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Diffstat (limited to 'contrib/llvm-project/llvm/include/llvm/Transforms/Utils/ScalarEvolutionExpander.h')
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diff --git a/contrib/llvm-project/llvm/include/llvm/Transforms/Utils/ScalarEvolutionExpander.h b/contrib/llvm-project/llvm/include/llvm/Transforms/Utils/ScalarEvolutionExpander.h new file mode 100644 index 000000000000..547245cfb963 --- /dev/null +++ b/contrib/llvm-project/llvm/include/llvm/Transforms/Utils/ScalarEvolutionExpander.h @@ -0,0 +1,511 @@ +//===---- 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 |