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//===- llvm/CodeGen/SlotIndexes.h - Slot indexes representation -*- 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 SlotIndex and related classes. The purpose of SlotIndex

// is to describe a position at which a register can become live, or cease to

// be live.

//

// SlotIndex is mostly a proxy for entries of the SlotIndexList, a class which

// is held is LiveIntervals and provides the real numbering. This allows

// LiveIntervals to perform largely transparent renumbering.

//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_SLOTINDEXES_H

#define LLVM_CODEGEN_SLOTINDEXES_H

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/IntervalMap.h"

#include "llvm/ADT/PointerIntPair.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/ilist.h"

#include "llvm/CodeGen/MachineBasicBlock.h"

#include "llvm/CodeGen/MachineFunction.h"

#include "llvm/CodeGen/MachineFunctionPass.h"

#include "llvm/CodeGen/MachineInstr.h"

#include "llvm/CodeGen/MachineInstrBundle.h"

#include "llvm/Support/Allocator.h"

#include <algorithm>

#include <cassert>

#include <iterator>

#include <utility>

namespace llvm {

class raw_ostream;

  /// This class represents an entry in the slot index list held in the

  /// SlotIndexes pass. It should not be used directly. See the

  /// SlotIndex & SlotIndexes classes for the public interface to this

  /// information.

  class IndexListEntry : public ilist_node<IndexListEntry> {

    MachineInstr *mi;

    unsigned index;

  public:

    IndexListEntry(MachineInstr *mi, unsigned index) : mi(mi), index(index) {}

    MachineInstr* getInstr() const { return mi; }

    void setInstr(MachineInstr *mi) {

      this->mi = mi;

    }

    unsigned getIndex() const { return index; }

    void setIndex(unsigned index) {

      this->index = index;

    }

#ifdef EXPENSIVE_CHECKS

    // When EXPENSIVE_CHECKS is defined, "erased" index list entries will

    // actually be moved to a "graveyard" list, and have their pointers

    // poisoned, so that dangling SlotIndex access can be reliably detected.

    void setPoison() {

      intptr_t tmp = reinterpret_cast<intptr_t>(mi);

      assert(((tmp & 0x1) == 0x0) && "Pointer already poisoned?");

      tmp |= 0x1;

      mi = reinterpret_cast<MachineInstr*>(tmp);

    }

    bool isPoisoned() const { return (reinterpret_cast<intptr_t>(mi) & 0x1) == 0x1; }

#endif // EXPENSIVE_CHECKS

  };

  template <>

  struct ilist_alloc_traits<IndexListEntry>

      : public ilist_noalloc_traits<IndexListEntry> {};

  /// SlotIndex - An opaque wrapper around machine indexes.

  class SlotIndex {

    friend class SlotIndexes;

    enum Slot {

      /// Basic block boundary.  Used for live ranges entering and leaving a

      /// block without being live in the layout neighbor.  Also used as the

      /// def slot of PHI-defs.

      Slot_Block,

      /// Early-clobber register use/def slot.  A live range defined at

      /// Slot_EarlyClobber interferes with normal live ranges killed at

      /// Slot_Register.  Also used as the kill slot for live ranges tied to an

      /// early-clobber def.

      Slot_EarlyClobber,

      /// Normal register use/def slot.  Normal instructions kill and define

      /// register live ranges at this slot.

      Slot_Register,

      /// Dead def kill point.  Kill slot for a live range that is defined by

      /// the same instruction (Slot_Register or Slot_EarlyClobber), but isn't

      /// used anywhere.

      Slot_Dead,

      Slot_Count

    };

    PointerIntPair<IndexListEntry*, 2, unsigned> lie;

    IndexListEntry* listEntry() const {

      assert(isValid() && "Attempt to compare reserved index.");

#ifdef EXPENSIVE_CHECKS

      assert(!lie.getPointer()->isPoisoned() &&

             "Attempt to access deleted list-entry.");

#endif // EXPENSIVE_CHECKS

      return lie.getPointer();

    }

    unsigned getIndex() const {

      return listEntry()->getIndex() | getSlot();

    }

    /// Returns the slot for this SlotIndex.

