diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index f95ca17..3264590 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -18,6 +18,7 @@
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclTemplate.h"
+#include "clang/AST/EvaluatedExprVisitor.h"
 #include "clang/AST/RecordLayout.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/Lex/LiteralSupport.h"
@@ -2664,6 +2665,60 @@
   return isEvaluatable(Ctx);
 }
 
+namespace {
+  /// \brief Look for a call to a non-trivial function within an expression.
+  class NonTrivialCallFinder : public EvaluatedExprVisitor<NonTrivialCallFinder>
+  {
+    typedef EvaluatedExprVisitor<NonTrivialCallFinder> Inherited;
+    
+    bool NonTrivial;
+    
+  public:
+    explicit NonTrivialCallFinder(ASTContext &Context) 
+    : EvaluatedExprVisitor(Context), NonTrivial(false) { }
+    
+    bool hasNonTrivialCall() const { return NonTrivial; }
+    
+    void VisitCallExpr(CallExpr *E) {
+      if (CXXMethodDecl *Method
+          = dyn_cast_or_null<CXXMethodDecl>(E->getCalleeDecl())) {
+        if (Method->isTrivial()) {
+          // Recurse to children of the call.
+          Inherited::VisitStmt(E);
+          return;
+        }
+      }
+      
+      NonTrivial = true;
+    }
+    
+    void VisitCXXConstructExpr(CXXConstructExpr *E) {
+      if (E->getConstructor()->isTrivial()) {
+        // Recurse to children of the call.
+        Inherited::VisitStmt(E);
+        return;
+      }
+      
+      NonTrivial = true;
+    }
+    
+    void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
+      if (E->getTemporary()->getDestructor()->isTrivial()) {
+        Inherited::VisitStmt(E);
+        return;
+      }
+      
+      NonTrivial = true;
+    }
+  };
+}
+
+bool Expr::hasNonTrivialCall(ASTContext &Ctx) {
+  NonTrivialCallFinder Finder(Ctx);
+  Finder.Visit(this);
+  return Finder.hasNonTrivialCall();  
+}
+
 /// isNullPointerConstant - C99 6.3.2.3p3 - Return whether this is a null 
 /// pointer constant or not, as well as the specific kind of constant detected.
 /// Null pointer constants can be integer constant expressions with the
diff --git a/lib/AST/StmtPrinter.cpp b/lib/AST/StmtPrinter.cpp
index c83bfad..51296ad 100644
--- a/lib/AST/StmtPrinter.cpp
+++ b/lib/AST/StmtPrinter.cpp
@@ -1545,11 +1545,12 @@
 
 static const char *getTypeTraitName(BinaryTypeTrait BTT) {
   switch (BTT) {
-  case BTT_IsBaseOf:         return "__is_base_of";
-  case BTT_IsConvertible:    return "__is_convertible";
-  case BTT_IsSame:           return "__is_same";
-  case BTT_TypeCompatible:   return "__builtin_types_compatible_p";
-  case BTT_IsConvertibleTo:  return "__is_convertible_to";
+  case BTT_IsBaseOf:              return "__is_base_of";
+  case BTT_IsConvertible:         return "__is_convertible";
+  case BTT_IsSame:                return "__is_same";
+  case BTT_TypeCompatible:        return "__builtin_types_compatible_p";
+  case BTT_IsConvertibleTo:       return "__is_convertible_to";
+  case BTT_IsTriviallyAssignable: return "__is_trivially_assignable";
   }
   llvm_unreachable("Binary type trait not covered by switch");
 }
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index a9993f9..0e00996 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -700,6 +700,7 @@
                                                             != tok::identifier)
            .Case("is_polymorphic", LangOpts.CPlusPlus)
            .Case("is_trivial", LangOpts.CPlusPlus)
+           .Case("is_trivially_assignable", LangOpts.CPlusPlus)
            .Case("is_trivially_copyable", LangOpts.CPlusPlus)
            .Case("is_union", LangOpts.CPlusPlus)
            .Case("modules", LangOpts.Modules)
diff --git a/lib/Parse/ParseExpr.cpp b/lib/Parse/ParseExpr.cpp
index d2e8752..fdf40e8 100644
--- a/lib/Parse/ParseExpr.cpp
+++ b/lib/Parse/ParseExpr.cpp
@@ -1140,6 +1140,7 @@
   case tok::kw___is_same:
   case tok::kw___is_convertible:
   case tok::kw___is_convertible_to:
+  case tok::kw___is_trivially_assignable:
     return ParseBinaryTypeTrait();
 
