path: root/contrib/libs/llvm12/include/llvm/Transforms/Utils/ScalarEvolutionExpander.h

#pragma once

#ifdef __GNUC__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-parameter"
#endif

//===---- llvm/Analysis/ScalarEvolutionExpander.h - SCEV Exprs --*- 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 defines the classes used to generate code from scalar expressions.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_SCALAREVOLUTIONEXPANDER_H
#define LLVM_ANALYSIS_SCALAREVOLUTIONEXPANDER_H

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ScalarEvolutionNormalization.h"
#include "llvm/Analysis/TargetFolder.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Support/CommandLine.h"

namespace llvm {
extern cl::opt<unsigned> SCEVCheapExpansionBudget; 

/// Return true if the given expression is safe to expand in the sense that 
/// all materialized values are safe to speculate anywhere their operands are 
/// defined. 
bool isSafeToExpand(const SCEV *S, ScalarEvolution &SE); 

/// Return true if the given expression is safe to expand in the sense that 
/// all materialized values are defined and safe to speculate at the specified 
/// location and their operands are defined at this location. 
bool isSafeToExpandAt(const SCEV *S, const Instruction *InsertionPoint, 
                      ScalarEvolution &SE); 

/// struct for holding enough information to help calculate the cost of the 
/// given SCEV when expanded into IR. 
struct SCEVOperand { 
  explicit SCEVOperand(unsigned Opc, int Idx, const SCEV *S) : 
    ParentOpcode(Opc), OperandIdx(Idx), S(S) { } 
  /// LLVM instruction opcode that uses the operand. 
  unsigned ParentOpcode; 
  /// The use index of an expanded instruction. 
  int OperandIdx; 
  /// The SCEV operand to be costed. 
  const SCEV* S; 
}; 

/// This class uses information about analyze scalars to rewrite expressions 
/// in canonical form. 
/// 
/// Clients should create an instance of this class when rewriting is needed, 
/// and destroy it when finished to allow the release of the associated 
/// memory. 
class SCEVExpander : public SCEVVisitor<SCEVExpander, Value *> { 
  ScalarEvolution &SE; 
  const DataLayout &DL; 

  // New instructions receive a name to identify them with the current pass. 
  const char *IVName; 

  /// Indicates whether LCSSA phis should be created for inserted values. 
  bool PreserveLCSSA; 

  // InsertedExpressions caches Values for reuse, so must track RAUW. 
  DenseMap<std::pair<const SCEV *, Instruction *>, TrackingVH<Value>> 
      InsertedExpressions; 

  // InsertedValues only flags inserted instructions so needs no RAUW. 
  DenseSet<AssertingVH<Value>> InsertedValues; 
  DenseSet<AssertingVH<Value>> InsertedPostIncValues; 

  /// Keep track of the existing IR values re-used during expansion. 
  /// FIXME: Ideally re-used instructions would not be added to 
  /// InsertedValues/InsertedPostIncValues. 
  SmallPtrSet<Value *, 16> ReusedValues; 

  /// A memoization of the "relevant" loop for a given SCEV. 
  DenseMap<const SCEV *, const Loop *> RelevantLoops; 

  /// Addrecs referring to any of the given loops are expanded in post-inc 
  /// mode. For example, expanding {1,+,1}<L> in post-inc mode returns the add 
  /// instruction that adds one to the phi for {0,+,1}<L>, as opposed to a new 
  /// phi starting at 1. This is only supported in non-canonical mode. 
  PostIncLoopSet PostIncLoops; 

  /// When this is non-null, addrecs expanded in the loop it indicates should 
  /// be inserted with increments at IVIncInsertPos. 
  const Loop *IVIncInsertLoop; 

  /// When expanding addrecs in the IVIncInsertLoop loop, insert the IV 
  /// increment at this position. 
  Instruction *IVIncInsertPos; 

  /// Phis that complete an IV chain. Reuse 
  DenseSet<AssertingVH<PHINode>> ChainedPhis; 

  /// When true, SCEVExpander tries to expand expressions in "canonical" form. 
  /// When false, expressions are expanded in a more literal form. 
  /// 
  /// In "canonical" form addrecs are expanded as arithmetic based on a 
  /// canonical induction variable. Note that CanonicalMode doesn't guarantee 
  /// that all expressions are expanded in "canonical" form. For some 
  /// expressions literal mode can be preferred. 
  bool CanonicalMode; 

