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- #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_TRANSFORMS_UTILS_SCALAREVOLUTIONEXPANDER_H
- #define LLVM_TRANSFORMS_UTILS_SCALAREVOLUTIONEXPANDER_H
- #include "llvm/ADT/DenseMap.h"
- #include "llvm/ADT/DenseSet.h"
- #include "llvm/ADT/SmallVector.h"
- #include "llvm/Analysis/InstSimplifyFolder.h"
- #include "llvm/Analysis/ScalarEvolutionExpressions.h"
- #include "llvm/Analysis/ScalarEvolutionNormalization.h"
- #include "llvm/Analysis/TargetTransformInfo.h"
- #include "llvm/IR/IRBuilder.h"
- #include "llvm/IR/ValueHandle.h"
- #include "llvm/Support/CommandLine.h"
- #include "llvm/Support/InstructionCost.h"
- namespace llvm {
- extern cl::opt<unsigned> SCEVCheapExpansionBudget;
- /// 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;
- // The induction variables generated.
- SmallVector<WeakVH, 2> InsertedIVs;
- /// 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<InstSimplifyFolder, 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;
- #ifdef LLVM_ENABLE_ABI_BREAKING_CHECKS
- 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(), InstSimplifyFolder(DL),
- IRBuilderCallbackInserter(
- [this](Instruction *I) { rememberInstruction(I); })) {
- #ifdef LLVM_ENABLE_ABI_BREAKING_CHECKS
- DebugType = "";
- #endif
- }
- ~SCEVExpander() {
- // Make sure the insert point guard stack is consistent.
- assert(InsertPointGuards.empty());
- }
- #ifdef LLVM_ENABLE_ABI_BREAKING_CHECKS
- 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();
- InsertedIVs.clear();
- }
- ScalarEvolution *getSE() { return &SE; }
- const SmallVectorImpl<WeakVH> &getInsertedIVs() const { return InsertedIVs; }
- /// Return a vector containing all instructions inserted during expansion.
- SmallVector<Instruction *, 32> getAllInsertedInstructions() const {
- SmallVector<Instruction *, 32> Result;
- for (const auto &VH : InsertedValues) {
- Value *V = VH;
- if (ReusedValues.contains(V))
- continue;
- if (auto *Inst = dyn_cast<Instruction>(V))
- Result.push_back(Inst);
- }
- for (const 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.
- ///
- /// \p At is a parameter which specifies point in code where user is going to
- /// expand these expressions. Sometimes this knowledge can lead to
- /// a less pessimistic cost estimation.
- bool isHighCostExpansion(ArrayRef<const SCEV *> Exprs, 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;
- InstructionCost Cost = 0;
- unsigned ScaledBudget = Budget * TargetTransformInfo::TCC_Basic;
- for (auto *Expr : Exprs)
- Worklist.emplace_back(-1, -1, Expr);
- while (!Worklist.empty()) {
- const SCEVOperand WorkItem = Worklist.pop_back_val();
- if (isHighCostExpansionHelper(WorkItem, L, *At, Cost, ScaledBudget, *TTI,
- Processed, Worklist))
- return true;
- }
- assert(Cost <= ScaledBudget && "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 \p IncV (with all subexpressions requried for its
- /// computation) before \p InsertPos. If \p RecomputePoisonFlags is set, drops
- /// all poison-generating flags from instructions being hoisted and tries to
- /// re-infer them in the new location. It should be used when we are going to
- /// introduce a new use in the new position that didn't exist before, and may
- /// trigger new UB in case of poison.
- bool hoistIVInc(Instruction *IncV, Instruction *InsertPos,
- bool RecomputePoisonFlags = false);
- /// 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);
- /// 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, and the expander is capable of expanding the expression.
- bool isSafeToExpand(const SCEV *S) const;
- /// 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) const;
- /// 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);
- }
- /// 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);
- }
- /// 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 SCEVComparePredicate.
- Value *expandComparePredicate(const SCEVComparePredicate *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.
- ///
- Value *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) const;
- 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);
- /// 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);
- /// Recursive helper function for isHighCostExpansion.
- bool isHighCostExpansionHelper(const SCEVOperand &WorkItem, Loop *L,
- const Instruction &At, InstructionCost &Cost,
- unsigned Budget,
- 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);
- /// We want to cast \p V. What would be the best place for such a cast?
- BasicBlock::iterator GetOptimalInsertionPointForCastOf(Value *V) const;
- /// 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.
- Value *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 *expandMinMaxExpr(const SCEVNAryExpr *S, Intrinsic::ID IntrinID,
- Twine Name, bool IsSequential = false);
- 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 *visitSequentialUMinExpr(const SCEVSequentialUMinExpr *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 fixupInsertPoints(Instruction *I);
- /// Create LCSSA PHIs for \p V, if it is required for uses at the Builder's
- /// current insertion point.
- Value *fixupLCSSAFormFor(Value *V);
- };
- /// Helper to remove instructions inserted during SCEV expansion, unless they
- /// are marked as used.
- class SCEVExpanderCleaner {
- SCEVExpander &Expander;
- /// Indicates whether the result of the expansion is used. If false, the
- /// instructions added during expansion are removed.
- bool ResultUsed;
- public:
- SCEVExpanderCleaner(SCEVExpander &Expander)
- : Expander(Expander), ResultUsed(false) {}
- ~SCEVExpanderCleaner() { cleanup(); }
- /// Indicate that the result of the expansion is used.
- void markResultUsed() { ResultUsed = true; }
- void cleanup();
- };
- } // namespace llvm
- #endif
- #ifdef __GNUC__
- #pragma GCC diagnostic pop
- #endif
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