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

src/IceTargetLoweringX86Base.h

Index: src/IceTargetLoweringX86Base.h
diff --git a/src/IceTargetLoweringX86Base.h b/src/IceTargetLoweringX86Base.h
index 2de51af770b8ca650da3a251715d18ceb7311350..f004d6e89b5dc7e5c198b1b3c60a2408541a9ef8 100644
--- a/src/IceTargetLoweringX86Base.h
+++ b/src/IceTargetLoweringX86Base.h
@@ -271,6 +271,10 @@ protected:
   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);