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 * \file fast_math.cc
22 * \brief Replaces non linear activation functions with their fast but approximate counterparts.
23 */
24#include <tvm/relay/analysis.h>
25#include <tvm/relay/attrs/nn.h>
26#include <tvm/relay/expr_functor.h>
27#include <tvm/relay/op.h>
28#include <tvm/relay/transform.h>
29
30#include "pattern_utils.h"
31
32namespace tvm {
33namespace relay {
34
35class FastMathMutator : public ExprRewriter {
36 public:
37 FastMathMutator()
38 : exp_op_(Op::Get("exp")),
39 erf_op_(Op::Get("erf")),
40 tanh_op_(Op::Get("tanh")),
41 softmax_op_(Op::Get("nn.softmax")) {}
42
43 Expr Rewrite_(const CallNode* pre, const Expr& post) override {
44 if (pre->op == exp_op_) {
45 return FastExp(post.as<CallNode>()->args[0]);
46 } else if (pre->op == erf_op_) {
47 return FastErf(post.as<CallNode>()->args[0]);
48 } else if (pre->op == tanh_op_) {
49 return FastTanh(post.as<CallNode>()->args[0]);
50 } else if (pre->op == softmax_op_) {
51 return FastSoftmax(post.as<CallNode>()->args[0], post.as<CallNode>()->attrs);
52 }
53 return post;
54 }
55
56 private:
57 // Cache the following ops. They will be used in the passes repeatedly for
58 // operator equivalence checking so that the registry lookup overhead can be
59 // reduced.
60 const Op& exp_op_;
61 const Op& erf_op_;
62 const Op& tanh_op_;
63 const Op& softmax_op_;
64};
65
66Expr FastMath(const Expr& e) {
67 auto rewriter = FastMathMutator();
68 return PostOrderRewrite(e, &rewriter);
69}
70
71namespace transform {
72
73Pass FastMath() {
74 runtime::TypedPackedFunc<Function(Function, IRModule, PassContext)> pass_func =
75 [=](Function f, IRModule m, PassContext pc) { return Downcast<Function>(FastMath(f)); };
76 return CreateFunctionPass(pass_func, 4, "FastMath", {"InferType"});
77}
78
79TVM_REGISTER_GLOBAL("relay._transform.FastMath").set_body_typed(FastMath);
80
81} // namespace transform
82
83} // namespace relay
84} // namespace tvm
85