler_ppc.cpp	Mon Dec 03 16:25:27 2018 +0100
+++ b/src/hotspot/cpu/ppc/c1_LIRAssembler_ppc.cpp	Tue Mar 26 11:51:41 2019 +0100
@@ -1455,13 +1455,11 @@
           break;
       }
     } else {
-      if (opr2->is_address()) {
-        DEBUG_ONLY( Unimplemented(); ) // Seems to be unused at the moment.
-        LIR_Address *addr = opr2->as_address_ptr();
-        BasicType type = addr->type();
-        if (type == T_OBJECT) { __ ld(R0, index_or_disp(addr), addr->base()->as_register()); }
-        else                  { __ lwa(R0, index_or_disp(addr), addr->base()->as_register()); }
-        __ cmpd(BOOL_RESULT, opr1->as_register(), R0);
+      assert(opr1->type() != T_ADDRESS && opr2->type() != T_ADDRESS, "currently unsupported");
+      if (opr1->type() == T_OBJECT || opr1->type() == T_ARRAY) {
+        // There are only equal/notequal comparisons on objects.
+        assert(condition == lir_cond_equal || condition == lir_cond_notEqual, "oops");
+        __ cmpd(BOOL_RESULT, opr1->as_register(), opr2->as_register());
       } else {
         if (unsigned_comp) {
           __ cmplw(BOOL_RESULT, opr1->as_register(), opr2->as_register());
@@ -1497,14 +1495,6 @@
     } else {
       ShouldNotReachHere();
     }
-  } else if (opr1->is_address()) {
-    DEBUG_ONLY( Unimplemented(); ) // Seems to be unused at the moment.
-    LIR_Address * addr = opr1->as_address_ptr();
-    BasicType type = addr->type();
-    assert (opr2->is_constant(), "Checking");
-    if (type == T_OBJECT) { __ ld(R0, index_or_disp(addr), addr->base()->as_register()); }
-    else                  { __ lwa(R0, index_or_disp(addr), addr->base()->as_register()); }
-    __ cmpdi(BOOL_RESULT, R0, opr2->as_constant_ptr()->as_jint());
   } else {
     ShouldNotReachHere();
   }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/compiler/codegen/TestOopCmp.java	Tue Mar 26 11:51:41 2019 +0100
@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2019 SAP SE. 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 8221083
+ * @requires vm.bits == 64 & vm.opt.final.UseCompressedOops == true
+ * @summary On ppc64, C1 erroneously emits a 32-bit compare instruction for oop compares.
+ * @modules java.base/jdk.internal.misc:+open
+ * @library /test/lib /
+ * @build sun.hotspot.WhiteBox
+ * @run driver ClassFileInstaller sun.hotspot.WhiteBox
+ *                                sun.hotspot.WhiteBox$WhiteBoxPermission
+ * @run main/othervm -Xbatch -XX:-UseTLAB -Xmx4m -XX:+UseSerialGC -XX:HeapBaseMinAddress=0x700000000
+ *      -XX:CompileCommand=compileonly,compiler.codegen.TestOopCmp::nullTest
+ *      -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -Xbootclasspath/a:.
+ *      compiler.codegen.TestOopCmp
+ * @author volker.simonis@gmail.com
+ */
+
+package compiler.codegen;
+
+import sun.hotspot.WhiteBox;
+
+public class TestOopCmp {
+
+    private static Object nullObj = null;
+
+    public static boolean nullTest(Object o) {
+        if (o == nullObj) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    public static void main(String args[]) {
+
+        WhiteBox WB = WhiteBox.getWhiteBox();
+
+        // The test is started with -XX:HeapBaseMinAddress=0x700000000 and a
+        // small heap of only 4mb. This works pretty reliable and at least on
+        // Linux/Windows/Solaris we will get a heap starting at 0x700000000.
+        // The test also runs with -XX:+UseSerialGC which means that we'll get
+        // eden starting at 0x700000000.
+        // Calling 'System.gc()' will clean up all the objects from eden, so if
+        // eden starts at 0x700000000 the first allocation right after the
+        // system GC will be allcoated right at address 0x700000000.
+        System.gc();
+        String s = new String("I'm not null!!!");
+        if (WB.getObjectAddress(s) == 0x700000000L) {
+            System.out.println("Got object at address 0x700000000");
+        }
+
+        // We call 'nullTest()' with the newly allocated String object. If it was
+        // allocated at 0x700000000, its 32 least-significant bits will be 0 and a
+        // 32-bit comparison with 'nullObj' (which is 'null') will yield true and
+        // result in a test failure.
+        // If the code generated for 'nullTest()' correctly performs a 64-bit
+        // comparison or if we didn't manage to allcoate 's' at 0x700000000 the
+        // test will always succeed.
+        for (int i = 0; i < 30_000; i++) {
+            if (nullTest(s)) {
+                throw new RuntimeException("Comparing non-null object with null returned 'true'");
+            }
+        }
+    }
+}