diff --git a/include/clang/Lex/HeaderSearch.h b/include/clang/Lex/HeaderSearch.h
index 84dd6eb..fb1a862 100644
--- a/include/clang/Lex/HeaderSearch.h
+++ b/include/clang/Lex/HeaderSearch.h
@@ -240,7 +240,7 @@
   
 public:
   HeaderSearch(IntrusiveRefCntPtr<HeaderSearchOptions> HSOpts,
-               FileManager &FM, DiagnosticsEngine &Diags,
+               SourceManager &SourceMgr, DiagnosticsEngine &Diags,
                const LangOptions &LangOpts, const TargetInfo *Target);
   ~HeaderSearch();
 
diff --git a/include/clang/Lex/ModuleMap.h b/include/clang/Lex/ModuleMap.h
index b7982a1..3a17157 100644
--- a/include/clang/Lex/ModuleMap.h
+++ b/include/clang/Lex/ModuleMap.h
@@ -37,7 +37,7 @@
 class ModuleMapParser;
   
 class ModuleMap {
-  SourceManager *SourceMgr;
+  SourceManager &SourceMgr;
   IntrusiveRefCntPtr<DiagnosticsEngine> Diags;
   const LangOptions &LangOpts;
   const TargetInfo *Target;
@@ -178,9 +178,9 @@
 public:
   /// \brief Construct a new module map.
   ///
-  /// \param FileMgr The file manager used to find module files and headers.
-  /// This file manager should be shared with the header-search mechanism, since
-  /// they will refer to the same headers.
+  /// \param SourceMgr The source manager used to find module files and headers.
+  /// This source manager should be shared with the header-search mechanism,
+  /// since they will refer to the same headers.
   ///
   /// \param DC A diagnostic consumer that will be cloned for use in generating
   /// diagnostics.
@@ -188,7 +188,7 @@
   /// \param LangOpts Language options for this translation unit.
   ///
   /// \param Target The target for this translation unit.
-  ModuleMap(FileManager &FileMgr, DiagnosticConsumer &DC,
+  ModuleMap(SourceManager &SourceMgr, DiagnosticConsumer &DC,
             const LangOptions &LangOpts, const TargetInfo *Target,
             HeaderSearch &HeaderInfo);
 
diff --git a/lib/Frontend/ASTUnit.cpp b/lib/Frontend/ASTUnit.cpp
index 610c20d..a8c5876 100644
--- a/lib/Frontend/ASTUnit.cpp
+++ b/lib/Frontend/ASTUnit.cpp
@@ -707,7 +707,7 @@
   AST->HSOpts = new HeaderSearchOptions();
   
   AST->HeaderInfo.reset(new HeaderSearch(AST->HSOpts,
-                                         AST->getFileManager(),
+                                         AST->getSourceManager(),
                                          AST->getDiagnostics(),
                                          AST->ASTFileLangOpts,
                                          /*Target=*/0));
diff --git a/lib/Frontend/CompilerInstance.cpp b/lib/Frontend/CompilerInstance.cpp
index 9f0ca3b..5d3fd45 100644
--- a/lib/Frontend/CompilerInstance.cpp
+++ b/lib/Frontend/CompilerInstance.cpp
@@ -218,7 +218,7 @@
 
   // Create the Preprocessor.
   HeaderSearch *HeaderInfo = new HeaderSearch(&getHeaderSearchOpts(),
-                                              getFileManager(),
+                                              getSourceManager(),
                                               getDiagnostics(),
                                               getLangOpts(),
                                               &getTarget());
@@ -851,29 +851,6 @@
   FrontendOpts.Inputs.clear();
   InputKind IK = getSourceInputKindFromOptions(*Invocation->getLangOpts());
 
