llvm-6502/include/llvm/Analysis/LoopInfo.h
2004-04-12 20:26:17 +00:00

286 lines
10 KiB
C++

//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- 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 file defines the LoopInfo class that is used to identify natural loops
// and determine the loop depth of various nodes of the CFG. 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 function, the basic blocks the make up the
// loop, the nesting depth of the loop, and the successor blocks of the loop.
//
// It can calculate on the fly a variety of different bits of information, such
// as whether there is a preheader for the loop, the number of back edges to the
// header, and whether or not a particular block branches out of the loop.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_LOOP_INFO_H
#define LLVM_ANALYSIS_LOOP_INFO_H
#include "llvm/Pass.h"
#include "Support/GraphTraits.h"
#include <set>
namespace llvm {
class DominatorSet;
class LoopInfo;
//===----------------------------------------------------------------------===//
/// Loop class - Instances of this class are used to represent loops that are
/// detected in the flow graph
///
class Loop {
Loop *ParentLoop;
std::vector<Loop*> SubLoops; // Loops contained entirely within this one
std::vector<BasicBlock*> Blocks; // First entry is the header node
std::vector<BasicBlock*> ExitBlocks; // Reachable blocks outside the loop
unsigned LoopDepth; // Nesting depth of this loop
Loop(const Loop &); // DO NOT IMPLEMENT
const Loop &operator=(const Loop &); // DO NOT IMPLEMENT
public:
/// Loop ctor - This creates an empty loop.
Loop() : ParentLoop(0), LoopDepth(0) {
}
unsigned getLoopDepth() const { return LoopDepth; }
BasicBlock *getHeader() const { return Blocks.front(); }
Loop *getParentLoop() const { return ParentLoop; }
/// contains - Return true of the specified basic block is in this loop
///
bool contains(const BasicBlock *BB) const;
/// iterator/begin/end - Return the loops contained entirely within this loop.
///
typedef std::vector<Loop*>::const_iterator iterator;
iterator begin() const { return SubLoops.begin(); }
iterator end() const { return SubLoops.end(); }
/// getBlocks - Get a list of the basic blocks which make up this loop.
///
const std::vector<BasicBlock*> &getBlocks() const { return Blocks; }
/// getExitBlocks - Return all of the successor blocks of this loop. These
/// are the blocks _outside of the current loop_ which are branched to.
///
const std::vector<BasicBlock*> &getExitBlocks() const { return ExitBlocks; }
/// isLoopExit - True if terminator in the block can branch to another block
/// that is outside of the current loop. The reached block should be in the
/// ExitBlocks list.
///
bool isLoopExit(const BasicBlock *BB) const;
/// getNumBackEdges - Calculate the number of back edges to the loop header
///
unsigned getNumBackEdges() const;
/// hasExitBlock - Return true if the current loop has the specified block as
/// an exit block...
bool hasExitBlock(BasicBlock *BB) const {
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
if (ExitBlocks[i] == BB)
return true;
return false;
}
/// getLoopPreheader - If there is a preheader for this loop, return it. A
/// loop has a preheader if there is only one edge to the header of the loop
/// from outside of the loop. If this is the case, the block branching to the
/// header of the loop is the preheader node. The "preheaders" pass can be
/// "Required" to ensure that there is always a preheader node for every loop.
///
/// This method returns null if there is no preheader for the loop (either
/// because the loop is dead or because multiple blocks branch to the header
/// node of this loop).
///
BasicBlock *getLoopPreheader() const;
/// addBasicBlockToLoop - This method is used by other analyses to update loop
/// information. NewBB is set to be a new member of the current loop.
/// Because of this, it is added as a member of all parent loops, and is added
/// to the specified LoopInfo object as being in the current basic block. It
/// is not valid to replace the loop header with this method.
///
void addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI);
/// changeExitBlock - This method is used to update loop information. All
/// instances of the specified Old basic block are removed from the exit list
/// and replaced with New.
///
void changeExitBlock(BasicBlock *Old, BasicBlock *New);
/// replaceChildLoopWith - This is used when splitting loops up. It replaces
/// the OldChild entry in our children list with NewChild, and updates the
/// parent pointer of OldChild to be null and the NewChild to be this loop.
/// This updates the loop depth of the new child.
void replaceChildLoopWith(Loop *OldChild, Loop *NewChild);
/// addChildLoop - Add the specified loop to be a child of this loop. This
/// updates the loop depth of the new child.
///
void addChildLoop(Loop *NewChild);
/// removeChildLoop - This removes the specified child from being a subloop of
/// this loop. The loop is not deleted, as it will presumably be inserted
/// into another loop.
