[ET-VK] Runtime support for NamedDataMap

Summary:

Allow VulkanBackend to load constant tensors from the NamedDataMap instead of the constant data section of the delegate blob.

## Motivation

This enables several key results:

* Unblocks delegate retargetability with other backends
* Allows reducing peak memory usage when loading models by freeing constant weight data as it gets moved to the GPU

## Changes

* Allow `TensorRef` to be constructed with a `FreeableBuffer` rvalue
* Add ability to load constant data from `NamedDataMap` in `VulkanBackend.cpp`
* When prepacking, free the constant data pointer once it's been copied to the staging buffer

Test Plan:
CI

Validate results by collecting memory measurements in the next few diffs.

[ghstack-poisoned]

Author: SS-JIA

backends/vulkan/runtime/VulkanBackend.cpp

@@ -22,6 +22,7 @@
 #include <executorch/runtime/core/event_tracer_hooks_delegate.h>
 #endif // ET_EVENT_TRACER_ENABLED
 #include <executorch/runtime/core/exec_aten/util/tensor_util.h>
+#include <executorch/runtime/executor/pte_data_map.h>
 #include <executorch/runtime/platform/compiler.h>
 #include <executorch/runtime/platform/profiler.h>
 
@@ -47,6 +48,7 @@ using executorch::runtime::Error;
 using executorch::runtime::EValue;
 using executorch::runtime::FreeableBuffer;
 using executorch::runtime::kTensorDimensionLimit;
+using executorch::runtime::NamedDataMap;
 using executorch::runtime::Result;
 using executorch::runtime::Span;
 
@@ -69,8 +71,29 @@ using UIntVector = const flatbuffers::Vector<uint32_t>*;
 const uint8_t* get_constant_data_ptr(
     VkGraphPtr flatbuffer_graph,
     const int32_t buffer_idx,
-    const uint8_t* constant_data) {
+    const uint8_t* constant_data,
+    const NamedDataMap* named_data_map,
+    std::vector<FreeableBuffer>& loaded_buffers_from_map) {
   VkBytesPtr constant_bytes = flatbuffer_graph->constants()->Get(buffer_idx);
+
+  // Check if there's a named key for this constant data
+  if (constant_bytes->named_key() != nullptr && named_data_map != nullptr) {
+    const std::string& data_name = constant_bytes->named_key()->str();
+    Result<FreeableBuffer> buffer = named_data_map->get_data(data_name.c_str());
+    if (!buffer.ok()) {
+      ET_LOG(
+          Error,
+          "Failed to get constant data for key %s from named_data_map. Error code: %u",
+          data_name.c_str(),
+          static_cast<uint32_t>(buffer.error()));
+      return nullptr;
+    }
+    const uint8_t* data_ptr = static_cast<const uint8_t*>(buffer.get().data());
+    loaded_buffers_from_map.push_back(std::move(buffer.get()));
+    return data_ptr;
+  }
+
+  // Fallback to offset-based access
   return constant_data + constant_bytes->offset();
 }
 
@@ -166,17 +189,22 @@ class GraphBuilder {
   ComputeGraph* compute_graph_;
   VkGraphPtr flatbuffer_;
   const uint8_t* constant_data_;
+  const NamedDataMap* named_data_map_;
+  std::vector<FreeableBuffer> loaded_buffers_from_map_;
 
   std::vector<ValueRef> ref_mapping_;
 
  public:
   explicit GraphBuilder(
       ComputeGraph* compute_graph,
       VkGraphPtr flatbuffer,
-      const uint8_t* constant_data)
+      const uint8_t* constant_data,
+      const NamedDataMap* named_data_map)
       : compute_graph_(compute_graph),
         flatbuffer_(flatbuffer),
         constant_data_(constant_data),
+        named_data_map_(named_data_map),
+        loaded_buffers_from_map_(),
         ref_mapping_() {}
 
   void resize(uint32_t size) {
@@ -212,10 +240,27 @@ class GraphBuilder {
 
     ValueRef ref;
     if (tensor_fb->constant_id() >= 0) {
-      const uint8_t* tensor_data = get_constant_data_ptr(
-          flatbuffer_, tensor_fb->constant_id(), constant_data_);
+      VkBytesPtr constant_bytes =
+          flatbuffer_->constants()->Get(tensor_fb->constant_id());
+
+      if (constant_bytes->named_key() != nullptr &&
+          constant_bytes->offset() == UINT64_MAX &&
+          named_data_map_ != nullptr) {
+        const std::string& data_name = constant_bytes->named_key()->str();
+        Result<FreeableBuffer> buffer =
+            named_data_map_->get_data(data_name.c_str());
 
