Index: test/PCH/Inputs/__va_list_tag.h
===================================================================
--- test/PCH/Inputs/__va_list_tag.h	(revision 0)
+++ test/PCH/Inputs/__va_list_tag.h	(revision 0)
@@ -0,0 +1,5 @@
+// Header for PCH test __va_list_tag.h
+
+typedef __builtin_va_list va_list;
+
+extern int myvfprintf(const char * , va_list);
Index: test/PCH/__va_list_tag.c
===================================================================
--- test/PCH/__va_list_tag.c	(revision 0)
+++ test/PCH/__va_list_tag.c	(revision 0)
@@ -0,0 +1,10 @@
+// Test this without pch.
+// RUN: %clang_cc1 -triple=x86_64-unknown-freebsd7.0 -include %S/Inputs/__va_list_tag.h %s -emit-llvm -o -
+
+// Test with pch.
+// RUN: %clang_cc1 -triple=x86_64-unknown-freebsd7.0 -emit-pch -x c-header -o %t %S/Inputs/__va_list_tag.h
+// RUN: %clang_cc1 -triple=x86_64-unknown-freebsd7.0 -include-pch %t %s -verify
+
+int myvprintf(const char *fmt, va_list args) {
+    return myvfprintf(fmt, args);
+}
Index: include/clang/AST/ASTContext.h
===================================================================
--- include/clang/AST/ASTContext.h	(revision 159405)
+++ include/clang/AST/ASTContext.h	(working copy)
@@ -599,6 +599,10 @@
   mutable QualType AutoDeductTy;     // Deduction against 'auto'.
   mutable QualType AutoRRefDeductTy; // Deduction against 'auto &&'.
 
+  // Type used to help define __builtin_va_list for some targets.
+  // The type is built when constructing 'BuiltinVaListDecl'.
+  mutable QualType VaListTagTy;
+
   ASTContext(LangOptions& LOpts, SourceManager &SM, const TargetInfo *t,
              IdentifierTable &idents, SelectorTable &sels,
              Builtin::Context &builtins,
Index: include/clang/Serialization/ASTBitCodes.h
===================================================================
--- include/clang/Serialization/ASTBitCodes.h	(revision 159405)
+++ include/clang/Serialization/ASTBitCodes.h	(working copy)
@@ -640,7 +640,9 @@
       /// \brief ARC's unbridged-cast placeholder type.
       PREDEF_TYPE_ARC_UNBRIDGED_CAST = 34,
       /// \brief The pseudo-object placeholder type.
-      PREDEF_TYPE_PSEUDO_OBJECT = 35
+      PREDEF_TYPE_PSEUDO_OBJECT = 35,
+      /// \brief The __va_list_tag placeholder type.
+      PREDEF_TYPE_VA_LIST_TAG = 36
     };
 
     /// \brief The number of predefined type IDs that are reserved for
Index: lib/AST/ASTContext.cpp
===================================================================
--- lib/AST/ASTContext.cpp	(revision 159405)
+++ lib/AST/ASTContext.cpp	(working copy)
@@ -5113,6 +5113,7 @@
   }
   VaListTagDecl->completeDefinition();
   QualType VaListTagType = Context->getRecordType(VaListTagDecl);
+  Context->VaListTagTy = VaListTagType;
 
   // } __va_list_tag;
   TypedefDecl *VaListTagTypedefDecl
@@ -5186,6 +5187,7 @@
   }
   VaListTagDecl->completeDefinition();
   QualType VaListTagType = Context->getRecordType(VaListTagDecl);
+  Context->VaListTagTy = VaListTagType;
 
   // } __va_list_tag;
   TypedefDecl *VaListTagTypedefDecl
Index: lib/Serialization/ASTCommon.h
===================================================================
--- lib/Serialization/ASTCommon.h	(revision 159405)
+++ lib/Serialization/ASTCommon.h	(working copy)
@@ -50,6 +50,8 @@
     return TypeIdx(PREDEF_TYPE_AUTO_DEDUCT).asTypeID(FastQuals);
   if (T == Context.AutoRRefDeductTy)
     return TypeIdx(PREDEF_TYPE_AUTO_RREF_DEDUCT).asTypeID(FastQuals);
+  if (T == Context.VaListTagTy)
+    return TypeIdx(PREDEF_TYPE_VA_LIST_TAG).asTypeID(FastQuals);
 
   return IdxForType(T).asTypeID(FastQuals);
 }
Index: lib/Serialization/ASTReader.cpp
===================================================================
--- lib/Serialization/ASTReader.cpp	(revision 159405)
+++ lib/Serialization/ASTReader.cpp	(working copy)
@@ -4461,6 +4461,9 @@
       T = Context.ARCUnbridgedCastTy;
       break;
 
+    case PREDEF_TYPE_VA_LIST_TAG:
+      T = Context.VaListTagTy;
+      break;
     }
 
     assert(!T.isNull() && "Unknown predefined type");