Subzero: Clean up some uses of *_cast<>.

src/IceCfg.cpp

 //===- subzero/src/IceCfg.cpp - Control flow graph implementation ---------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 898 matching lines @@
           bool Invalid = false;
           constexpr bool IsDest = true;
           if (!Dest->getLiveRange().containsValue(InstNumber, IsDest))
             Invalid = true;
           // Check that this instruction actually *begins* Dest's live range,
           // by checking that Dest is not live in the previous instruction. As
           // a special exception, we don't check this for the first instruction
           // of the block, because a Phi temporary may be live at the end of
           // the previous block, and if it is also assigned in the first
           // instruction of this block, the adjacent live ranges get merged.
-          if (static_cast<class Inst *>(&Instr) != FirstInst &&
-              !Instr.isDestRedefined() &&
+          if (&Instr != FirstInst && !Instr.isDestRedefined() &&
               Dest->getLiveRange().containsValue(InstNumber - 1, IsDest))
             Invalid = true;
           if (Invalid) {
             Valid = false;
             Str << "Liveness error: inst " << Instr.getNumber() << " dest ";
             Dest->dump(this);
             Str << " live range " << Dest->getLiveRange() << "\n";
           }
         }
       }
@@ skipping 204 matching lines @@
     }
   }
   // Print each basic block
   for (CfgNode *Node : Nodes)
     Node->dump(this);
   if (isVerbose(IceV_Instructions))
     Str << "}\n";
 }
 
 } // end of namespace Ice