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// Copyright (c) 2018 Google LLC.
//
// Licensed 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.
#ifndef SOURCE_OPT_LICM_PASS_H_
#define SOURCE_OPT_LICM_PASS_H_
#include "opt/basic_block.h"
#include "opt/instruction.h"
#include "opt/loop_descriptor.h"
#include "opt/pass.h"
#include <queue>
namespace spvtools {
namespace opt {
class LICMPass : public Pass {
public:
LICMPass() {}
const char* name() const override { return "loop-invariant-code-motion"; }
Status Process(ir::IRContext*) override;
private:
// Searches the IRContext for functions and processes each, moving invariants
// outside loops within the function where possible
// Returns true if a change was made to a function within the IRContext
bool ProcessIRContext();
// Checks the function for loops, calling ProcessLoop on each one found.
// Returns true if a change was made to the function, false otherwise.
bool ProcessFunction(ir::Function* f);
// Checks for invariants in the loop and attempts to move them to the loops
// preheader. Works from inner loop to outer when nested loops are found.
// Returns true if a change was made to the loop, false otherwise.
bool ProcessLoop(ir::Loop* loop, ir::Function* f);
// Analyses each instruction in |bb|, hoisting invariants to |pre_header_bb|.
// Each child of |bb| wrt to |dom_tree| is pushed to |loop_bbs|
bool AnalyseAndHoistFromBB(ir::Loop* loop, ir::Function* f,
ir::BasicBlock* bb,
std::vector<ir::BasicBlock*>* loop_bbs);
// Returns true if |bb| is immediately contained in |loop|
bool IsImmediatelyContainedInLoop(ir::Loop* loop, ir::Function* f,
ir::BasicBlock* bb);
// Move the instruction to the given BasicBlock
// This method will update the instruction to block mapping for the context
void HoistInstruction(ir::Loop* loop, ir::Instruction* inst);
};
} // namespace opt
} // namespace spvtools
#endif // SOURCE_OPT_LICM_PASS_H_
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