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//===-- llvm/CodeGen/PhysRegTracker.h - Physical Register Tracker -*- 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 a physical register tracker. The tracker
// tracks physical register usage through addRegUse and
// delRegUse. isRegAvail checks if a physical register is available or
// not taking into consideration register aliases.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_PHYSREGTRACKER_H
#define LLVM_CODEGEN_PHYSREGTRACKER_H

#include "llvm/Target/TargetRegisterInfo.h"

namespace llvm {

    class PhysRegTracker {
        const TargetRegisterInfo* tri_;
        std::vector<unsigned> regUse_;

    public:
        explicit PhysRegTracker(const TargetRegisterInfo& tri)
            : tri_(&tri),
              regUse_(tri_->getNumRegs(), 0) {
        }

        PhysRegTracker(const PhysRegTracker& rhs)
            : tri_(rhs.tri_),
              regUse_(rhs.regUse_) {
        }

        const PhysRegTracker& operator=(const PhysRegTracker& rhs) {
            tri_ = rhs.tri_;
            regUse_ = rhs.regUse_;
            return *this;
        }

        void addRegUse(unsigned physReg) {
            assert(TargetRegisterInfo::isPhysicalRegister(physReg) &&
                   "should be physical register!");
            ++regUse_[physReg];
            for (const unsigned* as = tri_->getAliasSet(physReg); *as; ++as)
                ++regUse_[*as];
        }

        void delRegUse(unsigned physReg) {
            assert(TargetRegisterInfo::isPhysicalRegister(physReg) &&
                   "should be physical register!");
            assert(regUse_[physReg] != 0);
            --regUse_[physReg];
            for (const unsigned* as = tri_->getAliasSet(physReg); *as; ++as) {
                assert(regUse_[*as] != 0);
                --regUse_[*as];
            }
        }

        bool isRegAvail(unsigned physReg) const {
            assert(TargetRegisterInfo::isPhysicalRegister(physReg) &&
                   "should be physical register!");
            return regUse_[physReg] == 0;
        }
    };

} // End llvm namespace

#endif