    Slot getSlot() const {

      return static_cast<Slot>(lie.getInt());

    }

  public:

    enum {

      /// The default distance between instructions as returned by distance().

      /// This may vary as instructions are inserted and removed.

      InstrDist = 4 * Slot_Count

    };

    /// Construct an invalid index.

    SlotIndex() = default;

    // Creates a SlotIndex from an IndexListEntry and a slot. Generally should

    // not be used. This method is only public to facilitate writing certain

    // unit tests.

    SlotIndex(IndexListEntry *entry, unsigned slot) : lie(entry, slot) {}

    // Construct a new slot index from the given one, and set the slot.

    SlotIndex(const SlotIndex &li, Slot s) : lie(li.listEntry(), unsigned(s)) {

      assert(lie.getPointer() != nullptr &&

             "Attempt to construct index with 0 pointer.");

    }

    /// Returns true if this is a valid index. Invalid indices do

    /// not point into an index table, and cannot be compared.

    bool isValid() const {

      return lie.getPointer();

    }

    /// Return true for a valid index.

    explicit operator bool() const { return isValid(); }

    /// Print this index to the given raw_ostream.

    void print(raw_ostream &os) const;

    /// Dump this index to stderr.

    void dump() const;

    /// Compare two SlotIndex objects for equality.

    bool operator==(SlotIndex other) const {

      return lie == other.lie;

    }

    /// Compare two SlotIndex objects for inequality.

    bool operator!=(SlotIndex other) const {

      return lie != other.lie;

    }

    /// Compare two SlotIndex objects. Return true if the first index

    /// is strictly lower than the second.

    bool operator<(SlotIndex other) const {

      return getIndex() < other.getIndex();

    }

    /// Compare two SlotIndex objects. Return true if the first index

    /// is lower than, or equal to, the second.

    bool operator<=(SlotIndex other) const {

      return getIndex() <= other.getIndex();

    }

    /// Compare two SlotIndex objects. Return true if the first index

    /// is greater than the second.

    bool operator>(SlotIndex other) const {

      return getIndex() > other.getIndex();

    }

    /// Compare two SlotIndex objects. Return true if the first index

    /// is greater than, or equal to, the second.

    bool operator>=(SlotIndex other) const {

      return getIndex() >= other.getIndex();

    }

    /// isSameInstr - Return true if A and B refer to the same instruction.

    static bool isSameInstr(SlotIndex A, SlotIndex B) {

      return A.lie.getPointer() == B.lie.getPointer();

    }

    /// isEarlierInstr - Return true if A refers to an instruction earlier than

    /// B. This is equivalent to A < B && !isSameInstr(A, B).

    static bool isEarlierInstr(SlotIndex A, SlotIndex B) {

      return A.listEntry()->getIndex() < B.listEntry()->getIndex();

    }

    /// Return true if A refers to the same instruction as B or an earlier one.

    /// This is equivalent to !isEarlierInstr(B, A).

    static bool isEarlierEqualInstr(SlotIndex A, SlotIndex B) {

      return !isEarlierInstr(B, A);

    }

    /// Return the distance from this index to the given one.

    int distance(SlotIndex other) const {

      return other.getIndex() - getIndex();

    }

    /// Return the scaled distance from this index to the given one, where all

    /// slots on the same instruction have zero distance, assuming that the slot

    /// indices are packed as densely as possible. There are normally gaps

    /// between instructions, so this assumption often doesn't hold. This

    /// results in this function often returning a value greater than the actual

    /// instruction distance.

    int getApproxInstrDistance(SlotIndex other) const {

      return (other.listEntry()->getIndex() - listEntry()->getIndex())

        / Slot_Count;

    }

    /// isBlock - Returns true if this is a block boundary slot.

    bool isBlock() const { return getSlot() == Slot_Block; }

    /// isEarlyClobber - Returns true if this is an early-clobber slot.

    bool isEarlyClobber() const { return getSlot() == Slot_EarlyClobber; }

    /// isRegister - Returns true if this is a normal register use/def slot.

