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

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.

lib/Frontend/CompilerInstance.cpp

@@ -1653,8 +1653,10 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
     // Retrieve the cached top-level module.
     Module = Known->second;    
   } else if (ModuleName == getLangOpts().CurrentModule) {
-    // This is the module we're building. 
-    Module = PP->getHeaderSearchInfo().lookupModule(ModuleName);
+    // This is the module we're building.
+    Module = PP->getHeaderSearchInfo().lookupModule(
+        ModuleName, /*AllowSearch*/ true,
+        /*AllowExtraModuleMapSearch*/ !IsInclusionDirective);
     /// FIXME: perhaps we should (a) look for a module using the module name
     //  to file map (PrebuiltModuleFiles) and (b) diagnose if still not found?
     //if (Module == nullptr) {
@@ -1666,7 +1668,8 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
     Known = KnownModules.insert(std::make_pair(Path[0].first, Module)).first;
   } else {
     // Search for a module with the given name.
-    Module = PP->getHeaderSearchInfo().lookupModule(ModuleName);
+    Module = PP->getHeaderSearchInfo().lookupModule(ModuleName, true,
+                                                    !IsInclusionDirective);
     HeaderSearchOptions &HSOpts =
         PP->getHeaderSearchInfo().getHeaderSearchOpts();
 
@@ -1743,7 +1746,8 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
                                    ImportLoc, ARRFlags)) {
     case ASTReader::Success: {
       if (Source != ModuleCache && !Module) {
-        Module = PP->getHeaderSearchInfo().lookupModule(ModuleName);
+        Module = PP->getHeaderSearchInfo().lookupModule(ModuleName, true,
+                                                        !IsInclusionDirective);
         if (!Module || !Module->getASTFile() ||
             FileMgr->getFile(ModuleFileName) != Module->getASTFile()) {
           // Error out if Module does not refer to the file in the prebuilt
@@ -1874,7 +1878,8 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
             PrivateModule, PP->getIdentifierInfo(Module->Name)->getTokenID());
         PrivPath.push_back(std::make_pair(&II, Path[0].second));
 
-        if (PP->getHeaderSearchInfo().lookupModule(PrivateModule))
+        if (PP->getHeaderSearchInfo().lookupModule(PrivateModule, true,
+                                                   !IsInclusionDirective))
           Sub =
               loadModule(ImportLoc, PrivPath, Visibility, IsInclusionDirective);
         if (Sub) {

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);

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.

test/Modules/Inputs/autoload-subdirectory/a.h

@@ -0,0 +1,9 @@
+#include "b.h"
+
+class foo {
+  int x, y;
+
+public:
+  foo(){};
+  ~foo(){};
+};

test/Modules/Inputs/autoload-subdirectory/b.h

@@ -0,0 +1 @@
+class bar {};

test/Modules/Inputs/autoload-subdirectory/c.h

@@ -0,0 +1,7 @@
+class nyan {
+  bool x, y;
+
+public:
+  nyan(){};
+  ~nyan(){};
+};

test/Modules/Inputs/autoload-subdirectory/include/module.modulemap

@@ -0,0 +1,3 @@
+module a { header "a.h" }
+module b { header "b.h" }
+module c { header "c.h" }

test/Modules/Inputs/autoload-subdirectory/module.modulemap

@@ -0,0 +1,3 @@
+module a { header "a.h" }
+module b { header "b.h" }
+module c { header "c.h" }

test/Modules/autoload-subdirectory.cpp

@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -fmodules -fmodule-name=Foo -I %S/Inputs/autoload-subdirectory/ %s -verify
+// expected-no-diagnostics
+
+#include "a.h"
+#import "c.h"
+
+int main() {
+  foo neko;
+  return 0;
+}