   case tok::kw___array_rank:
diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index ccd038c..19bc220 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -2454,6 +2454,7 @@
   case tok::kw___is_same:                    return BTT_IsSame;
   case tok::kw___builtin_types_compatible_p: return BTT_TypeCompatible;
   case tok::kw___is_convertible_to:          return BTT_IsConvertibleTo;
+  case tok::kw___is_trivially_assignable:    return BTT_IsTriviallyAssignable;
   }
 }
 
diff --git a/lib/Parse/ParseTentative.cpp b/lib/Parse/ParseTentative.cpp
index 35c418c..011c28a 100644
--- a/lib/Parse/ParseTentative.cpp
+++ b/lib/Parse/ParseTentative.cpp
@@ -689,6 +689,7 @@
   case tok::kw___is_pod:
   case tok::kw___is_polymorphic:
   case tok::kw___is_trivial:
+  case tok::kw___is_trivially_assignable:
   case tok::kw___is_trivially_copyable:
   case tok::kw___is_union:
   case tok::kw___uuidof:
diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index 30f143a..708db1c 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -3301,6 +3301,54 @@
     ExprResult Result = Init.Perform(Self, To, Kind, MultiExprArg(&FromPtr, 1));
     return !Result.isInvalid() && !SFINAE.hasErrorOccurred();
   }
+      
+  case BTT_IsTriviallyAssignable: {
+    // C++11 [meta.unary.prop]p3:
+    //   is_trivially_assignable is defined as:
+    //     is_assignable<T, U>::value is true and the assignment, as defined by
+    //     is_assignable, is known to call no operation that is not trivial
+    //
+    //   is_assignable is defined as:
+    //     The expression declval<T>() = declval<U>() is well-formed when 
+    //     treated as an unevaluated operand (Clause 5).
+    //
+    //   For both, T and U shall be complete types, (possibly cv-qualified) 
+    //   void, or arrays of unknown bound.
+    if (!LhsT->isVoidType() && !LhsT->isIncompleteArrayType() &&
+        Self.RequireCompleteType(KeyLoc, LhsT, 
+          diag::err_incomplete_type_used_in_type_trait_expr))
+      return false;
+    if (!RhsT->isVoidType() && !RhsT->isIncompleteArrayType() &&
+        Self.RequireCompleteType(KeyLoc, RhsT, 
+          diag::err_incomplete_type_used_in_type_trait_expr))
+      return false;
+
+    // cv void is never assignable.
+    if (LhsT->isVoidType() || RhsT->isVoidType())
+      return false;
+
+    // Build expressions that emulate the effect of declval<T>() and 
+    // declval<U>().
+    if (LhsT->isObjectType() || LhsT->isFunctionType())
+      LhsT = Self.Context.getRValueReferenceType(LhsT);
+    if (RhsT->isObjectType() || RhsT->isFunctionType())
+      RhsT = Self.Context.getRValueReferenceType(RhsT);
+    OpaqueValueExpr Lhs(KeyLoc, LhsT.getNonLValueExprType(Self.Context),
+                        Expr::getValueKindForType(LhsT));
+    OpaqueValueExpr Rhs(KeyLoc, RhsT.getNonLValueExprType(Self.Context),
+                        Expr::getValueKindForType(RhsT));
+    
+    // Attempt the assignment in an unevaluated context within a SFINAE 
+    // trap at translation unit scope.
+    EnterExpressionEvaluationContext Unevaluated(Self, Sema::Unevaluated);
+    Sema::SFINAETrap SFINAE(Self, /*AccessCheckingSFINAE=*/true);
+    Sema::ContextRAII TUContext(Self, Self.Context.getTranslationUnitDecl());
+    ExprResult Result = Self.BuildBinOp(/*S=*/0, KeyLoc, BO_Assign, &Lhs, &Rhs);
+    if (Result.isInvalid() || SFINAE.hasErrorOccurred())
+      return false;
+
+    return !Result.get()->hasNonTrivialCall(Self.Context);
+  }
   }
   llvm_unreachable("Unknown type trait or not implemented");
 }
@@ -3333,6 +3381,7 @@
   case BTT_IsSame:         ResultType = Context.BoolTy; break;
   case BTT_TypeCompatible: ResultType = Context.IntTy; break;
   case BTT_IsConvertibleTo: ResultType = Context.BoolTy; break;
+  case BTT_IsTriviallyAssignable: ResultType = Context.BoolTy;
   }
 
   return Owned(new (Context) BinaryTypeTraitExpr(KWLoc, BTT, LhsTSInfo,