[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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@336660 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 7 deletions

diff --git a/lib/Lex/HeaderSearch.cpp b/lib/Lex/HeaderSearch.cpp
index 312bd2d061..b1a2ef1212 100644
--- a/lib/Lex/HeaderSearch.cpp
+++ b/lib/Lex/HeaderSearch.cpp
@@ -198,14 +198,15 @@ std::string HeaderSearch::getCachedModuleFileName(StringRef ModuleName,
   return Result.str().str();
 }
 
-Module *HeaderSearch::lookupModule(StringRef ModuleName, bool AllowSearch) {
+Module *HeaderSearch::lookupModule(StringRef ModuleName, bool AllowSearch,
+                                   bool AllowExtraModuleMapSearch) {
   // Look in the module map to determine if there is a module by this name.
   Module *Module = ModMap.findModule(ModuleName);
   if (Module || !AllowSearch || !HSOpts->ImplicitModuleMaps)
     return Module;
 
   StringRef SearchName = ModuleName;
-  Module = lookupModule(ModuleName, SearchName);
+  Module = lookupModule(ModuleName, SearchName, AllowExtraModuleMapSearch);
 
   // The facility for "private modules" -- adjacent, optional module maps named
   // module.private.modulemap that are supposed to define private submodules --
@@ -216,13 +217,14 @@ Module *HeaderSearch::lookupModule(StringRef ModuleName, bool AllowSearch) {
   // could force building unwanted dependencies into the parent module and cause
   // dependency cycles.
   if (!Module && SearchName.consume_back("_Private"))
-    Module = lookupModule(ModuleName, SearchName);
+    Module = lookupModule(ModuleName, SearchName, AllowExtraModuleMapSearch);
   if (!Module && SearchName.consume_back("Private"))
-    Module = lookupModule(ModuleName, SearchName);
+    Module = lookupModule(ModuleName, SearchName, AllowExtraModuleMapSearch);
   return Module;
 }
 
-Module *HeaderSearch::lookupModule(StringRef ModuleName, StringRef SearchName) {
+Module *HeaderSearch::lookupModule(StringRef ModuleName, StringRef SearchName,
+                                   bool AllowExtraModuleMapSearch) {
   Module *Module = nullptr;
 
   // Look through the various header search paths to load any available module
@@ -281,8 +283,9 @@ Module *HeaderSearch::lookupModule(StringRef ModuleName, StringRef SearchName) {
       continue;
 
     // Load all module maps in the immediate subdirectories of this search
-    // directory.
-    loadSubdirectoryModuleMaps(SearchDirs[Idx]);
+    // directory if ModuleName was from @import.
+    if (AllowExtraModuleMapSearch)
+      loadSubdirectoryModuleMaps(SearchDirs[Idx]);
 
     // Look again for the module.
     Module = ModMap.findModule(ModuleName);