-  // Get or create the module map that we'll use to build this module.
-  SmallString<128> TempModuleMapFileName;
-  if (const FileEntry *ModuleMapFile
-                                  = ModMap.getContainingModuleMapFile(Module)) {
-    // Use the module map where this module resides.
-    FrontendOpts.Inputs.push_back(FrontendInputFile(ModuleMapFile->getName(), 
-                                                    IK));
-  } else {
-    // Create a temporary module map file.
-    int FD;
-    if (llvm::sys::fs::createTemporaryFile(Module->Name, "map", FD,
-                                           TempModuleMapFileName)) {
-      ImportingInstance.getDiagnostics().Report(diag::err_module_map_temp_file)
-        << TempModuleMapFileName;
-      return;
-    }
-    // Print the module map to this file.
-    llvm::raw_fd_ostream OS(FD, /*shouldClose=*/true);
-    Module->print(OS);
-    FrontendOpts.Inputs.push_back(
-      FrontendInputFile(TempModuleMapFileName.str().str(), IK));
-  }
-
   // Don't free the remapped file buffers; they are owned by our caller.
   PPOpts.RetainRemappedFileBuffers = true;
     
@@ -900,6 +877,26 @@
   SourceMgr.pushModuleBuildStack(Module->getTopLevelModuleName(),
     FullSourceLoc(ImportLoc, ImportingInstance.getSourceManager()));
 
+  // Get or create the module map that we'll use to build this module.
+  std::string InferredModuleMapContent;
+  if (const FileEntry *ModuleMapFile =
+          ModMap.getContainingModuleMapFile(Module)) {
+    // Use the module map where this module resides.
+    FrontendOpts.Inputs.push_back(
+        FrontendInputFile(ModuleMapFile->getName(), IK));
+  } else {
+    llvm::raw_string_ostream OS(InferredModuleMapContent);
+    Module->print(OS);
+    OS.flush();
+    FrontendOpts.Inputs.push_back(
+        FrontendInputFile("__inferred_module.map", IK));
+
+    const llvm::MemoryBuffer *ModuleMapBuffer =
+        llvm::MemoryBuffer::getMemBuffer(InferredModuleMapContent);
+    ModuleMapFile = Instance.getFileManager().getVirtualFile(
+        "__inferred_module.map", InferredModuleMapContent.size(), 0);
+    SourceMgr.overrideFileContents(ModuleMapFile, ModuleMapBuffer);
+  }
 
   // Construct a module-generating action.
   GenerateModuleAction CreateModuleAction(Module->IsSystem);
@@ -917,8 +914,6 @@
   // be nice to do this with RemoveFileOnSignal when we can. However, that
   // doesn't make sense for all clients, so clean this up manually.
   Instance.clearOutputFiles(/*EraseFiles=*/true);
-  if (!TempModuleMapFileName.empty())
-    llvm::sys::fs::remove(TempModuleMapFileName.str());
 
   // We've rebuilt a module. If we're allowed to generate or update the global
   // module index, record that fact in the importing compiler instance.
diff --git a/lib/Lex/HeaderSearch.cpp b/lib/Lex/HeaderSearch.cpp
index 84d205a..2da2c9e 100644
--- a/lib/Lex/HeaderSearch.cpp
+++ b/lib/Lex/HeaderSearch.cpp
@@ -44,11 +44,11 @@
 ExternalHeaderFileInfoSource::~ExternalHeaderFileInfoSource() {}
 
 HeaderSearch::HeaderSearch(IntrusiveRefCntPtr<HeaderSearchOptions> HSOpts,
-                           FileManager &FM, DiagnosticsEngine &Diags,
+                           SourceManager &SourceMgr, DiagnosticsEngine &Diags,
                            const LangOptions &LangOpts, 
                            const TargetInfo *Target)
-  : HSOpts(HSOpts), FileMgr(FM), FrameworkMap(64),
-    ModMap(FileMgr, *Diags.getClient(), LangOpts, Target, *this)
+  : HSOpts(HSOpts), FileMgr(SourceMgr.getFileManager()), FrameworkMap(64),
+    ModMap(SourceMgr, *Diags.getClient(), LangOpts, Target, *this)
 {
   AngledDirIdx = 0;
   SystemDirIdx = 0;
diff --git a/lib/Lex/ModuleMap.cpp b/lib/Lex/ModuleMap.cpp
index 25d68ac..54007c7 100644
--- a/lib/Lex/ModuleMap.cpp
+++ b/lib/Lex/ModuleMap.cpp
@@ -83,18 +83,18 @@
   return Context;
 }
 
