llvm/llvm/lib/CodeGen/RegAllocEvictionAdvisor.h

//===- RegAllocEvictionAdvisor.h - Interference resolution ------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_REGALLOCEVICTIONADVISOR_H
#define LLVM_CODEGEN_REGALLOCEVICTIONADVISOR_H

#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/Register.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/MC/MCRegister.h"
#include "llvm/Pass.h"

namespace llvm {
class AllocationOrder;
class LiveInterval;
class LiveIntervals;
class LiveRegMatrix;
class MachineFunction;
class MachineRegisterInfo;
class RegisterClassInfo;
class TargetRegisterInfo;
class VirtRegMap;

SmallVirtRegSet;

// Live ranges pass through a number of stages as we try to allocate them.
// Some of the stages may also create new live ranges:
//
// - Region splitting.
// - Per-block splitting.
// - Local splitting.
// - Spilling.
//
// Ranges produced by one of the stages skip the previous stages when they are
// dequeued. This improves performance because we can skip interference checks
// that are unlikely to give any results. It also guarantees that the live
// range splitting algorithm terminates, something that is otherwise hard to
// ensure.
enum LiveRangeStage { … };

/// Cost of evicting interference - used by default advisor, and the eviction
/// chain heuristic in RegAllocGreedy.
// FIXME: this can be probably made an implementation detail of the default
// advisor, if the eviction chain logic can be refactored.
struct EvictionCost { … };

/// Interface to the eviction advisor, which is responsible for making a
/// decision as to which live ranges should be evicted (if any).
class RAGreedy;
class RegAllocEvictionAdvisor { … };

/// ImmutableAnalysis abstraction for fetching the Eviction Advisor. We model it
/// as an analysis to decouple the user from the implementation insofar as
/// dependencies on other analyses goes. The motivation for it being an
/// immutable pass is twofold:
/// - in the ML implementation case, the evaluator is stateless but (especially
/// in the development mode) expensive to set up. With an immutable pass, we set
/// it up once.
/// - in the 'development' mode ML case, we want to capture the training log
/// during allocation (this is a log of features encountered and decisions
/// made), and then measure a score, potentially a few steps after allocation
/// completes. So we need the properties of an immutable pass to keep the logger
/// state around until we can make that measurement.
///
/// Because we need to offer additional services in 'development' mode, the
/// implementations of this analysis need to implement RTTI support.
class RegAllocEvictionAdvisorAnalysis : public ImmutablePass { … };

/// Specialization for the API used by the analysis infrastructure to create
/// an instance of the eviction advisor.
template <> Pass *callDefaultCtor<RegAllocEvictionAdvisorAnalysis>();

RegAllocEvictionAdvisorAnalysis *createReleaseModeAdvisor();

RegAllocEvictionAdvisorAnalysis *createDevelopmentModeAdvisor();

// TODO: move to RegAllocEvictionAdvisor.cpp when we move implementation
// out of RegAllocGreedy.cpp
class DefaultEvictionAdvisor : public RegAllocEvictionAdvisor { … };
} // namespace llvm

#endif // LLVM_CODEGEN_REGALLOCEVICTIONADVISOR_H