zhiics commented on a change in pull request #4771: [Relay] Added Merge Composite pass URL: https://github.com/apache/incubator-tvm/pull/4771#discussion_r375530819
########## File path: src/relay/pass/merge_composite.cc ########## @@ -0,0 +1,205 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ + +/*! + * \file src/relay/pass/merge_composite.cc + * \brief Merges expressions matching patterns into functions marked + * as 'composite'. This is primarily intended to be used alongside the + * external codegen infrastructure to support the case where multiple + * Relay operators map to a single external operator. + */ + +#include <tvm/te/operation.h> +#include <tvm/relay/analysis.h> +#include <tvm/relay/expr_functor.h> +#include <tvm/relay/op_attr_types.h> +#include <tvm/relay/transform.h> + +namespace tvm { +namespace relay { +namespace merge_composite { + + +class MergeCompositeWrapper : public ExprMutator { + public: + explicit MergeCompositeWrapper(const std::string& pattern_name, const Expr& pattern) + : pattern_name_(pattern_name), pattern_(pattern) {} + + Expr ExtractPattern(const Var& pattern, const Expr& root, + Map<std::string, Array<Expr>>* var_map) { + if (var_map->find(pattern->name_hint()) == var_map->end()) { + // if we haven't encountered this var yet, make a new free var and associate + // it with the value at 'root' + auto free_var = VarNode::make(pattern->name_hint(), Type()); + var_map->Set(pattern->name_hint(), Array<Expr>({free_var, root})); + return std::move(free_var); + } else { + // if we have encountered this var already, return the free var that was created + return (*var_map)[pattern->name_hint()][0]; + } + } + + Expr ExtractPattern(const Constant& pattern, const Expr& root, + Map<std::string, Array<Expr>>* var_map) { + return root; + } + + /* How does this work? + * + * A pattern consists of Relay expression containing only operator call nodes, constants + * and free variables. The free variables indicate where the pattern can 'attach' in your + * graph. This function takes the final call node of the pattern and the call node currently + * being traversed in the Relay graph. It traverses through the pattern in lockstep with call node + * from the graph (referred to as the 'root' node here) to check they're identical. If at any point + * they differ, an empty expression is returned to signify the extract failed. If a free var is + * reached in the pattern, the corresponding value in the root is associated with the name of the + * free var (via the var_map) so that when we construct the composite function, the inputs match + * up correctly with the rest of the graph. The return value of this function when successful is + * a new Relay expression ready to be wrapped into a composite function. + */ + Expr ExtractPattern(const Call& pattern, const Call& root, + Map<std::string, Array<Expr>>* var_map) { + // check to make sure both calls are to operators (not functions) + if (!pattern->op->IsInstance<OpNode>() || !root->op->IsInstance<OpNode>()) + return Expr(); + if (pattern->op.as<OpNode>()->name != root->op.as<OpNode>()->name) + return Expr(); + + unsigned int i = 0; + Array<Expr> new_args; + for (const auto& arg : pattern->args) { + Expr new_arg; + if (arg->IsInstance<CallNode>()) { + // fail if the root argument is not also a call node + if (!root->args[i]->IsInstance<CallNode>()) { + return Expr(); + } + // if it's a call node, recursively call this function + new_arg = ExtractPattern(Downcast<Call>(arg), + Downcast<Call>(root->args[i]), + var_map); + } else if (arg->IsInstance<VarNode>()) { + // if there's a var in the pattern, it must be a free var + // so call the function to update the var_map + new_arg = ExtractPattern(Downcast<Var>(arg), + root->args[i], + var_map); + } else if (arg->IsInstance<ConstantNode>()) { + // if there's a constant, simply get the corresponding + // value of the constant from the root + new_arg = ExtractPattern(Downcast<Constant>(arg), + root->args[i], + var_map); + } + if (!new_arg.defined()) { + return Expr(); + } + new_args.push_back(new_arg); + i++; + } + return CallNode::make(root->op, new_args, root->attrs); + } + + Expr VisitExpr_(const CallNode* cn) { + Call call = GetRef<Call>(cn); + if (call->op->IsInstance<FunctionNode>()) { + Function func = Downcast<Function>(call->op); + CHECK(func.defined()); + const auto name_node = FunctionGetAttr(func, attr::kComposite).as<tir::StringImmNode>(); + // don't step into existing composite functions + if (name_node->value != "") { + tvm::Array<tvm::relay::Expr> new_args; + for (const auto& arg : call->args) { + auto new_e = this->Mutate(arg); + new_args.push_back(new_e); + } + return CallNode::make(call->op, new_args, call->attrs); + } + } + + Expr expr = ExprMutator::VisitExpr_(cn); + call = Downcast<Call>(expr); + if (!call->op->IsInstance<OpNode>()) + return std::move(call); + + // only call patterns are supported + Call pattern = Downcast<Call>(pattern_); + CHECK(pattern.defined()); + Map<std::string, Array<Expr>> args_map; + auto extract = ExtractPattern(pattern, call, &args_map); + if (extract.defined()) { + auto free_vars = FreeVars(extract); + // make the composite function + auto f = FunctionNode::make(free_vars, extract, call->checked_type_, {}, Attrs()); + f = FunctionSetAttr(f, attr::kComposite, tir::StringImmNode::make(pattern_name_)); + f = FunctionSetAttr(f, attr::kPrimitive, tvm::Integer(1)); + // find the expressions associated with the free vars using the args_map + // this tells us which expressions should be given as inputs to the composite function + Array<Expr> args; + for (const auto& free_var : free_vars) { + args.push_back(args_map[free_var->name_hint()][1]); + } + auto new_call = CallNode::make(f, args); + return std::move(new_call); + } + return std::move(call); + } + + private: + /*! \brief The name of the pattern to match */ + std::string pattern_name_; + /*! \brief The pattern to match */ + Expr pattern_; +}; + +Expr MergeComposite(const Expr& expr, + const Array<tir::StringImm>& pattern_names, const Array<Expr>& patterns) { + CHECK(pattern_names.size() == patterns.size()); Review comment: CHECK_EQ ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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