--- a/src/share/vm/opto/chaitin.cpp	Wed Aug 19 17:59:00 2015 -0700
+++ b/src/share/vm/opto/chaitin.cpp	Tue Aug 18 16:10:34 2015 +0200
@@ -990,9 +990,13 @@
         // FOUR registers!
 #ifdef ASSERT
         if (is_vect) {
-          assert(lrgmask.is_aligned_sets(lrg.num_regs()), "vector should be aligned");
-          assert(!lrg._fat_proj, "sanity");
-          assert(RegMask::num_registers(kreg) == lrg.num_regs(), "sanity");
+          if (lrg.num_regs() != 0) {
+            assert(lrgmask.is_aligned_sets(lrg.num_regs()), "vector should be aligned");
+            assert(!lrg._fat_proj, "sanity");
+            assert(RegMask::num_registers(kreg) == lrg.num_regs(), "sanity");
+          } else {
+            assert(n->is_Phi(), "not all inputs processed only if Phi");
+          }
         }
 #endif
         if (!is_vect && lrg.num_regs() == 2 && !lrg._fat_proj && rm.is_misaligned_pair()) {

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/compiler/regalloc/TestVectorRegAlloc.java	Tue Aug 18 16:10:34 2015 +0200
@@ -0,0 +1,69 @@
+/*
+ * 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 8131969
+ * @summary assert in register allocation code when vector Phi for a loop is processed because code assumes all inputs already processed
+ * @run main/othervm -Xbatch TestVectorRegAlloc
+ *
+ */
+
+public class TestVectorRegAlloc {
+
+    static int test_helper_i;
+    static boolean test_helper() {
+        test_helper_i++;
+        return (test_helper_i & 7) != 0;
+    }
+
+    static void test(double[] src, double[] dst, boolean flag) {
+        double j = 0.0;
+        while(test_helper()) {
+            for (int i = 0; i < src.length; i++) {
+                dst[i] = src[i] + j;
+            }
+            // Loop will be unswitched and ReplicateD of zero will be
+            // split through the Phi of outer loop
+            for (int i = 0; i < src.length; i++) {
+                double k;
+                if (flag) {
+                    k = j;
+                } else {
+                    k = 0;
+                }
+                dst[i] = src[i] + k;
+            }
+            j++;
+        }
+    }
+
+    static public void main(String[] args) {
+        double[] src = new double[10];
+        double[] dst = new double[10];
+        for (int i = 0; i < 20000; i++) {
+            test(src, dst, (i % 2) == 0);
+        }
+    }
+}