-      ref = compute_graph_->add_tensorref(dims_vector, dtype, tensor_data);
+        VK_CHECK_COND(
+            buffer.ok(),
+            "Failed to get constant data for key %s from named_data_map. Error code: %u",
+            data_name.c_str(),
+            static_cast<uint32_t>(buffer.error()));
+        ref = compute_graph_->add_tensorref(
+            dims_vector, dtype, std::move(buffer.get()));
+      } else {
+        const uint8_t* tensor_data = constant_data_ + constant_bytes->offset();
+        ref = compute_graph_->add_tensorref(dims_vector, dtype, tensor_data);
+      }
     } else {
       ref = compute_graph_->add_tensor(
           dims_vector,
@@ -479,8 +524,10 @@ class VulkanBackend final : public ::executorch::runtime::BackendInterface {
     return true;
   }
 
-  ET_NODISCARD Error
-  compileModel(const void* buffer_pointer, ComputeGraph* compute_graph) const {
+  ET_NODISCARD Error compileModel(
+      const void* buffer_pointer,
+      ComputeGraph* compute_graph,
+      const NamedDataMap* named_data_map) const {
     Result<VulkanDelegateHeader> header =
         VulkanDelegateHeader::parse(buffer_pointer);
 
@@ -506,7 +553,8 @@ class VulkanBackend final : public ::executorch::runtime::BackendInterface {
 
     VkGraphPtr flatbuffer_graph = vkgraph::GetVkGraph(flatbuffer_data);
 
-    GraphBuilder builder(compute_graph, flatbuffer_graph, constant_data);
+    GraphBuilder builder(
+        compute_graph, flatbuffer_graph, constant_data, named_data_map);
 
     builder.build_graph();
 
@@ -532,7 +580,8 @@ class VulkanBackend final : public ::executorch::runtime::BackendInterface {
     graph_config.external_adapter = vkapi::set_and_get_external_adapter();
     new (compute_graph) ComputeGraph(graph_config);
 
-    Error err = compileModel(processed->data(), compute_graph);
+    const NamedDataMap* named_data_map = context.get_named_data_map();
+    Error err = compileModel(processed->data(), compute_graph, named_data_map);
 
     // This backend does not need its processed data after compiling the
     // model.

backends/vulkan/runtime/graph/ComputeGraph.cpp

@@ -480,6 +480,17 @@ ValueRef ComputeGraph::add_tensorref(
   return idx;
 }
 
+ValueRef ComputeGraph::add_tensorref(
+    const std::vector<int64_t>& sizes,
+    const vkapi::ScalarType dtype,
+    executorch::runtime::FreeableBuffer&& buffer) {
+  ValueRef idx(static_cast<int>(values_.size()));
+  check_no_active_value_ptrs();
+  values_.emplace_back(TensorRef(sizes, dtype, std::move(buffer)));
+  total_constant_nbytes_ += values_.back().toConstTensorRef().nbytes();
+  return idx;
+}
+
 ValueRef ComputeGraph::add_staging(
     const vkapi::ScalarType dtype,
     const size_t numel) {

backends/vulkan/runtime/graph/ComputeGraph.h

@@ -693,6 +693,16 @@ class ComputeGraph final {
       const vkapi::ScalarType dtype,
       const void* const data);
 