    /// Note that early-clobber slots may also be used for uses and defs.

    bool isRegister() const { return getSlot() == Slot_Register; }

    /// isDead - Returns true if this is a dead def kill slot.

    bool isDead() const { return getSlot() == Slot_Dead; }

    /// Returns the base index for associated with this index. The base index

    /// is the one associated with the Slot_Block slot for the instruction

    /// pointed to by this index.

    SlotIndex getBaseIndex() const {

      return SlotIndex(listEntry(), Slot_Block);

    }

    /// Returns the boundary index for associated with this index. The boundary

    /// index is the one associated with the Slot_Block slot for the instruction

    /// pointed to by this index.

    SlotIndex getBoundaryIndex() const {

      return SlotIndex(listEntry(), Slot_Dead);

    }

    /// Returns the register use/def slot in the current instruction for a

    /// normal or early-clobber def.

    SlotIndex getRegSlot(bool EC = false) const {

      return SlotIndex(listEntry(), EC ? Slot_EarlyClobber : Slot_Register);

    }

    /// Returns the dead def kill slot for the current instruction.

    SlotIndex getDeadSlot() const {

      return SlotIndex(listEntry(), Slot_Dead);

    }

    /// Returns the next slot in the index list. This could be either the

    /// next slot for the instruction pointed to by this index or, if this

    /// index is a STORE, the first slot for the next instruction.

    /// WARNING: This method is considerably more expensive than the methods

    /// that return specific slots (getUseIndex(), etc). If you can - please

    /// use one of those methods.

    SlotIndex getNextSlot() const {

      Slot s = getSlot();

      if (s == Slot_Dead) {

        return SlotIndex(&*++listEntry()->getIterator(), Slot_Block);

      }

      return SlotIndex(listEntry(), s + 1);

    }

    /// Returns the next index. This is the index corresponding to the this

    /// index's slot, but for the next instruction.

    SlotIndex getNextIndex() const {

      return SlotIndex(&*++listEntry()->getIterator(), getSlot());

    }

    /// Returns the previous slot in the index list. This could be either the

    /// previous slot for the instruction pointed to by this index or, if this

    /// index is a Slot_Block, the last slot for the previous instruction.

    /// WARNING: This method is considerably more expensive than the methods

    /// that return specific slots (getUseIndex(), etc). If you can - please

    /// use one of those methods.

    SlotIndex getPrevSlot() const {

      Slot s = getSlot();

      if (s == Slot_Block) {

        return SlotIndex(&*--listEntry()->getIterator(), Slot_Dead);

      }

      return SlotIndex(listEntry(), s - 1);

    }

    /// Returns the previous index. This is the index corresponding to this

    /// index's slot, but for the previous instruction.

    SlotIndex getPrevIndex() const {

      return SlotIndex(&*--listEntry()->getIterator(), getSlot());

    }

  };

  inline raw_ostream& operator<<(raw_ostream &os, SlotIndex li) {

    li.print(os);

    return os;

  }

  using IdxMBBPair = std::pair<SlotIndex, MachineBasicBlock *>;

  /// SlotIndexes pass.

  ///

  /// This pass assigns indexes to each instruction.

  class SlotIndexes : public MachineFunctionPass {

  private:

    // IndexListEntry allocator.

    BumpPtrAllocator ileAllocator;

    using IndexList = ilist<IndexListEntry>;

    IndexList indexList;

    MachineFunction *mf = nullptr;

    using Mi2IndexMap = DenseMap<const MachineInstr *, SlotIndex>;

    Mi2IndexMap mi2iMap;

    /// MBBRanges - Map MBB number to (start, stop) indexes.

    SmallVector<std::pair<SlotIndex, SlotIndex>, 8> MBBRanges;

    /// Idx2MBBMap - Sorted list of pairs of index of first instruction

    /// and MBB id.

