Implement alignof for vla types.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@61305 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index d829fac..a5d5bc2 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -670,8 +670,13 @@
       }
       return CGF.GetVLASize(VAT);
     }
-    // FIXME: This should be an UNSUPPORTED error.
-    assert(0 && "alignof VLAs not implemented yet");
+    
+    // alignof
+    QualType BaseType = CGF.getContext().getBaseElementType(VAT);
+    uint64_t Align = CGF.getContext().getTypeAlign(BaseType);
+
+    Align /= 8;  // Return alignment in bytes, not bits.
+    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Align));
   }
   
   std::pair<uint64_t, unsigned> Info = CGF.getContext().getTypeInfo(TypeToSize);