diff --git a/lib/Frontend/ASTUnit.cpp b/lib/Frontend/ASTUnit.cpp
index 4a956ff..c1115ae 100644
--- a/lib/Frontend/ASTUnit.cpp
+++ b/lib/Frontend/ASTUnit.cpp
@@ -801,6 +801,7 @@
     break;
 
   case ASTReader::Failure:
+  case ASTReader::Missing:
   case ASTReader::OutOfDate:
   case ASTReader::VersionMismatch:
   case ASTReader::ConfigurationMismatch:
diff --git a/lib/Frontend/ChainedIncludesSource.cpp b/lib/Frontend/ChainedIncludesSource.cpp
index f414f93..3b31bf6 100644
--- a/lib/Frontend/ChainedIncludesSource.cpp
+++ b/lib/Frontend/ChainedIncludesSource.cpp
@@ -47,6 +47,7 @@
     return Reader.take();
 
   case ASTReader::Failure:
+  case ASTReader::Missing:
   case ASTReader::OutOfDate:
   case ASTReader::VersionMismatch:
   case ASTReader::ConfigurationMismatch:
diff --git a/lib/Frontend/CompilerInstance.cpp b/lib/Frontend/CompilerInstance.cpp
index ce6572a..d5c1a27 100644
--- a/lib/Frontend/CompilerInstance.cpp
+++ b/lib/Frontend/CompilerInstance.cpp
@@ -338,6 +338,7 @@
     // Unrecoverable failure: don't even try to process the input file.
     break;
 
+  case ASTReader::Missing:
   case ASTReader::OutOfDate:
   case ASTReader::VersionMismatch:
   case ASTReader::ConfigurationMismatch:
@@ -945,88 +946,6 @@
     } else
       ModuleFileName = PP->getHeaderSearchInfo().getModuleFileName(ModuleName);
 
-    if (ModuleFileName.empty()) {
-      getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_found)
-        << ModuleName
-        << SourceRange(ImportLoc, ModuleNameLoc);
-      LastModuleImportLoc = ImportLoc;
-      LastModuleImportResult = ModuleLoadResult();
-      return LastModuleImportResult;
-    }
-    
-    const FileEntry *ModuleFile
-      = getFileManager().getFile(ModuleFileName, /*OpenFile=*/false,
-                                 /*CacheFailure=*/false);
-    bool BuildingModule = false;
-    if (!ModuleFile && Module) {
-      // The module is not cached, but we have a module map from which we can
-      // build the module.
-
-      // Check whether there is a cycle in the module graph.
-      ModuleBuildStack Path = getSourceManager().getModuleBuildStack();
-      ModuleBuildStack::iterator Pos = Path.begin(), PosEnd = Path.end();
-      for (; Pos != PosEnd; ++Pos) {
-        if (Pos->first == ModuleName)
-          break;
-      }
-
-      if (Pos != PosEnd) {
-        SmallString<256> CyclePath;
-        for (; Pos != PosEnd; ++Pos) {
-          CyclePath += Pos->first;
-          CyclePath += " -> ";
-        }
-        CyclePath += ModuleName;
-
-        getDiagnostics().Report(ModuleNameLoc, diag::err_module_cycle)
-          << ModuleName << CyclePath;
-        return ModuleLoadResult();
-      }
-
-      // Check whether we have already attempted to build this module (but
-      // failed).
-      if (getPreprocessorOpts().FailedModules &&
-          getPreprocessorOpts().FailedModules->hasAlreadyFailed(ModuleName)) {
-        getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_built)
-          << ModuleName
-          << SourceRange(ImportLoc, ModuleNameLoc);
-        ModuleBuildFailed = true;
-        return ModuleLoadResult();
-      }
-
-      BuildingModule = true;
-      compileModule(*this, ModuleNameLoc, Module, ModuleFileName);
-      ModuleFile = FileMgr->getFile(ModuleFileName, /*OpenFile=*/false,
-                                    /*CacheFailure=*/false);
-
-      if (!ModuleFile && getPreprocessorOpts().FailedModules)
-        getPreprocessorOpts().FailedModules->addFailed(ModuleName);
-    }
-
-    if (!ModuleFile) {
-      getDiagnostics().Report(ModuleNameLoc,
-                              BuildingModule? diag::err_module_not_built
-                                            : diag::err_module_not_found)
-        << ModuleName
-        << SourceRange(ImportLoc, ModuleNameLoc);
-      ModuleBuildFailed = true;
-      return ModuleLoadResult();
-    }
-
-    // If there is already a module file associated with this module, make sure
-    // it is the same as the module file we're looking for. Otherwise, we
-    // have two module files for the same module.
-    if (const FileEntry *CurModuleFile = Module? Module->getASTFile() : 0) {
-      if (CurModuleFile != ModuleFile) {
-        getDiagnostics().Report(ModuleNameLoc, diag::err_module_file_conflict)
-          << ModuleName
-          << CurModuleFile->getName()
-          << ModuleFile->getName();
-        ModuleBuildFailed = true;
-        return ModuleLoadResult();
-      }
-    }
-
     // If we don't already have an ASTReader, create one now.
     if (!ModuleManager) {
       if (!hasASTContext())
@@ -1056,21 +975,53 @@
         ModuleManager->StartTranslationUnit(&getASTConsumer());
     }
 
