125 lines
3.9 KiB
C++
125 lines
3.9 KiB
C++
// Copyright (c) 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef SOURCE_OPT_FOLDING_RULES_H_
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#define SOURCE_OPT_FOLDING_RULES_H_
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#include <cstdint>
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#include <unordered_map>
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#include <vector>
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#include "source/opt/constants.h"
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namespace spvtools {
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namespace opt {
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// Folding Rules:
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//
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// The folding mechanism is built around the concept of a |FoldingRule|. A
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// folding rule is a function that implements a method of simplifying an
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// instruction.
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//
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// The inputs to a folding rule are:
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// |inst| - the instruction to be simplified.
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// |constants| - if an in-operands is an id of a constant, then the
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// corresponding value in |constants| contains that
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// constant value. Otherwise, the corresponding entry in
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// |constants| is |nullptr|.
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//
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// A folding rule returns true if |inst| can be simplified using this rule. If
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// the instruction can be simplified, then |inst| is changed to the simplified
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// instruction. Otherwise, |inst| remains the same.
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//
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// See folding_rules.cpp for examples on how to write a folding rule. It is
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// important to note that if |inst| can be folded to the result of an
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// instruction that feed it, then |inst| should be changed to an OpCopyObject
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// that copies that id.
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//
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// Be sure to add new folding rules to the table of folding rules in the
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// constructor for FoldingRules. The new rule should be added to the list for
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// every opcode that it applies to. Note that earlier rules in the list are
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// given priority. That is, if an earlier rule is able to fold an instruction,
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// the later rules will not be attempted.
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using FoldingRule = std::function<bool(
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IRContext* context, Instruction* inst,
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const std::vector<const analysis::Constant*>& constants)>;
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class FoldingRules {
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public:
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using FoldingRuleSet = std::vector<FoldingRule>;
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explicit FoldingRules(IRContext* ctx) : context_(ctx) {}
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virtual ~FoldingRules() = default;
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const FoldingRuleSet& GetRulesForInstruction(Instruction* inst) const {
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if (inst->opcode() != spv::Op::OpExtInst) {
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auto it = rules_.find(inst->opcode());
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if (it != rules_.end()) {
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return it->second;
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}
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} else {
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uint32_t ext_inst_id = inst->GetSingleWordInOperand(0);
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uint32_t ext_opcode = inst->GetSingleWordInOperand(1);
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auto it = ext_rules_.find({ext_inst_id, ext_opcode});
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if (it != ext_rules_.end()) {
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return it->second;
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}
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}
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return empty_vector_;
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}
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IRContext* context() { return context_; }
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// Adds the folding rules for the object.
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virtual void AddFoldingRules();
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protected:
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struct hasher {
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size_t operator()(const spv::Op& op) const noexcept {
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return std::hash<uint32_t>()(uint32_t(op));
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}
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};
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// The folding rules for core instructions.
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std::unordered_map<spv::Op, FoldingRuleSet, hasher> rules_;
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// The folding rules for extended instructions.
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struct Key {
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uint32_t instruction_set;
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uint32_t opcode;
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};
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friend bool operator<(const Key& a, const Key& b) {
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if (a.instruction_set < b.instruction_set) {
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return true;
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}
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if (a.instruction_set > b.instruction_set) {
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return false;
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}
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return a.opcode < b.opcode;
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}
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std::map<Key, FoldingRuleSet> ext_rules_;
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private:
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IRContext* context_;
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FoldingRuleSet empty_vector_;
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};
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} // namespace opt
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} // namespace spvtools
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#endif // SOURCE_OPT_FOLDING_RULES_H_
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