Teach bugpoint to be a little bit smarter and avoid repeating work

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13132 91177308-0d34-0410-b5e6-96231b3b80d8

tools/bugpoint/Miscompilation.cpp

@@ -108,7 +108,11 @@ ReduceMiscompilingPasses::doTest(std::vector<const PassInfo*> &Prefix,
     exit(1);
   }
   removeFile(BytecodeResult);  // No longer need the file on disk
-    
+
+  // Don't check if there are no passes in the suffix.
+  if (Suffix.empty())
+    return NoFailure;
+  
   std::cout << "Checking to see if '" << getPassesString(Suffix)
             << "' passes compile correctly after the '"
             << getPassesString(Prefix) << "' passes: ";