1/*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19
20/*!
21 *
22 * \file to_gnf.cc
23 *
24 * \brief Turn A normal form into graph normal form.
25 */
26#include <tvm/relay/analysis.h>
27#include <tvm/relay/expr_functor.h>
28#include <tvm/relay/transform.h>
29
30#include "let_list.h"
31
32namespace tvm {
33namespace relay {
34
35class UseVarVisitor : public ExprVisitor {
36 public:
37 explicit UseVarVisitor(const Var& v) : v(v) {}
38
39 static bool UseVar(const Var& v, const Expr& e) {
40 UseVarVisitor uv(v);
41 uv(e);
42 return uv.use_var;
43 }
44
45 private:
46 bool use_var = false;
47 Var v;
48
49 void VisitExpr_(const VarNode* vn) override { use_var = use_var || (v == GetRef<Var>(vn)); }
50};
51
52class GNF : public ExprMutator {
53 private:
54 std::unordered_map<Var, Expr, ObjectPtrHash, ObjectPtrEqual> var_map_;
55 Expr VisitExpr_(const VarNode* vn) override {
56 Var v = GetRef<Var>(vn);
57 return var_map_.count(v) == 0 ? v : var_map_.at(v);
58 }
59
60 static bool UseVar(const Var& v, const Expr& e) { return UseVarVisitor::UseVar(v, e); }
61
62 static Expr WrapRec(const Var& var, const Expr& val) {
63 return UseVar(var, val) ? Let(var, val, var) : val;
64 }
65
66 Expr VisitExpr_(const LetNode* ln) override {
67 var_map_.insert(std::pair<Var, Expr>(ln->var, WrapRec(ln->var, VisitExpr(ln->value))));
68 return VisitExpr(ln->body);
69 }
70};
71
72Expr ToGraphNormalForm(const Expr& e) { return GNF()(e); }
73
74namespace transform {
75
76Pass ToGraphNormalForm() {
77 runtime::TypedPackedFunc<Function(Function, IRModule, PassContext)> pass_func =
78 [=](Function f, IRModule m, PassContext pc) {
79 return Downcast<Function>(ToGraphNormalForm(f));
80 };
81 return CreateFunctionPass(pass_func, 1, "ToGraphNormalForm", {});
82}
83
84TVM_REGISTER_GLOBAL("relay._transform.ToGraphNormalForm").set_body_typed(ToGraphNormalForm);
85
86} // namespace transform
87
88} // namespace relay
89} // namespace tvm
90