[Fixed Point Arithmetic] Fixed Point to Boolean Cast

This patch is a part of https://reviews.llvm.org/D48456 in an attempt to split
the casting logic up into smaller patches. This contains the code for casting
from fixed point types to boolean types.

Differential Revision: https://reviews.llvm.org/D53308

llvm-svn: 345063
diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index e1ad656..b8b6685 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -870,6 +870,7 @@
     case CK_FloatingToBoolean:
     case CK_FloatingCast:
     case CK_FixedPointCast:
+    case CK_FixedPointToBoolean:
     case CK_ZeroToOCLOpaqueType:
       return nullptr;
     }