//===- MemorySSAUpdater.h - Memory SSA Updater-------------------*- C++ -*-===//

//

//                     The LLVM Compiler Infrastructure

//

// This file is distributed under the University of Illinois Open Source

// License. See LICENSE.TXT for details.

//

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

//

// \file

// An automatic updater for MemorySSA that handles arbitrary insertion,

// deletion, and moves.  It performs phi insertion where necessary, and

// automatically updates the MemorySSA IR to be correct.

// While updating loads or removing instructions is often easy enough to not

// need this, updating stores should generally not be attemped outside this

// API.

//

// Basic API usage:

// Create the memory access you want for the instruction (this is mainly so

// we know where it is, without having to duplicate the entire set of create

// functions MemorySSA supports).

// Call insertDef or insertUse depending on whether it's a MemoryUse or a

// MemoryDef.

// That's it.

//

// For moving, first, move the instruction itself using the normal SSA

// instruction moving API, then just call moveBefore, moveAfter,or moveTo with

// the right arguments.

//

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

#ifndef LLVM_ANALYSIS_MEMORYSSAUPDATER_H

#define LLVM_ANALYSIS_MEMORYSSAUPDATER_H

#include "llvm/ADT/SmallPtrSet.h"

#include "llvm/ADT/SmallSet.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/Analysis/MemorySSA.h"

#include "llvm/IR/BasicBlock.h"

#include "llvm/IR/Dominators.h"

#include "llvm/IR/Module.h"

#include "llvm/IR/OperandTraits.h"

#include "llvm/IR/Type.h"

#include "llvm/IR/Use.h"

#include "llvm/IR/User.h"

#include "llvm/IR/Value.h"

#include "llvm/IR/ValueHandle.h"

#include "llvm/Pass.h"

#include "llvm/Support/Casting.h"

#include "llvm/Support/ErrorHandling.h"

namespace llvm {

class Function;

class Instruction;

class MemoryAccess;

class LLVMContext;

class raw_ostream;

class MemorySSAUpdater {

private:

  MemorySSA *MSSA;

  /// We use WeakVH rather than a costly deletion to deal with dangling pointers.

  /// MemoryPhis are created eagerly and sometimes get zapped shortly afterwards.

  SmallVector<WeakVH, 16> InsertedPHIs;

  SmallPtrSet<BasicBlock *, 8> VisitedBlocks;

  SmallSet<AssertingVH<MemoryPhi>, 8> NonOptPhis;

public:

  MemorySSAUpdater(MemorySSA *MSSA) : MSSA(MSSA) {}

  /// Insert a definition into the MemorySSA IR.  RenameUses will rename any use

  /// below the new def block (and any inserted phis).  RenameUses should be set

  /// to true if the definition may cause new aliases for loads below it.  This

  /// is not the case for hoisting or sinking or other forms of code *movement*.

  /// It *is* the case for straight code insertion.

  /// For example:

  /// store a

  /// if (foo) { }

  /// load a

  ///

  /// Moving the store into the if block, and calling insertDef, does not

  /// require RenameUses.

  /// However, changing it to:

  /// store a

  /// if (foo) { store b }

  /// load a

  /// Where a mayalias b, *does* require RenameUses be set to true.

  void insertDef(MemoryDef *Def, bool RenameUses = false);

  void insertUse(MemoryUse *Use);

  void moveBefore(MemoryUseOrDef *What, MemoryUseOrDef *Where);

  void moveAfter(MemoryUseOrDef *What, MemoryUseOrDef *Where);

  void moveToPlace(MemoryUseOrDef *What, BasicBlock *BB,

                   MemorySSA::InsertionPlace Where);

  /// `From` block was spliced into `From` and `To`.

  /// Move all accesses from `From` to `To` starting at instruction `Start`.

  /// `To` is newly created BB, so empty of MemorySSA::MemoryAccesses.

  /// Edges are already updated, so successors of `To` with MPhi nodes need to

  /// update incoming block.

  /// |------|        |------|

  /// | From |        | From |

  /// |      |        |------|

  /// |      |           ||

  /// |      |   =>      \/

  /// |      |        |------|  <- Start

  /// |      |        |  To  |

  /// |------|        |------|

  void moveAllAfterSpliceBlocks(BasicBlock *From, BasicBlock *To,

                                Instruction *Start);

  /// `From` block was merged into `To`. All instructions were moved and

  /// `From` is an empty block with successor edges; `From` is about to be

  /// deleted. Move all accesses from `From` to `To` starting at instruction

  /// `Start`. `To` may have multiple successors, `From` has a single

  /// predecessor. `From` may have successors with MPhi nodes, replace their

  /// incoming block with `To`.