Loop *removeChildLoop(iterator OldChild);
/// addExitBlock - Add the specified exit block to the loop.
///
void addExitBlock(BasicBlock *BB) {
ExitBlocks.push_back(BB);
}
/// addBlockEntry - This adds a basic block directly to the basic block list.
/// This should only be used by transformations that create new loops. Other
/// transformations should use addBasicBlockToLoop.
void addBlockEntry(BasicBlock *BB) {
Blocks.push_back(BB);
}
/// removeBlockFromLoop - This removes the specified basic block from the
/// current loop, updating the Blocks and ExitBlocks lists as appropriate.
/// This does not update the mapping in the LoopInfo class.
void removeBlockFromLoop(BasicBlock *BB);
void print(std::ostream &O, unsigned Depth = 0) const;
void dump() const;
private:
friend class LoopInfo;
Loop(BasicBlock *BB) : ParentLoop(0) {
Blocks.push_back(BB); LoopDepth = 0;
}
~Loop() {
for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
delete SubLoops[i];
}
void setLoopDepth(unsigned Level) {
LoopDepth = Level;
for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
SubLoops[i]->setLoopDepth(Level+1);
}
};
//===----------------------------------------------------------------------===//
/// LoopInfo - This class builds and contains all of the top level loop
/// structures in the specified function.
///
class LoopInfo : public FunctionPass {
// BBMap - Mapping of basic blocks to the inner most loop they occur in
std::map<BasicBlock*, Loop*> BBMap;
std::vector<Loop*> TopLevelLoops;
friend class Loop;
public:
~LoopInfo() { releaseMemory(); }
/// iterator/begin/end - The interface to the top-level loops in the current
/// function.
///
typedef std::vector<Loop*>::const_iterator iterator;
iterator begin() const { return TopLevelLoops.begin(); }
iterator end() const { return TopLevelLoops.end(); }
/// getLoopFor - Return the inner most loop that BB lives in. If a basic
/// block is in no loop (for example the entry node), null is returned.
///
const Loop *getLoopFor(const BasicBlock *BB) const {
std::map<BasicBlock *, Loop*>::const_iterator I=BBMap.find((BasicBlock*)BB);
return I != BBMap.end() ? I->second : 0;
}
/// operator[] - same as getLoopFor...
///
inline const Loop *operator[](const BasicBlock *BB) const {
return getLoopFor(BB);
}
/// getLoopDepth - Return the loop nesting level of the specified block...
///
unsigned getLoopDepth(const BasicBlock *BB) const {
const Loop *L = getLoopFor(BB);
return L ? L->getLoopDepth() : 0;
}
// isLoopHeader - True if the block is a loop header node
bool isLoopHeader(BasicBlock *BB) const {
return getLoopFor(BB)->getHeader() == BB;
}
/// runOnFunction - Calculate the natural loop information.
///
virtual bool runOnFunction(Function &F);
virtual void releaseMemory();
void print(std::ostream &O) const;
/// getAnalysisUsage - Requires dominator sets
///
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
/// changeLoopFor - Change the top-level loop that contains BB to the
/// specified loop. This should be used by transformations that restructure
/// the loop hierarchy tree.
void changeLoopFor(BasicBlock *BB, Loop *L);
/// changeTopLevelLoop - Replace the specified loop in the top-level loops
/// list with the indicated loop.
void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop);
static void stub(); // Noop
private:
void Calculate(const DominatorSet &DS);
Loop *ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS);
void MoveSiblingLoopInto(Loop *NewChild, Loop *NewParent);
void InsertLoopInto(Loop *L, Loop *Parent);
};
// Make sure that any clients of this file link in LoopInfo.cpp
static IncludeFile
LOOP_INFO_INCLUDE_FILE((void*)&LoopInfo::stub);
// Allow clients to walk the list of nested loops...
template <> struct GraphTraits<const Loop*> {
typedef const Loop NodeType;
typedef std::vector<Loop*>::const_iterator ChildIteratorType;
static NodeType *getEntryNode(const Loop *L) { return L; }
static inline ChildIteratorType child_begin(NodeType *N) {
return N->begin();
}
static inline ChildIteratorType child_end(NodeType *N) {
return N->end();
}
};
template <> struct GraphTraits<Loop*> {
typedef Loop NodeType;
typedef std::vector<Loop*>::const_iterator ChildIteratorType;
static NodeType *getEntryNode(Loop *L) { return L; }
static inline ChildIteratorType child_begin(NodeType *N) {
return N->begin();
}
static inline ChildIteratorType child_end(NodeType *N) {
return N->end();
}
};
} // End llvm namespace
#endif