1 files changed, 19 insertions, 9 deletions

diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index 0b136ae..824b2bb 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -482,7 +482,7 @@ void ModuleMap::diagnoseHeaderInclusion(Module *RequestingModule,
 
   if (RequestingModule) {
     resolveUses(RequestingModule, /*Complain=*/false);
-    resolveHeaderDirectives(RequestingModule);
+    resolveHeaderDirectives(RequestingModule, /*File=*/llvm::None);
   }
 
   bool Excluded = false;
@@ -1191,25 +1191,35 @@ void ModuleMap::resolveHeaderDirectives(const FileEntry *File) const {
   auto BySize = LazyHeadersBySize.find(File->getSize());
   if (BySize != LazyHeadersBySize.end()) {
     for (auto *M : BySize->second)
-      resolveHeaderDirectives(M);
+      resolveHeaderDirectives(M, File);
     LazyHeadersBySize.erase(BySize);
   }
 
   auto ByModTime = LazyHeadersByModTime.find(File->getModificationTime());
   if (ByModTime != LazyHeadersByModTime.end()) {
     for (auto *M : ByModTime->second)
-      resolveHeaderDirectives(M);
+      resolveHeaderDirectives(M, File);
     LazyHeadersByModTime.erase(ByModTime);
   }
 }
 
-void ModuleMap::resolveHeaderDirectives(Module *Mod) const {
+void ModuleMap::resolveHeaderDirectives(
+    Module *Mod, llvm::Optional<const FileEntry *> File) const {
   bool NeedsFramework = false;
-  for (auto &Header : Mod->UnresolvedHeaders)
-    // This operation is logically const; we're just changing how we represent
-    // the header information for this file.
-    const_cast<ModuleMap*>(this)->resolveHeader(Mod, Header, NeedsFramework);
-  Mod->UnresolvedHeaders.clear();
+  SmallVector<Module::UnresolvedHeaderDirective, 1> NewHeaders;
+  const auto Size = File ? File.getValue()->getSize() : 0;
+  const auto ModTime = File ? File.getValue()->getModificationTime() : 0;
+
+  for (auto &Header : Mod->UnresolvedHeaders) {
+    if (File && ((Header.ModTime && Header.ModTime != ModTime) ||
+                 (Header.Size && Header.Size != Size)))
+      NewHeaders.push_back(Header);
+    else
+      // This operation is logically const; we're just changing how we represent
+      // the header information for this file.
+      const_cast<ModuleMap *>(this)->resolveHeader(Mod, Header, NeedsFramework);
+  }
+  Mod->UnresolvedHeaders.swap(NewHeaders);
 }
 
 void ModuleMap::addHeader(Module *Mod, Module::Header Header,