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//===-- llvm/CodeGen/AllocationOrder.h - Allocation Order -*- C++ -*-------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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_CODEGEN_ALLOCATIONORDER_H
#define LLVM_CODEGEN_ALLOCATIONORDER_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/MC/MCRegisterInfo.h"
namespace llvm {
class RegisterClassInfo;
class VirtRegMap;
class AllocationOrder {
SmallVector<MCPhysReg, 16> Hints;
ArrayRef<MCPhysReg> Order;
int Pos;
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.
AllocationOrder(unsigned VirtReg,
const VirtRegMap &VRM,
const RegisterClassInfo &RegClassInfo);
/// 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.
unsigned next(unsigned Limit = 0) {
if (Pos < 0)
return Hints.end()[Pos++];
if (!Limit)
Limit = Order.size();
while (Pos < int(Limit)) {
unsigned Reg = Order[Pos++];
if (!isHint(Reg))
return Reg;
}
return 0;
}
/// As next(), but allow duplicates to be returned, and stop before the
/// Limit'th register in the RegisterClassInfo allocation order.
///
/// This can produce more than Limit registers if there are hints.
unsigned nextWithDups(unsigned Limit) {
if (Pos < 0)
return Hints.end()[Pos++];
if (Pos < int(Limit))
return Order[Pos++];
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 std::find(Hints.begin(), Hints.end(), PhysReg) != Hints.end();
}
};
} // end namespace llvm
#endif
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