--- a/hotspot/src/cpu/x86/vm/c1_LIRGenerator_x86.cpp	Mon Dec 07 15:01:24 2015 +0100
+++ b/hotspot/src/cpu/x86/vm/c1_LIRGenerator_x86.cpp	Mon Dec 07 15:00:46 2015 +0000
@@ -736,19 +736,6 @@
   obj.load_item();
   offset.load_nonconstant();
 
-  if (type == objectType) {
-    cmp.load_item_force(FrameMap::rax_oop_opr);
-    val.load_item();
-  } else if (type == intType) {
-    cmp.load_item_force(FrameMap::rax_opr);
-    val.load_item();
-  } else if (type == longType) {
-    cmp.load_item_force(FrameMap::long0_opr);
-    val.load_item_force(FrameMap::long1_opr);
-  } else {
-    ShouldNotReachHere();
-  }
-
   LIR_Opr addr = new_pointer_register();
   LIR_Address* a;
   if(offset.result()->is_constant()) {
@@ -785,6 +772,19 @@
                 true /* do_load */, false /* patch */, NULL);
   }
 
+  if (type == objectType) {
+    cmp.load_item_force(FrameMap::rax_oop_opr);
+    val.load_item();
+  } else if (type == intType) {
+    cmp.load_item_force(FrameMap::rax_opr);
+    val.load_item();
+  } else if (type == longType) {
+    cmp.load_item_force(FrameMap::long0_opr);
+    val.load_item_force(FrameMap::long1_opr);
+  } else {
+    ShouldNotReachHere();
+  }
+
   LIR_Opr ill = LIR_OprFact::illegalOpr;  // for convenience
   if (type == objectType)
     __ cas_obj(addr, cmp.result(), val.result(), ill, ill);

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/compiler/intrinsics/unsafe/UnsafeTwoCASLong.java	Mon Dec 07 15:00:46 2015 +0000
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2015, 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 8143930
+ * @summary C1 LinearScan asserts when compiling two back-to-back CompareAndSwapLongs
+ * @modules java.base/jdk.internal.misc
+ * @run testng/othervm -Diters=200000 -XX:TieredStopAtLevel=1 UnsafeTwoCASLong
+ */
+
+import org.testng.annotations.Test;
+
+import java.lang.reflect.Field;
+
+import static org.testng.Assert.*;
+
+public class UnsafeTwoCASLong {
+    static final int ITERS = Integer.getInteger("iters", 1);
+    static final jdk.internal.misc.Unsafe UNSAFE;
+    static final long V_OFFSET;
+
+    static {
+        try {
+            Field f = jdk.internal.misc.Unsafe.class.getDeclaredField("theUnsafe");
+            f.setAccessible(true);
+            UNSAFE = (jdk.internal.misc.Unsafe) f.get(null);
+        } catch (Exception e) {
+            throw new RuntimeException("Unable to get Unsafe instance.", e);
+        }
+
+        try {
+            Field vField = UnsafeTwoCASLong.class.getDeclaredField("v");
+            V_OFFSET = UNSAFE.objectFieldOffset(vField);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    long v;
+
+    @Test
+    public void testFieldInstance() {
+        UnsafeTwoCASLong t = new UnsafeTwoCASLong();
+        for (int c = 0; c < ITERS; c++) {
+            testAccess(t, V_OFFSET);
+        }
+    }
+
+    static void testAccess(Object base, long offset) {
+        UNSAFE.compareAndSwapLong(base, offset, 1L, 2L);
+        UNSAFE.compareAndSwapLong(base, offset, 2L, 1L);
+    }
+
+}
+