  /// When invoked from LSR, the expander is in "strength reduction" mode. The 
  /// only difference is that phi's are only reused if they are already in 
  /// "expanded" form. 
  bool LSRMode; 

  typedef IRBuilder<TargetFolder, IRBuilderCallbackInserter> BuilderType; 
  BuilderType Builder; 

  // RAII object that stores the current insertion point and restores it when 
  // the object is destroyed. This includes the debug location.  Duplicated 
  // from InsertPointGuard to add SetInsertPoint() which is used to updated 
  // InsertPointGuards stack when insert points are moved during SCEV 
  // expansion. 
  class SCEVInsertPointGuard { 
    IRBuilderBase &Builder; 
    AssertingVH<BasicBlock> Block; 
    BasicBlock::iterator Point; 
    DebugLoc DbgLoc; 
    SCEVExpander *SE; 

    SCEVInsertPointGuard(const SCEVInsertPointGuard &) = delete; 
    SCEVInsertPointGuard &operator=(const SCEVInsertPointGuard &) = delete; 

  public: 
    SCEVInsertPointGuard(IRBuilderBase &B, SCEVExpander *SE) 
        : Builder(B), Block(B.GetInsertBlock()), Point(B.GetInsertPoint()), 
          DbgLoc(B.getCurrentDebugLocation()), SE(SE) { 
      SE->InsertPointGuards.push_back(this); 
    } 

    ~SCEVInsertPointGuard() { 
      // These guards should always created/destroyed in FIFO order since they 
      // are used to guard lexically scoped blocks of code in 
      // ScalarEvolutionExpander. 
      assert(SE->InsertPointGuards.back() == this); 
      SE->InsertPointGuards.pop_back(); 
      Builder.restoreIP(IRBuilderBase::InsertPoint(Block, Point)); 
      Builder.SetCurrentDebugLocation(DbgLoc); 
    } 
 
    BasicBlock::iterator GetInsertPoint() const { return Point; } 
    void SetInsertPoint(BasicBlock::iterator I) { Point = I; } 
  }; 
 
  /// Stack of pointers to saved insert points, used to keep insert points 
  /// consistent when instructions are moved. 
  SmallVector<SCEVInsertPointGuard *, 8> InsertPointGuards; 
 
#ifndef NDEBUG
  const char *DebugType; 
#endif

  friend struct SCEVVisitor<SCEVExpander, Value *>; 

public: 
  /// Construct a SCEVExpander in "canonical" mode. 
  explicit SCEVExpander(ScalarEvolution &se, const DataLayout &DL, 
                        const char *name, bool PreserveLCSSA = true) 
      : SE(se), DL(DL), IVName(name), PreserveLCSSA(PreserveLCSSA), 
        IVIncInsertLoop(nullptr), IVIncInsertPos(nullptr), CanonicalMode(true), 
        LSRMode(false), 
        Builder(se.getContext(), TargetFolder(DL), 
                IRBuilderCallbackInserter( 
                    [this](Instruction *I) { rememberInstruction(I); })) { 
#ifndef NDEBUG
    DebugType = ""; 
#endif
  } 

  ~SCEVExpander() { 
    // Make sure the insert point guard stack is consistent. 
    assert(InsertPointGuards.empty()); 
  } 

#ifndef NDEBUG
  void setDebugType(const char *s) { DebugType = s; } 
#endif

  /// Erase the contents of the InsertedExpressions map so that users trying 
  /// to expand the same expression into multiple BasicBlocks or different 
  /// places within the same BasicBlock can do so. 
  void clear() { 
    InsertedExpressions.clear(); 
    InsertedValues.clear(); 
    InsertedPostIncValues.clear(); 
    ReusedValues.clear(); 
    ChainedPhis.clear(); 
  } 
 
