--- a/hotspot/src/share/vm/c1/c1_GraphBuilder.cpp	Wed Jan 18 19:37:52 2017 -0800
+++ b/hotspot/src/share/vm/c1/c1_GraphBuilder.cpp	Thu Jan 19 08:10:11 2017 +0100
@@ -3298,7 +3298,9 @@
   // for osr compile, bailout if some requirements are not fulfilled
   if (osr_bci != -1) {
     BlockBegin* osr_block = blm.bci2block()->at(osr_bci);
-    assert(osr_block->is_set(BlockBegin::was_visited_flag),"osr entry must have been visited for osr compile");
+    if (!osr_block->is_set(BlockBegin::was_visited_flag)) {
+      BAILOUT("osr entry must have been visited for osr compile");
+    }
 
     // check if osr entry point has empty stack - we cannot handle non-empty stacks at osr entry points
     if (!osr_block->state()->stack_is_empty()) {

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/compiler/c1/Test8172751.java	Thu Jan 19 08:10:11 2017 +0100
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2017, 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 8172751
+ * @summary OSR compilation at unreachable bci causes C1 crash
+ *
+ * @run main/othervm -XX:-BackgroundCompilation compiler.c1.Test8172751
+ */
+
+package compiler.c1;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MutableCallSite;
+
+public class Test8172751 {
+    private static final MethodHandle CONSTANT_TRUE = MethodHandles.constant(boolean.class, true);
+    private static final MethodHandle CONSTANT_FALSE = MethodHandles.constant(boolean.class, false);
+    private static final MutableCallSite CALL_SITE = new MutableCallSite(CONSTANT_FALSE);
+    private static final int LIMIT = 1_000_000;
+    private static volatile int counter;
+
+    private static boolean doSomething() {
+        return counter++ < LIMIT;
+    }
+
+    private static void executeLoop() {
+        /*
+         * Start off with executing the first loop, then change the call site
+         * target so as to switch over to the second loop but continue running
+         * in the first loop. Eventually, an OSR compilation of the first loop
+         * is triggered. Yet C1 will not find the OSR entry, since it will
+         * have optimized out the first loop already during parsing.
+         */
+        if (CALL_SITE.getTarget() == CONSTANT_FALSE) {
+            int count = 0;
+            while (doSomething()) {
+                if (count++ == 1) {
+                    flipSwitch();
+                }
+            }
+        } else {
+            while (doSomething()) {
+            }
+        }
+    }
+
+    private static void flipSwitch() {
+        CALL_SITE.setTarget(CONSTANT_TRUE);
+    }
+
+    public static void main(String[] args) {
+        executeLoop();
+    }
+}