Add support for undef values in ICE IR.

src/llvm2ice.cpp

 //===- subzero/src/llvm2ice.cpp - Driver for testing ----------------------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines a driver that uses LLVM capabilities to parse a
@@ skipping 99 matching lines @@
       return Ctx->getConstantInt(convertIntegerType(CI->getType()),
                                  CI->getZExtValue());
     } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(Const)) {
       Ice::Type Type = convertType(CFP->getType());
       if (Type == Ice::IceType_f32)
         return Ctx->getConstantFloat(CFP->getValueAPF().convertToFloat());
       else if (Type == Ice::IceType_f64)
         return Ctx->getConstantDouble(CFP->getValueAPF().convertToDouble());
       llvm_unreachable("Unexpected floating point type");
       return NULL;
+    } else if (const UndefValue *CU = dyn_cast<UndefValue>(Const)) {
+      return Ctx->getConstantUndef(convertType(CU->getType()));
     } else {
       llvm_unreachable("Unhandled constant type");
       return NULL;
     }
   }
 
 private:
   // LLVM values (instructions, etc.) are mapped directly to ICE variables.
   // mapValueToIceVar has a version that forces an ICE type on the variable,
   // and a version that just uses convertType on V.
@@ skipping 595 matching lines @@
                   << " sec\n";
       }
     }
   }
 
   if (!DisableTranslation && Func)
     Func->getTarget()->emitConstants();
 
   return ExitStatus;
 }