Migrate C Interface API Generation to C++

Using the new name transformations added in apache#9088, the C interface API is now generated in C++ rather than in Python. This is intended to be a no-op for the actual users of this change and thus I've undone some of my overzealous sanitizing to match that expectation.

Follow up PRs will clean up any remaining name transformation inconsistencies.

Fixes apache#8792

python/tvm/micro/model_library_format.py

@@ -25,13 +25,14 @@
 import tarfile
 import typing
 
+import tvm
 from tvm.ir.type import TupleType
 from .._ffi import get_global_func
-from .interface_api import generate_c_interface_header
 from ..contrib import utils
 from ..driver import build_module
 from ..runtime import ndarray as _nd
 from ..relay.backend import executor_factory
+from ..relay.backend.name_transforms import to_c_variable_style, prefix_generated_name
 from ..relay import param_dict
 from ..tir import expr
 
@@ -43,6 +44,20 @@ class UnsupportedInModelLibraryFormatError(Exception):
     """Raised when export_model_library_format does not support the given Module tree."""
 
 
+def generate_c_interface_header(module_name, inputs, outputs, include_path):
+    """Generate C Interface header to be included in MLF"""
+    mangled_name = to_c_variable_style(prefix_generated_name(module_name))
+    metadata_header = os.path.join(include_path, f"{mangled_name}.h")
+
+    interface_c_create = tvm._ffi.get_global_func("runtime.InterfaceCCreate")
+    interface_c_module = interface_c_create(module_name, inputs, outputs)
+
+    with open(metadata_header, "w") as header_file:
+        header_file.write(interface_c_module.get_source())
+
+    return metadata_header
+
+
 def _populate_codegen_dir(mod, codegen_dir: str, module_name: str = None):
     """Populate the codegen sub-directory as part of a Model Library Format export.
 

python/tvm/relay/backend/name_transforms.py

@@ -48,6 +48,18 @@ def to_c_variable_style(original_name: str):
     return _backend.ToCVariableStyle(original_name)
 
 
+def to_c_constant_style(original_name: str):
+    """Transform a name to the C constant style assuming it is
+    appropriately constructed using the prefixing functions
+
+    Parameters
+    ----------
+    original_name : str
+        Original name to transform
+    """
+    return _backend.ToCConstantStyle(original_name)
+
+
 def _preprocess_names(names: Union[List[str], str]):
     """Preprocesses name strings into format for C++ functions
 

src/relay/backend/name_transforms.cc

@@ -62,6 +62,14 @@ std::string ToCVariableStyle(const std::string& original_name) {
   return variable_name;
 }
 
+std::string ToCConstantStyle(const std::string& original_name) {
+  ICHECK_EQ(original_name.find("TVM"), 0) << "Constant not TVM prefixed";
+  std::string constant_name = ToCVariableStyle(original_name);
+
+  std::transform(constant_name.begin(), constant_name.end(), constant_name.begin(), ::toupper);
+  return constant_name;
+}
+
 std::string CombineNames(const Array<String>& names) {
   std::stringstream combine_stream;
   ICHECK(!names.empty()) << "Name segments empty";
@@ -79,22 +87,16 @@ std::string CombineNames(const Array<String>& names) {
 std::string SanitizeName(const std::string& name) {
   ICHECK(!name.empty()) << "Name is empty";
 
-  auto multipleSeparators = [](char before, char after) {
-    return before == '_' && before == after;
-  };
   auto isNotAlnum = [](char c) { return !std::isalnum(c); };
   std::string sanitized_input = name;
   std::replace_if(sanitized_input.begin(), sanitized_input.end(), isNotAlnum, '_');
 
-  sanitized_input.erase(
-      std::unique(sanitized_input.begin(), sanitized_input.end(), multipleSeparators),
-      sanitized_input.end());
-
   return sanitized_input;
 }
 
