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//===- llvm/Analysis/InductionVariable.h - Induction variables --*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This interface is used to identify and classify induction variables that
// exist in the program. Induction variables must contain a PHI node that
// exists in a loop header. Because of this, they are identified an managed by
// this PHI node.
//
// Induction variables are classified into a type. Knowing that an induction
// variable is of a specific type can constrain the values of the start and
// step. For example, a SimpleLinear induction variable must have a start and
// step values that are constants.
//
// Induction variables can be created with or without loop information. If no
// loop information is available, induction variables cannot be recognized to be
// more than SimpleLinear variables.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_INDUCTIONVARIABLE_H
#define LLVM_ANALYSIS_INDUCTIONVARIABLE_H
#include <iosfwd>
class Value;
class PHINode;
class Instruction;
class LoopInfo; class Loop;
class InductionVariable {
public:
enum iType { // Identify the type of this induction variable
Canonical, // Starts at 0, counts by 1
SimpleLinear, // Simple linear: Constant start, constant step
Linear, // General linear: loop invariant start, and step
Unknown, // Unknown type. Start & Step are null
} InductionType;
Value *Start, *Step, *End; // Start, step, and end expressions for this indvar
PHINode *Phi; // The PHI node that corresponds to this indvar
public:
// Create an induction variable for the specified value. If it is a PHI, and
// if it's recognizable, classify it and fill in instance variables.
//
InductionVariable(PHINode *PN, LoopInfo *LoopInfo = 0);
// Classify Induction
static enum iType Classify(const Value *Start, const Value *Step,
const Loop *L = 0);
// Get number of times this loop will execute. Returns NULL if unpredictable.
Value* getExecutionCount(LoopInfo *LoopInfo);
void print(std::ostream &OS) const;
};
#endif
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