#include "llvm/Pass.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Support/DataTypes.h"
+#include "llvm/Support/ValueHandle.h"
#include <iosfwd>
namespace llvm {
class Type;
class SCEVHandle;
class ScalarEvolution;
+ class TargetData;
/// SCEV - This class represent an analyzed expression in the program. These
/// are reference counted opaque objects that the client is not allowed to
/// marker.
struct SCEVCouldNotCompute : public SCEV {
SCEVCouldNotCompute();
+ ~SCEVCouldNotCompute();
// None of these methods are valid for this object.
virtual bool isLoopInvariant(const Loop *L) const;
static bool classof(const SCEV *S);
};
+ /// 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);
+ };
+
/// SCEVHandle - This class is used to maintain the SCEV object's refcounts,
/// freeing the objects when the last reference is dropped.
class SCEVHandle {
- SCEV *S;
+ const SCEV *S;
SCEVHandle(); // DO NOT IMPLEMENT
public:
- SCEVHandle(const SCEV *s) : S(const_cast<SCEV*>(s)) {
+ SCEVHandle(const SCEV *s) : S(s) {
assert(S && "Cannot create a handle to a null SCEV!");
S->addRef();
}
}
~SCEVHandle() { S->dropRef(); }
- operator SCEV*() const { return S; }
+ operator const SCEV*() const { return S; }
- SCEV &operator*() const { return *S; }
- SCEV *operator->() const { return S; }
+ const SCEV &operator*() const { return *S; }
+ const SCEV *operator->() const { return S; }
- bool operator==(SCEV *RHS) const { return S == RHS; }
- bool operator!=(SCEV *RHS) const { return S != RHS; }
+ bool operator==(const SCEV *RHS) const { return S == RHS; }
+ bool operator!=(const SCEV *RHS) const { return S != RHS; }
const SCEVHandle &operator=(SCEV *RHS) {
if (S != RHS) {
template<typename From> struct simplify_type;
template<> struct simplify_type<const SCEVHandle> {
- typedef SCEV* SimpleType;
+ typedef const SCEV* SimpleType;
static SimpleType getSimplifiedValue(const SCEVHandle &Node) {
return Node;
}
/// they must ask this class for services.
///
class ScalarEvolution : public FunctionPass {
- void *Impl; // ScalarEvolution uses the pimpl pattern
+ friend class SCEVCallbackVH;
+
+ /// 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);
+
+ /// 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);
+
public:
static char ID; // Pass identification, replacement for typeid
- ScalarEvolution() : FunctionPass(&ID), Impl(0) {}
+ ScalarEvolution();
/// isSCEVable - Test if values of the given type are analyzable within
/// the SCEV framework. This primarily includes integer types, and it
/// getSCEV - Return a SCEV expression handle for the full generality of the
/// specified expression.
- SCEVHandle getSCEV(Value *V) const;
+ SCEVHandle getSCEV(Value *V);
SCEVHandle getConstant(ConstantInt *V);
SCEVHandle getConstant(const APInt& Val);
/// extended, it is sign extended.
SCEVHandle getTruncateOrSignExtend(const SCEVHandle &V, const Type *Ty);
+ /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of
+ /// the input value to the specified type. If the type must be extended,
+ /// it is zero extended. The conversion must not be narrowing.
+ SCEVHandle getNoopOrZeroExtend(const SCEVHandle &V, const Type *Ty);
+
+ /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of
+ /// the input value to the specified type. If the type must be extended,
+ /// it is sign extended. The conversion must not be narrowing.
+ SCEVHandle getNoopOrSignExtend(const SCEVHandle &V, const Type *Ty);
+
+ /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
+ /// input value to the specified type. The conversion must not be
+ /// widening.
+ SCEVHandle getTruncateOrNoop(const SCEVHandle &V, const Type *Ty);
+
/// getIntegerSCEV - Given an integer or FP type, create a constant for the
/// specified signed integer value and return a SCEV for the constant.
SCEVHandle getIntegerSCEV(int Val, const Type *Ty);
///
/// If this value is not computable at this scope, a SCEVCouldNotCompute
/// object is returned.
- SCEVHandle getSCEVAtScope(Value *V, const Loop *L) const;
+ SCEVHandle getSCEVAtScope(const SCEV *S, const Loop *L);
+
+ /// getSCEVAtScope - This is a convenience function which does
+ /// getSCEVAtScope(getSCEV(V), L).
+ SCEVHandle getSCEVAtScope(Value *V, const Loop *L);
/// isLoopGuardedByCond - Test whether entry to the loop is protected by
- /// a conditional between LHS and RHS.
+ /// a conditional between LHS and RHS. This is used to help avoid max
+ /// expressions in loop trip counts.
bool isLoopGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
- SCEV *LHS, SCEV *RHS);
+ const SCEV *LHS, const SCEV *RHS);
/// getBackedgeTakenCount - If the specified loop has a predictable
/// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
/// loop-invariant backedge-taken count (see
/// hasLoopInvariantBackedgeTakenCount).
///
- SCEVHandle getBackedgeTakenCount(const Loop *L) const;
+ SCEVHandle getBackedgeTakenCount(const Loop *L);
+
+ /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
+ /// return the least SCEV value that is known never to be less than the
+ /// actual backedge taken count.
+ SCEVHandle getMaxBackedgeTakenCount(const Loop *L);
/// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop
/// has an analyzable loop-invariant backedge-taken count.
- bool hasLoopInvariantBackedgeTakenCount(const Loop *L) const;
+ bool hasLoopInvariantBackedgeTakenCount(const Loop *L);
/// forgetLoopBackedgeTakenCount - This method should be called by the
/// client when it has changed a loop in a way that may effect
/// is deleted.
void forgetLoopBackedgeTakenCount(const Loop *L);
- /// deleteValueFromRecords - This method should be called by the
- /// client before it removes a Value from the program, to make sure
- /// that no dangling references are left around.
- void deleteValueFromRecords(Value *V) const;
-
virtual bool runOnFunction(Function &F);
virtual void releaseMemory();
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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