8027353: Exact intrinsics: assert(n != NULL) failed: must not be null

Reviewed-by: kvn, roland

src/share/vm/opto/library_call.cpp

@@ -2056,7 +2056,7 @@ bool LibraryCallKit::inline_math_subtractExactL(bool is_decrement) {
   if (is_decrement) {
     arg2 = longcon(1);
   } else {
-    Node* arg2 = argument(2); // type long
+    arg2 = argument(2); // type long
     // argument(3) == TOP
   }
 

test/compiler/intrinsics/mathexact/SubExactLConstantTest.java

@@ -24,6 +24,7 @@
 /*
  * @test
  * @bug 8026844
+ * @bug 8027353
  * @summary Test constant subtractExact
  * @compile SubExactLConstantTest.java Verify.java
  * @run main SubExactLConstantTest

test/compiler/intrinsics/mathexact/SubExactLNonConstantTest.java

@@ -24,6 +24,7 @@
 /*
  * @test
  * @bug 8026844
+ * @bug 8027353
  * @summary Test non constant subtractExact
  * @compile SubExactLNonConstantTest.java Verify.java
  * @run main SubExactLNonConstantTest