  /// Return a vector containing all instructions inserted during expansion. 
  SmallVector<Instruction *, 32> getAllInsertedInstructions() const { 
    SmallVector<Instruction *, 32> Result; 
    for (auto &VH : InsertedValues) { 
      Value *V = VH; 
      if (ReusedValues.contains(V)) 
        continue; 
      if (auto *Inst = dyn_cast<Instruction>(V)) 
        Result.push_back(Inst); 
    }
    for (auto &VH : InsertedPostIncValues) { 
      Value *V = VH; 
      if (ReusedValues.contains(V)) 
        continue; 
      if (auto *Inst = dyn_cast<Instruction>(V)) 
        Result.push_back(Inst); 
    } 

    return Result; 
  } 
 
  /// Return true for expressions that can't be evaluated at runtime 
  /// within given \b Budget. 
  /// 
  /// At is a parameter which specifies point in code where user is going to 
  /// expand this expression. Sometimes this knowledge can lead to 
  /// a less pessimistic cost estimation. 
  bool isHighCostExpansion(const SCEV *Expr, Loop *L, unsigned Budget, 
                           const TargetTransformInfo *TTI, 
                           const Instruction *At) { 
    assert(TTI && "This function requires TTI to be provided."); 
    assert(At && "This function requires At instruction to be provided."); 
    if (!TTI)      // In assert-less builds, avoid crashing 
      return true; // by always claiming to be high-cost. 
    SmallVector<SCEVOperand, 8> Worklist; 
    SmallPtrSet<const SCEV *, 8> Processed; 
    int BudgetRemaining = Budget * TargetTransformInfo::TCC_Basic; 
    Worklist.emplace_back(-1, -1, Expr); 
    while (!Worklist.empty()) { 
      const SCEVOperand WorkItem = Worklist.pop_back_val(); 
      if (isHighCostExpansionHelper(WorkItem, L, *At, BudgetRemaining, 
                                    *TTI, Processed, Worklist)) 
        return true; 
    }
    assert(BudgetRemaining >= 0 && "Should have returned from inner loop."); 
    return false; 
  } 

  /// Return the induction variable increment's IV operand. 
  Instruction *getIVIncOperand(Instruction *IncV, Instruction *InsertPos, 
                               bool allowScale); 

  /// Utility for hoisting an IV increment. 
  bool hoistIVInc(Instruction *IncV, Instruction *InsertPos); 

  /// replace congruent phis with their most canonical representative. Return 
  /// the number of phis eliminated. 
  unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT, 
                               SmallVectorImpl<WeakTrackingVH> &DeadInsts, 
                               const TargetTransformInfo *TTI = nullptr); 

  /// Insert code to directly compute the specified SCEV expression into the 
  /// program.  The code is inserted into the specified block. 
  Value *expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I) { 
    return expandCodeForImpl(SH, Ty, I, true); 
  } 

  /// Insert code to directly compute the specified SCEV expression into the 
  /// program.  The code is inserted into the SCEVExpander's current 
  /// insertion point. If a type is specified, the result will be expanded to 
  /// have that type, with a cast if necessary. 
  Value *expandCodeFor(const SCEV *SH, Type *Ty = nullptr) { 
    return expandCodeForImpl(SH, Ty, true); 
  } 

  /// Generates a code sequence that evaluates this predicate.  The inserted 
  /// instructions will be at position \p Loc.  The result will be of type i1 
  /// and will have a value of 0 when the predicate is false and 1 otherwise. 
  Value *expandCodeForPredicate(const SCEVPredicate *Pred, Instruction *Loc); 

  /// A specialized variant of expandCodeForPredicate, handling the case when 
  /// we are expanding code for a SCEVEqualPredicate. 
  Value *expandEqualPredicate(const SCEVEqualPredicate *Pred, Instruction *Loc); 

  /// Generates code that evaluates if the \p AR expression will overflow. 
  Value *generateOverflowCheck(const SCEVAddRecExpr *AR, Instruction *Loc, 
                               bool Signed); 

  /// A specialized variant of expandCodeForPredicate, handling the case when 
  /// we are expanding code for a SCEVWrapPredicate. 
  Value *expandWrapPredicate(const SCEVWrapPredicate *P, Instruction *Loc); 

  /// A specialized variant of expandCodeForPredicate, handling the case when 
  /// we are expanding code for a SCEVUnionPredicate. 
  Value *expandUnionPredicate(const SCEVUnionPredicate *Pred, Instruction *Loc); 

  /// Set the current IV increment loop and position. 
  void setIVIncInsertPos(const Loop *L, Instruction *Pos) { 
    assert(!CanonicalMode && 
           "IV increment positions are not supported in CanonicalMode"); 
    IVIncInsertLoop = L; 
    IVIncInsertPos = Pos; 
  } 

  /// Enable post-inc expansion for addrecs referring to the given 
  /// loops. Post-inc expansion is only supported in non-canonical mode. 
  void setPostInc(const PostIncLoopSet &L) { 
    assert(!CanonicalMode && 
           "Post-inc expansion is not supported in CanonicalMode"); 
    PostIncLoops = L; 
  } 