-ModuleMap::ModuleMap(FileManager &FileMgr, DiagnosticConsumer &DC,
+ModuleMap::ModuleMap(SourceManager &SourceMgr, DiagnosticConsumer &DC,
                      const LangOptions &LangOpts, const TargetInfo *Target,
                      HeaderSearch &HeaderInfo)
-  : LangOpts(LangOpts), Target(Target), HeaderInfo(HeaderInfo),
-    BuiltinIncludeDir(0), CompilingModule(0), SourceModule(0)
-{
+    : SourceMgr(SourceMgr), LangOpts(LangOpts), Target(Target),
+      HeaderInfo(HeaderInfo), BuiltinIncludeDir(0), CompilingModule(0),
+      SourceModule(0) {
   IntrusiveRefCntPtr<DiagnosticIDs> DiagIDs(new DiagnosticIDs);
   Diags = IntrusiveRefCntPtr<DiagnosticsEngine>(
             new DiagnosticsEngine(DiagIDs, new DiagnosticOptions));
   Diags->setClient(new ForwardingDiagnosticConsumer(DC),
                    /*ShouldOwnClient=*/true);
-  SourceMgr = new SourceManager(*Diags, FileMgr);
+  Diags->setSourceManager(&SourceMgr);
 }
 
 ModuleMap::~ModuleMap() {
@@ -103,8 +103,6 @@
        I != IEnd; ++I) {
     delete I->getValue();
   }
-  
-  delete SourceMgr;
 }
 
 void ModuleMap::setTarget(const TargetInfo &Target) {
@@ -224,7 +222,7 @@
   // frameworks moving from top-level frameworks to embedded frameworks tend
   // to be symlinked from the top-level location to the embedded location,
   // and we need to resolve lookups as if we had found the embedded location.
-  StringRef DirName = SourceMgr->getFileManager().getCanonicalName(Dir);
+  StringRef DirName = SourceMgr.getFileManager().getCanonicalName(Dir);
 
   // Keep walking up the directory hierarchy, looking for a directory with
   // an umbrella header.
@@ -301,7 +299,7 @@
       break;
     
     // Resolve the parent path to a directory entry.
-    Dir = SourceMgr->getFileManager().getDirectory(DirName);
+    Dir = SourceMgr.getFileManager().getDirectory(DirName);
   } while (Dir);
   
   return KnownHeader();
@@ -375,7 +373,7 @@
       break;
     
     // Resolve the parent path to a directory entry.
-    Dir = SourceMgr->getFileManager().getDirectory(DirName);
+    Dir = SourceMgr.getFileManager().getDirectory(DirName);
   } while (Dir);
   
   return false;
@@ -480,7 +478,7 @@
   if (Module *Mod = lookupModuleQualified(ModuleName, Parent))
     return Mod;
   
-  FileManager &FileMgr = SourceMgr->getFileManager();
+  FileManager &FileMgr = SourceMgr.getFileManager();
 
   // If the framework has a parent path from which we're allowed to infer
   // a framework module, do so.
@@ -492,7 +490,7 @@
     // top-level framework, and we need to infer as if we were naming the
     // top-level framework.
     StringRef FrameworkDirName
-      = SourceMgr->getFileManager().getCanonicalName(FrameworkDir);
+      = SourceMgr.getFileManager().getCanonicalName(FrameworkDir);
 
     bool canInfer = false;
     if (llvm::sys::path::has_parent_path(FrameworkDirName)) {
@@ -654,11 +652,11 @@
 
 const FileEntry *
 ModuleMap::getContainingModuleMapFile(Module *Module) const {
-  if (Module->DefinitionLoc.isInvalid() || !SourceMgr)
+  if (Module->DefinitionLoc.isInvalid())
     return 0;
 
