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/*
* Copyright (C) 2014 The Android Open Source Project
*
* 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 ART_COMPILER_OPTIMIZING_PARALLEL_MOVE_RESOLVER_H_
#define ART_COMPILER_OPTIMIZING_PARALLEL_MOVE_RESOLVER_H_
#include "base/value_object.h"
#include "utils/growable_array.h"
namespace art {
class HParallelMove;
class Location;
class MoveOperands;
/**
* Helper class to resolve a set of parallel moves. Architecture dependent code
* generator must have their own subclass that implements the `EmitMove` and `EmitSwap`
* operations.
*/
class ParallelMoveResolver : public ValueObject {
public:
explicit ParallelMoveResolver(ArenaAllocator* allocator) : moves_(allocator, 32) {}
virtual ~ParallelMoveResolver() {}
// Resolve a set of parallel moves, emitting assembler instructions.
void EmitNativeCode(HParallelMove* parallel_move);
protected:
class ScratchRegisterScope : public ValueObject {
public:
ScratchRegisterScope(ParallelMoveResolver* resolver,
int blocked,
int if_scratch,
int number_of_registers);
~ScratchRegisterScope();
int GetRegister() const { return reg_; }
bool IsSpilled() const { return spilled_; }
private:
ParallelMoveResolver* resolver_;
int reg_;
bool spilled_;
};
bool IsScratchLocation(Location loc);
// Allocate a scratch register for performing a move. The method will try to use
// a register that is the destination of a move, but that move has not been emitted yet.
int AllocateScratchRegister(int blocked, int if_scratch, int register_count, bool* spilled);
// Emit a move.
virtual void EmitMove(size_t index) = 0;
// Execute a move by emitting a swap of two operands.
virtual void EmitSwap(size_t index) = 0;
virtual void SpillScratch(int reg) = 0;
virtual void RestoreScratch(int reg) = 0;
// List of moves not yet resolved.
GrowableArray<MoveOperands*> moves_;
static constexpr int kNoRegister = -1;
private:
// Build the initial list of moves.
void BuildInitialMoveList(HParallelMove* parallel_move);
// Perform the move at the moves_ index in question (possibly requiring
// other moves to satisfy dependencies).
//
// Return whether another move in the dependency cycle needs to swap. This
// is to handle 64bits swaps:
// 1) In the case of register pairs, where we want the pair to swap first to avoid
// building pairs that are unexpected by the code generator. For example, if
// we were to swap R1 with R2, we would need to update all locations using
// R2 to R1. So a (R2,R3) pair register could become (R1,R3). We could make
// the code generator understand such pairs, but it's easier and cleaner to
// just not create such pairs and exchange pairs in priority.
// 2) Even when the architecture does not have pairs, we must handle 64bits swaps
// first. Consider the case: (R0->R1) (R1->S) (S->R0), where 'S' is a single
// stack slot. If we end up swapping S and R0, S will only contain the low bits
// of R0. If R0->R1 is for a 64bits instruction, R1 will therefore not contain
// the right value.
MoveOperands* PerformMove(size_t index);
DISALLOW_COPY_AND_ASSIGN(ParallelMoveResolver);
};
} // namespace art
#endif // ART_COMPILER_OPTIMIZING_PARALLEL_MOVE_RESOLVER_H_
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