1 //===- llvm/Analysis/ScalarEvolution.h - Scalar Evolution -------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // The ScalarEvolution class is an LLVM pass which can be used to analyze and
11 // catagorize scalar expressions in loops. It specializes in recognizing
12 // general induction variables, representing them with the abstract and opaque
13 // SCEV class. Given this analysis, trip counts of loops and other important
14 // properties can be obtained.
16 // This analysis is primarily useful for induction variable substitution and
17 // strength reduction.
19 //===----------------------------------------------------------------------===//
21 #ifndef LLVM_ANALYSIS_SCALAREVOLUTION_H
22 #define LLVM_ANALYSIS_SCALAREVOLUTION_H
24 #include "llvm/Pass.h"
35 /// SCEV - This class represent an analyzed expression in the program. These
36 /// are reference counted opaque objects that the client is not allowed to
37 /// do much with directly.
40 const unsigned SCEVType; // The SCEV baseclass this node corresponds to
41 mutable unsigned RefCount;
43 friend class SCEVHandle;
44 void addRef() const { ++RefCount; }
45 void dropRef() const {
50 SCEV(const SCEV &); // DO NOT IMPLEMENT
51 void operator=(const SCEV &); // DO NOT IMPLEMENT
55 SCEV(unsigned SCEVTy) : SCEVType(SCEVTy), RefCount(0) {}
57 /// getNegativeSCEV - Return the SCEV object corresponding to -V.
59 static SCEVHandle getNegativeSCEV(const SCEVHandle &V);
61 /// getMinusSCEV - Return LHS-RHS.
63 static SCEVHandle getMinusSCEV(const SCEVHandle &LHS,
64 const SCEVHandle &RHS);
67 unsigned getSCEVType() const { return SCEVType; }
69 /// getValueRange - Return the tightest constant bounds that this value is
70 /// known to have. This method is only valid on integer SCEV objects.
71 virtual ConstantRange getValueRange() const;
73 /// isLoopInvariant - Return true if the value of this SCEV is unchanging in
74 /// the specified loop.
75 virtual bool isLoopInvariant(const Loop *L) const = 0;
77 /// hasComputableLoopEvolution - Return true if this SCEV changes value in a
78 /// known way in the specified loop. This property being true implies that
79 /// the value is variant in the loop AND that we can emit an expression to
80 /// compute the value of the expression at any particular loop iteration.
81 virtual bool hasComputableLoopEvolution(const Loop *L) const = 0;
83 /// getType - Return the LLVM type of this SCEV expression.
85 virtual const Type *getType() const = 0;
87 /// replaceSymbolicValuesWithConcrete - If this SCEV internally references
88 /// the symbolic value "Sym", construct and return a new SCEV that produces
89 /// the same value, but which uses the concrete value Conc instead of the
90 /// symbolic value. If this SCEV does not use the symbolic value, it
93 replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
94 const SCEVHandle &Conc) const = 0;
96 /// print - Print out the internal representation of this scalar to the
97 /// specified stream. This should really only be used for debugging
99 virtual void print(std::ostream &OS) const = 0;
101 /// dump - This method is used for debugging.
106 inline std::ostream &operator<<(std::ostream &OS, const SCEV &S) {
111 /// SCEVCouldNotCompute - An object of this class is returned by queries that
112 /// could not be answered. For example, if you ask for the number of
113 /// iterations of a linked-list traversal loop, you will get one of these.
114 /// None of the standard SCEV operations are valid on this class, it is just a
116 struct SCEVCouldNotCompute : public SCEV {
117 SCEVCouldNotCompute();
119 // None of these methods are valid for this object.
120 virtual bool isLoopInvariant(const Loop *L) const;
121 virtual const Type *getType() const;
122 virtual bool hasComputableLoopEvolution(const Loop *L) const;
123 virtual void print(std::ostream &OS) const;
125 replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
126 const SCEVHandle &Conc) const;
128 /// Methods for support type inquiry through isa, cast, and dyn_cast:
129 static inline bool classof(const SCEVCouldNotCompute *S) { return true; }
130 static bool classof(const SCEV *S);
133 /// SCEVHandle - This class is used to maintain the SCEV object's refcounts,
134 /// freeing the objects when the last reference is dropped.
137 SCEVHandle(); // DO NOT IMPLEMENT
139 SCEVHandle(const SCEV *s) : S(const_cast<SCEV*>(s)) {
140 assert(S && "Cannot create a handle to a null SCEV!");
143 SCEVHandle(const SCEVHandle &RHS) : S(RHS.S) {
146 ~SCEVHandle() { S->dropRef(); }
148 operator SCEV*() const { return S; }
150 SCEV &operator*() const { return *S; }
151 SCEV *operator->() const { return S; }
153 bool operator==(SCEV *RHS) const { return S == RHS; }
154 bool operator!=(SCEV *RHS) const { return S != RHS; }
156 const SCEVHandle &operator=(SCEV *RHS) {
165 const SCEVHandle &operator=(const SCEVHandle &RHS) {
175 template<typename From> struct simplify_type;
176 template<> struct simplify_type<const SCEVHandle> {
177 typedef SCEV* SimpleType;
178 static SimpleType getSimplifiedValue(const SCEVHandle &Node) {
182 template<> struct simplify_type<SCEVHandle>
183 : public simplify_type<const SCEVHandle> {};
185 /// ScalarEvolution - This class is the main scalar evolution driver. Because
186 /// client code (intentionally) can't do much with the SCEV objects directly,
187 /// they must ask this class for services.
189 class ScalarEvolution : public FunctionPass {
190 void *Impl; // ScalarEvolution uses the pimpl pattern
192 ScalarEvolution() : Impl(0) {}
194 /// getSCEV - Return a SCEV expression handle for the full generality of the
195 /// specified expression.
196 SCEVHandle getSCEV(Value *V) const;
198 /// hasSCEV - Return true if the SCEV for this value has already been
200 bool hasSCEV(Value *V) const;
202 /// setSCEV - Insert the specified SCEV into the map of current SCEVs for
203 /// the specified value.
204 void setSCEV(Value *V, const SCEVHandle &H);
206 /// getSCEVAtScope - Return a SCEV expression handle for the specified value
207 /// at the specified scope in the program. The L value specifies a loop
208 /// nest to evaluate the expression at, where null is the top-level or a
209 /// specified loop is immediately inside of the loop.
211 /// This method can be used to compute the exit value for a variable defined
212 /// in a loop by querying what the value will hold in the parent loop.
214 /// If this value is not computable at this scope, a SCEVCouldNotCompute
215 /// object is returned.
216 SCEVHandle getSCEVAtScope(Value *V, const Loop *L) const;
218 /// getIterationCount - If the specified loop has a predictable iteration
219 /// count, return it, otherwise return a SCEVCouldNotCompute object.
220 SCEVHandle getIterationCount(const Loop *L) const;
222 /// hasLoopInvariantIterationCount - Return true if the specified loop has
223 /// an analyzable loop-invariant iteration count.
224 bool hasLoopInvariantIterationCount(const Loop *L) const;
226 /// deleteInstructionFromRecords - This method should be called by the
227 /// client before it removes an instruction from the program, to make sure
228 /// that no dangling references are left around.
229 void deleteInstructionFromRecords(Instruction *I) const;
231 virtual bool runOnFunction(Function &F);
232 virtual void releaseMemory();
233 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
234 virtual void print(std::ostream &OS, const Module* = 0) const;