UnimplementedLoweringError's message now includes the instruction name.

src/IceInst.h

 //===- subzero/src/IceInst.h - High-level instructions ----------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 58 matching lines @@
     JumpTable,    // not part of LLVM/PNaCl bitcode
     // Anything >= Target is an InstTarget subclass. Note that the value-spaces
     // are shared across targets. To avoid confusion over the definition of
     // shared values, an object specific to one target should never be passed
     // to a different target.
     Target,
     Target_Max = std::numeric_limits<uint8_t>::max(),
   };
   static_assert(Target <= Target_Max, "Must not be above max.");
   InstKind getKind() const { return Kind; }
+  virtual IceString getInstName() const;
 
   InstNumberT getNumber() const { return Number; }
   void renumber(Cfg *Func);
   enum {
     NumberDeleted = -1,
     NumberSentinel = 0,
     NumberInitial = 2,
     NumberExtended = NumberInitial - 1
   };
 
@@ skipping 192 matching lines @@
 #undef X
         _num
   };
 
   static InstArithmetic *create(Cfg *Func, OpKind Op, Variable *Dest,
                                 Operand *Source1, Operand *Source2) {
     return new (Func->allocate<InstArithmetic>())
         InstArithmetic(Func, Op, Dest, Source1, Source2);
   }
   OpKind getOp() const { return Op; }
+
+  virtual IceString getInstName() const override;
+
   static const char *getOpName(OpKind Op);
   bool isCommutative() const;
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Inst) {
     return Inst->getKind() == Arithmetic;
   }
 
 private:
   InstArithmetic(Cfg *Func, OpKind Op, Variable *Dest, Operand *Source1,
                  Operand *Source2);
@@ skipping 688 matching lines @@
   static void noteHead(Ice::Inst *, Ice::Inst *) {}
   void deleteNode(Ice::Inst *) {}
 
 private:
   mutable ilist_half_node<Ice::Inst> Sentinel;
 };
 
 } // end of namespace llvm
 
 #endif // SUBZERO_SRC_ICEINST_H