    SmallVector<IdxMBBPair, 8> idx2MBBMap;

    IndexListEntry* createEntry(MachineInstr *mi, unsigned index) {

      IndexListEntry *entry =

          static_cast<IndexListEntry *>(ileAllocator.Allocate(

              sizeof(IndexListEntry), alignof(IndexListEntry)));

      new (entry) IndexListEntry(mi, index);

      return entry;

    }

    /// Renumber locally after inserting curItr.

    void renumberIndexes(IndexList::iterator curItr);

  public:

    static char ID;

    SlotIndexes();

    ~SlotIndexes() override;

    void getAnalysisUsage(AnalysisUsage &au) const override;

    void releaseMemory() override;

    bool runOnMachineFunction(MachineFunction &fn) override;

    /// Dump the indexes.

    void dump() const;

    /// Repair indexes after adding and removing instructions.

    void repairIndexesInRange(MachineBasicBlock *MBB,

                              MachineBasicBlock::iterator Begin,

                              MachineBasicBlock::iterator End);

    /// Returns the zero index for this analysis.

    SlotIndex getZeroIndex() {

      assert(indexList.front().getIndex() == 0 && "First index is not 0?");

      return SlotIndex(&indexList.front(), 0);

    }

    /// Returns the base index of the last slot in this analysis.

    SlotIndex getLastIndex() {

      return SlotIndex(&indexList.back(), 0);

    }

    /// Returns true if the given machine instr is mapped to an index,

    /// otherwise returns false.

    bool hasIndex(const MachineInstr &instr) const {

      return mi2iMap.count(&instr);

    }

    /// Returns the base index for the given instruction.

    SlotIndex getInstructionIndex(const MachineInstr &MI,

                                  bool IgnoreBundle = false) const {

      // Instructions inside a bundle have the same number as the bundle itself.

      auto BundleStart = getBundleStart(MI.getIterator());

      auto BundleEnd = getBundleEnd(MI.getIterator());

      // Use the first non-debug instruction in the bundle to get SlotIndex.

      const MachineInstr &BundleNonDebug =

          IgnoreBundle ? MI

                       : *skipDebugInstructionsForward(BundleStart, BundleEnd);

      assert(!BundleNonDebug.isDebugInstr() &&

             "Could not use a debug instruction to query mi2iMap.");

      Mi2IndexMap::const_iterator itr = mi2iMap.find(&BundleNonDebug);

      assert(itr != mi2iMap.end() && "Instruction not found in maps.");

      return itr->second;

    }

    /// Returns the instruction for the given index, or null if the given

    /// index has no instruction associated with it.

    MachineInstr* getInstructionFromIndex(SlotIndex index) const {

      return index.isValid() ? index.listEntry()->getInstr() : nullptr;

    }

    /// Returns the next non-null index, if one exists.

    /// Otherwise returns getLastIndex().

    SlotIndex getNextNonNullIndex(SlotIndex Index) {

      IndexList::iterator I = Index.listEntry()->getIterator();

      IndexList::iterator E = indexList.end();

      while (++I != E)

        if (I->getInstr())

          return SlotIndex(&*I, Index.getSlot());

      // We reached the end of the function.

      return getLastIndex();

    }

    /// getIndexBefore - Returns the index of the last indexed instruction

    /// before MI, or the start index of its basic block.

    /// MI is not required to have an index.

    SlotIndex getIndexBefore(const MachineInstr &MI) const {

      const MachineBasicBlock *MBB = MI.getParent();

      assert(MBB && "MI must be inserted in a basic block");

      MachineBasicBlock::const_iterator I = MI, B = MBB->begin();

      while (true) {

        if (I == B)

          return getMBBStartIdx(MBB);

        --I;

        Mi2IndexMap::const_iterator MapItr = mi2iMap.find(&*I);

        if (MapItr != mi2iMap.end())

          return MapItr->second;

      }

    }

    /// getIndexAfter - Returns the index of the first indexed instruction

    /// after MI, or the end index of its basic block.

    /// MI is not required to have an index.

    SlotIndex getIndexAfter(const MachineInstr &MI) const {

      const MachineBasicBlock *MBB = MI.getParent();

      assert(MBB && "MI must be inserted in a basic block");

      MachineBasicBlock::const_iterator I = MI, E = MBB->end();

      while (true) {

        ++I;

        if (I == E)

          return getMBBEndIdx(MBB);

        Mi2IndexMap::const_iterator MapItr = mi2iMap.find(&*I);

        if (MapItr != mi2iMap.end())

          return MapItr->second;

      }

    }

    /// Return the (start,end) range of the given basic block number.

    const std::pair<SlotIndex, SlotIndex> &

    getMBBRange(unsigned Num) const {

      return MBBRanges[Num];

    }

    /// Return the (start,end) range of the given basic block.

    const std::pair<SlotIndex, SlotIndex> &

    getMBBRange(const MachineBasicBlock *MBB) const {

      return getMBBRange(MBB->getNumber());

    }

    /// Returns the first index in the given basic block number.

