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llvm-mirror/include/llvm/Analysis/LoopInfo.h
Chris Lattner f3471861a6 new method
llvm-svn: 23314
2005-09-12 17:03:16 +00:00

343 lines
12 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 loop and the basic blocks the 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
// * the trip count
// * etc...
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_LOOP_INFO_H
#define LLVM_ANALYSIS_LOOP_INFO_H
#include "llvm/Pass.h"
#include "llvm/ADT/GraphTraits.h"
namespace llvm {
struct DominatorSet;
class LoopInfo;
class PHINode;
class Instruction;
//===----------------------------------------------------------------------===//
/// 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
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) {}
~Loop() {
for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
delete SubLoops[i];
}
unsigned getLoopDepth() const {
unsigned D = 0;
for (const Loop *CurLoop = this; CurLoop; CurLoop = CurLoop->ParentLoop)
++D;
return D;
}
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.
///
const std::vector<Loop*> &getSubLoops() const { return SubLoops; }
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; }
typedef std::vector<BasicBlock*>::const_iterator block_iterator;
block_iterator block_begin() const { return Blocks.begin(); }
block_iterator block_end() const { return Blocks.end(); }
/// isLoopExit - True if terminator in the block can branch to another block
/// that is outside of the current loop.
///
bool isLoopExit(const BasicBlock *BB) const;
/// getNumBackEdges - Calculate the number of back edges to the loop header
///
unsigned getNumBackEdges() const;
/// isLoopInvariant - Return true if the specified value is loop invariant
///
bool isLoopInvariant(Value *V) const;
//===--------------------------------------------------------------------===//
// APIs for simple analysis of the loop.
//
// Note that all of these methods can fail on general loops (ie, there may not
// be a preheader, etc). For best success, the loop simplification and
// induction variable canonicalization pass should be used to normalize loops
// for easy analysis. These methods assume canonical loops.
/// getExitBlocks - Return all of the successor blocks of this loop. These
/// are the blocks _outside of the current loop_ which are branched to.
///
void getExitBlocks(std::vector<BasicBlock*> &Blocks) const;
/// 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.
///
/// This method returns null if there is no preheader for the loop.
///
BasicBlock *getLoopPreheader() const;
/// getLoopLatch - If there is a latch block for this loop, return it. A
/// latch block is the canonical backedge for a loop. A loop header in normal
/// form has two edges into it: one from a preheader and one from a latch
/// block.
BasicBlock *getLoopLatch() const;
/// getCanonicalInductionVariable - Check to see if the loop has a canonical
/// induction variable: an integer recurrence that starts at 0 and increments
/// by one each time through the loop. If so, return the phi node that
/// corresponds to it.
///
PHINode *getCanonicalInductionVariable() const;
/// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
/// the canonical induction variable value for the "next" iteration of the
/// loop. This always succeeds if getCanonicalInductionVariable succeeds.
///
Instruction *getCanonicalInductionVariableIncrement() const;
/// getTripCount - Return a loop-invariant LLVM value indicating the number of
/// times the loop will be executed. Note that this means that the backedge
/// of the loop executes N-1 times. If the trip-count cannot be determined,
/// this returns null.
///
Value *getTripCount() const;
//===--------------------------------------------------------------------===//
// APIs for updating loop information after changing the CFG
//
/// 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);
/// 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);
/// 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);
}
/// moveToHeader - This method is used to move BB (which must be part of this
/// loop) to be the loop header of the loop (the block that dominates all
/// others).
void moveToHeader(BasicBlock *BB) {
if (Blocks[0] == BB) return;
for (unsigned i = 0; ; ++i) {
assert(i != Blocks.size() && "Loop does not contain BB!");
if (Blocks[i] == BB) {
Blocks[i] = Blocks[0];
Blocks[0] = BB;
return;
}
}
}
/// removeBlockFromLoop - This removes the specified basic block from the
/// current loop, updating the Blocks 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);
}
};
//===----------------------------------------------------------------------===//
/// 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.
///
Loop *getLoopFor(const BasicBlock *BB) const {
std::map<BasicBlock *, Loop*>::const_iterator I=
BBMap.find(const_cast<BasicBlock*>(BB));
return I != BBMap.end() ? I->second : 0;
}
/// operator[] - same as getLoopFor...
///
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 {
const Loop *L = getLoopFor(BB);
return L && L->getHeader() == BB;
}
/// runOnFunction - Calculate the natural loop information.
///
virtual bool runOnFunction(Function &F);
virtual void releaseMemory();
void print(std::ostream &O, const Module* = 0) const;
/// getAnalysisUsage - Requires dominator sets
///
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
/// removeLoop - This removes the specified top-level loop from this loop info
/// object. The loop is not deleted, as it will presumably be inserted into
/// another loop.
Loop *removeLoop(iterator I);
/// 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);
/// addTopLevelLoop - This adds the specified loop to the collection of
/// top-level loops.
void addTopLevelLoop(Loop *New) {
assert(New->getParentLoop() == 0 && "Loop already in subloop!");
TopLevelLoops.push_back(New);
}
/// removeBlock - This method completely removes BB from all data structures,
/// including all of the Loop objects it is nested in and our mapping from
/// BasicBlocks to loops.
void removeBlock(BasicBlock *BB);
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