[turbofan] Create ExplicitOperands to specify operands without virtual registers

src/compiler/instruction-selector-impl.h

Index: src/compiler/instruction-selector-impl.h
diff --git a/src/compiler/instruction-selector-impl.h b/src/compiler/instruction-selector-impl.h
index 2ee099f9a8721df845a9640446632a67d0e050f7..c30977076e993a2fad4ef8a4dd33ba696e95ebee 100644
--- a/src/compiler/instruction-selector-impl.h
+++ b/src/compiler/instruction-selector-impl.h
@@ -114,6 +114,11 @@ class OperandGenerator {
                                   reg.code(), GetVReg(node)));
   }
 
+  InstructionOperand UseExplicit(Register reg) {
+    MachineType machine_type = InstructionSequence::DefaultRepresentation();
+    return ExplicitOperand(LocationOperand::REGISTER, machine_type, reg.code());
+  }
+
   InstructionOperand UseImmediate(Node* node) {
     return sequence()->AddImmediate(ToConstant(node));
   }