  /// |------|        |------|

  /// |  To  |        |  To  |

  /// |------|        |      |

  ///    ||      =>   |      |

  ///    \/           |      |

  /// |------|        |      |  <- Start

  /// | From |        |      |

  /// |------|        |------|

  void moveAllAfterMergeBlocks(BasicBlock *From, BasicBlock *To,

                               Instruction *Start);

  // The below are utility functions. Other than creation of accesses to pass

  // to insertDef, and removeAccess to remove accesses, you should generally

  // not attempt to update memoryssa yourself. It is very non-trivial to get

  // the edge cases right, and the above calls already operate in near-optimal

  // time bounds.

  /// Create a MemoryAccess in MemorySSA at a specified point in a block,

  /// with a specified clobbering definition.

  ///

  /// Returns the new MemoryAccess.

  /// This should be called when a memory instruction is created that is being

  /// used to replace an existing memory instruction. It will *not* create PHI

  /// nodes, or verify the clobbering definition. The insertion place is used

  /// solely to determine where in the memoryssa access lists the instruction

  /// will be placed. The caller is expected to keep ordering the same as

  /// instructions.

  /// It will return the new MemoryAccess.

  /// Note: If a MemoryAccess already exists for I, this function will make it

  /// inaccessible and it *must* have removeMemoryAccess called on it.

  MemoryAccess *createMemoryAccessInBB(Instruction *I, MemoryAccess *Definition,

                                       const BasicBlock *BB,

                                       MemorySSA::InsertionPlace Point);

  /// Create a MemoryAccess in MemorySSA before or after an existing

  /// MemoryAccess.

  ///

  /// Returns the new MemoryAccess.

  /// This should be called when a memory instruction is created that is being

  /// used to replace an existing memory instruction. It will *not* create PHI

  /// nodes, or verify the clobbering definition.

  ///

  /// Note: If a MemoryAccess already exists for I, this function will make it

  /// inaccessible and it *must* have removeMemoryAccess called on it.

  MemoryUseOrDef *createMemoryAccessBefore(Instruction *I,

                                           MemoryAccess *Definition,

                                           MemoryUseOrDef *InsertPt);

  MemoryUseOrDef *createMemoryAccessAfter(Instruction *I,

                                          MemoryAccess *Definition,

                                          MemoryAccess *InsertPt);

  /// Remove a MemoryAccess from MemorySSA, including updating all

  /// definitions and uses.

  /// This should be called when a memory instruction that has a MemoryAccess

  /// associated with it is erased from the program.  For example, if a store or

  /// load is simply erased (not replaced), removeMemoryAccess should be called

  /// on the MemoryAccess for that store/load.

  void removeMemoryAccess(MemoryAccess *);

  /// Remove MemoryAccess for a given instruction, if a MemoryAccess exists.

  /// This should be called when an instruction (load/store) is deleted from

  /// the program.

  void removeMemoryAccess(const Instruction *I) {

    if (MemoryAccess *MA = MSSA->getMemoryAccess(I))

      removeMemoryAccess(MA);

  }

  /// Remove all MemoryAcceses in a set of BasicBlocks about to be deleted.

  /// Assumption we make here: all uses of deleted defs and phi must either

  /// occur in blocks about to be deleted (thus will be deleted as well), or

  /// they occur in phis that will simply lose an incoming value.

  /// Deleted blocks still have successor info, but their predecessor edges and

  /// Phi nodes may already be updated. Instructions in DeadBlocks should be

  /// deleted after this call.

  void removeBlocks(const SmallPtrSetImpl<BasicBlock *> &DeadBlocks);

  /// Get handle on MemorySSA.

  MemorySSA* getMemorySSA() const { return MSSA; }

private:

  // Move What before Where in the MemorySSA IR.

  template <class WhereType>

  void moveTo(MemoryUseOrDef *What, BasicBlock *BB, WhereType Where);

  // Move all memory accesses from `From` to `To` starting at `Start`.

  // Restrictions apply, see public wrappers of this method.

  void moveAllAccesses(BasicBlock *From, BasicBlock *To, Instruction *Start);

  MemoryAccess *getPreviousDef(MemoryAccess *);

  MemoryAccess *getPreviousDefInBlock(MemoryAccess *);

  MemoryAccess *

  getPreviousDefFromEnd(BasicBlock *,

                        DenseMap<BasicBlock *, TrackingVH<MemoryAccess>> &);

  MemoryAccess *

  getPreviousDefRecursive(BasicBlock *,

                          DenseMap<BasicBlock *, TrackingVH<MemoryAccess>> &);

  MemoryAccess *recursePhi(MemoryAccess *Phi);

  template <class RangeType>

  MemoryAccess *tryRemoveTrivialPhi(MemoryPhi *Phi, RangeType &Operands);

  void fixupDefs(const SmallVectorImpl<WeakVH> &);

};

} // end namespace llvm

#endif // LLVM_ANALYSIS_MEMORYSSAUPDATER_H