Reapply r336660: [Modules] Autoload subdirectory modulemaps with specific LangOpts

Summary:
Reproducer and errors:
https://bugs.llvm.org/show_bug.cgi?id=37878

lookupModule was falling back to loadSubdirectoryModuleMaps when it couldn't
find ModuleName in (proper) search paths. This was causing iteration over all
files in the search path subdirectories for example "/usr/include/foobar" in
bugzilla case.

Users don't expect Clang to load modulemaps in subdirectories implicitly, and
also the disk access is not cheap.

if (AllowExtraModuleMapSearch) true with ObjC with @import ModuleName.

Reviewers: rsmith, aprantl, bruno

Subscribers: cfe-commits, teemperor, v.g.vassilev

Differential Revision: https://reviews.llvm.org/D48367

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@337430 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 2 deletions

diff --git a/include/clang/Lex/HeaderSearch.h b/include/clang/Lex/HeaderSearch.h
index fd52000954..b7147c54fa 100644
--- a/include/clang/Lex/HeaderSearch.h
+++ b/include/clang/Lex/HeaderSearch.h
@@ -529,8 +529,12 @@ public:
   /// search directories to produce a module definition. If not, this lookup
   /// will only return an already-known module.
   ///
+  /// \param AllowExtraModuleMapSearch Whether we allow to search modulemaps
+  /// in subdirectories.
+  ///
   /// \returns The module with the given name.
-  Module *lookupModule(StringRef ModuleName, bool AllowSearch = true);
+  Module *lookupModule(StringRef ModuleName, bool AllowSearch = true,
+                       bool AllowExtraModuleMapSearch = false);
 
   /// Try to find a module map file in the given directory, returning
   /// \c nullptr if none is found.
@@ -595,8 +599,12 @@ private:
   /// but for compatibility with some buggy frameworks, additional attempts
   /// may be made to find the module under a related-but-different search-name.
   ///
+  /// \param AllowExtraModuleMapSearch Whether we allow to search modulemaps
+  /// in subdirectories.
+  ///
   /// \returns The module named ModuleName.
-  Module *lookupModule(StringRef ModuleName, StringRef SearchName);
+  Module *lookupModule(StringRef ModuleName, StringRef SearchName,
+                       bool AllowExtraModuleMapSearch = false);
 
   /// Retrieve a module with the given name, which may be part of the
   /// given framework.