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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
namespace llvm {
class RegisterClassInfo;
class VirtRegMap;
class AllocationOrder {
const unsigned *Begin;
const unsigned *End;
const unsigned *Pos;
const RegisterClassInfo &RCI;
unsigned Hint;
bool OwnedBegin;
public:
/// AllocationOrder - 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);
~AllocationOrder();
/// next - 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() {
// First take the hint.
if (!Pos) {
Pos = Begin;
if (Hint)
return Hint;
}
// Then look at the order from TRI.
while (Pos != End) {
unsigned Reg = *Pos++;
if (Reg != Hint)
return Reg;
}
return 0;
}
/// rewind - Start over from the beginning.
void rewind() { Pos = 0; }
/// isHint - Return true if PhysReg is a preferred register.
bool isHint(unsigned PhysReg) const { return PhysReg == Hint; }
};
} // end namespace llvm
#endif
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