[Modules] Make r180934 more efficient by only loading top-level module maps in system header directories.

llvm-svn: 181643

1 files changed, 14 insertions, 0 deletions

diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index b8556dde0b2..8a99ed29883 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -1146,6 +1146,20 @@ void HeaderSearch::collectAllModules(SmallVectorImpl<Module *> &Modules) {
   }
 }
 
+void HeaderSearch::loadTopLevelSystemModules() {
+  // Load module maps for each of the header search directories.
+  for (unsigned Idx = 0, N = SearchDirs.size(); Idx != N; ++Idx) {
+    // We only care about normal system header directories.
+    if (!SearchDirs[Idx].isNormalDir() ||
+        SearchDirs[Idx].getDirCharacteristic() != SrcMgr::C_System) {
+      continue;
+    }
+
+    // Try to load a module map file for the search directory.
+    loadModuleMapFile(SearchDirs[Idx].getDir());
+  }
+}
+
 void HeaderSearch::loadSubdirectoryModuleMaps(DirectoryLookup &SearchDir) {
   if (SearchDir.haveSearchedAllModuleMaps())
     return;