+  /*
+   * Add a `TensorRef` value to the graph with the specific properties. A
+   * `TensorRef` is a reference to a `api::vTensor` whose data is stored in a
+   * FreeableBuffer. The TensorRef will take ownership of the FreeableBuffer.
+   */
+  ValueRef add_tensorref(
+      const std::vector<int64_t>& sizes,
+      const vkapi::ScalarType dtype,
+      executorch::runtime::FreeableBuffer&& buffer);
+
   /*
    * Add a staging buffer to the graph. Staging buffers are data buffers that
    * use memory that is visible to both the CPU and GPU, and therefore is used

backends/vulkan/runtime/graph/Logging.cpp

@@ -86,7 +86,7 @@ void ComputeGraph::print_readable() {
       ss << v_tensor.sizes();
       std::cout << ss.str();
     } else if (val.isTensorRef()) {
-      const TensorRef tensor_ref = val.toTensorRef();
+      const TensorRef& tensor_ref = val.toTensorRef();
       std::stringstream ss;
       ss << tensor_ref.sizes;
       std::cout << ss.str();

backends/vulkan/runtime/graph/containers/Constant.cpp

@@ -14,7 +14,22 @@ TensorRef::TensorRef(
     const std::vector<int64_t>& t_sizes,
     vkapi::ScalarType t_dtype,
     const void* const t_data)
-    : sizes{}, dtype{t_dtype}, data{t_data} {
+    : sizes{}, dtype{t_dtype}, data{t_data}, buffer{} {
+  size_t ndim = t_sizes.size();
+  sizes.resize(ndim);
+  for (int i = 0; i < ndim; ++i) {
+    sizes[i] = t_sizes.at(i);
+  }
+}
+
+TensorRef::TensorRef(
+    const std::vector<int64_t>& t_sizes,
+    vkapi::ScalarType t_dtype,
+    executorch::runtime::FreeableBuffer&& t_buffer)
+    : sizes{},
+      dtype{t_dtype},
+      data{t_buffer.data()},
+      buffer{std::move(t_buffer)} {
   size_t ndim = t_sizes.size();
   sizes.resize(ndim);
   for (int i = 0; i < ndim; ++i) {

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

@@ -9,6 +9,7 @@
 #pragma once
 
 #include <executorch/backends/vulkan/runtime/api/Context.h>
+#include <executorch/runtime/core/freeable_buffer.h>
 
 namespace vkcompute {
 
@@ -24,14 +25,30 @@ struct TensorRef final {
   vkapi::ScalarType dtype;
   const void* data;
 
+  // Optional FreeableBuffer for managing memory lifecycle
+  // This will be empty (default constructed) for the raw pointer constructor
+  executorch::runtime::FreeableBuffer buffer;
+
   explicit TensorRef(
       const std::vector<int64_t>& t_sizes,
       vkapi::ScalarType t_dtype,
       const void* const t_data);
 
+  // Constructor that takes ownership of a FreeableBuffer
+  explicit TensorRef(
+      const std::vector<int64_t>& t_sizes,
+      vkapi::ScalarType t_dtype,
+      executorch::runtime::FreeableBuffer&& t_buffer);
+
   inline size_t nbytes() const {
     return utils::multiply_integers(sizes) * vkapi::element_size(dtype);
   }
+
+  // Manually free the buffer if needed (though it will be freed automatically
+  // on destruction)
+  void free_buffer() {
+    buffer.Free();
+  }
 };
 
 } // namespace vkcompute

backends/vulkan/runtime/graph/ops/PrepackNode.cpp

@@ -64,6 +64,9 @@ api::StagingBuffer PrepackNode::create_staging_buffer(ComputeGraph* graph) {
   graph->update_staging_nbytes_in_cmd(staging.buffer().mem_size_as_size_t());
   size_t nbytes = numel * vkapi::element_size(tref->dtype);
   staging.copy_from(tref->data, nbytes);
+  // Once the staging buffer is copied, if the TensorRef owns a FreeableBuffer,
+  // it can be freed.
+  tref->free_buffer();
   return staging;
 }
 

backends/vulkan/serialization/schema.fbs

@@ -118,6 +118,7 @@ table VkValue {
 table VkBytes {
   offset:ulong;
   length:ulong;
+  named_key:string;
 }
 
 table VkGraph {

backends/vulkan/serialization/vulkan_graph_schema.py

@@ -137,6 +137,7 @@ class VkValue:
 class VkBytes:
     offset: int
     length: int
+    named_key: str = ""
 
 
 @dataclass