 TVM_REGISTER_GLOBAL("relay.backend.ToCFunctionStyle").set_body_typed(ToCFunctionStyle);
 TVM_REGISTER_GLOBAL("relay.backend.ToCVariableStyle").set_body_typed(ToCVariableStyle);
+TVM_REGISTER_GLOBAL("relay.backend.ToCConstantStyle").set_body_typed(ToCConstantStyle);
 TVM_REGISTER_GLOBAL("relay.backend.PrefixName").set_body_typed(PrefixName);
 TVM_REGISTER_GLOBAL("relay.backend.PrefixGeneratedName").set_body_typed(PrefixGeneratedName);
 TVM_REGISTER_GLOBAL("relay.backend.SanitizeName").set_body_typed(SanitizeName);

src/relay/backend/name_transforms.h

@@ -35,6 +35,9 @@
  * ToCVariableStyle(PrefixGeneratedName(CombineNames({"model", "Devices"})))
  * // tvmgen_model_devices
  *
+ * ToCConstantStyle(PrefixGeneratedName(CombineNames({"model", "Devices"})))
+ * // TVMGEN_MODEL_DEVICES
+ *
  */
 
 #include <tvm/runtime/container/array.h>
@@ -68,6 +71,14 @@ std::string ToCFunctionStyle(const std::string& original_name);
  */
 std::string ToCVariableStyle(const std::string& original_name);
 
+/*!
+ * \brief Transform a name to the C constant style assuming it is
+ * appropriately constructed using the prefixing functions
+ * \param name Original name
+ * \return Transformed function in the C constant style
+ */
+std::string ToCConstantStyle(const std::string& original_name);
+
 /*!
  * \brief Combine names together for use as a generated name
  * \param names Vector of strings to combine

src/target/source/interface_c.cc

@@ -0,0 +1,137 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/*!
+ * \file interface_c.cc
+ * \brief Generates a C interface header for a given modules inputs and outputs
+ */
+
+#include <tvm/runtime/container/array.h>
+#include <tvm/runtime/container/string.h>
+#include <tvm/runtime/module.h>
+#include <tvm/runtime/packed_func.h>
+#include <tvm/runtime/registry.h>
+
+#include <string>
+
+#include "../../relay/backend/name_transforms.h"
+
+namespace tvm {
+namespace codegen {
+
+using runtime::PackedFunc;
+using namespace tvm::relay::backend;
+
+class InterfaceCNode : public runtime::ModuleNode {
+ public:
+  InterfaceCNode(std::string module_name, Array<String> inputs, Array<String> outputs)
+      : module_name_(module_name), inputs_(inputs), outputs_(outputs) {}
+  const char* type_key() const { return "h"; }
+
+  std::string GetSource(const std::string& format) final {
+    std::stringstream code;
+
+    EmitUpperHeaderGuard(code);
+    EmitBrief(code, "Input tensor pointers");
+    EmitStruct(code, "inputs", inputs_);
+    EmitBrief(code, "Output tensor pointers");
+    EmitStruct(code, "outputs", outputs_);
+    EmitRunFunction(code);
+    EmitLowerHeaderGuard(code);
+
+    return code.str();
+  }
+
+  PackedFunc GetFunction(const std::string& name, const ObjectPtr<Object>& sptr_to_self) final {
+    return PackedFunc(nullptr);
+  }
+
+ private:
+  void EmitUpperHeaderGuard(std::stringstream& code_stream) {
+    std::string header_guard_name = ToCConstantStyle(PrefixGeneratedName({module_name_, "H"}));
+    code_stream << "#ifndef " << header_guard_name << "_\n"
+                << "#define " << header_guard_name << "_\n"
+                << "#include <stdint.h>\n\n"
+                << "#ifdef __cplusplus\n"
+                << "extern \"C\" {\n"
+                << "#endif\n\n";
+  }
+
+  void EmitLowerHeaderGuard(std::stringstream& code_stream) {
+    std::string header_guard_name = ToCConstantStyle(PrefixGeneratedName({module_name_, "H"}));
+    code_stream << "\n#ifdef __cplusplus\n"
+                << "}\n"
+                << "#endif\n\n"
+                << "#endif // " << header_guard_name << "_\n";
+  }
+
+  void EmitBrief(std::stringstream& code_stream, const std::string& description) {
+    code_stream << "/*!\n"
+                << " * \\brief " << description << " for TVM module \"" << module_name_ << "\" \n"
+                << " */\n";
+  }
+
+  void EmitStruct(std::stringstream& code_stream, const std::string& suffix,
+                  Array<String> properties) {
+    std::string struct_name = ToCVariableStyle(PrefixGeneratedName({module_name_, suffix}));
+    code_stream << "struct " << struct_name << " {\n";
+
+    std::vector<std::string> sanitized_properties;
+    for (const String& property : properties) {
+      std::string sanitized_property = SanitizeName(property);
+      ICHECK(std::find(sanitized_properties.begin(), sanitized_properties.end(),
+                       sanitized_property) == sanitized_properties.end())
+          << "Sanitized input tensor name clash" << sanitized_property;
+      code_stream << "  void* " << sanitized_property << ";\n";
+      sanitized_properties.push_back(sanitized_property);
+    }
+    code_stream << "};\n\n";
+  }
+
+  void EmitRunFunction(std::stringstream& code_stream) {
+    std::string run_function = ToCVariableStyle(PrefixGeneratedName({module_name_, "run"}));
+    std::string inputs_struct = ToCVariableStyle(PrefixGeneratedName({module_name_, "inputs"}));
+    std::string outputs_struct = ToCVariableStyle(PrefixGeneratedName({module_name_, "outputs"}));
+
+    code_stream << "/*!\n"
+                << " * \\brief entrypoint function for TVM module \"" << module_name_ << "\"\n"
+                << " * \\param inputs Input tensors for the module \n"
+                << " * \\param outputs Output tensors for the module \n"
+                << " */\n"
+                << "int32_t " << run_function << "(\n"
+                << "  struct " << inputs_struct << "* inputs,\n"
+                << "  struct " << outputs_struct << "* outputs\n"
+                << ");\n";
+  }
+
+  std::string module_name_;
+  Array<String> inputs_;
+  Array<String> outputs_;
+};
+
+runtime::Module InterfaceCCreate(std::string module_name, Array<String> inputs,
+                                 Array<String> outputs) {
+  auto n = make_object<InterfaceCNode>(module_name, inputs, outputs);
+  return runtime::Module(n);
+}
+
+TVM_REGISTER_GLOBAL("runtime.InterfaceCCreate").set_body_typed(InterfaceCCreate);
+
+}  // namespace codegen
+}  // namespace tvm

