+ /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be
+ /// notified whenever a Value is deleted.
+ class SCEVCallbackVH : public CallbackVH {
+ ScalarEvolution *SE;
+ virtual void deleted();
+ virtual void allUsesReplacedWith(Value *New);
+ public:
+ SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0);
+ };
+
+ friend class SCEVCallbackVH;
+ friend class SCEVExpander;
+
+ /// F - The function we are analyzing.
+ ///
+ Function *F;
+
+ /// LI - The loop information for the function we are currently analyzing.
+ ///
+ LoopInfo *LI;
+
+ /// TD - The target data information for the target we are targetting.
+ ///
+ TargetData *TD;
+
+ /// UnknownValue - This SCEV is used to represent unknown trip counts and
+ /// things.
+ SCEVHandle UnknownValue;
+
+ /// Scalars - This is a cache of the scalars we have analyzed so far.
+ ///
+ std::map<SCEVCallbackVH, SCEVHandle> Scalars;
+
+ /// BackedgeTakenInfo - Information about the backedge-taken count
+ /// of a loop. This currently inclues an exact count and a maximum count.
+ ///
+ struct BackedgeTakenInfo {
+ /// Exact - An expression indicating the exact backedge-taken count of
+ /// the loop if it is known, or a SCEVCouldNotCompute otherwise.
+ SCEVHandle Exact;
+
+ /// Exact - An expression indicating the least maximum backedge-taken
+ /// count of the loop that is known, or a SCEVCouldNotCompute.
+ SCEVHandle Max;
+
+ /*implicit*/ BackedgeTakenInfo(SCEVHandle exact) :
+ Exact(exact), Max(exact) {}
+
+ /*implicit*/ BackedgeTakenInfo(const SCEV *exact) :
+ Exact(exact), Max(exact) {}
+
+ BackedgeTakenInfo(SCEVHandle exact, SCEVHandle max) :
+ Exact(exact), Max(max) {}
+
+ /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any
+ /// computed information, or whether it's all SCEVCouldNotCompute
+ /// values.
+ bool hasAnyInfo() const {
+ return !isa<SCEVCouldNotCompute>(Exact) ||
+ !isa<SCEVCouldNotCompute>(Max);
+ }
+ };
+
+ /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for
+ /// this function as they are computed.
+ std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts;
+
+ /// ConstantEvolutionLoopExitValue - This map contains entries for all of
+ /// the PHI instructions that we attempt to compute constant evolutions for.
+ /// This allows us to avoid potentially expensive recomputation of these
+ /// properties. An instruction maps to null if we are unable to compute its
+ /// exit value.
+ std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue;
+
+ /// ValuesAtScopes - This map contains entries for all the instructions
+ /// that we attempt to compute getSCEVAtScope information for without
+ /// using SCEV techniques, which can be expensive.
+ std::map<Instruction *, std::map<const Loop *, Constant *> > ValuesAtScopes;
+
+ /// createSCEV - We know that there is no SCEV for the specified value.
+ /// Analyze the expression.
+ SCEVHandle createSCEV(Value *V);
+
+ /// createNodeForPHI - Provide the special handling we need to analyze PHI
+ /// SCEVs.
+ SCEVHandle createNodeForPHI(PHINode *PN);
+
+ /// createNodeForGEP - Provide the special handling we need to analyze GEP
+ /// SCEVs.
+ SCEVHandle createNodeForGEP(User *GEP);
+
+ /// ReplaceSymbolicValueWithConcrete - This looks up the computed SCEV value
+ /// for the specified instruction and replaces any references to the
+ /// symbolic value SymName with the specified value. This is used during
+ /// PHI resolution.
+ void ReplaceSymbolicValueWithConcrete(Instruction *I,
+ const SCEVHandle &SymName,
+ const SCEVHandle &NewVal);
+
+ /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given
+ /// loop, lazily computing new values if the loop hasn't been analyzed
+ /// yet.
+ const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L);
+
+ /// ComputeBackedgeTakenCount - Compute the number of times the specified
+ /// loop will iterate.
+ BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L);
+
+ /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition
+ /// of 'icmp op load X, cst', try to see if we can compute the trip count.
+ SCEVHandle
+ ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI,
+ Constant *RHS,
+ const Loop *L,
+ ICmpInst::Predicate p);
+
+ /// ComputeBackedgeTakenCountExhaustively - If the trip is known to execute
+ /// a constant number of times (the condition evolves only from constants),
+ /// try to evaluate a few iterations of the loop until we get the exit
+ /// condition gets a value of ExitWhen (true or false). If we cannot
+ /// evaluate the trip count of the loop, return UnknownValue.
+ SCEVHandle ComputeBackedgeTakenCountExhaustively(const Loop *L, Value *Cond,
+ bool ExitWhen);
+
+ /// HowFarToZero - Return the number of times a backedge comparing the
+ /// specified value to zero will execute. If not computable, return
+ /// UnknownValue.
+ SCEVHandle HowFarToZero(const SCEV *V, const Loop *L);
+
+ /// HowFarToNonZero - Return the number of times a backedge checking the
+ /// specified value for nonzero will execute. If not computable, return
+ /// UnknownValue.
+ SCEVHandle HowFarToNonZero(const SCEV *V, const Loop *L);
+
+ /// HowManyLessThans - Return the number of times a backedge containing the
+ /// specified less-than comparison will execute. If not computable, return
+ /// UnknownValue. isSigned specifies whether the less-than is signed.
+ BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
+ const Loop *L, bool isSigned);
+
+ /// getLoopPredecessor - If the given loop's header has exactly one unique
+ /// predecessor outside the loop, return it. Otherwise return null.
+ BasicBlock *getLoopPredecessor(const Loop *L);
+
+ /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
+ /// (which may not be an immediate predecessor) which has exactly one
+ /// successor from which BB is reachable, or null if no such block is
+ /// found.
+ BasicBlock* getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB);
+
+ /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
+ /// in the header of its containing loop, we know the loop executes a
+ /// constant number of times, and the PHI node is just a recurrence
+ /// involving constants, fold it.
+ Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs,
+ const Loop *L);
+
+ /// forgetLoopPHIs - Delete the memoized SCEVs associated with the
+ /// PHI nodes in the given loop. This is used when the trip count of
+ /// the loop may have changed.
+ void forgetLoopPHIs(const Loop *L);
+