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.

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 +44,18 @@ 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())
+
+
 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

@@ -47,6 +47,18 @@ 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 prefix_name(names: Union[List[str], str]):
     """Apply TVM-specific prefix to a function name
 

src/relay/backend/name_transforms.cc

@@ -60,6 +60,13 @@ std::string ToCVariableStyle(const std::string& original_name) {
   return variable_name;
 }
 
+std::string ToCConstantStyle(const std::string& original_name) {
+  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());
@@ -77,22 +84,16 @@ std::string CombineNames(const Array<String>& names) {
 std::string SanitiseName(const std::string& name) {
   ICHECK(!name.empty());
 
-  auto multipleSeparators = [](char before, char after) {
-    return before == '_' && before == after;
-  };
   auto isNotAlnum = [](char c) { return !std::isalnum(c); };
   std::string sanitised_input = name;
   std::replace_if(sanitised_input.begin(), sanitised_input.end(), isNotAlnum, '_');
 
-  sanitised_input.erase(
-      std::unique(sanitised_input.begin(), sanitised_input.end(), multipleSeparators),
-      sanitised_input.end());
-
   return sanitised_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.SanitiseName").set_body_typed(SanitiseName);

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 +1,132 @@
+/*
+ * 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;
+    std::string mangled_module_name = ToCVariableStyle(PrefixGeneratedName({module_name_}));
+    std::string header_guard_name = ToCConstantStyle(PrefixGeneratedName({module_name_}));
+
+    EmitUpperHeaderGuard(code, header_guard_name);
+    EmitBrief(code, "Input tensor pointers");
+    EmitStruct(code, mangled_module_name, "inputs", inputs_);
+    EmitBrief(code, "Output tensor pointers");
+    EmitStruct(code, mangled_module_name, "outputs", outputs_);
+    EmitRunFunction(code, mangled_module_name);
+    EmitLowerHeaderGuard(code, header_guard_name);
+
+    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, const std::string& header_guard_name) {
+    code_stream << "#ifndef " << header_guard_name << "_H_\n"
+                << "#define " << header_guard_name << "_H_\n"
+                << "#include <stdint.h>\n\n"
+                << "#ifdef __cplusplus\n"
+                << "extern \"C\" {\n"
+                << "#endif\n\n";
+  }
+
+  void EmitLowerHeaderGuard(std::stringstream& code_stream, const std::string& header_guard_name) {
+    code_stream << "\n#ifdef __cplusplus\n"
+                << "}\n"
+                << "#endif\n\n"
+                << "#endif // " << header_guard_name << "_H_\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& mangled_module_name,
+                  const std::string& suffix, Array<String> properties) {
+    code_stream << "struct " << mangled_module_name << "_" << suffix << " {\n";
+
+    std::vector<std::string> sanitised_properties;
+    for (const String& property : properties) {
+      std::string sanitised_property = SanitiseName(property);
+      ICHECK(std::find(sanitised_properties.begin(), sanitised_properties.end(),
+                       sanitised_property) == sanitised_properties.end())
+          << "Sanitized input tensor name clash" << sanitised_property;
+      code_stream << "  void* " << sanitised_property << ";\n";
+      sanitised_properties.push_back(sanitised_property);
+    }
+    code_stream << "};\n\n";
+  }
+
+  void EmitRunFunction(std::stringstream& code_stream, const std::string& mangled_module_name) {
+    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 " << mangled_module_name << "_run(\n"
+                << "  struct " << mangled_module_name << "_inputs* inputs,\n"
+                << "  struct " << mangled_module_name << "_outputs* 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

@@ -40,6 +40,13 @@ 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(""), InternalError);
+}
+
 TEST(NameTransforms, PrefixName) {
   ASSERT_EQ(PrefixName({"Woof"}), "TVM_Woof");
   ASSERT_EQ(PrefixName({"woof"}), "TVM_woof");
@@ -69,10 +76,10 @@ TEST(NameTransforms, CombineNames) {
 }
 
 TEST(NameTransforms, SanitiseName) {
-  ASSERT_EQ(SanitiseName("+_+ "), "_");
+  ASSERT_EQ(SanitiseName("+_+ "), "____");
   ASSERT_EQ(SanitiseName("input+"), "input_");
   ASSERT_EQ(SanitiseName("input-"), "input_");
-  ASSERT_EQ(SanitiseName("input++"), "input_");
+  ASSERT_EQ(SanitiseName("input++"), "input__");
   ASSERT_EQ(SanitiseName("woof:1"), "woof_1");
   EXPECT_THROW(SanitiseName(""), InternalError);
 }