Enables llvm dyn_cast for Assemblers.

src/IceCfg.h

 //===- subzero/src/IceCfg.h - Control flow graph ----------------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares the Cfg class, which represents the control flow
@@ skipping 109 matching lines @@
   const VarList &getArgs() const { return Args; }
   VarList &getArgs() { return Args; }
   void addImplicitArg(Variable *Arg);
   const VarList &getImplicitArgs() const { return ImplicitArgs; }
 
   // Miscellaneous accessors.
   TargetLowering *getTarget() const { return Target.get(); }
   VariablesMetadata *getVMetadata() const { return VMetadata.get(); }
   Liveness *getLiveness() const { return Live.get(); }
   template <typename T = Assembler> T *getAssembler() const {
-    return static_cast<T *>(TargetAssembler.get());
+    return llvm::dyn_cast<T>(TargetAssembler.get());
   }
   Assembler *releaseAssembler() { return TargetAssembler.release(); }
   std::unique_ptr<VariableDeclarationList> getGlobalInits() {
     return std::move(GlobalInits);
   }
   bool hasComputedFrame() const;
   bool getFocusedTiming() const { return FocusedTiming; }
   void setFocusedTiming() { FocusedTiming = true; }
 
   // Returns true if Var is a global variable that is used by the profiling
@@ skipping 101 matching lines @@
   // other uses are possible.
   ICE_TLS_DECLARE_FIELD(const Cfg *, CurrentCfg);
 
 public:
   static void TlsInit() { ICE_TLS_INIT_FIELD(CurrentCfg); }
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICECFG_H