[RELAY][BYOC] Support composite functions in AnnotateTarget

This patch introduces support to annotate composite functions
in the AnnotateTarget pass. In order for a composite function
to be annotated, you should name it according to the style:

{codegen}.{name}
eg. dnnl.add_relu

Change-Id: I73d6c0b506153d866f6d1feb203b32dad59f2871

src/relay/transforms/annotate_target.cc

@@ -49,10 +49,25 @@ class AnnotateTargetWrapper : public ExprMutator {
     if (expr->IsInstance<CallNode>()) {
       Call call = Downcast<Call>(expr);
       auto fannotate = Op::GetAttr<FTVMAnnotateTarget>("target." + target_);
-      Op op = Downcast<Op>(call->op);
-      CHECK(op.defined());
-      if (fannotate.count(op)) {
-        return fannotate[op](call->attrs, call->args);
+      if (call->op->IsInstance<OpNode>()) {
+        Op op = Downcast<Op>(call->op);
+        CHECK(op.defined());
+        if (fannotate.count(op)) {
+          return fannotate[op](call->attrs, call->args);
+        }
+      }
+      // handle composite functions
+      else if (call->op->IsInstance<FunctionNode>()) {
+        Function func = Downcast<Function>(call->op);
+        CHECK(func.defined());
+        auto comp_name = func->GetAttr<tir::StringImm>(attr::kComposite);
+        if (comp_name.defined()) {
+          size_t i = comp_name->value.find('.');
+          if(i != std::string::npos) {
+            std::string target = comp_name->value.substr(0, i);
+            if (target == target_) return true;
+          }
+        }
       }
     }
     if (expr->IsInstance<TupleGetItemNode>()) {
@@ -77,7 +92,6 @@ class AnnotateTargetWrapper : public ExprMutator {
   }
 
   Expr VisitExpr_(const CallNode* cn) {
-    // TODO(@zhiics, @comaniac) Handle composite functions.
     auto new_e = ExprMutator::VisitExpr_(cn);
 
     Call call = Downcast<Call>(new_e);
@@ -130,13 +144,22 @@ class AnnotateTargetWrapper : public ExprMutator {
     }
   }
 
-  Expr VisitExpr_(const FunctionNode* op) {
-    auto new_e = ExprMutator::VisitExpr_(op);
+  Expr VisitExpr_(const FunctionNode* fn) {
+    Function func;
+    Expr new_body;
+    // don't step into composite functions
+    if (fn->GetAttr<tir::StringImm>(attr::kComposite).defined()) {
+      func = GetRef<Function>(fn);
+      new_body = func->body;
+    } else {
+      auto new_e = ExprMutator::VisitExpr_(fn);
+      func = Downcast<Function>(new_e);
+      new_body = InsertEnd(func->body);
+    }
 
-    auto func = Downcast<Function>(new_e);
     return Function(
       func->params,
-      InsertEnd(func->body),
+      new_body,
       func->ret_type,
       func->type_params,
       func->attrs);

tests/python/relay/test_annotate_target.py

@@ -219,7 +219,53 @@ def after():
     assert tvm.ir.structural_equal(expected, result)
 
 
+def test_composite_function():
+    def before():
+        a = relay.var('a', shape=(10, 10))
+        b = relay.var('b', shape=(10, 10))
+
+        # add_relu function
+        in_1 = relay.var('in_1', shape=(10, 10))
+        in_2 = relay.var('in_2', shape=(10, 10))
+        add_node = relay.add(in_1, in_2)
+        relu_node = relay.nn.relu(add_node)
+        add_relu = relay.Function([in_1, in_2], relu_node)
+        add_relu = add_relu.with_attr("Composite", tvm.tir.StringImm("test.add_relu"))
+
+        # merged function
+        r = relay.Call(add_relu, [a, b])
+        f = relay.Function([a, b], r)
+        mod = tvm.IRModule.from_expr(f)
+        return mod
+
+    def after():
+        a = relay.var('a', shape=(10, 10))
+        b = relay.var('b', shape=(10, 10))
+
+        # add_relu function
+        in_1 = relay.var('in_1', shape=(10, 10))
+        in_2 = relay.var('in_2', shape=(10, 10))
+        add_node = relay.add(in_1, in_2)
+        relu_node = relay.nn.relu(add_node)
+        add_relu = relay.Function([in_1, in_2], relu_node)
+        add_relu = add_relu.with_attr("Composite", tvm.tir.StringImm("test.add_relu"))
+
+        # merged function
+        cb_1 = relay.annotation.compiler_begin(a, "test")
+        cb_2 = relay.annotation.compiler_begin(b, "test")
+        r = relay.Call(add_relu, [cb_1, cb_2])
+        ce_1 = relay.annotation.compiler_end(r, "test")
+        f = relay.Function([a, b], ce_1)
+        mod = tvm.IRModule.from_expr(f)
+        return mod
+
+    result = transform.AnnotateTarget("test")(before())
+    expected = transform.InferType()(after())
+    assert tvm.ir.structural_equal(expected, result)
+
+
 if __name__ == "__main__":
     test_multiple_ends()
     test_extern_dnnl()
     test_extern_dnnl_mobilenet()
+    test_composite_function()