Add -fmodule-map-file option.

With this option, arbitrarily named module map files can be specified
to be loaded as required for headers in the respective (sub)directories.

This, together with the extern module declaration allows for specifying
module maps in a modular fashion without the need for files called
"module.map".

Among other things, this allows a directory to contain two modules that
are completely independent of one another.

Review: http://llvm-reviews.chandlerc.com/D1697.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191284 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/Modules.rst b/docs/Modules.rst
index 02393d7..912cdaf 100644
--- a/docs/Modules.rst
+++ b/docs/Modules.rst
@@ -194,6 +194,9 @@
 ``-fmodule-name=module-id``
   Consider a source file as a part of the given module.
 
+``-fmodule-map-file=<file>``
+  Load the given module map file if a header from its directory or one of its subdirectories is loaded.
+
 Module Map Language
 ===================
 
diff --git a/include/clang/Driver/CC1Options.td b/include/clang/Driver/CC1Options.td
index d5a8b77..1b96ef3 100644
--- a/include/clang/Driver/CC1Options.td
+++ b/include/clang/Driver/CC1Options.td
@@ -483,9 +483,12 @@
 
 def nostdsysteminc : Flag<["-"], "nostdsysteminc">,
   HelpText<"Disable standard system #include directories">;
-def fmodule_name : Joined<["-"], "fmodule-name=">, 
+def fmodule_name : Joined<["-"], "fmodule-name=">,
   MetaVarName<"<name>">,
-  HelpText<"Specify the name of the module to build">;           
+  HelpText<"Specify the name of the module to build">;
+def fmodule_map_file : Joined<["-"], "fmodule-map-file=">,
+  MetaVarName<"<file>">,
+  HelpText<"Load this module map file">;
 def fdisable_module_hash : Flag<["-"], "fdisable-module-hash">,
   HelpText<"Disable the module hash">;
 def c_isystem : JoinedOrSeparate<["-"], "c-isystem">, MetaVarName<"<directory>">,
diff --git a/include/clang/Lex/HeaderSearchOptions.h b/include/clang/Lex/HeaderSearchOptions.h
index 830f48d..0b21c0d 100644
--- a/include/clang/Lex/HeaderSearchOptions.h
+++ b/include/clang/Lex/HeaderSearchOptions.h
@@ -120,6 +120,9 @@
   /// of computing the module hash.
   llvm::SetVector<std::string> ModulesIgnoreMacros;
 
+  /// \brief The set of user-provided module-map-files.
+  llvm::SetVector<std::string> ModuleMapFiles;
+
   /// Include the compiler builtin includes.
   unsigned UseBuiltinIncludes : 1;
 
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index c8c6768..afba109 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -896,6 +896,9 @@
     StringRef MacroDef = (*it)->getValue();
     Opts.ModulesIgnoreMacros.insert(MacroDef.split('=').first);
   }
+  std::vector<std::string> ModuleMapFiles =
+      Args.getAllArgValues(OPT_fmodule_map_file);
+  Opts.ModuleMapFiles.insert(ModuleMapFiles.begin(), ModuleMapFiles.end());
 
   // Add -I..., -F..., and -index-header-map options in order.
   bool IsIndexHeaderMap = false;
diff --git a/lib/Lex/HeaderSearch.cpp b/lib/Lex/HeaderSearch.cpp
index ec84bb1..5bcc4ea 100644
--- a/lib/Lex/HeaderSearch.cpp
+++ b/lib/Lex/HeaderSearch.cpp
@@ -941,28 +941,50 @@
     DirName = llvm::sys::path::parent_path(DirName);
     if (DirName.empty())
       return false;
-    
+
     // Determine whether this directory exists.
     const DirectoryEntry *Dir = FileMgr.getDirectory(DirName);
     if (!Dir)
       return false;
     
-    // Try to load the module map file in this directory.
+    // Load user-specified module map files in 'Dir'.
+    bool ModuleMapFound = false;
+    for (llvm::SetVector<std::string>::iterator
+             I = HSOpts->ModuleMapFiles.begin(),
+             E = HSOpts->ModuleMapFiles.end();
+         I != E; ++I) {
+      StringRef ModuleMapFileDir = llvm::sys::path::parent_path(*I);
+      if (!llvm::sys::fs::equivalent(ModuleMapFileDir, DirName))
+        continue;
+
+      const FileEntry *File = FileMgr.getFile(*I);
+      if (!File)
+        continue;
+
+      loadModuleMapFile(File, /*IsSystem=*/false);
+      ModuleMapFound = true;
+    }
+
+    // Try to load the "module.map" file in this directory.
     switch (loadModuleMapFile(Dir, IsSystem)) {
     case LMM_NewlyLoaded:
     case LMM_AlreadyLoaded:
-      // Success. All of the directories we stepped through inherit this module
-      // map file.
-      for (unsigned I = 0, N = FixUpDirectories.size(); I != N; ++I)
-        DirectoryHasModuleMap[FixUpDirectories[I]] = true;
-      
-      return true;
+      ModuleMapFound = true;
+      break;
 
     case LMM_NoDirectory:
     case LMM_InvalidModuleMap:
       break;
     }
 
+    if (ModuleMapFound) {
+      // Success. All of the directories we stepped through inherit this module
+      // map file.
+      for (unsigned I = 0, N = FixUpDirectories.size(); I != N; ++I)
+        DirectoryHasModuleMap[FixUpDirectories[I]] = true;
+      return true;
+    }
+
     // If we hit the top of our search, we're done.
     if (Dir == Root)
       return false;
diff --git a/test/Modules/Inputs/modular_maps/module.map b/test/Modules/Inputs/modular_maps/modulea.map
similarity index 100%
rename from test/Modules/Inputs/modular_maps/module.map
rename to test/Modules/Inputs/modular_maps/modulea.map
diff --git a/test/Modules/modular_maps.cpp b/test/Modules/modular_maps.cpp
index c521fb2..5070f7d 100644
--- a/test/Modules/modular_maps.cpp
+++ b/test/Modules/modular_maps.cpp
@@ -1,5 +1,5 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -x objective-c++ -fmodules-cache-path=%t -fmodules -I %S/Inputs/modular_maps %s -verify
+// RUN: %clang_cc1 -x objective-c++ -fmodules-cache-path=%t -fmodules -fmodule-map-file=%S/Inputs/modular_maps/modulea.map -I %S/Inputs/modular_maps %s -verify
 
 #include "a.h"
 #include "b.h" // expected-error {{private header}}