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299 lines
11 KiB
C++
299 lines
11 KiB
C++
//===- llvm/Analysis/ScalarEvolution.h - Scalar Evolution -------*- 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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// The ScalarEvolution class is an LLVM pass which can be used to analyze and
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// catagorize scalar expressions in loops. It specializes in recognizing
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// general induction variables, representing them with the abstract and opaque
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// SCEV class. Given this analysis, trip counts of loops and other important
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// properties can be obtained.
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//
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// This analysis is primarily useful for induction variable substitution and
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// strength reduction.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_SCALAREVOLUTION_H
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#define LLVM_ANALYSIS_SCALAREVOLUTION_H
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#include "llvm/Pass.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Support/DataTypes.h"
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#include "llvm/Support/Streams.h"
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#include <set>
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namespace llvm {
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class APInt;
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class ConstantInt;
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class Instruction;
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class Type;
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class ConstantRange;
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class SCEVHandle;
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class ScalarEvolution;
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/// SCEV - This class represent an analyzed expression in the program. These
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/// are reference counted opaque objects that the client is not allowed to
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/// do much with directly.
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///
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class SCEV {
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const unsigned SCEVType; // The SCEV baseclass this node corresponds to
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mutable unsigned RefCount;
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friend class SCEVHandle;
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void addRef() const { ++RefCount; }
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void dropRef() const {
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if (--RefCount == 0)
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delete this;
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}
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SCEV(const SCEV &); // DO NOT IMPLEMENT
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void operator=(const SCEV &); // DO NOT IMPLEMENT
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protected:
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virtual ~SCEV();
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public:
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explicit SCEV(unsigned SCEVTy) : SCEVType(SCEVTy), RefCount(0) {}
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unsigned getSCEVType() const { return SCEVType; }
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/// getValueRange - Return the tightest constant bounds that this value is
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/// known to have. This method is only valid on integer SCEV objects.
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virtual ConstantRange getValueRange() const;
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/// isLoopInvariant - Return true if the value of this SCEV is unchanging in
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/// the specified loop.
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virtual bool isLoopInvariant(const Loop *L) const = 0;
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/// hasComputableLoopEvolution - Return true if this SCEV changes value in a
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/// known way in the specified loop. This property being true implies that
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/// the value is variant in the loop AND that we can emit an expression to
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/// compute the value of the expression at any particular loop iteration.
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virtual bool hasComputableLoopEvolution(const Loop *L) const = 0;
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/// getType - Return the LLVM type of this SCEV expression.
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///
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virtual const Type *getType() const = 0;
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/// getBitWidth - Get the bit width of the type, if it has one, 0 otherwise.
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///
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uint32_t getBitWidth() const;
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/// replaceSymbolicValuesWithConcrete - If this SCEV internally references
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/// the symbolic value "Sym", construct and return a new SCEV that produces
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/// the same value, but which uses the concrete value Conc instead of the
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/// symbolic value. If this SCEV does not use the symbolic value, it
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/// returns itself.
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virtual SCEVHandle
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replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
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const SCEVHandle &Conc,
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ScalarEvolution &SE) const = 0;
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/// print - Print out the internal representation of this scalar to the
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/// specified stream. This should really only be used for debugging
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/// purposes.
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virtual void print(std::ostream &OS) const = 0;
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void print(std::ostream *OS) const { if (OS) print(*OS); }
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/// dump - This method is used for debugging.
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///
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void dump() const;
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};
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inline std::ostream &operator<<(std::ostream &OS, const SCEV &S) {
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S.print(OS);
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return OS;
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}
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/// SCEVCouldNotCompute - An object of this class is returned by queries that
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/// could not be answered. For example, if you ask for the number of
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/// iterations of a linked-list traversal loop, you will get one of these.
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/// None of the standard SCEV operations are valid on this class, it is just a
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/// marker.
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struct SCEVCouldNotCompute : public SCEV {
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SCEVCouldNotCompute();
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// None of these methods are valid for this object.
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virtual bool isLoopInvariant(const Loop *L) const;
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virtual const Type *getType() const;
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virtual bool hasComputableLoopEvolution(const Loop *L) const;
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virtual void print(std::ostream &OS) const;
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void print(std::ostream *OS) const { if (OS) print(*OS); }
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virtual SCEVHandle
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replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
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const SCEVHandle &Conc,
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ScalarEvolution &SE) const;
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/// Methods for support type inquiry through isa, cast, and dyn_cast:
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static inline bool classof(const SCEVCouldNotCompute *S) { return true; }
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static bool classof(const SCEV *S);
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};
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/// SCEVHandle - This class is used to maintain the SCEV object's refcounts,
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/// freeing the objects when the last reference is dropped.
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class SCEVHandle {
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SCEV *S;
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SCEVHandle(); // DO NOT IMPLEMENT
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public:
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SCEVHandle(const SCEV *s) : S(const_cast<SCEV*>(s)) {
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assert(S && "Cannot create a handle to a null SCEV!");
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S->addRef();
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}
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SCEVHandle(const SCEVHandle &RHS) : S(RHS.S) {
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S->addRef();
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}
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~SCEVHandle() { S->dropRef(); }
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operator SCEV*() const { return S; }
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SCEV &operator*() const { return *S; }
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SCEV *operator->() const { return S; }
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bool operator==(SCEV *RHS) const { return S == RHS; }
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bool operator!=(SCEV *RHS) const { return S != RHS; }
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const SCEVHandle &operator=(SCEV *RHS) {
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if (S != RHS) {
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S->dropRef();
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S = RHS;
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S->addRef();
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}
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return *this;
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}
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const SCEVHandle &operator=(const SCEVHandle &RHS) {
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if (S != RHS.S) {
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S->dropRef();
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S = RHS.S;
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S->addRef();
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}
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return *this;
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}
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};
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template<typename From> struct simplify_type;
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template<> struct simplify_type<const SCEVHandle> {
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typedef SCEV* SimpleType;
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static SimpleType getSimplifiedValue(const SCEVHandle &Node) {
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return Node;
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}
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};
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template<> struct simplify_type<SCEVHandle>
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: public simplify_type<const SCEVHandle> {};
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/// ScalarEvolution - This class is the main scalar evolution driver. Because
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/// client code (intentionally) can't do much with the SCEV objects directly,
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/// they must ask this class for services.