  /// Disable all post-inc expansion. 
  void clearPostInc() { 
    PostIncLoops.clear(); 

    // When we change the post-inc loop set, cached expansions may no 
    // longer be valid. 
    InsertedPostIncValues.clear(); 
  } 

  /// Disable the behavior of expanding expressions in canonical form rather 
  /// than in a more literal form. Non-canonical mode is useful for late 
  /// optimization passes. 
  void disableCanonicalMode() { CanonicalMode = false; } 

  void enableLSRMode() { LSRMode = true; } 

  /// Set the current insertion point. This is useful if multiple calls to 
  /// expandCodeFor() are going to be made with the same insert point and the 
  /// insert point may be moved during one of the expansions (e.g. if the 
  /// insert point is not a block terminator). 
  void setInsertPoint(Instruction *IP) { 
    assert(IP); 
    Builder.SetInsertPoint(IP); 
  } 

  /// Clear the current insertion point. This is useful if the instruction 
  /// that had been serving as the insertion point may have been deleted. 
  void clearInsertPoint() { Builder.ClearInsertionPoint(); } 

  /// Set location information used by debugging information. 
  void SetCurrentDebugLocation(DebugLoc L) { 
    Builder.SetCurrentDebugLocation(std::move(L)); 
  } 

  /// Get location information used by debugging information. 
  DebugLoc getCurrentDebugLocation() const { 
    return Builder.getCurrentDebugLocation(); 
  } 

  /// Return true if the specified instruction was inserted by the code 
  /// rewriter.  If so, the client should not modify the instruction. Note that 
  /// this also includes instructions re-used during expansion. 
  bool isInsertedInstruction(Instruction *I) const { 
    return InsertedValues.count(I) || InsertedPostIncValues.count(I); 
  } 

  void setChainedPhi(PHINode *PN) { ChainedPhis.insert(PN); } 

  /// Try to find the ValueOffsetPair for S. The function is mainly used to 
  /// check whether S can be expanded cheaply.  If this returns a non-None 
  /// value, we know we can codegen the `ValueOffsetPair` into a suitable 
  /// expansion identical with S so that S can be expanded cheaply. 
  /// 
  /// L is a hint which tells in which loop to look for the suitable value. 
  /// On success return value which is equivalent to the expanded S at point 
  /// At. Return nullptr if value was not found. 
  /// 
  /// Note that this function does not perform an exhaustive search. I.e if it 
  /// didn't find any value it does not mean that there is no such value. 
  /// 
  Optional<ScalarEvolution::ValueOffsetPair> 
  getRelatedExistingExpansion(const SCEV *S, const Instruction *At, Loop *L); 

  /// Returns a suitable insert point after \p I, that dominates \p 
  /// MustDominate. Skips instructions inserted by the expander. 
  BasicBlock::iterator findInsertPointAfter(Instruction *I, 
                                            Instruction *MustDominate); 

private: 
  LLVMContext &getContext() const { return SE.getContext(); } 

  /// Insert code to directly compute the specified SCEV expression into the 
  /// program. The code is inserted into the SCEVExpander's current 
  /// insertion point. If a type is specified, the result will be expanded to 
  /// have that type, with a cast if necessary. If \p Root is true, this 
  /// indicates that \p SH is the top-level expression to expand passed from 
  /// an external client call. 
  Value *expandCodeForImpl(const SCEV *SH, Type *Ty, bool Root); 

  /// Insert code to directly compute the specified SCEV expression into the 
  /// program. The code is inserted into the specified block. If \p 
  /// Root is true, this indicates that \p SH is the top-level expression to 
  /// expand passed from an external client call. 
  Value *expandCodeForImpl(const SCEV *SH, Type *Ty, Instruction *I, bool Root); 

  /// Recursive helper function for isHighCostExpansion. 
  bool isHighCostExpansionHelper( 
    const SCEVOperand &WorkItem, Loop *L, const Instruction &At, 
    int &BudgetRemaining, const TargetTransformInfo &TTI, 
    SmallPtrSetImpl<const SCEV *> &Processed, 
    SmallVectorImpl<SCEVOperand> &Worklist); 

  /// Insert the specified binary operator, doing a small amount of work to 
  /// avoid inserting an obviously redundant operation, and hoisting to an 
  /// outer loop when the opportunity is there and it is safe. 
  Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS, 
                     SCEV::NoWrapFlags Flags, bool IsSafeToHoist); 

