--- a/src/hotspot/share/prims/whitebox.cpp	Tue Jun 26 11:14:27 2018 -0400
+++ b/src/hotspot/share/prims/whitebox.cpp	Tue Jun 26 09:14:49 2018 -0700
@@ -855,7 +855,16 @@
 bool WhiteBox::compile_method(Method* method, int comp_level, int bci, Thread* THREAD) {
   // Screen for unavailable/bad comp level or null method
   AbstractCompiler* comp = CompileBroker::compiler(comp_level);
-  if (method == NULL || comp_level > MIN2((CompLevel) TieredStopAtLevel, CompLevel_highest_tier) || comp == NULL) {
+  if (method == NULL) {
+    tty->print_cr("WB error: request to compile NULL method");
+    return false;
+  }
+  if (comp_level > MIN2((CompLevel) TieredStopAtLevel, CompLevel_highest_tier)) {
+    tty->print_cr("WB error: invalid compilation level %d", comp_level);
+    return false;
+  }
+  if (comp == NULL) {
+    tty->print_cr("WB error: no compiler for requested compilation level %d", comp_level);
     return false;
   }
 
@@ -868,7 +877,17 @@
   // Compile method and check result
   nmethod* nm = CompileBroker::compile_method(mh, bci, comp_level, mh, mh->invocation_count(), CompileTask::Reason_Whitebox, THREAD);
   MutexLockerEx mu(Compile_lock);
-  return ((!is_blocking && mh->queued_for_compilation()) || nm != NULL);
+  bool is_queued = mh->queued_for_compilation();
+  if ((!is_blocking && is_queued) || nm != NULL) {
+    return true;
+  }
+  tty->print("WB error: failed to %s compile at level %d method ", is_blocking ? "blocking" : "", comp_level);
+  mh->print_short_name(tty);
+  tty->cr();
+  if (is_blocking && is_queued) {
+    tty->print_cr("WB error: blocking compilation is still in queue!");
+  }
+  return false;
 }
 
 WB_ENTRY(jboolean, WB_EnqueueMethodForCompilation(JNIEnv* env, jobject o, jobject method, jint comp_level, jint bci))