CrossDSOCFI - silence static analyzer dyn_cast<> null dereference warning. NFCI.

The static analyzer is warning about a potential null dereference, but we should be able to use cast<> directly and if not assert will fire for us.

llvm-svn: 375427
diff --git a/llvm/lib/Transforms/IPO/CrossDSOCFI.cpp b/llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
index 5f3d0c2..e20159b 100644
--- a/llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
+++ b/llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
@@ -104,7 +104,7 @@
   FunctionCallee C = M.getOrInsertFunction(
       "__cfi_check", Type::getVoidTy(Ctx), Type::getInt64Ty(Ctx),
       Type::getInt8PtrTy(Ctx), Type::getInt8PtrTy(Ctx));
-  Function *F = dyn_cast<Function>(C.getCallee());
+  Function *F = cast<Function>(C.getCallee());
   // Take over the existing function. The frontend emits a weak stub so that the
   // linker knows about the symbol; this pass replaces the function body.
   F->deleteBody();