Revert "Decrease number of bytes used by uninitialized tokens_ in KernelFunction (pytorch#160764)"

This reverts commit 30384ab.

(cherry picked from commit cd45fe7)

Author: pragupta

aten/src/ATen/core/boxing/KernelFunction.h

@@ -97,8 +97,8 @@ class TORCH_API KernelFunction final {
   KernelFunction();
   ~KernelFunction();
 
-  KernelFunction(const KernelFunction& other);
-  KernelFunction& operator=(const KernelFunction& other);
+  KernelFunction(const KernelFunction&) = default;
+  KernelFunction& operator=(const KernelFunction&) = default;
 
   KernelFunction(KernelFunction&&) noexcept = default;
 
@@ -276,6 +276,10 @@ class TORCH_API KernelFunction final {
   // Register a token to be invalidated when this KernelFunction is destroyed
   void registerToken(std::weak_ptr<KernelToken> token) const;
 
+  // List of tokens that need to be invalidated when this KernelFunction is
+  // destroyed
+  mutable std::vector<std::weak_ptr<KernelToken>> tokens_;
+
  private:
   explicit KernelFunction(
       std::unique_ptr<OperatorKernel> functor,
@@ -290,9 +294,6 @@ class TORCH_API KernelFunction final {
   BoxedKernel boxed_kernel_func_;
   void* unboxed_kernel_func_;
   void* sym_unboxed_kernel_func_;
-  // List of tokens that need to be invalidated when this KernelFunction is
-  // destroyed (lazy allocation to save memory when empty)
-  mutable std::unique_ptr<std::vector<std::weak_ptr<KernelToken>>> tokens_;
 };
 
 // Token held by SafeKernelFunction that gets invalidated when KernelFunction is

aten/src/ATen/core/boxing/KernelFunction_impl.h

@@ -25,35 +25,13 @@ inline KernelFunction::KernelFunction()
       sym_unboxed_kernel_func_(nullptr) {}
 
 inline KernelFunction::~KernelFunction() {
-  if (tokens_) {
-    for (auto& weak_token : *tokens_) {
-      if (auto token = weak_token.lock()) {
-        token->invalidate();
-      }
+  for (auto& weak_token : tokens_) {
+    if (auto token = weak_token.lock()) {
+      token->invalidate();
     }
   }
 }
 
-inline KernelFunction::KernelFunction(const KernelFunction& other)
-    : boxed_kernel_func_(other.boxed_kernel_func_),
-      unboxed_kernel_func_(other.unboxed_kernel_func_),
-      sym_unboxed_kernel_func_(other.sym_unboxed_kernel_func_) {
-  // tokens_ is intentionally not copied as we only care about invalidating
-  // tokens if the original KernelFunction is destroyed
-}
-
-inline KernelFunction& KernelFunction::operator=(const KernelFunction& other) {
-  if (this != &other) {
-    boxed_kernel_func_ = other.boxed_kernel_func_;
-    unboxed_kernel_func_ = other.unboxed_kernel_func_;
-    sym_unboxed_kernel_func_ = other.sym_unboxed_kernel_func_;
-
-    // tokens_ is intentionally not copied as we only care about invalidating
-    // tokens if the original KernelFunction is destroyed
-  }
-  return *this;
-}
-
 inline KernelFunction::KernelFunction(
     std::unique_ptr<OperatorKernel> functor,
     InternalBoxedKernelFunction* boxed_kernel_func,
@@ -189,10 +167,7 @@ C10_ALWAYS_INLINE Return KernelFunction::call(
 
 inline void KernelFunction::registerToken(
     std::weak_ptr<KernelToken> token) const {
-  if (!tokens_) {
-    tokens_ = std::make_unique<std::vector<std::weak_ptr<KernelToken>>>();
-  }
-  tokens_->push_back(std::move(token));
+  tokens_.push_back(std::move(token));
 }
 
 inline KernelFunction KernelFunction::makeFromBoxedKernel(