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Bring function documentation for ScalarEvolutionExpander up to code by not repeating the function name in the comment documenting functionality. Reflow the edited comments where needed. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234847 91177308-0d34-0410-b5e6-96231b3b80d8
281 lines
11 KiB
C++
281 lines
11 KiB
C++
//===---- llvm/Analysis/ScalarEvolutionExpander.h - SCEV Exprs --*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the classes used to generate code from scalar expressions.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_SCALAREVOLUTIONEXPANDER_H
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#define LLVM_ANALYSIS_SCALAREVOLUTIONEXPANDER_H
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/Analysis/ScalarEvolutionNormalization.h"
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#include "llvm/Analysis/TargetFolder.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/ValueHandle.h"
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#include <set>
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namespace llvm {
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class TargetTransformInfo;
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/// Return true if the given expression is safe to expand in the sense that
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/// all materialized values are safe to speculate.
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bool isSafeToExpand(const SCEV *S, ScalarEvolution &SE);
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/// This class uses information about analyze scalars to
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/// rewrite expressions in canonical form.
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///
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/// Clients should create an instance of this class when rewriting is needed,
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/// and destroy it when finished to allow the release of the associated
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/// memory.
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class SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
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ScalarEvolution &SE;
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const DataLayout &DL;
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// New instructions receive a name to identifies them with the current pass.
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const char* IVName;
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// InsertedExpressions caches Values for reuse, so must track RAUW.
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std::map<std::pair<const SCEV *, Instruction *>, TrackingVH<Value> >
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InsertedExpressions;
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// InsertedValues only flags inserted instructions so needs no RAUW.
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std::set<AssertingVH<Value> > InsertedValues;
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std::set<AssertingVH<Value> > InsertedPostIncValues;
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/// A memoization of the "relevant" loop for a given SCEV.
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DenseMap<const SCEV *, const Loop *> RelevantLoops;
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/// \brief Addrecs referring to any of the given loops are expanded
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/// in post-inc mode. For example, expanding {1,+,1}<L> in post-inc mode
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/// returns the add instruction that adds one to the phi for {0,+,1}<L>,
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/// as opposed to a new phi starting at 1. This is only supported in
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/// non-canonical mode.
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PostIncLoopSet PostIncLoops;
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/// \brief When this is non-null, addrecs expanded in the loop it indicates
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/// should be inserted with increments at IVIncInsertPos.
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const Loop *IVIncInsertLoop;
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/// \brief When expanding addrecs in the IVIncInsertLoop loop, insert the IV
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/// increment at this position.
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Instruction *IVIncInsertPos;
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/// \brief Phis that complete an IV chain. Reuse
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std::set<AssertingVH<PHINode> > ChainedPhis;
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/// \brief When true, expressions are expanded in "canonical" form. In
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/// particular, addrecs are expanded as arithmetic based on a canonical
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/// induction variable. When false, expression are expanded in a more
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/// literal form.
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bool CanonicalMode;
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/// \brief When invoked from LSR, the expander is in "strength reduction"
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/// mode. The only difference is that phi's are only reused if they are
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/// already in "expanded" form.
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bool LSRMode;
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typedef IRBuilder<true, TargetFolder> BuilderType;
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BuilderType Builder;
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#ifndef NDEBUG
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const char *DebugType;
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#endif
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friend struct SCEVVisitor<SCEVExpander, Value*>;
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public:
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/// \brief Construct a SCEVExpander in "canonical" mode.
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explicit SCEVExpander(ScalarEvolution &se, const DataLayout &DL,
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const char *name)
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: SE(se), DL(DL), IVName(name), IVIncInsertLoop(nullptr),
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IVIncInsertPos(nullptr), CanonicalMode(true), LSRMode(false),
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Builder(se.getContext(), TargetFolder(DL)) {
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#ifndef NDEBUG
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DebugType = "";
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#endif
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}
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#ifndef NDEBUG
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void setDebugType(const char* s) { DebugType = s; }
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#endif
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/// \brief Erase the contents of the InsertedExpressions map so that users
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/// trying to expand the same expression into multiple BasicBlocks or
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/// different places within the same BasicBlock can do so.
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void clear() {
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InsertedExpressions.clear();
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InsertedValues.clear();
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InsertedPostIncValues.clear();
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ChainedPhis.clear();
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}
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/// \brief Return true for expressions that may incur non-trivial cost to
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/// evaluate at runtime.
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bool isHighCostExpansion(const SCEV *Expr, Loop *L) {
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SmallPtrSet<const SCEV *, 8> Processed;
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return isHighCostExpansionHelper(Expr, L, Processed);
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}
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/// \brief This method returns the canonical induction variable of the
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/// specified type for the specified loop (inserting one if there is none).
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/// A canonical induction variable starts at zero and steps by one on each
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/// iteration.
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PHINode *getOrInsertCanonicalInductionVariable(const Loop *L, Type *Ty);
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/// \brief Return the induction variable increment's IV operand.
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Instruction *getIVIncOperand(Instruction *IncV, Instruction *InsertPos,
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bool allowScale);
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/// \brief Utility for hoisting an IV increment.
