llvm/llvm/lib/CodeGen/RegAllocBase.h

//===- RegAllocBase.h - basic regalloc interface and driver -----*- 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
//
//===----------------------------------------------------------------------===//
//
// This file defines the RegAllocBase class, which is the skeleton of a basic
// register allocation algorithm and interface for extending it. It provides the
// building blocks on which to construct other experimental allocators and test
// the validity of two principles:
//
// - If virtual and physical register liveness is modeled using intervals, then
// on-the-fly interference checking is cheap. Furthermore, interferences can be
// lazily cached and reused.
//
// - Register allocation complexity, and generated code performance is
// determined by the effectiveness of live range splitting rather than optimal
// coloring.
//
// Following the first principle, interfering checking revolves around the
// LiveIntervalUnion data structure.
//
// To fulfill the second principle, the basic allocator provides a driver for
// incremental splitting. It essentially punts on the problem of register
// coloring, instead driving the assignment of virtual to physical registers by
// the cost of splitting. The basic allocator allows for heuristic reassignment
// of registers, if a more sophisticated allocator chooses to do that.
//
// This framework provides a way to engineer the compile time vs. code
// quality trade-off without relying on a particular theoretical solver.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_CODEGEN_REGALLOCBASE_H
#define LLVM_LIB_CODEGEN_REGALLOCBASE_H

#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegAllocCommon.h"
#include "llvm/CodeGen/RegisterClassInfo.h"

namespace llvm {

class LiveInterval;
class LiveIntervals;
class LiveRegMatrix;
class MachineInstr;
class MachineRegisterInfo;
template<typename T> class SmallVectorImpl;
class Spiller;
class TargetRegisterInfo;
class VirtRegMap;

/// RegAllocBase provides the register allocation driver and interface that can
/// be extended to add interesting heuristics.
///
/// Register allocators must override the selectOrSplit() method to implement
/// live range splitting. They must also override enqueue/dequeue to provide an
/// assignment order.
class RegAllocBase { … };

} // end namespace llvm

#endif // LLVM_LIB_CODEGEN_REGALLOCBASE_H