feat(compression): allocate resource variables in persistent buffer

Allocate resource variables in a persistent buffer when the input
tensor is compressed. Extend tests to validate operation.

BUG=part of #2636

tensorflow/lite/micro/kernels/assign_variable.cc

@@ -1,4 +1,4 @@
-/* Copyright 2021 The TensorFlow Authors. All Rights Reserved.
+/* Copyright 2024 The TensorFlow Authors. All Rights Reserved.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -26,6 +26,7 @@ limitations under the License.
 #include "tensorflow/lite/micro/micro_graph.h"
 #include "tensorflow/lite/micro/micro_log.h"
 #include "tensorflow/lite/micro/micro_resource_variable.h"
+#include "tensorflow/lite/micro/micro_utils.h"
 #include "tensorflow/lite/schema/schema_generated.h"
 
 namespace tflite {
@@ -35,6 +36,20 @@ namespace {
 constexpr int kInputVariableId = 0;
 constexpr int kInputValue = 1;
 
+#ifdef USE_TFLM_COMPRESSION
+
+struct OpData {
+  // scratch buffer for compressed input tensor
+  int scratch_index;
+};
+
+void* Init(TfLiteContext* context, const char* buffer, size_t length) {
+  TFLITE_DCHECK(context->AllocatePersistentBuffer != nullptr);
+  return context->AllocatePersistentBuffer(context, sizeof(OpData));
+}
+
+#endif  // USE_TFLM_COMPRESSION
+
 TfLiteStatus Prepare(TfLiteContext* context, TfLiteNode* node) {
   TF_LITE_ENSURE_EQ(context, NumInputs(node), 2);
   TF_LITE_ENSURE_EQ(context, NumOutputs(node), 0);
@@ -70,6 +85,17 @@ TfLiteStatus Prepare(TfLiteContext* context, TfLiteNode* node) {
                                           context, input_value));
   }
 
+#ifdef USE_TFLM_COMPRESSION
+
+  TFLITE_DCHECK(node->user_data != nullptr);
+  OpData* data = static_cast<OpData*>(node->user_data);
+  // Compression scratch buffers.
+  // These will only be allocated if the tensor is compressed.
+  data->scratch_index =
+      micro_context->AllocateDecompressionScratchBuffer(node, kInputValue);
+
+#endif  // USE_TFLM_COMPRESSION
+
   micro_context->DeallocateTempTfLiteTensor(input_value);
   return kTfLiteOk;
 }
@@ -93,15 +119,36 @@ TfLiteStatus Eval(TfLiteContext* context, TfLiteNode* node) {
         "ResourceVariables and pass it to the interpreter.");
     return kTfLiteError;
   }
+
+#ifdef USE_TFLM_COMPRESSION
+  OpData* data = static_cast<OpData*>(node->user_data);
+  const CompressionTensorData* comp_td =
+      micro_context->GetTensorCompressionData(node, kInputValue);
+  const void* buffer = tflite::micro::GetTensorData<void>(
+      micro_context, input_value, comp_td, data->scratch_index);
+#else   // USE_TFLM_COMPRESSION
+  const void* buffer = tflite::micro::GetTensorData<void>(input_value);
+#endif  // USE_TFLM_COMPRESSION
+
   TF_LITE_ENSURE_OK(context,
-                    resources->Assign(input_id->data.i32[0], input_value));
+                    resources->Assign(input_id->data.i32[0],
+                                      EvalTensorBytes(input_value), buffer));
   return kTfLiteOk;
 }
 
 }  // namespace.
 
+#ifdef USE_TFLM_COMPRESSION
+
+TFLMRegistration Register_ASSIGN_VARIABLE() {
+  return tflite::micro::RegisterOp(Init, Prepare, Eval);
+
+#else  // USE_TFLM_COMPRESSION
+
 TFLMRegistration Register_ASSIGN_VARIABLE() {
   return tflite::micro::RegisterOp(nullptr, Prepare, Eval);
+
+#endif  // USE_TFLM_COMPRESSION
 }
 
 }  // namespace tflite

tensorflow/lite/micro/micro_resource_variable.cc

@@ -1,4 +1,4 @@
-/* Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+/* Copyright 2024 The TensorFlow Authors. All Rights Reserved.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -113,8 +113,8 @@ TfLiteStatus MicroResourceVariables::Allocate(int id, TfLiteContext* context,
   return kTfLiteOk;
 }
 
-TfLiteStatus MicroResourceVariables::Assign(int id,
-                                            const TfLiteEvalTensor* tensor) {
+TfLiteStatus MicroResourceVariables::Assign(int id, size_t count_bytes,
+                                            const void* input_buffer) {
   if (id < 0 || id >= num_resource_variables_) {
     MicroPrintf("Attempting to read non-existent resource variable %d", id);
     return kTfLiteError;
@@ -128,8 +128,9 @@ TfLiteStatus MicroResourceVariables::Assign(int id,
         "with a TfLiteTensor first.");
     return kTfLiteError;
   }
-  TFLITE_DCHECK(EvalTensorBytes(tensor) == variable.bytes);
-  memcpy(variable.resource_buffer, tensor->data.raw, variable.bytes);
+  TFLITE_DCHECK(count_bytes == variable.bytes);
+  TFLITE_DCHECK(input_buffer != nullptr);
+  memcpy(variable.resource_buffer, input_buffer, variable.bytes);
   return kTfLiteOk;
 }
 

tensorflow/lite/micro/micro_resource_variable.h

@@ -1,4 +1,4 @@
-/* Copyright 2021 The TensorFlow Authors. All Rights Reserved.
+/* Copyright 2024 The TensorFlow Authors. All Rights Reserved.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -46,10 +46,10 @@ class MicroResourceVariables {
   TfLiteStatus Allocate(int id, TfLiteContext* context,
                         const TfLiteTensor* tensor);
 
-  // Copies input tensor contents to the resource buffer.
+  // Copies input_buffer contents to the resource buffer.
   // AllocateResourceVariable with a TFLite tensor must have been called first
   // in order to allocate the resource buffer.
-  TfLiteStatus Assign(int id, const TfLiteEvalTensor* tensor);
+  TfLiteStatus Assign(int id, size_t count_bytes, const void* input_buffer);
 
   // Zeros out all resource buffers.
   TfLiteStatus ResetAll();

tensorflow/lite/micro/micro_resource_variable_test.cc

@@ -1,4 +1,4 @@
-/* Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+/* Copyright 2024 The TensorFlow Authors. All Rights Reserved.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@ limitations under the License.
 #include "tensorflow/lite/micro/micro_resource_variable.h"
 
 #include "tensorflow/lite/c/common.h"
+#include "tensorflow/lite/micro/micro_utils.h"
 #include "tensorflow/lite/micro/test_helpers.h"
 #include "tensorflow/lite/micro/testing/micro_test.h"
 
@@ -120,7 +121,9 @@ TF_LITE_MICRO_TEST(VerifyAssignAndReadResourceBuffer) {
 
       .type = kTfLiteFloat32,
   };
-  resource_variables->Assign(id, &assign_tensor);
+  resource_variables->Assign(
+      id, tflite::EvalTensorBytes(&assign_tensor),
+      tflite::micro::GetTensorData<void>(&assign_tensor));
 
   int32_t buffer[32];
   TfLiteEvalTensor read_tensor = {