-  return SourceMgr->getFileEntryForID(
-           SourceMgr->getFileID(Module->DefinitionLoc));
+  return SourceMgr.getFileEntryForID(
+           SourceMgr.getFileID(Module->DefinitionLoc));
 }
 
 void ModuleMap::dump() {
@@ -2110,15 +2108,15 @@
     return Known->second;
 
   assert(Target != 0 && "Missing target information");
-  FileID ID = SourceMgr->createFileID(File, SourceLocation(), SrcMgr::C_User);
-  const llvm::MemoryBuffer *Buffer = SourceMgr->getBuffer(ID);
+  FileID ID = SourceMgr.createFileID(File, SourceLocation(), SrcMgr::C_User);
+  const llvm::MemoryBuffer *Buffer = SourceMgr.getBuffer(ID);
   if (!Buffer)
     return ParsedModuleMap[File] = true;
   
   // Parse this module map file.
-  Lexer L(ID, SourceMgr->getBuffer(ID), *SourceMgr, MMapLangOpts);
+  Lexer L(ID, SourceMgr.getBuffer(ID), SourceMgr, MMapLangOpts);
   Diags->getClient()->BeginSourceFile(MMapLangOpts);
-  ModuleMapParser Parser(L, *SourceMgr, Target, *Diags, *this, File->getDir(),
+  ModuleMapParser Parser(L, SourceMgr, Target, *Diags, *this, File->getDir(),
                          BuiltinIncludeDir, IsSystem);
   bool Result = Parser.parseModuleMapFile();
   Diags->getClient()->EndSourceFile();
diff --git a/test/Modules/Inputs/declare-use/module.map b/test/Modules/Inputs/declare-use/module.map
index ae3e908..774fc37 100644
--- a/test/Modules/Inputs/declare-use/module.map
+++ b/test/Modules/Inputs/declare-use/module.map
@@ -1,43 +1,43 @@
-module A {
+module XA {
   header "a.h"
 }
 
-module B {
+module XB {
   header "b.h"
 }
 
-module C {
+module XC {
   header "c.h"
-  use A
+  use XA
 }
 
-module D {
+module XD {
   header "d.h"
-  use A
+  use XA
 }
 
-module E {
+module XE {
   header "e.h"
-  use A
-  use B
+  use XA
+  use XB
 }
 
-module F {
+module XF {
   header "f.h"
-  use A
-  use B
+  use XA
+  use XB
 }
 
-module G {
+module XG {
   header "g.h"
   header "g1.h"
-  use C
-  use E
+  use XC
+  use XE
 }
 
-module H {
+module XH {
   header "h.h"
   header "h1.h"
-  use C
-  use E
+  use XC
+  use XE
 }
diff --git a/test/Modules/Inputs/private1/module.map b/test/Modules/Inputs/private1/module.map
index 445c801..0904fe6 100644
--- a/test/Modules/Inputs/private1/module.map
+++ b/test/Modules/Inputs/private1/module.map
@@ -1,4 +1,4 @@
-module libPrivate1 {
+module libPrivate {
   header "public1.h"
   private header "private1.h"
 }
diff --git a/test/Modules/Inputs/private2/module.map b/test/Modules/Inputs/private2/module.map
index 6c5efb6..3d2a578 100644
--- a/test/Modules/Inputs/private2/module.map
+++ b/test/Modules/Inputs/private2/module.map
@@ -1,4 +1,4 @@
-module libPrivate2 {
+module libPrivateN2 {
   header "public2.h"
   private header "private2.h"
 }
diff --git a/test/Modules/declare-use1.cpp b/test/Modules/declare-use1.cpp
index 5bb7e2a..4508017 100644
--- a/test/Modules/declare-use1.cpp
+++ b/test/Modules/declare-use1.cpp
@@ -1,5 +1,5 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -x objective-c++ -fmodules-cache-path=%t -fmodules -fmodules-decluse -fmodule-name=G -I %S/Inputs/declare-use %s -verify
+// RUN: %clang_cc1 -x objective-c++ -fmodules-cache-path=%t -fmodules -fmodules-decluse -fmodule-name=XG -I %S/Inputs/declare-use %s -verify
 
