[GitHub] [tvm] Mousius commented on a change in pull request #8423: Implementation of relay_to_tir target hook

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

Mousius commented on a change in pull request #8423:
URL: https://github.com/apache/tvm/pull/8423#discussion_r708476290



##########
File path: src/relay/backend/te_compiler.cc
##########
@@ -185,16 +192,25 @@ class TECompilerImpl : public TECompilerNode {
     }
     cur_ccache_key_ = key;
 
-    // No need to lower external functions for now. We will invoke the external
-    // codegen tool once and lower all functions together.
     if (key->source_func->GetAttr<String>(attr::kCompiler).defined()) {
       auto ir_module = IRModule();
       const auto name_node = key->source_func->GetAttr<String>(tvm::attr::kGlobalSymbol);
       ICHECK(name_node.defined()) << "External function has not been attached a name yet.";
+
       auto func_name = GetUniqueName(name_node.value(), &name_map_);
       auto target = Target("ext_dev");
       auto global_var = GlobalVar(func_name);
       global_var->checked_type_ = key->source_func->checked_type();
+
+      auto code_gen_name = key->source_func->GetAttr<String>(attr::kCompiler).value();
+      auto target_kind = tvm::TargetKind::Get(code_gen_name);
+      auto custom_lowering_to_tir =
+          target_kind ? target_kind.value().GetRegisteredHook("relay_to_tir") : nullptr;
+      if (custom_lowering_to_tir != nullptr) {
+        target = key->target;
+        ir_module->Update((*custom_lowering_to_tir)(key->source_func, key->target));
+      }
+

Review comment:
       Regarding the `Target`, is your proposal an `AnnotateTargets` pass which goes through `device_context_map_` and annotates all the call sites ahead of `LowerTE` and other passes? If this was just implemented for `Call` would that be sufficient for current `LowerTE` ? We'd still need to explicitly annotate `host_target` on the `IRModule`.
   
   The `relay_to_runtime` in https://github.com/apache/tvm-rfcs/pull/10/files registers the external codegen (code name BYOC) as `Target` hooks and then it's a matter of changing `kCompiler` to `kTarget`, so I think that's included in implementation of that RFC :smile_cat: 




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