[ET-VK] Store unique ptr to Tensor in Value instead of inlined tensor object, to reduce Value struct size from 448 to 80 bytes.

Pull Request resolved: #7145

This diff aims to reduce the size of the Value struct in the Executorch Vulkan runtime by storing a unique pointer to the Tensor object instead of an inlined tensor object. This change reduces the size of the Value struct from 448 bytes to 80 bytes, which can improve performance and reduce memory usage.
ghstack-source-id: 256911524
@exported-using-ghexport

Differential Revision: [D66655991](https://our.internmc.facebook.com/intern/diff/D66655991/)

---------

Co-authored-by: Vivek Trivedi <[email protected]>

Author: pytorchbot

backends/vulkan/runtime/graph/containers/Value.h

@@ -58,7 +58,7 @@ struct Value final {
       bool as_bool;
     } u;
 
-    api::vTensor as_tensor;
+    std::unique_ptr<api::vTensor> as_tensor;
     api::StagingBuffer as_staging;
     TensorRef as_tensorref;
 
@@ -106,15 +106,18 @@ struct Value final {
     rhs.payload.member_name.~dtor_name();                                \
     break;
 
+#define CASE_MOVE_UNIQUE_PTR_TYPE(type_tag, member_name)      \
+  case type_tag:                                              \
+    payload.member_name = std::move(rhs.payload.member_name); \
+    break;
+
   Value(Value&& rhs) noexcept : tag(rhs.tag) {
     switch (tag) {
       // Scalar types
       CASE_MOVE_TRIVIALLY_COPYABLE_TYPE(TypeTag::INT, as_int);
       CASE_MOVE_TRIVIALLY_COPYABLE_TYPE(TypeTag::DOUBLE, as_double);
       CASE_MOVE_TRIVIALLY_COPYABLE_TYPE(TypeTag::BOOL, as_bool);
-      // Tensor and tensor adjacent types
-      CASE_MOVE_MOVEABLE_TYPE(
-          TypeTag::TENSOR, api::vTensor, as_tensor, vTensor);
+      // Tensor adjacent types
       CASE_MOVE_MOVEABLE_TYPE(
           TypeTag::STAGING, api::StagingBuffer, as_staging, StagingBuffer);
       CASE_MOVE_MOVEABLE_TYPE(
@@ -132,6 +135,8 @@ struct Value final {
       CASE_MOVE_MOVEABLE_TYPE(
           TypeTag::STRING, std::string, as_string, basic_string);
       CASE_MOVE_MOVEABLE_TYPE(TypeTag::SYMINT, SymInt, as_symint, SymInt);
+      // Tensor type
+      CASE_MOVE_UNIQUE_PTR_TYPE(TypeTag::TENSOR, as_tensor);
 
       case TypeTag::NONE:
         clearToNone();
@@ -142,6 +147,7 @@ struct Value final {
 
 #undef CASE_MOVE_TRIVIALLY_COPYABLE_TYPE
 #undef CASE_MOVE_MOVEABLE_TYPE
+#undef CASE_MOVE_UNIQUE_PTR_TYPE
 
   //
   // Accessors
@@ -157,9 +163,6 @@ struct Value final {
 
   ~Value() {
     switch (tag) {
-      case TypeTag::TENSOR:
-        payload.as_tensor.~vTensor();
-        break;
       case TypeTag::STAGING:
         payload.as_staging.~StagingBuffer();
         break;
@@ -184,6 +187,9 @@ struct Value final {
       case TypeTag::SYMINT:
         payload.as_symint.~SymInt();
         break;
+      case TypeTag::TENSOR:
+        payload.as_tensor.reset();
+        break;
       // Manually list out the types so that if a type here is added later and
       // not handled the compiler can catch it.
       case TypeTag::NONE:
@@ -252,12 +258,6 @@ struct Value final {
     return payload.member_name;                             \
   }
 
-  SUPPORT_TRIVIALLY_MOVEABLE_TYPE(
-      api::vTensor,
-      Tensor,
-      TypeTag::TENSOR,
-      as_tensor);
-
   SUPPORT_TRIVIALLY_MOVEABLE_TYPE(
       api::StagingBuffer,
       Staging,
@@ -302,9 +302,36 @@ struct Value final {
 
   SUPPORT_TRIVIALLY_MOVEABLE_TYPE(SymInt, SymInt, TypeTag::SYMINT, as_symint);
 
-#undef SUPPORT_TRIVIALLY_COPYABLE_TYPE
 #undef SUPPORT_TRIVIALLY_MOVEABLE_TYPE
 
+#define SUPPORT_UNIQUE_PTR_TYPE(type, type_name, type_tag, member_name) \
+  explicit Value(type t) : tag(type_tag) {                              \
+    payload.member_name = std::make_unique<type>(std::move(t));         \
+  }                                                                     \
+  inline bool is##type_name() const {                                   \
+    return tag == type_tag;                                             \
+  }                                                                     \
+  inline type& to##type_name() const {                                  \
+    VK_CHECK_COND(                                                      \
+        is##type_name(),                                                \
+        "Expected value to have type " #type_name ", got ",             \
+        tag,                                                            \
+        " instead.");                                                   \
+    return *payload.member_name;                                        \
+  }                                                                     \
+  inline const type& toConst##type_name() const {                       \
+    VK_CHECK_COND(                                                      \
+        is##type_name(),                                                \
+        "Expected value to have type " #type_name ", got ",             \
+        tag,                                                            \
+        " instead.");                                                   \
+    return *payload.member_name;                                        \
+  }
+
+  SUPPORT_UNIQUE_PTR_TYPE(api::vTensor, Tensor, TypeTag::TENSOR, as_tensor);
+
+#undef SUPPORT_UNIQUE_PTR_TYPE
+
  private:
   Payload payload;
   TypeTag tag;

backends/vulkan/test/vulkan_compute_api_test.cpp

@@ -1087,8 +1087,8 @@ TEST_F(VulkanComputeAPITest, print_object_sizes) {
 
   // Current known size on 64 bit system: 1040 B
   EXPECT_TRUE(sizeof(vTensor) < 1200);
-  // Current known size on 64 bit system: 1056 B
-  EXPECT_TRUE(sizeof(Value) < 1200);
+  // Current known size on 64 bit system: 120 B
+  EXPECT_TRUE(sizeof(Value) < 128);
   // Current known size on 64 bit system: 120 B
   EXPECT_TRUE(sizeof(StagingBuffer) < 500);
   // Current known size on 64 bit system: 384 B