diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 30eaae14d7..e53804c86d 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -1703,9 +1703,11 @@ public:
     { return Visit(E->getChosenSubExpr(Info.Ctx)); }
   bool VisitUnaryExtension(const UnaryOperator *E)
     { return Visit(E->getSubExpr()); }
+  bool VisitUnaryReal(const UnaryOperator *E);
+  bool VisitUnaryImag(const UnaryOperator *E);
 
-  // FIXME: Missing: __real__/__imag__, array subscript of vector,
-  //                 member of vector, ImplicitValueInitExpr
+  // FIXME: Missing: array subscript of vector, member of vector,
+  //                 ImplicitValueInitExpr
 };
 } // end anonymous namespace
 
@@ -1791,6 +1793,22 @@ bool FloatExprEvaluator::VisitCallExpr(const CallExpr *E) {
   }
 }
 
+bool FloatExprEvaluator::VisitUnaryReal(const UnaryOperator *E) {
+  ComplexValue CV;
+  if (!EvaluateComplex(E->getSubExpr(), CV, Info))
+    return false;
+  Result = CV.FloatReal;
+  return true;
+}
+
+bool FloatExprEvaluator::VisitUnaryImag(const UnaryOperator *E) {
+  ComplexValue CV;
+  if (!EvaluateComplex(E->getSubExpr(), CV, Info))
+    return false;
+  Result = CV.FloatImag;
+  return true;
+}
+
 bool FloatExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
   if (E->getOpcode() == UnaryOperator::Deref)
     return false;
diff --git a/test/CodeGen/complex.c b/test/CodeGen/complex.c
index ca606109f8..055383ebbb 100644
--- a/test/CodeGen/complex.c
+++ b/test/CodeGen/complex.c
@@ -89,3 +89,7 @@ void t6() {
   --ci1;
 }
 
+// <rdar://problem/7958272>
+double t7(double _Complex c) {
+  return __builtin_fabs(__real__(c));
+}