    SlotIndex getMBBStartIdx(unsigned Num) const {

      return getMBBRange(Num).first;

    }

    /// Returns the first index in the given basic block.

    SlotIndex getMBBStartIdx(const MachineBasicBlock *mbb) const {

      return getMBBRange(mbb).first;

    }

    /// Returns the last index in the given basic block number.

    SlotIndex getMBBEndIdx(unsigned Num) const {

      return getMBBRange(Num).second;

    }

    /// Returns the last index in the given basic block.

    SlotIndex getMBBEndIdx(const MachineBasicBlock *mbb) const {

      return getMBBRange(mbb).second;

    }

    /// Iterator over the idx2MBBMap (sorted pairs of slot index of basic block

    /// begin and basic block)

    using MBBIndexIterator = SmallVectorImpl<IdxMBBPair>::const_iterator;

    /// Move iterator to the next IdxMBBPair where the SlotIndex is greater or

    /// equal to \p To.

    MBBIndexIterator advanceMBBIndex(MBBIndexIterator I, SlotIndex To) const {

      return std::partition_point(

          I, idx2MBBMap.end(),

          [=](const IdxMBBPair &IM) { return IM.first < To; });

    }

    /// Get an iterator pointing to the IdxMBBPair with the biggest SlotIndex

    /// that is greater or equal to \p Idx.

    MBBIndexIterator findMBBIndex(SlotIndex Idx) const {

      return advanceMBBIndex(idx2MBBMap.begin(), Idx);

    }

    /// Returns an iterator for the begin of the idx2MBBMap.

    MBBIndexIterator MBBIndexBegin() const {

      return idx2MBBMap.begin();

    }

    /// Return an iterator for the end of the idx2MBBMap.

    MBBIndexIterator MBBIndexEnd() const {

      return idx2MBBMap.end();

    }

    /// Returns the basic block which the given index falls in.

    MachineBasicBlock* getMBBFromIndex(SlotIndex index) const {

      if (MachineInstr *MI = getInstructionFromIndex(index))

        return MI->getParent();

      MBBIndexIterator I = findMBBIndex(index);

      // Take the pair containing the index

      MBBIndexIterator J =

        ((I != MBBIndexEnd() && I->first > index) ||

         (I == MBBIndexEnd() && !idx2MBBMap.empty())) ? std::prev(I) : I;

      assert(J != MBBIndexEnd() && J->first <= index &&

             index < getMBBEndIdx(J->second) &&

             "index does not correspond to an MBB");

      return J->second;

    }

    /// Insert the given machine instruction into the mapping. Returns the

    /// assigned index.

    /// If Late is set and there are null indexes between mi's neighboring

    /// instructions, create the new index after the null indexes instead of

    /// before them.

    SlotIndex insertMachineInstrInMaps(MachineInstr &MI, bool Late = false) {

      assert(!MI.isInsideBundle() &&

             "Instructions inside bundles should use bundle start's slot.");

      assert(mi2iMap.find(&MI) == mi2iMap.end() && "Instr already indexed.");

      // Numbering debug instructions could cause code generation to be

      // affected by debug information.

      assert(!MI.isDebugInstr() && "Cannot number debug instructions.");

      assert(MI.getParent() != nullptr && "Instr must be added to function.");

      // Get the entries where MI should be inserted.

      IndexList::iterator prevItr, nextItr;

      if (Late) {

        // Insert MI's index immediately before the following instruction.

        nextItr = getIndexAfter(MI).listEntry()->getIterator();

        prevItr = std::prev(nextItr);

      } else {

        // Insert MI's index immediately after the preceding instruction.

        prevItr = getIndexBefore(MI).listEntry()->getIterator();

        nextItr = std::next(prevItr);

      }

      // Get a number for the new instr, or 0 if there's no room currently.

