llvm/llvm/include/llvm/Support/GenericLoopInfo.h

//===- GenericLoopInfo - Generic Loop Info for graphs -----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the LoopInfoBase class that is used to identify natural
// loops and determine the loop depth of various nodes in a generic graph of
// blocks.  A natural loop has exactly one entry-point, which is called the
// header. Note that natural loops may actually be several loops that share the
// same header node.
//
// This analysis calculates the nesting structure of loops in a function.  For
// each natural loop identified, this analysis identifies natural loops
// contained entirely within the loop and the basic blocks that make up the
// loop.
//
// It can calculate on the fly various bits of information, for example:
//
//  * whether there is a preheader for the loop
//  * the number of back edges to the header
//  * whether or not a particular block branches out of the loop
//  * the successor blocks of the loop
//  * the loop depth
//  * etc...
//
// Note that this analysis specifically identifies *Loops* not cycles or SCCs
// in the graph.  There can be strongly connected components in the graph which
// this analysis will not recognize and that will not be represented by a Loop
// instance.  In particular, a Loop might be inside such a non-loop SCC, or a
// non-loop SCC might contain a sub-SCC which is a Loop.
//
// For an overview of terminology used in this API (and thus all of our loop
// analyses or transforms), see docs/LoopTerminology.rst.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_GENERICLOOPINFO_H
#define LLVM_SUPPORT_GENERICLOOPINFO_H

#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetOperations.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/GenericDomTree.h"

namespace llvm {

template <class N, class M> class LoopInfoBase;
template <class N, class M> class LoopBase;

//===----------------------------------------------------------------------===//
/// Instances of this class are used to represent loops that are detected in the
/// flow graph.
///
template <class BlockT, class LoopT> class LoopBase { … };

template <class BlockT, class LoopT>
raw_ostream &operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) { … }

//===----------------------------------------------------------------------===//
/// This class builds and contains all of the top-level loop
/// structures in the specified function.
///

template <class BlockT, class LoopT> class LoopInfoBase { … };

} // namespace llvm

#endif // LLVM_SUPPORT_GENERICLOOPINFO_H