-    // Try to load the module we found.
-    unsigned ARRFlags = ASTReader::ARR_None;
-    if (Module)
-      ARRFlags |= ASTReader::ARR_OutOfDate;
-    switch (ModuleManager->ReadAST(ModuleFile->getName(),
-                                   serialization::MK_Module, ImportLoc,
-                                   ARRFlags)) {
+    // Try to load the module file.
+    unsigned ARRFlags = ASTReader::ARR_OutOfDate | ASTReader::ARR_Missing;
+    switch (ModuleManager->ReadAST(ModuleFileName, serialization::MK_Module,
+                                   ImportLoc, ARRFlags)) {
     case ASTReader::Success:
       break;
 
     case ASTReader::OutOfDate: {
-      // The module file is out-of-date. Rebuild it.
-      getFileManager().invalidateCache(ModuleFile);
+      // The module file is out-of-date. Remove it, then rebuild it.
       bool Existed;
       llvm::sys::fs::remove(ModuleFileName, Existed);
+    }
+    // Fall through to build the module again.
+
+    case ASTReader::Missing: {
+      // The module file is (now) missing. Build it.
+
+      // If we don't have a module, we don't know how to build the module file.
+      // Complain and return.
+      if (!Module) {
+        getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_found)
+          << ModuleName
+          << SourceRange(ImportLoc, ModuleNameLoc);
+        ModuleBuildFailed = true;
+        return ModuleLoadResult();
+      }
+
+      // Check whether there is a cycle in the module graph.
+      ModuleBuildStack ModPath = getSourceManager().getModuleBuildStack();
+      ModuleBuildStack::iterator Pos = ModPath.begin(), PosEnd = ModPath.end();
+      for (; Pos != PosEnd; ++Pos) {
+        if (Pos->first == ModuleName)
+          break;
+      }
+
+      if (Pos != PosEnd) {
+        SmallString<256> CyclePath;
+        for (; Pos != PosEnd; ++Pos) {
+          CyclePath += Pos->first;
+          CyclePath += " -> ";
+        }
+        CyclePath += ModuleName;
+
+        getDiagnostics().Report(ModuleNameLoc, diag::err_module_cycle)
+          << ModuleName << CyclePath;
+        return ModuleLoadResult();
+      }
 
       // Check whether we have already attempted to build this module (but
       // failed).
@@ -1083,15 +1034,23 @@
         return ModuleLoadResult();
       }
 
+      // Try to compile the module.
       compileModule(*this, ModuleNameLoc, Module, ModuleFileName);
 
-      // Try loading the module again.
-      ModuleFile = FileMgr->getFile(ModuleFileName, /*OpenFile=*/false,
-                                    /*CacheFailure=*/false);
-      if (!ModuleFile ||
-          ModuleManager->ReadAST(ModuleFileName,
+      // Try to read the module file, now that we've compiled it.
+      ASTReader::ASTReadResult ReadResult
+        = ModuleManager->ReadAST(ModuleFileName,
                                  serialization::MK_Module, ImportLoc,
-                                 ASTReader::ARR_None) != ASTReader::Success) {
+                                 ASTReader::ARR_Missing);
+      if (ReadResult != ASTReader::Success) {
+        if (ReadResult == ASTReader::Missing) {
+          getDiagnostics().Report(ModuleNameLoc,
+                                  Module? diag::err_module_not_built
+                                        : diag::err_module_not_found)
+            << ModuleName
+            << SourceRange(ImportLoc, ModuleNameLoc);
+        }
+
         if (getPreprocessorOpts().FailedModules)
           getPreprocessorOpts().FailedModules->addFailed(ModuleName);
         KnownModules[Path[0].first] = 0;
@@ -1125,10 +1084,6 @@
                  .findModule((Path[0].first->getName()));
     }
 
-    if (Module) {
-      Module->setASTFile(ModuleFile);
-    }
-    
     // Cache the result of this top-level module lookup for later.
     Known = KnownModules.insert(std::make_pair(Path[0].first, Module)).first;
   }