[silgen] Tell prepareEpilog to emit a rethrow block instead of calling prepareRethrowEpilog.

The code inside of prepareEpilog that does this just calls prepareRethrowEpilog,
so this code is not needed.

rdar://34222540

Author: gottesmm

lib/SILGen/SILGen.cpp

@@ -1252,23 +1252,19 @@ class SourceFileScope {
 
       sgm.TopLevelSGF = new SILGenFunction(sgm, *toplevel);
       sgm.TopLevelSGF->MagicFunctionName = sgm.SwiftModule->getName();
-      sgm.TopLevelSGF->prepareEpilog(Type(), false,
-                                 CleanupLocation::getModuleCleanupLocation());
-
-      sgm.TopLevelSGF->prepareRethrowEpilog(
-                                 CleanupLocation::getModuleCleanupLocation());
+      auto moduleCleanupLoc = CleanupLocation::getModuleCleanupLocation();
+      sgm.TopLevelSGF->prepareEpilog(Type(), true, moduleCleanupLoc);
 
       // Create the argc and argv arguments.
-      auto PrologueLoc = RegularLocation::getModuleLocation();
-      PrologueLoc.markAsPrologue();
+      auto prologueLoc = RegularLocation::getModuleLocation();
+      prologueLoc.markAsPrologue();
       auto entry = sgm.TopLevelSGF->B.getInsertionBB();
       auto paramTypeIter =
           sgm.TopLevelSGF->F.getConventions().getParameterSILTypes().begin();
       entry->createFunctionArgument(*paramTypeIter);
       entry->createFunctionArgument(*std::next(paramTypeIter));
 
-      scope.emplace(sgm.TopLevelSGF->Cleanups,
-                    CleanupLocation::getModuleCleanupLocation());
+      scope.emplace(sgm.TopLevelSGF->Cleanups, moduleCleanupLoc);
     }
   }