[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 2e95bec0cc17188fbfc8d1997bbba90771d7fc3a..f89a10b62b8cb7b1179c312ef0c4fa3cc300fcda 100644
--- a/src/compiler/code-generator-impl.h
+++ b/src/compiler/code-generator-impl.h
@@ -96,11 +96,11 @@ 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) {