diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -1363,6 +1363,19 @@
     return Visit(E->getSubExpr(), T);
   }
 
+  llvm::Constant *VisitUnaryOperator(UnaryOperator *U, QualType T) {
+    switch (U->getOpcode()) {
+    default:
+      break;
+    case UO_Minus:
+      if (llvm::Constant *C = Visit(U->getSubExpr(), T))
+        if (auto *CI = dyn_cast<llvm::ConstantInt>(C))
+          return llvm::ConstantInt::get(CGM.getLLVMContext(), -CI->getValue());
+      break;
+    }
+    return nullptr;
+  }
+
   // Utility methods
   llvm::Type *ConvertType(QualType T) {
     return CGM.getTypes().ConvertType(T);