      // In the latter case we'll force a renumber later.

      unsigned dist = ((nextItr->getIndex() - prevItr->getIndex())/2) & ~3u;

      unsigned newNumber = prevItr->getIndex() + dist;

      // Insert a new list entry for MI.

      IndexList::iterator newItr =

          indexList.insert(nextItr, createEntry(&MI, newNumber));

      // Renumber locally if we need to.

      if (dist == 0)

        renumberIndexes(newItr);

      SlotIndex newIndex(&*newItr, SlotIndex::Slot_Block);

      mi2iMap.insert(std::make_pair(&MI, newIndex));

      return newIndex;

    }

    /// Removes machine instruction (bundle) \p MI from the mapping.

    /// This should be called before MachineInstr::eraseFromParent() is used to

    /// remove a whole bundle or an unbundled instruction.

    /// If \p AllowBundled is set then this can be used on a bundled

    /// instruction; however, this exists to support handleMoveIntoBundle,

    /// and in general removeSingleMachineInstrFromMaps should be used instead.

    void removeMachineInstrFromMaps(MachineInstr &MI,

                                    bool AllowBundled = false);

    /// Removes a single machine instruction \p MI from the mapping.

    /// This should be called before MachineInstr::eraseFromBundle() is used to

    /// remove a single instruction (out of a bundle).

    void removeSingleMachineInstrFromMaps(MachineInstr &MI);

    /// ReplaceMachineInstrInMaps - Replacing a machine instr with a new one in

    /// maps used by register allocator. \returns the index where the new

    /// instruction was inserted.

    SlotIndex replaceMachineInstrInMaps(MachineInstr &MI, MachineInstr &NewMI) {

      Mi2IndexMap::iterator mi2iItr = mi2iMap.find(&MI);

      if (mi2iItr == mi2iMap.end())

        return SlotIndex();

      SlotIndex replaceBaseIndex = mi2iItr->second;

      IndexListEntry *miEntry(replaceBaseIndex.listEntry());

      assert(miEntry->getInstr() == &MI &&

             "Mismatched instruction in index tables.");

      miEntry->setInstr(&NewMI);

      mi2iMap.erase(mi2iItr);

      mi2iMap.insert(std::make_pair(&NewMI, replaceBaseIndex));

      return replaceBaseIndex;

    }

    /// Add the given MachineBasicBlock into the maps.

    /// If it contains any instructions then they must already be in the maps.

    /// This is used after a block has been split by moving some suffix of its

    /// instructions into a newly created block.

    void insertMBBInMaps(MachineBasicBlock *mbb) {

      assert(mbb != &mbb->getParent()->front() &&

             "Can't insert a new block at the beginning of a function.");

      auto prevMBB = std::prev(MachineFunction::iterator(mbb));

      // Create a new entry to be used for the start of mbb and the end of

      // prevMBB.

      IndexListEntry *startEntry = createEntry(nullptr, 0);

      IndexListEntry *endEntry = getMBBEndIdx(&*prevMBB).listEntry();

      IndexListEntry *insEntry =

          mbb->empty() ? endEntry

                       : getInstructionIndex(mbb->front()).listEntry();

      IndexList::iterator newItr =

          indexList.insert(insEntry->getIterator(), startEntry);

      SlotIndex startIdx(startEntry, SlotIndex::Slot_Block);

      SlotIndex endIdx(endEntry, SlotIndex::Slot_Block);

      MBBRanges[prevMBB->getNumber()].second = startIdx;

      assert(unsigned(mbb->getNumber()) == MBBRanges.size() &&

             "Blocks must be added in order");

      MBBRanges.push_back(std::make_pair(startIdx, endIdx));

      idx2MBBMap.push_back(IdxMBBPair(startIdx, mbb));

      renumberIndexes(newItr);

      llvm::sort(idx2MBBMap, less_first());

    }

  };

  // Specialize IntervalMapInfo for half-open slot index intervals.

  template <>

  struct IntervalMapInfo<SlotIndex> : IntervalMapHalfOpenInfo<SlotIndex> {

  };

} // end namespace llvm

#endif // LLVM_CODEGEN_SLOTINDEXES_H