 #include "g.h"
 #include "e.h"
diff --git a/test/Modules/declare-use2.cpp b/test/Modules/declare-use2.cpp
index 807962c..a2ec55e 100644
--- a/test/Modules/declare-use2.cpp
+++ b/test/Modules/declare-use2.cpp
@@ -1,5 +1,5 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -x objective-c++ -fmodules-cache-path=%t -fmodules -fmodules-decluse -fmodule-name=H -I %S/Inputs/declare-use %s -verify
+// RUN: %clang_cc1 -x objective-c++ -fmodules-cache-path=%t -fmodules -fmodules-decluse -fmodule-name=XH -I %S/Inputs/declare-use %s -verify
 
 #include "h.h"
 #include "e.h"
diff --git a/test/Modules/private1.cpp b/test/Modules/private1.cpp
index e4eec0a..811a233 100644
--- a/test/Modules/private1.cpp
+++ b/test/Modules/private1.cpp
@@ -2,7 +2,7 @@
 // RUN: %clang_cc1 -x objective-c -fmodules-cache-path=%t -fmodules -I %S/Inputs/private0 -I %S/Inputs/private1 -I %S/Inputs/private2 %s -verify
 
 #include "common.h"
-@import libPrivate1;
+@import libPrivateN2;
 #include "private1.h" // expected-error {{use of private header from outside its module}}
 #include "public2.h"
 #include "private2.h" // expected-error {{use of private header from outside its module}}
diff --git a/unittests/Basic/SourceManagerTest.cpp b/unittests/Basic/SourceManagerTest.cpp
index 8e7f4a0..d94cfe9 100644
--- a/unittests/Basic/SourceManagerTest.cpp
+++ b/unittests/Basic/SourceManagerTest.cpp
@@ -73,7 +73,7 @@
   FileID mainFileID = SourceMgr.createMainFileIDForMemBuffer(buf);
 
   VoidModuleLoader ModLoader;
-  HeaderSearch HeaderInfo(new HeaderSearchOptions, FileMgr, Diags, LangOpts, 
+  HeaderSearch HeaderInfo(new HeaderSearchOptions, SourceMgr, Diags, LangOpts, 
                           &*Target);
   Preprocessor PP(new PreprocessorOptions(), Diags, LangOpts, Target.getPtr(),
                   SourceMgr, HeaderInfo, ModLoader,
@@ -188,7 +188,7 @@
   SourceMgr.overrideFileContents(headerFile, headerBuf);
 
   VoidModuleLoader ModLoader;
-  HeaderSearch HeaderInfo(new HeaderSearchOptions, FileMgr, Diags, LangOpts, 
+  HeaderSearch HeaderInfo(new HeaderSearchOptions, SourceMgr, Diags, LangOpts, 
                           &*Target);
   Preprocessor PP(new PreprocessorOptions(), Diags, LangOpts, Target.getPtr(),
                   SourceMgr, HeaderInfo, ModLoader,
@@ -286,7 +286,7 @@
   SourceMgr.overrideFileContents(headerFile, headerBuf);
 
   VoidModuleLoader ModLoader;
-  HeaderSearch HeaderInfo(new HeaderSearchOptions, FileMgr, Diags, LangOpts, 
+  HeaderSearch HeaderInfo(new HeaderSearchOptions, SourceMgr, Diags, LangOpts, 
                           &*Target);
   Preprocessor PP(new PreprocessorOptions(), Diags, LangOpts, Target.getPtr(),
                   SourceMgr, HeaderInfo, ModLoader,
diff --git a/unittests/Lex/LexerTest.cpp b/unittests/Lex/LexerTest.cpp
index a8e25cb..40ce928 100644
--- a/unittests/Lex/LexerTest.cpp
+++ b/unittests/Lex/LexerTest.cpp
@@ -62,7 +62,7 @@
     (void) SourceMgr.createMainFileIDForMemBuffer(buf);
 
     VoidModuleLoader ModLoader;
-    HeaderSearch HeaderInfo(new HeaderSearchOptions, FileMgr, Diags, LangOpts,
+    HeaderSearch HeaderInfo(new HeaderSearchOptions, SourceMgr, Diags, LangOpts,
                             Target.getPtr());
     Preprocessor PP(new PreprocessorOptions(), Diags, LangOpts, Target.getPtr(),
                     SourceMgr, HeaderInfo, ModLoader, /*IILookup =*/ 0,
diff --git a/unittests/Lex/PPCallbacksTest.cpp b/unittests/Lex/PPCallbacksTest.cpp
index fd407b5..9405a84 100644
--- a/unittests/Lex/PPCallbacksTest.cpp
+++ b/unittests/Lex/PPCallbacksTest.cpp
@@ -162,7 +162,8 @@
     VoidModuleLoader ModLoader;
 
