Subzero: Use "pxor reg,reg" to load a floating-point scalar 0.0 value.

src/IceTargetLoweringX86Base.h

 //===- subzero/src/IceTargetLoweringX86Base.h - x86 lowering ----*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 253 matching lines @@
   /// Returns the smallest type which is equal to or larger than Size bytes. If
   /// one doesn't exist then the largest type smaller than Size bytes is
   /// returned. The type is suitable for memory copies as described at
   /// largestTypeInSize.
   static Type firstTypeThatFitsSize(uint32_t Size,
                                     uint32_t MaxSize = NoSizeLimit);
 
   Variable *copyToReg8(Operand *Src, int32_t RegNum = Variable::NoRegister);
   Variable *copyToReg(Operand *Src, int32_t RegNum = Variable::NoRegister);
 
+  /// Returns a register containing all zeros, without affecting the FLAGS
+  /// register, using the best instruction for the type.
+  Variable *makeZeroedRegister(Type Ty, int32_t RegNum = Variable::NoRegister);
+
   /// \name Returns a vector in a register with the given constant entries.
   /// @{
   Variable *makeVectorOfZeros(Type Ty, int32_t RegNum = Variable::NoRegister);
   Variable *makeVectorOfOnes(Type Ty, int32_t RegNum = Variable::NoRegister);
   Variable *makeVectorOfMinusOnes(Type Ty,
                                   int32_t RegNum = Variable::NoRegister);
   Variable *makeVectorOfHighOrderBits(Type Ty,
                                       int32_t RegNum = Variable::NoRegister);
   Variable *makeVectorOfFabsMask(Type Ty,
                                  int32_t RegNum = Variable::NoRegister);
@@ skipping 464 matching lines @@
   lowerIcmp64(const InstIcmp *Icmp, const InstBr *Br);
 
   BoolFolding FoldingInfo;
 };
 } // end of namespace X86Internal
 } // end of namespace Ice
 
 #include "IceTargetLoweringX86BaseImpl.h"
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGX86BASE_H