support AnnotateTarget multiple runs

src/relay/transforms/annotate_target.cc

@@ -33,8 +33,12 @@ namespace tvm {
 namespace relay {
 namespace annotate_target {
 
-const PackedFunc* begin_op = runtime::Registry::Get("relay.op.annotation._make.compiler_begin");
-const PackedFunc* end_op = runtime::Registry::Get("relay.op.annotation._make.compiler_end");
+static const Op& compiler_begin_op = Op::Get("annotation.compiler_begin");
+static const Op& compiler_end_op = Op::Get("annotation.compiler_end");
+
+const PackedFunc* make_begin_op =
+    runtime::Registry::Get("relay.op.annotation._make.compiler_begin");
+const PackedFunc* make_end_op = runtime::Registry::Get("relay.op.annotation._make.compiler_end");
 
 // A helper class to insert annotation boundaries for a program region that will
 // be handled by a specific compiler.
@@ -59,26 +63,40 @@ class AnnotateTargetWrapper : public ExprMutator {
     std::string ref_target = "";
     Array<Expr> compiler_ends;
     for (auto arg : args) {
-      if (op_expr_to_target_.find(arg) != op_expr_to_target_.end()) {
-        std::string arg_target = op_expr_to_target_[arg];
-        compiler_ends.push_back(InsertAnnotation(arg, arg_target, end_op));
-        if (ref_target == "") {
-          ref_target = arg_target;
-        } else if (ref_target != arg_target) {
-          ref_target = "default";
+      std::string arg_target = "defualt";
+      const CallNode* call = arg.as<CallNode>();
+
+      if (call && call->op == compiler_begin_op) {
+        // Argument is already compiler begin node meaning that this is not the first time
+        // running this pass, so we simply remove it and will add a new one later.
+        CHECK_EQ(call->args.size(), 1U);
+        const CallNode* end = call->args[0].as<CallNode>();
+        if (end->op == compiler_end_op) {
+          arg_target = end->attrs.as<CompilerAttrs>()->compiler;
         }
+        compiler_ends.push_back(call->args[0]);
+      } else if (op_expr_to_target_.find(arg) != op_expr_to_target_.end()) {
+        arg_target = op_expr_to_target_[arg];
+        compiler_ends.push_back(InsertAnnotation(arg, arg_target, make_end_op));
       } else {
         // Input vars.
         compiler_ends.push_back(arg);
       }
+
+      // Maintain reference target in case the target of the current node is unassigned.
+      if (ref_target == "") {
+        ref_target = arg_target;
+      } else if (ref_target != arg_target) {
+        ref_target = "default";
+      }
     }
 
     // Determine compiler begin target.
     std::string op_target = (target == "") ? ref_target : target;
 
     Array<Expr> compiler_begins;
     for (const auto& end : compiler_ends) {
-      compiler_begins.push_back(InsertAnnotation(end, op_target, begin_op));
+      compiler_begins.push_back(InsertAnnotation(end, op_target, make_begin_op));
     }
 
     return {op_target, compiler_begins};
@@ -94,8 +112,34 @@ class AnnotateTargetWrapper : public ExprMutator {
     // Supported targets for this node. The order implies the priority.
     std::vector<std::string> supported_targets;
 
+    auto op_node = cn->op.as<OpNode>();
+
+    // This graph has annotations, meaning that this is not the first time running this pass.
+    if (op_node && cn->op == compiler_begin_op) {
+      // Bypass compiler begin due to lack of target information. It will be processed
+      // when the following op handling arguments.
+      CHECK_EQ(cn->args.size(), 1U);
+      return VisitExpr(cn->args[0]);
+    } else if (op_node && cn->op == compiler_end_op) {
+      // Override compiler end with the new target.
+      CHECK_EQ(cn->args.size(), 1U);
+      auto input_expr = VisitExpr(cn->args[0]);
+      CHECK(op_expr_to_target_.find(input_expr) != op_expr_to_target_.end());
+      return InsertAnnotation(input_expr, op_expr_to_target_[input_expr], make_end_op);
+    }
+
+    // Peek the first argument. If it is compiler begin then this node had annotated by
+    // another target before, so we also consider that target as a supported target.
+    const CallNode* first_arg_call = cn->args[0].as<CallNode>();
+    if (first_arg_call && first_arg_call->op == compiler_begin_op) {
+      std::string arg_target = first_arg_call->attrs.as<CompilerAttrs>()->compiler;
+      if (arg_target != "default") {
+        supported_targets.push_back(arg_target);
+      }
+    }
+
     // Check which targets this op can be offloaded.
-    if (cn->op->IsInstance<OpNode>()) {
+    if (op_node) {
       // TVM operators: Check target specific op checking function and add to supported_targets
       // if it is supported.
       Op op = Downcast<Op>(cn->op);
@@ -179,7 +223,7 @@ class AnnotateTargetWrapper : public ExprMutator {
       func = Downcast<Function>(new_e);
       new_body = func->body;
       if (op_expr_to_target_.find(func->body) != op_expr_to_target_.end()) {
-        new_body = InsertAnnotation(func->body, op_expr_to_target_[func->body], end_op);
+        new_body = InsertAnnotation(func->body, op_expr_to_target_[func->body], make_end_op);
         op_expr_to_target_[new_body] = op_expr_to_target_[func->body];
       }
     }

tests/python/relay/test_pass_annotate_target.py

@@ -338,10 +338,37 @@ def after():
     assert tvm.ir.structural_equal(expected, result)
 
 
+def test_multiple_runs():
+    @reg.register("nn.relu", "target.A")
+    def relu(attrs, args):  # pylint: disable=unused-variable
+        return True
+
+    @reg.register("add", "target.B")
+    def add(attrs, args):  # pylint: disable=unused-variable
+        return True
+
+    def before():
+        x = relay.var("x", shape=(10, 5))
+        a_1 = relay.nn.relu(x)
+        a_2 = relay.abs(a_1)
+        a_3 = relay.nn.relu(a_1)
+        out = relay.add(a_2, a_3)
+
+        f = relay.Function([x], out)
+        mod = tvm.IRModule.from_expr(f)
+        return mod
+
+    mod = transform.AnnotateTarget("A")(before())
+    mod = transform.AnnotateTarget("B")(mod)
+    expected = transform.AnnotateTarget(["A", "B"])(before())
+    assert tvm.ir.structural_equal(expected, mod)
+
+
 if __name__ == "__main__":
     test_extern_dnnl()
     test_composite_function()
     #test_extern_dnnl_mobilenet()
     test_multiple_ends()
     test_type_propagation()
     test_tuple()
+    test_multiple_runs()