[modules] Fix 37878; 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

llvm-svn: 336660

1 files changed, 3 insertions, 1 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 32772436678..78ca5f7406c 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -2626,7 +2626,9 @@ ASTReader::ReadControlBlock(ModuleFile &F,
              "MODULE_DIRECTORY found before MODULE_NAME");
       // If we've already loaded a module map file covering this module, we may
       // have a better path for it (relative to the current build).
-      Module *M = PP.getHeaderSearchInfo().lookupModule(F.ModuleName);
+      Module *M = PP.getHeaderSearchInfo().lookupModule(
+          F.ModuleName, /*AllowSearch*/ true,
+          /*AllowExtraModuleMapSearch*/ true);
       if (M && M->Directory) {
         // If we're implicitly loading a module, the base directory can't
         // change between the build and use.