131 lines
4.3 KiB
C++
131 lines
4.3 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_CONST_FOLDING_RULES_H_
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#define SOURCE_OPT_CONST_FOLDING_RULES_H_
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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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// Constant Folding Rules:
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//
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// The folding mechanism is built around the concept of a |ConstantFoldingRule|.
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// A constant folding rule is a function that implements a method of simplifying
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// an instruction to a constant.
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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 constant folding rule returns a pointer to an Constant if |inst| can be
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// simplified using this rule. Otherwise, it returns |nullptr|.
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//
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// See const_folding_rules.cpp for examples on how to write a constant folding
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// rule.
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//
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// Be sure to add new constant folding rules to the table of constant folding
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// rules in the constructor for ConstantFoldingRules. The new rule should be
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// added to the list for every opcode that it applies to. Note that earlier
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// rules in the list are given priority. That is, if an earlier rule is able to
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// fold an instruction, the later rules will not be attempted.
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using ConstantFoldingRule = std::function<const analysis::Constant*(
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IRContext* ctx, Instruction* inst,
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const std::vector<const analysis::Constant*>& constants)>;
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class ConstantFoldingRules {
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protected:
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// The |Key| and |Value| structs are used to by-pass a "decorated name length
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// exceeded, name was truncated" warning on VS2013 and VS2015.
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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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struct Value {
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std::vector<ConstantFoldingRule> value;
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void push_back(ConstantFoldingRule rule) { value.push_back(rule); }
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};
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public:
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ConstantFoldingRules(IRContext* ctx) : context_(ctx) {}
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virtual ~ConstantFoldingRules() = default;
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// Returns true if there is at least 1 folding rule for |opcode|.
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bool HasFoldingRule(const Instruction* inst) const {
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return !GetRulesForInstruction(inst).empty();
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}
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// Returns true if there is at least 1 folding rule for |inst|.
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const std::vector<ConstantFoldingRule>& GetRulesForInstruction(
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const Instruction* inst) const {
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if (inst->opcode() != SpvOpExtInst) {
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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.value;
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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.value;
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}
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}
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return empty_vector_;
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}
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// Add the folding rules.
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virtual void AddFoldingRules();
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protected:
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// |rules[opcode]| is the set of rules that can be applied to instructions
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// with |opcode| as the opcode.
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std::unordered_map<uint32_t, Value> rules_;
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// The folding rules for extended instructions.
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std::map<Key, Value> ext_rules_;
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private:
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// The context that the instruction to be folded will be a part of.
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IRContext* context_;
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// The empty set of rules to be used as the default return value in
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// |GetRulesForInstruction|.
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std::vector<ConstantFoldingRule> 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_CONST_FOLDING_RULES_H_
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