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///
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class ScalarEvolution : public FunctionPass {
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void *Impl; // ScalarEvolution uses the pimpl pattern
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public:
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static char ID; // Pass identification, replacement for typeid
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ScalarEvolution() : FunctionPass((intptr_t)&ID), Impl(0) {}
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/// getSCEV - Return a SCEV expression handle for the full generality of the
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/// specified expression.
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SCEVHandle getSCEV(Value *V) const;
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SCEVHandle getConstant(ConstantInt *V);
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SCEVHandle getConstant(const APInt& Val);
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SCEVHandle getTruncateExpr(const SCEVHandle &Op, const Type *Ty);
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SCEVHandle getZeroExtendExpr(const SCEVHandle &Op, const Type *Ty);
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SCEVHandle getSignExtendExpr(const SCEVHandle &Op, const Type *Ty);
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SCEVHandle getAddExpr(std::vector<SCEVHandle> &Ops);
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SCEVHandle getAddExpr(const SCEVHandle &LHS, const SCEVHandle &RHS) {
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std::vector<SCEVHandle> Ops;
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Ops.push_back(LHS);
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Ops.push_back(RHS);
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return getAddExpr(Ops);
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}
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SCEVHandle getAddExpr(const SCEVHandle &Op0, const SCEVHandle &Op1,
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const SCEVHandle &Op2) {
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std::vector<SCEVHandle> Ops;
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Ops.push_back(Op0);
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Ops.push_back(Op1);
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Ops.push_back(Op2);
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return getAddExpr(Ops);
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}
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SCEVHandle getMulExpr(std::vector<SCEVHandle> &Ops);
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SCEVHandle getMulExpr(const SCEVHandle &LHS, const SCEVHandle &RHS) {
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std::vector<SCEVHandle> Ops;
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Ops.push_back(LHS);
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Ops.push_back(RHS);
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return getMulExpr(Ops);
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}
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SCEVHandle getSDivExpr(const SCEVHandle &LHS, const SCEVHandle &RHS);
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SCEVHandle getAddRecExpr(const SCEVHandle &Start, const SCEVHandle &Step,
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const Loop *L);
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SCEVHandle getAddRecExpr(std::vector<SCEVHandle> &Operands,
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const Loop *L);
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SCEVHandle getAddRecExpr(const std::vector<SCEVHandle> &Operands,
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const Loop *L) {
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std::vector<SCEVHandle> NewOp(Operands);
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return getAddRecExpr(NewOp, L);
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}
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SCEVHandle getSMaxExpr(const SCEVHandle &LHS, const SCEVHandle &RHS);
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SCEVHandle getSMaxExpr(std::vector<SCEVHandle> Operands);
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SCEVHandle getUnknown(Value *V);
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/// getNegativeSCEV - Return the SCEV object corresponding to -V.
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///
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SCEVHandle getNegativeSCEV(const SCEVHandle &V);
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/// getMinusSCEV - Return LHS-RHS.
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///
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SCEVHandle getMinusSCEV(const SCEVHandle &LHS,
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const SCEVHandle &RHS);
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/// getIntegerSCEV - Given an integer or FP type, create a constant for the
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/// specified signed integer value and return a SCEV for the constant.
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SCEVHandle getIntegerSCEV(int Val, const Type *Ty);
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/// hasSCEV - Return true if the SCEV for this value has already been
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/// computed.
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bool hasSCEV(Value *V) const;
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/// setSCEV - Insert the specified SCEV into the map of current SCEVs for
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/// the specified value.
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void setSCEV(Value *V, const SCEVHandle &H);
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/// getSCEVAtScope - Return a SCEV expression handle for the specified value
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/// at the specified scope in the program. The L value specifies a loop
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/// nest to evaluate the expression at, where null is the top-level or a
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/// specified loop is immediately inside of the loop.
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///
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/// This method can be used to compute the exit value for a variable defined
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/// in a loop by querying what the value will hold in the parent loop.
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///
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/// If this value is not computable at this scope, a SCEVCouldNotCompute
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/// object is returned.
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SCEVHandle getSCEVAtScope(Value *V, const Loop *L) const;
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/// getIterationCount - If the specified loop has a predictable iteration
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/// count, return it, otherwise return a SCEVCouldNotCompute object.
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SCEVHandle getIterationCount(const Loop *L) const;
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/// hasLoopInvariantIterationCount - Return true if the specified loop has
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/// an analyzable loop-invariant iteration count.
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bool hasLoopInvariantIterationCount(const Loop *L) const;
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/// deleteValueFromRecords - This method should be called by the
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/// client before it removes a Value from the program, to make sure
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/// that no dangling references are left around.
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void deleteValueFromRecords(Value *V) const;
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virtual bool runOnFunction(Function &F);
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virtual void releaseMemory();
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virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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virtual void print(std::ostream &OS, const Module* = 0) const;
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void print(std::ostream *OS, const Module* M = 0) const {
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if (OS) print(*OS, M);
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}
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};
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}
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#endif
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