ART: Make ManagedRegister ValueObject

Make ManagedRegister a value class, and ensure it is trivially
copyable.

Bug: 32619234
Test: m
Change-Id: Ie39b7f59a01ed293891e97110db3f5262f25fb4e
diff --git a/compiler/utils/managed_register.h b/compiler/utils/managed_register.h
index bb30f46..184cdf5 100644
--- a/compiler/utils/managed_register.h
+++ b/compiler/utils/managed_register.h
@@ -17,8 +17,11 @@
 #ifndef ART_COMPILER_UTILS_MANAGED_REGISTER_H_
 #define ART_COMPILER_UTILS_MANAGED_REGISTER_H_
 
+#include <type_traits>
 #include <vector>
 
+#include "base/value_object.h"
+
 namespace art {
 
 namespace arm {
@@ -42,17 +45,14 @@
 class X86_64ManagedRegister;
 }
 
-class ManagedRegister {
+class ManagedRegister : public ValueObject {
  public:
   // ManagedRegister is a value class. There exists no method to change the
   // internal state. We therefore allow a copy constructor and an
   // assignment-operator.
-  constexpr ManagedRegister(const ManagedRegister& other) : id_(other.id_) { }
+  constexpr ManagedRegister(const ManagedRegister& other) = default;
 
-  ManagedRegister& operator=(const ManagedRegister& other) {
-    id_ = other.id_;
-    return *this;
-  }
+  ManagedRegister& operator=(const ManagedRegister& other) = default;
 
   constexpr arm::ArmManagedRegister AsArm() const;
   constexpr arm64::Arm64ManagedRegister AsArm64() const;
@@ -85,6 +85,9 @@
   int id_;
 };
 
+static_assert(std::is_trivially_copyable<ManagedRegister>::value,
+              "ManagedRegister should be trivially copyable");
+
 class ManagedRegisterSpill : public ManagedRegister {
  public:
   // ManagedRegisterSpill contains information about data type size and location in caller frame