1 files changed, 17 insertions, 22 deletions

diff --git a/clang/lib/Serialization/ModuleManager.cpp b/clang/lib/Serialization/ModuleManager.cpp
index c5b4dd120cb..0a9ea69d695 100644
--- a/clang/lib/Serialization/ModuleManager.cpp
+++ b/clang/lib/Serialization/ModuleManager.cpp
@@ -109,8 +109,15 @@ ModuleManager::addModule(StringRef FileName, ModuleKind Type,
         ec = llvm::MemoryBuffer::getSTDIN(New->Buffer);
         if (ec)
           ErrorStr = ec.message();
-      } else
-        New->Buffer.reset(FileMgr.getBufferForFile(FileName, &ErrorStr));
+      } else {
+        // Leave the FileEntry open so if it gets read again by another
+        // ModuleManager it must be the same underlying file.
+        // FIXME: Because FileManager::getFile() doesn't guarantee that it will
+        // give us an open file, this may not be 100% reliable.
+        New->Buffer.reset(FileMgr.getBufferForFile(New->File, &ErrorStr,
+                                                   /*IsVolatile*/false,
+                                                   /*ShouldClose*/false));
+      }
       
       if (!New->Buffer)
         return Missing;
@@ -135,31 +142,16 @@ ModuleManager::addModule(StringRef FileName, ModuleKind Type,
   return NewModule? NewlyLoaded : AlreadyLoaded;
 }
 
-static void getModuleFileAncestors(
-    ModuleFile *F,
-    llvm::SmallPtrSetImpl<ModuleFile *> &Ancestors) {
-  Ancestors.insert(F);
-  for (ModuleFile *Importer : F->ImportedBy)
-    getModuleFileAncestors(Importer, Ancestors);
-}
-
-void ModuleManager::removeModules(ModuleIterator first, ModuleIterator last,
-                                  ModuleMap *modMap) {
+void ModuleManager::removeModules(
+    ModuleIterator first, ModuleIterator last,
+    llvm::SmallPtrSetImpl<ModuleFile *> &LoadedSuccessfully,
+    ModuleMap *modMap) {
   if (first == last)
     return;
 
   // Collect the set of module file pointers that we'll be removing.
   llvm::SmallPtrSet<ModuleFile *, 4> victimSet(first, last);
 
-  // The last module file caused the load failure, so it and its ancestors in
-  // the module dependency tree will be rebuilt (or there was an error), so
-  // there should be no references to them. Collect the files to remove from
-  // the cache below, since rebuilding them will create new files at the old
-  // locations.
-  llvm::SmallPtrSet<ModuleFile *, 4> Ancestors;
-  getModuleFileAncestors(*(last-1), Ancestors);
-  assert(Ancestors.count(*first) && "non-dependent module loaded");
-
   // Remove any references to the now-destroyed modules.
   for (unsigned i = 0, n = Chain.size(); i != n; ++i) {
     Chain[i]->ImportedBy.remove_if([&](ModuleFile *MF) {
@@ -178,7 +170,10 @@ void ModuleManager::removeModules(ModuleIterator first, ModuleIterator last,
       }
     }
 
-    if (Ancestors.count(*victim))
+    // Files that didn't make it through ReadASTCore successfully will be
+    // rebuilt (or there was an error). Invalidate them so that we can load the
+    // new files that will be renamed over the old ones.
+    if (LoadedSuccessfully.count(*victim) == 0)
       FileMgr.invalidateCache((*victim)->File);
 
     delete *victim;