AllocationOrder.h
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//===-- llvm/CodeGen/AllocationOrder.h - Allocation Order -*- 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 implements an allocation order for virtual registers.
//
// The preferred allocation order for a virtual register depends on allocation
// hints and target hooks. The AllocationOrder class encapsulates all of that.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIB_CODEGEN_ALLOCATIONORDER_H
#define LLVM_LIB_CODEGEN_ALLOCATIONORDER_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/MC/MCRegister.h"
namespace llvm {
class RegisterClassInfo;
class VirtRegMap;
class LiveRegMatrix;
class LLVM_LIBRARY_VISIBILITY AllocationOrder {
const SmallVector<MCPhysReg, 16> Hints;
ArrayRef<MCPhysReg> Order;
int Pos = 0;
// If HardHints is true, *only* Hints will be returned.
const bool HardHints;
public:
/// Create a new AllocationOrder for VirtReg.
/// @param VirtReg Virtual register to allocate for.
/// @param VRM Virtual register map for function.
/// @param RegClassInfo Information about reserved and allocatable registers.
static AllocationOrder create(unsigned VirtReg, const VirtRegMap &VRM,
const RegisterClassInfo &RegClassInfo,
const LiveRegMatrix *Matrix);
/// Create an AllocationOrder given the Hits, Order, and HardHits values.
/// Use the create method above - the ctor is for unittests.
AllocationOrder(SmallVector<MCPhysReg, 16> &&Hints, ArrayRef<MCPhysReg> Order,
bool HardHints)
: Hints(std::move(Hints)), Order(Order),
Pos(-static_cast<int>(this->Hints.size())), HardHints(HardHints) {}
/// Get the allocation order without reordered hints.
ArrayRef<MCPhysReg> getOrder() const { return Order; }
/// Return the next physical register in the allocation order, or 0.
/// It is safe to call next() again after it returned 0, it will keep
/// returning 0 until rewind() is called.
MCPhysReg next(unsigned Limit = 0) {
if (Pos < 0)
return Hints.end()[Pos++];
if (HardHints)
return 0;
if (!Limit)
Limit = Order.size();
while (Pos < int(Limit)) {
unsigned Reg = Order[Pos++];
if (!isHint(Reg))
return Reg;
}
return 0;
}
/// Start over from the beginning.
void rewind() { Pos = -int(Hints.size()); }
/// Return true if the last register returned from next() was a preferred register.
bool isHint() const { return Pos <= 0; }
/// Return true if PhysReg is a preferred register.
bool isHint(unsigned PhysReg) const { return is_contained(Hints, PhysReg); }
};
} // end namespace llvm
#endif