  /// Arrange for there to be a cast of V to Ty at IP, reusing an existing 
  /// cast if a suitable one exists, moving an existing cast if a suitable one 
  /// exists but isn't in the right place, or creating a new one. 
  Value *ReuseOrCreateCast(Value *V, Type *Ty, Instruction::CastOps Op, 
                           BasicBlock::iterator IP); 

  /// Insert a cast of V to the specified type, which must be possible with a 
  /// noop cast, doing what we can to share the casts. 
  Value *InsertNoopCastOfTo(Value *V, Type *Ty); 

  /// Expand a SCEVAddExpr with a pointer type into a GEP instead of using 
  /// ptrtoint+arithmetic+inttoptr. 
  Value *expandAddToGEP(const SCEV *const *op_begin, const SCEV *const *op_end, 
                        PointerType *PTy, Type *Ty, Value *V); 
  Value *expandAddToGEP(const SCEV *Op, PointerType *PTy, Type *Ty, Value *V); 

  /// Find a previous Value in ExprValueMap for expand. 
  ScalarEvolution::ValueOffsetPair 
  FindValueInExprValueMap(const SCEV *S, const Instruction *InsertPt); 

  Value *expand(const SCEV *S); 

  /// Determine the most "relevant" loop for the given SCEV. 
  const Loop *getRelevantLoop(const SCEV *); 

  Value *visitConstant(const SCEVConstant *S) { return S->getValue(); } 

  Value *visitPtrToIntExpr(const SCEVPtrToIntExpr *S); 

  Value *visitTruncateExpr(const SCEVTruncateExpr *S); 

  Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S); 

  Value *visitSignExtendExpr(const SCEVSignExtendExpr *S); 

  Value *visitAddExpr(const SCEVAddExpr *S); 

  Value *visitMulExpr(const SCEVMulExpr *S); 

  Value *visitUDivExpr(const SCEVUDivExpr *S); 

  Value *visitAddRecExpr(const SCEVAddRecExpr *S); 

  Value *visitSMaxExpr(const SCEVSMaxExpr *S); 

  Value *visitUMaxExpr(const SCEVUMaxExpr *S); 

  Value *visitSMinExpr(const SCEVSMinExpr *S); 

  Value *visitUMinExpr(const SCEVUMinExpr *S); 

  Value *visitUnknown(const SCEVUnknown *S) { return S->getValue(); } 

  void rememberInstruction(Value *I); 

  bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L); 

  bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L); 

  Value *expandAddRecExprLiterally(const SCEVAddRecExpr *); 
  PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized, 
                                     const Loop *L, Type *ExpandTy, Type *IntTy, 
                                     Type *&TruncTy, bool &InvertStep); 
  Value *expandIVInc(PHINode *PN, Value *StepV, const Loop *L, Type *ExpandTy, 
                     Type *IntTy, bool useSubtract); 

  void hoistBeforePos(DominatorTree *DT, Instruction *InstToHoist, 
                      Instruction *Pos, PHINode *LoopPhi); 

  void fixupInsertPoints(Instruction *I); 
 
  /// If required, create LCSSA PHIs for \p Users' operand \p OpIdx. If new 
  /// LCSSA PHIs have been created, return the LCSSA PHI available at \p User. 
  /// If no PHIs have been created, return the unchanged operand \p OpIdx. 
  Value *fixupLCSSAFormFor(Instruction *User, unsigned OpIdx); 
}; 
 
/// Helper to remove instructions inserted during SCEV expansion, unless they 
/// are marked as used. 
class SCEVExpanderCleaner { 
  SCEVExpander &Expander; 
 
  DominatorTree &DT; 
 
  /// Indicates whether the result of the expansion is used. If false, the 
  /// instructions added during expansion are removed. 
  bool ResultUsed; 
 
public: 
  SCEVExpanderCleaner(SCEVExpander &Expander, DominatorTree &DT) 
      : Expander(Expander), DT(DT), ResultUsed(false) {} 
 
  ~SCEVExpanderCleaner(); 
 
  /// Indicate that the result of the expansion is used. 
  void markResultUsed() { ResultUsed = true; } 
}; 
} // namespace llvm 
 
#endif

#ifdef __GNUC__
#pragma GCC diagnostic pop
#endif