[turbofan] Create ExplicitOperands to specify operands without virtual registers

src/compiler/code-generator-impl.h

Index: src/compiler/code-generator-impl.h
diff --git a/src/compiler/code-generator-impl.h b/src/compiler/code-generator-impl.h
index 8dd50018fc4758acb88bc24aa6e24c824f12586a..45f77913bd383837ac64aabc644a87a58080577d 100644
--- a/src/compiler/code-generator-impl.h
+++ b/src/compiler/code-generator-impl.h
@@ -100,11 +100,11 @@ class InstructionOperandConverter {
   }
 
   Register ToRegister(InstructionOperand* op) {
-    return RegisterOperand::cast(op)->GetRegister();
+    return LocationOperand::cast(op)->GetRegister();
   }
 
   DoubleRegister ToDoubleRegister(InstructionOperand* op) {
-    return DoubleRegisterOperand::cast(op)->GetDoubleRegister();
+    return LocationOperand::cast(op)->GetDoubleRegister();
   }
 
   Constant ToConstant(InstructionOperand* op) {