Enhance load_method to support optional planned memory allocator

- Updated the load_method signature to accept an optional runtime::HierarchicalAllocator parameter.

Author: cptspacemanspiff

extension/module/module.cpp

@@ -11,7 +11,9 @@
 #include <executorch/extension/data_loader/file_data_loader.h>
 #include <executorch/extension/data_loader/mmap_data_loader.h>
 #include <executorch/extension/memory_allocator/malloc_memory_allocator.h>
+#include <executorch/runtime/core/hierarchical_allocator.h>
 #include <executorch/runtime/platform/runtime.h>
+#include <memory>
 
 /**
  * Unwrap a Result to obtain its value (direct object, not a pointer).
@@ -125,33 +127,42 @@ runtime::Result<std::unordered_set<std::string>> Module::method_names() {
 
 runtime::Error Module::load_method(
     const std::string& method_name,
-    torch::executor::EventTracer* event_tracer) {
+    torch::executor::EventTracer* event_tracer,
+    runtime::HierarchicalAllocator* planned_memory_allocator) {
   if (!is_method_loaded(method_name)) {
     ET_CHECK_OK_OR_RETURN_ERROR(load());
 
     MethodHolder method_holder;
-    const auto method_metadata =
-        ET_UNWRAP(program_->method_meta(method_name.c_str()));
-    const auto planned_buffersCount =
-        method_metadata.num_memory_planned_buffers();
-    method_holder.planned_buffers.reserve(planned_buffersCount);
-    method_holder.planned_spans.reserve(planned_buffersCount);
-
-    for (auto index = 0; index < planned_buffersCount; ++index) {
-      const auto buffer_size =
-          method_metadata.memory_planned_buffer_size(index).get();
-      method_holder.planned_buffers.emplace_back(buffer_size);
-      method_holder.planned_spans.emplace_back(
-          method_holder.planned_buffers.back().data(), buffer_size);
+    runtime::HierarchicalAllocator* planned_memory = nullptr;
+
+    // we were not given a planned memory allocator, so we need to create one:
+    if (planned_memory_allocator == nullptr) {
+      const auto method_metadata =
+          ET_UNWRAP(program_->method_meta(method_name.c_str()));
+      const auto planned_buffersCount =
+          method_metadata.num_memory_planned_buffers();
+      method_holder.planned_buffers.reserve(planned_buffersCount);
+      method_holder.planned_spans.reserve(planned_buffersCount);
+
+      for (auto index = 0; index < planned_buffersCount; ++index) {
+        const auto buffer_size =
+            method_metadata.memory_planned_buffer_size(index).get();
+        method_holder.planned_buffers.emplace_back(buffer_size);
+        method_holder.planned_spans.emplace_back(
+            method_holder.planned_buffers.back().data(), buffer_size);
+      }
+      method_holder.planned_memory =
+          std::make_unique<runtime::HierarchicalAllocator>(runtime::Span(
+              method_holder.planned_spans.data(),
+              method_holder.planned_spans.size()));
+      planned_memory = method_holder.planned_memory.get();
+    } else {
+      // we were given a planned memory allocator, so we use it:
+      planned_memory = planned_memory_allocator;
     }
-    method_holder.planned_memory =
-        std::make_unique<runtime::HierarchicalAllocator>(runtime::Span(
-            method_holder.planned_spans.data(),
-            method_holder.planned_spans.size()));
+
     method_holder.memory_manager = std::make_unique<runtime::MemoryManager>(
-        memory_allocator_.get(),
-        method_holder.planned_memory.get(),
-        temp_allocator_.get());
+        memory_allocator_.get(), planned_memory, temp_allocator_.get());
     method_holder.method = ET_UNWRAP_UNIQUE(program_->load_method(
         method_name.c_str(),
         method_holder.memory_manager.get(),

extension/module/module.h

@@ -143,7 +143,8 @@ class Module {
   ET_NODISCARD
   runtime::Error load_method(
       const std::string& method_name,
-      torch::executor::EventTracer* event_tracer = nullptr);
+      torch::executor::EventTracer* event_tracer = nullptr,
+      runtime::HierarchicalAllocator* planned_memory_allocator = nullptr);
 
   /**
    * Load the 'forward' method from the program and set up memory management if