llvm-6502/include/llvm/Analysis/InductionVariable.h
Misha Brukman a27229013f Added capability to get execution count of a loop if it is a predictable
number of iterations.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4113 91177308-0d34-0410-b5e6-96231b3b80d8
2002-10-11 05:34:32 +00:00

57 lines
2.1 KiB
C++

//===- llvm/Analysis/InductionVariable.h - Induction variable ----*- C++ -*--=//
//
// 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
Cannonical, // 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