blob: be1c7ec7c6fc1ed9744a4f5f405f94f2730c5d87 [file] [log] [blame]
* 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include "base/macros.h"
#include "primitive.h"
#include "utils/growable_array.h"
namespace art {
class CodeGenerator;
class HBasicBlock;
class HGraph;
class HInstruction;
class HParallelMove;
class LiveInterval;
class Location;
class SsaLivenessAnalysis;
* An implementation of a linear scan register allocator on an `HGraph` with SSA form.
class RegisterAllocator {
RegisterAllocator(ArenaAllocator* allocator,
CodeGenerator* codegen,
const SsaLivenessAnalysis& analysis);
// Main entry point for the register allocator. Given the liveness analysis,
// allocates registers to live intervals.
void AllocateRegisters();
// Validate that the register allocator did not allocate the same register to
// intervals that intersect each other. Returns false if it did not.
bool Validate(bool log_fatal_on_failure) {
processing_core_registers_ = true;
if (!ValidateInternal(log_fatal_on_failure)) {
return false;
processing_core_registers_ = false;
return ValidateInternal(log_fatal_on_failure);
// Helper method for validation. Used by unit testing.
static bool ValidateIntervals(const GrowableArray<LiveInterval*>& intervals,
size_t number_of_spill_slots,
const CodeGenerator& codegen,
ArenaAllocator* allocator,
bool processing_core_registers,
bool log_fatal_on_failure);
static bool CanAllocateRegistersFor(const HGraph& graph, InstructionSet instruction_set);
static bool Supports(InstructionSet instruction_set) {
return instruction_set == kX86
|| instruction_set == kArm
|| instruction_set == kX86_64
|| instruction_set == kThumb2;
size_t GetNumberOfSpillSlots() const {
return spill_slots_.Size();
// Main methods of the allocator.
void LinearScan();
bool TryAllocateFreeReg(LiveInterval* interval);
bool AllocateBlockedReg(LiveInterval* interval);
void Resolve();
// Add `interval` in the sorted list of unhandled intervals.
void AddToUnhandled(LiveInterval* interval);
// Split `interval` at the position `at`. The new interval starts at `at`.
LiveInterval* Split(LiveInterval* interval, size_t at);
// Returns whether `reg` is blocked by the code generator.
bool IsBlocked(int reg) const;
// Update the interval for the register in `location` to cover [start, end).
void BlockRegister(Location location, size_t start, size_t end, Primitive::Type type);
// Allocate a spill slot for the given interval.
void AllocateSpillSlotFor(LiveInterval* interval);
void AllocateOneSpillSlot(LiveInterval* interval, size_t end);
void AllocateTwoSpillSlots(LiveInterval* interval, size_t end);
// Connect adjacent siblings within blocks.
void ConnectSiblings(LiveInterval* interval);
// Connect siblings between block entries and exits.
void ConnectSplitSiblings(LiveInterval* interval, HBasicBlock* from, HBasicBlock* to) const;
// Helper methods to insert parallel moves in the graph.
void InsertParallelMoveAtExitOf(HBasicBlock* block, Location source, Location destination) const;
void InsertParallelMoveAtEntryOf(HBasicBlock* block, Location source, Location destination) const;
void InsertMoveAfter(HInstruction* instruction, Location source, Location destination) const;
void AddInputMoveFor(HInstruction* instruction, Location source, Location destination) const;
void InsertParallelMoveAt(size_t position, Location source, Location destination) const;
// Helper methods.
void AllocateRegistersInternal();
bool ValidateInternal(bool log_fatal_on_failure) const;
void DumpInterval(std::ostream& stream, LiveInterval* interval) const;
ArenaAllocator* const allocator_;
CodeGenerator* const codegen_;
const SsaLivenessAnalysis& liveness_;
// List of intervals that must be processed, ordered by start position. Last entry
// is the interval that has the lowest start position.
GrowableArray<LiveInterval*> unhandled_;
// List of intervals that have been processed.
GrowableArray<LiveInterval*> handled_;
// List of intervals that are currently active when processing a new live interval.
// That is, they have a live range that spans the start of the new interval.
GrowableArray<LiveInterval*> active_;
// List of intervals that are currently inactive when processing a new live interval.
// That is, they have a lifetime hole that spans the start of the new interval.
GrowableArray<LiveInterval*> inactive_;
// Fixed intervals for physical registers. Such an interval covers the positions
// where an instruction requires a specific register.
GrowableArray<LiveInterval*> physical_register_intervals_;
// The spill slots allocated for live intervals.
GrowableArray<size_t> spill_slots_;
// True if processing core registers. False if processing floating
// point registers.
bool processing_core_registers_;
// Number of registers for the current register kind (core or floating point).
size_t number_of_registers_;
// Temporary array, allocated ahead of time for simplicity.
size_t* registers_array_;
// Blocked registers, as decided by the code generator.
bool* const blocked_registers_;
} // namespace art