     IntrusiveRefCntPtr<HeaderSearchOptions> HSOpts = new HeaderSearchOptions();
-    HeaderSearch HeaderInfo(HSOpts, FileMgr, Diags, LangOpts, Target.getPtr());
+    HeaderSearch HeaderInfo(HSOpts, SourceMgr, Diags, LangOpts,
+                            Target.getPtr());
     AddFakeHeader(HeaderInfo, HeaderPath, SystemHeader);
 
     IntrusiveRefCntPtr<PreprocessorOptions> PPOpts = new PreprocessorOptions();
@@ -198,7 +199,7 @@
     (void)SourceMgr.createMainFileIDForMemBuffer(sourceBuf);
 
     VoidModuleLoader ModLoader;
-    HeaderSearch HeaderInfo(new HeaderSearchOptions, FileMgr, Diags, 
+    HeaderSearch HeaderInfo(new HeaderSearchOptions, SourceMgr, Diags, 
                             OpenCLLangOpts, Target.getPtr());
 
     Preprocessor PP(new PreprocessorOptions(), Diags, OpenCLLangOpts, 
diff --git a/unittests/Lex/PPConditionalDirectiveRecordTest.cpp b/unittests/Lex/PPConditionalDirectiveRecordTest.cpp
index 082eced..58857fa 100644
--- a/unittests/Lex/PPConditionalDirectiveRecordTest.cpp
+++ b/unittests/Lex/PPConditionalDirectiveRecordTest.cpp
@@ -90,7 +90,7 @@
   SourceMgr.createMainFileIDForMemBuffer(buf);
 
   VoidModuleLoader ModLoader;
-  HeaderSearch HeaderInfo(new HeaderSearchOptions, FileMgr, Diags, LangOpts, 
+  HeaderSearch HeaderInfo(new HeaderSearchOptions, SourceMgr, Diags, LangOpts, 
                           Target.getPtr());
   Preprocessor PP(new PreprocessorOptions(), Diags, LangOpts,Target.getPtr(),
                   SourceMgr, HeaderInfo, ModLoader,
diff --git a/unittests/Tooling/ToolingTest.cpp b/unittests/Tooling/ToolingTest.cpp
index e435ea9..412af7a 100644
--- a/unittests/Tooling/ToolingTest.cpp
+++ b/unittests/Tooling/ToolingTest.cpp
@@ -131,6 +131,26 @@
   EXPECT_TRUE(Invocation.run());
 }
 
+TEST(ToolInvocation, TestVirtualModulesCompilation) {
+  // FIXME: Currently, this only tests that we don't exit with an error if a
+  // mapped module.map is found on the include path. In the future, expand this
+  // test to run a full modules enabled compilation, so we make sure we can
+  // rerun modules compilations with a virtual file system.
+  clang::FileManager Files((clang::FileSystemOptions()));
+  std::vector<std::string> Args;
+  Args.push_back("tool-executable");
+  Args.push_back("-Idef");
+  Args.push_back("-fsyntax-only");
+  Args.push_back("test.cpp");
+  clang::tooling::ToolInvocation Invocation(Args, new SyntaxOnlyAction, &Files);
+  Invocation.mapVirtualFile("test.cpp", "#include <abc>\n");
+  Invocation.mapVirtualFile("def/abc", "\n");
+  // Add a module.map file in the include directory of our header, so we trigger
+  // the module.map header search logic.
+  Invocation.mapVirtualFile("def/module.map", "\n");
+  EXPECT_TRUE(Invocation.run());
+}
+
 struct VerifyEndCallback : public SourceFileCallbacks {
   VerifyEndCallback() : BeginCalled(0), EndCalled(0), Matched(false) {}
   virtual bool handleBeginSource(CompilerInstance &CI,