tests/cpp/name_transforms_test.cc

@@ -42,6 +42,14 @@ TEST(NameTransforms, ToCVariableStyle) {
   EXPECT_THROW(ToCVariableStyle(""), InternalError);
 }
 
+TEST(NameTransforms, ToCConstantStyle) {
+  ASSERT_EQ(ToCConstantStyle("TVM_Woof"), "TVM_WOOF");
+  ASSERT_EQ(ToCConstantStyle("TVM_woof"), "TVM_WOOF");
+  ASSERT_EQ(ToCConstantStyle("TVM_woof_Woof"), "TVM_WOOF_WOOF");
+  EXPECT_THROW(ToCConstantStyle("Cake_Bakery"), InternalError);  // Incorrect prefix
+  EXPECT_THROW(ToCConstantStyle(""), InternalError);
+}
+
 TEST(NameTransforms, PrefixName) {
   ASSERT_EQ(PrefixName({"Woof"}), "TVM_Woof");
   ASSERT_EQ(PrefixName({"woof"}), "TVM_woof");
@@ -71,10 +79,10 @@ TEST(NameTransforms, CombineNames) {
 }
 
 TEST(NameTransforms, SanitizeName) {
-  ASSERT_EQ(SanitizeName("+_+ "), "_");
+  ASSERT_EQ(SanitizeName("+_+ "), "____");
   ASSERT_EQ(SanitizeName("input+"), "input_");
   ASSERT_EQ(SanitizeName("input-"), "input_");
-  ASSERT_EQ(SanitizeName("input++"), "input_");
+  ASSERT_EQ(SanitizeName("input++"), "input__");
   ASSERT_EQ(SanitizeName("woof:1"), "woof_1");
   EXPECT_THROW(SanitizeName(""), InternalError);
 }