1 files changed, 26 insertions, 1 deletions

diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index 89d95fc97d8..0753686a347 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -20,6 +20,7 @@
 #include "clang/Frontend/MultiplexConsumer.h"
 #include "clang/Parse/ParseAST.h"
 #include "clang/Serialization/ASTDeserializationListener.h"
+#include "clang/Serialization/ASTReader.h"
 #include "clang/Serialization/ChainedIncludesSource.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Timer.h"
@@ -239,6 +240,30 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
                                 DeserialListener);
       if (!CI.getASTContext().getExternalSource())
         goto failure;
+    } else if (!CI.getPreprocessorOpts().Modules.empty()) {
+      // Use PCH.
+      assert(hasPCHSupport() && "This action does not have PCH support!");
+      ASTDeserializationListener *DeserialListener =
+          Consumer->GetASTDeserializationListener();
+      if (CI.getPreprocessorOpts().DumpDeserializedPCHDecls)
+        DeserialListener = new DeserializedDeclsDumper(DeserialListener);
+      if (!CI.getPreprocessorOpts().DeserializedPCHDeclsToErrorOn.empty())
+        DeserialListener = new DeserializedDeclsChecker(CI.getASTContext(),
+                         CI.getPreprocessorOpts().DeserializedPCHDeclsToErrorOn,
+                                                        DeserialListener);
+
+      CI.createPCHExternalASTSource(CI.getPreprocessorOpts().Modules[0],
+                                    true, true, DeserialListener);
+
+      for (unsigned I = 1, E = CI.getPreprocessorOpts().Modules.size(); I != E;
+          ++I) {
+
+        ASTReader *ModMgr = CI.getModuleManager();
+        ModMgr->ReadAST(CI.getPreprocessorOpts().Modules[I],
+            serialization::MK_Module);
+      }
+      if (!CI.getASTContext().getExternalSource())
+        goto failure;
     }
 
     CI.setASTConsumer(Consumer.take());
@@ -246,7 +271,7 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
       goto failure;
   }
 
-  // Initialize builtin info as long as we aren't using an external AST
+  // Initialize built-in info as long as we aren't using an external AST
   // source.
   if (!CI.hasASTContext() || !CI.getASTContext().getExternalSource()) {
     Preprocessor &PP = CI.getPreprocessor();