lib/CodeGen/LiveIntervalAnalysis.h

//===-- llvm/CodeGen/LiveInterval.h - Live Interval Analysis ----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the LiveInterval analysis pass.  Given some numbering of
// each the machine instructions (in this implemention depth-first order) an
// interval [i, j) is said to be a live interval for register v if there is no
// instruction with number j' > j such that v is live at j' abd there is no
// instruction with number i' < i such that v is live at i'. In this
// implementation intervals can have holes, i.e. an interval might look like
// [1,20), [50,65), [1000,1001).
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_LIVEINTERVALS_H
#define LLVM_CODEGEN_LIVEINTERVALS_H

#include "llvm/CodeGen/MachineFunctionPass.h"
#include <list>

namespace llvm {

    class LiveVariables;
    class MRegisterInfo;
    class VirtRegMap;

    /// LiveRange structure - This represents a simple register range in the
    /// program, with an inclusive start point and an exclusive end point.
    /// These ranges are rendered as [start,end).
    struct LiveRange {
      unsigned start;  // Start point of the interval (inclusive)
      unsigned end;  // End point of the interval (exclusive)
      LiveRange(unsigned S, unsigned E) : start(S), end(E) {
        assert(S < E && "Cannot create empty or backwards range");
      }

      bool operator<(const LiveRange &LR) const {
        return start < LR.start || (start == LR.start && end < LR.end);
      }
      bool operator==(const LiveRange &LR) const {
        return start == LR.start && end == LR.end;
      }
    private:
      LiveRange(); // DO NOT IMPLEMENT
    };
    std::ostream& operator<<(std::ostream& os, const LiveRange &LR);

    struct LiveInterval {
        typedef std::vector<LiveRange> Ranges;
        unsigned reg;   // the register of this interval
        float weight;   // weight of this interval:
                        //     (number of uses *10^loopDepth)
        Ranges ranges;  // the ranges in which this register is live
        bool isDefinedOnce;  // True if there is one def of this register

        explicit LiveInterval(unsigned r);

        bool empty() const { return ranges.empty(); }

        bool spilled() const;

        /// start - Return the lowest numbered slot covered by interval.
        unsigned start() const {
            assert(!empty() && "empty interval for register");
            return ranges.front().start;
        }

        /// end - return the maximum point of the interval of the whole,
        /// exclusive.
        unsigned end() const {
            assert(!empty() && "empty interval for register");
            return ranges.back().end;
        }

        bool expiredAt(unsigned index) const {
            return end() <= (index + 1);
        }

        bool liveAt(unsigned index) const;

        bool overlaps(const LiveInterval& other) const;

        void addRange(LiveRange R);

        void join(const LiveInterval& other);

        bool operator<(const LiveInterval& other) const {
            return start() < other.start();
        }

        bool operator==(const LiveInterval& other) const {
            return reg == other.reg;
        }

    private:
        Ranges::iterator mergeRangesForward(Ranges::iterator it);
        Ranges::iterator mergeRangesBackward(Ranges::iterator it);
    };

    std::ostream& operator<<(std::ostream& os, const LiveInterval& li);

    class LiveIntervals : public MachineFunctionPass
    {
    public:
        typedef std::list<LiveInterval> Intervals;

    private:
        MachineFunction* mf_;
        const TargetMachine* tm_;
        const MRegisterInfo* mri_;
        MachineBasicBlock* currentMbb_;
        MachineBasicBlock::iterator currentInstr_;
        LiveVariables* lv_;

        typedef std::map<MachineInstr*, unsigned> Mi2IndexMap;
        Mi2IndexMap mi2iMap_;

        typedef std::vector<MachineInstr*> Index2MiMap;
        Index2MiMap i2miMap_;

        typedef std::map<unsigned, Intervals::iterator> Reg2IntervalMap;
        Reg2IntervalMap r2iMap_;

        typedef std::map<unsigned, unsigned> Reg2RegMap;
        Reg2RegMap r2rMap_;

        Intervals intervals_;

    public:
        struct InstrSlots
        {
            enum {
                LOAD  = 0,
                USE   = 1,
                DEF   = 2,
                STORE = 3,
                NUM   = 4,
            };
        };

        static unsigned getBaseIndex(unsigned index) {
            return index - (index % InstrSlots::NUM);
        }
        static unsigned getBoundaryIndex(unsigned index) {
            return getBaseIndex(index + InstrSlots::NUM - 1);
        }
        static unsigned getLoadIndex(unsigned index) {
            return getBaseIndex(index) + InstrSlots::LOAD;
        }
        static unsigned getUseIndex(unsigned index) {
            return getBaseIndex(index) + InstrSlots::USE;
        }
        static unsigned getDefIndex(unsigned index) {
            return getBaseIndex(index) + InstrSlots::DEF;
        }
        static unsigned getStoreIndex(unsigned index) {
            return getBaseIndex(index) + InstrSlots::STORE;
        }

        virtual void getAnalysisUsage(AnalysisUsage &AU) const;
        virtual void releaseMemory();

        /// runOnMachineFunction - pass entry point
        virtual bool runOnMachineFunction(MachineFunction&);

        LiveInterval& getInterval(unsigned reg) {
            assert(r2iMap_.count(reg)&& "Interval does not exist for register");
            return *r2iMap_.find(reg)->second;
        }

        /// getInstructionIndex - returns the base index of instr
        unsigned getInstructionIndex(MachineInstr* instr) const;

        /// getInstructionFromIndex - given an index in any slot of an
        /// instruction return a pointer the instruction
        MachineInstr* getInstructionFromIndex(unsigned index) const;

        Intervals& getIntervals() { return intervals_; }

        std::vector<LiveInterval*> addIntervalsForSpills(const LiveInterval& i,
                                                         VirtRegMap& vrm,
                                                         int slot);

    private:
        /// computeIntervals - compute live intervals
        void computeIntervals();

        /// joinIntervals - join compatible live intervals
        void joinIntervals();

        /// joinIntervalsInMachineBB - Join intervals based on move
        /// instructions in the specified basic block.
        void joinIntervalsInMachineBB(MachineBasicBlock *MBB);

        /// handleRegisterDef - update intervals for a register def
        /// (calls handlePhysicalRegisterDef and
        /// handleVirtualRegisterDef)
        void handleRegisterDef(MachineBasicBlock* mbb,
                               MachineBasicBlock::iterator mi,
                               unsigned reg);

        /// handleVirtualRegisterDef - update intervals for a virtual
        /// register def
        void handleVirtualRegisterDef(MachineBasicBlock* mbb,
                                      MachineBasicBlock::iterator mi,
                                      LiveInterval& interval);

        /// handlePhysicalRegisterDef - update intervals for a
        /// physical register def
        void handlePhysicalRegisterDef(MachineBasicBlock* mbb,
                                       MachineBasicBlock::iterator mi,
                                       LiveInterval& interval);

        bool overlapsAliases(const LiveInterval& lhs, 
                             const LiveInterval& rhs) const;


        LiveInterval& getOrCreateInterval(unsigned reg);

        /// rep - returns the representative of this register
        unsigned rep(unsigned reg);

        void printRegName(unsigned reg) const;
    };

} // End llvm namespace

#endif