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bool hoistIVInc(Instruction *IncV, Instruction *InsertPos);
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/// \brief replace congruent phis with their most canonical
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/// representative. Return the number of phis eliminated.
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unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT,
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SmallVectorImpl<WeakVH> &DeadInsts,
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const TargetTransformInfo *TTI = nullptr);
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/// \brief Insert code to directly compute the specified SCEV expression
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/// into the program. The inserted code is inserted into the specified
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/// block.
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Value *expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I);
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/// \brief Set the current IV increment loop and position.
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void setIVIncInsertPos(const Loop *L, Instruction *Pos) {
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assert(!CanonicalMode &&
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"IV increment positions are not supported in CanonicalMode");
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IVIncInsertLoop = L;
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IVIncInsertPos = Pos;
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}
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/// \brief Enable post-inc expansion for addrecs referring to the given
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/// loops. Post-inc expansion is only supported in non-canonical mode.
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void setPostInc(const PostIncLoopSet &L) {
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assert(!CanonicalMode &&
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"Post-inc expansion is not supported in CanonicalMode");
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PostIncLoops = L;
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}
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/// \brief Disable all post-inc expansion.
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void clearPostInc() {
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PostIncLoops.clear();
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// When we change the post-inc loop set, cached expansions may no
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// longer be valid.
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InsertedPostIncValues.clear();
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}
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/// \brief Disable the behavior of expanding expressions in canonical form
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/// rather than in a more literal form. Non-canonical mode is useful for
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/// late optimization passes.
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void disableCanonicalMode() { CanonicalMode = false; }
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void enableLSRMode() { LSRMode = true; }
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/// \brief Clear the current insertion point. This is useful if the
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/// instruction that had been serving as the insertion point may have been
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/// deleted.
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void clearInsertPoint() {
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Builder.ClearInsertionPoint();
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}
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/// \brief Return true if the specified instruction was inserted by the code
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/// rewriter. If so, the client should not modify the instruction.
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bool isInsertedInstruction(Instruction *I) const {
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return InsertedValues.count(I) || InsertedPostIncValues.count(I);
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}
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void setChainedPhi(PHINode *PN) { ChainedPhis.insert(PN); }
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private:
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LLVMContext &getContext() const { return SE.getContext(); }
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/// \brief Recursive helper function for isHighCostExpansion.
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bool isHighCostExpansionHelper(const SCEV *S, Loop *L,
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SmallPtrSetImpl<const SCEV *> &Processed);
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/// \brief Insert the specified binary operator, doing a small amount
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/// of work to avoid inserting an obviously redundant operation.
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Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS);
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/// \brief Arrange for there to be a cast of V to Ty at IP, reusing an
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/// existing cast if a suitable one exists, moving an existing cast if a
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/// suitable one exists but isn't in the right place, or or creating a new
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/// one.
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Value *ReuseOrCreateCast(Value *V, Type *Ty,
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Instruction::CastOps Op,
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BasicBlock::iterator IP);
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/// \brief Insert a cast of V to the specified type, which must be possible
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/// with a noop cast, doing what we can to share the casts.
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Value *InsertNoopCastOfTo(Value *V, Type *Ty);
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/// \brief Expand a SCEVAddExpr with a pointer type into a GEP
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/// instead of using ptrtoint+arithmetic+inttoptr.
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Value *expandAddToGEP(const SCEV *const *op_begin,
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const SCEV *const *op_end,
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PointerType *PTy, Type *Ty, Value *V);
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Value *expand(const SCEV *S);
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/// \brief Insert code to directly compute the specified SCEV expression
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/// into the program. The inserted code is inserted into the SCEVExpander's
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/// current insertion point. If a type is specified, the result will be
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/// expanded to have that type, with a cast if necessary.
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Value *expandCodeFor(const SCEV *SH, Type *Ty = nullptr);
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/// \brief Determine the most "relevant" loop for the given SCEV.
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const Loop *getRelevantLoop(const SCEV *);
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Value *visitConstant(const SCEVConstant *S) {
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return S->getValue();
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}
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Value *visitTruncateExpr(const SCEVTruncateExpr *S);
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Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
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Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
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Value *visitAddExpr(const SCEVAddExpr *S);
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Value *visitMulExpr(const SCEVMulExpr *S);
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Value *visitUDivExpr(const SCEVUDivExpr *S);
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Value *visitAddRecExpr(const SCEVAddRecExpr *S);
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Value *visitSMaxExpr(const SCEVSMaxExpr *S);
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Value *visitUMaxExpr(const SCEVUMaxExpr *S);
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Value *visitUnknown(const SCEVUnknown *S) {
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return S->getValue();
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}
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void rememberInstruction(Value *I);
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bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
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bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
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Value *expandAddRecExprLiterally(const SCEVAddRecExpr *);
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PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
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const Loop *L,
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Type *ExpandTy,
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Type *IntTy,
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Type *&TruncTy,
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bool &InvertStep);
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Value *expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
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Type *ExpandTy, Type *IntTy, bool useSubtract);
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};
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}
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#endif
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