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//===-- RegAllocBase.h - basic regalloc interface and driver --*- C++ -*---===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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/CodeGen/LiveInterval.h"
#include "llvm/CodeGen/RegisterClassInfo.h"
namespace llvm {
template<typename T> class SmallVectorImpl;
class TargetRegisterInfo;
class VirtRegMap;
class LiveIntervals;
class LiveRegMatrix;
class Spiller;
/// 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 {
virtual void anchor();
protected:
const TargetRegisterInfo *TRI;
MachineRegisterInfo *MRI;
VirtRegMap *VRM;
LiveIntervals *LIS;
LiveRegMatrix *Matrix;
RegisterClassInfo RegClassInfo;
RegAllocBase()
: TRI(nullptr), MRI(nullptr), VRM(nullptr), LIS(nullptr), Matrix(nullptr) {}
virtual ~RegAllocBase() {}
// A RegAlloc pass should call this before allocatePhysRegs.
void init(VirtRegMap &vrm, LiveIntervals &lis, LiveRegMatrix &mat);
// The top-level driver. The output is a VirtRegMap that us updated with
// physical register assignments.
void allocatePhysRegs();
// Get a temporary reference to a Spiller instance.
virtual Spiller &spiller() = 0;
/// enqueue - Add VirtReg to the priority queue of unassigned registers.
virtual void enqueue(LiveInterval *LI) = 0;
/// dequeue - Return the next unassigned register, or NULL.
virtual LiveInterval *dequeue() = 0;
// A RegAlloc pass should override this to provide the allocation heuristics.
// Each call must guarantee forward progess by returning an available PhysReg
// or new set of split live virtual registers. It is up to the splitter to
// converge quickly toward fully spilled live ranges.
virtual unsigned selectOrSplit(LiveInterval &VirtReg,
SmallVectorImpl<unsigned> &splitLVRs) = 0;
// Use this group name for NamedRegionTimer.
static const char TimerGroupName[];
/// Method called when the allocator is about to remove a LiveInterval.
virtual void aboutToRemoveInterval(LiveInterval &LI) {}
public:
/// VerifyEnabled - True when -verify-regalloc is given.
static bool VerifyEnabled;
private:
void seedLiveRegs();
};
} // end namespace llvm
#endif
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