#include "llvm/Pass.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Support/DataTypes.h"
+#include "llvm/Support/ValueHandle.h"
#include <iosfwd>
namespace llvm {
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
+ /// SCEV - This class represents an analyzed expression in the program. These
+ /// are reference-counted opaque objects that the client is not allowed to
/// do much with directly.
///
class SCEV {
///
bool isZero() const;
+ /// isOne - Return true if the expression is a constant one.
+ ///
+ bool isOne() const;
+
/// replaceSymbolicValuesWithConcrete - If this SCEV internally references
/// the symbolic value "Sym", construct and return a new SCEV that produces
/// the same value, but which uses the concrete value Conc instead of the
/// 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 {
+ /// 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;
/// Scalars - This is a cache of the scalars we have analyzed so far.
///
- std::map<Value*, SCEVHandle> Scalars;
+ 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*, SCEVHandle> BackedgeTakenCounts;
+ 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.
/// 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);
/// 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
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.
- SCEVHandle ComputeBackedgeTakenCount(const Loop *L);
+ 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.
/// HowFarToZero - Return the number of times a backedge comparing the
/// specified value to zero will execute. If not computable, return
/// UnknownValue.
- SCEVHandle HowFarToZero(SCEV *V, const Loop *L);
+ 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(SCEV *V, const Loop *L);
+ 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.
- SCEVHandle HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L,
- bool isSigned);
+ 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
Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs,
const Loop *L);
- /// getSCEVAtScope - Compute the value of the specified expression within
- /// the indicated loop (which may be null to indicate in no loop). If the
- /// expression cannot be evaluated, return UnknownValue itself.
- SCEVHandle getSCEVAtScope(SCEV *S, 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
/// 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);
/// This method can be used to compute the exit value for a variable defined
/// in a loop by querying what the value will hold in the parent loop.
///
- /// If this value is not computable at this scope, a SCEVCouldNotCompute
- /// object is returned.
+ /// In the case that a relevant loop exit value cannot be computed, the
+ /// original value V is returned.
+ 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
///
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);
/// 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);
-
virtual bool runOnFunction(Function &F);
virtual void releaseMemory();
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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