[GitHub] [tvm] areusch commented on a change in pull request #6917: Add Relay option to link parameters into runtime Modules

[GitBox <gi...@apache.org>]

areusch commented on a change in pull request #6917:
URL: https://github.com/apache/tvm/pull/6917#discussion_r529659051



##########
File path: src/target/source/codegen_c_host.cc
##########
@@ -57,6 +60,48 @@ void CodeGenCHost::AddFunction(const PrimFunc& f) {
   CodeGenC::AddFunction(f);
 }
 
+void CodeGenCHost::LinkParameters(Map<String, LinkedParam> params) {
+  PrintFuncPrefix();
+  stream << " " << tvm::runtime::symbol::tvm_lookup_linked_param
+         << "(void* args, int* arg_type_ids, int num_args, void* out_ret_value, "
+         << "int* out_ret_tcode, void* resource_handle) {\n";
+  ICHECK_EQ(GetUniqueName(tvm::runtime::symbol::tvm_lookup_linked_param),
+            tvm::runtime::symbol::tvm_lookup_linked_param)
+      << "builtin PackedFunc name already taken: " << tvm::runtime::symbol::tvm_lookup_linked_param;
+  stream << "    switch (((int64_t*) args)[0]) {\n"
+         << "    default:\n"
+         << "        out_ret_tcode[0] = " << kTVMNullptr << ";\n"
+         << "        return 0;\n";
+
+  function_names_.emplace_back(tvm::runtime::symbol::tvm_lookup_linked_param);
+  for (auto kv : params) {
+    decl_stream << "\n"
+                << "#ifdef __cplusplus\n"
+                << "extern \"C\" {\n"
+                << "#endif\n"
+                << "static const ";
+    int64_t num_elements = 1;
+    for (int64_t dim : kv.second->param.Shape()) {
+      num_elements *= dim;
+    }
+    PrintType(kv.second->param.DataType(), decl_stream);
+    decl_stream << " " << ::tvm::runtime::symbol::tvm_param_prefix << kv.first << "["
+                << num_elements << "] = {\n";
+    NDArrayDataToC(kv.second->param, 4, decl_stream);
+    decl_stream << "};\n"
+                << "#ifdef __cplusplus\n"
+                << "}  // extern \"C\"\n"
+                << "#endif\n";
+    stream << "    case " << kv.second->id << ":\n"
+           << "        ((uint64_t*)out_ret_value)[0] = (uint64_t) (uintptr_t) "
+           << ::tvm::runtime::symbol::tvm_param_prefix << kv.first << ";\n"
+           << "        out_ret_tcode[0] = " << kTVMOpaqueHandle << ";\n"
+           << "        return 0;\n";

Review comment:
       it would be nice to return a specific error code here (this was my original implementation), but unfortunately it's not easy to catch on the other side. we need to do a bit more legwork to be able to catch specific function return values in c++/python. as it stands, returning nullptr from this function is specific enough, and has the benefit that an exception flow isn't triggered by default for non-parameters.




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