-//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator --------*- 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...
+// 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.
+// contained entirely within the loop and the basic blocks the make up 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.
+// 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...
//
//===----------------------------------------------------------------------===//
#define LLVM_ANALYSIS_LOOP_INFO_H
#include "llvm/Pass.h"
-#include <set>
+#include "llvm/ADT/GraphTraits.h"
+
+namespace llvm {
-class DominatorSet;
+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
+/// 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
+ 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];
+ }
- inline unsigned getLoopDepth() const { return LoopDepth; }
- inline BasicBlock *getHeader() const { return Blocks.front(); }
- inline Loop *getParentLoop() const { return ParentLoop; }
+ 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;
- /// getSubLoops - Return the loops contained entirely within this loop
+ /// 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; }
-
- /// 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; }
+ 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. The reached block should be in the
- /// ExitBlocks list.
+ /// that is outside of the current loop.
///
bool isLoopExit(const BasicBlock *BB) const;
///
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. The "preheaders" pass can be
- /// "Required" to ensure that there is always a preheader node for every loop.
+ /// header of the loop is the preheader node.
///
- /// 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).
+ /// This method returns null if there is no preheader for the loop.
///
BasicBlock *getLoopPreheader() 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
///
void addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI);
- /// changeExitBlock - This method is used to update loop information. One
- /// instance of the specified Old basic block is removed from the exit list
- /// and replaced with 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 changeExitBlock(BasicBlock *Old, BasicBlock *New);
+ void addChildLoop(Loop *NewChild);
- void print(std::ostream &O) const;
-private:
- friend class LoopInfo;
- inline Loop(BasicBlock *BB) : ParentLoop(0) {
- Blocks.push_back(BB); LoopDepth = 0;
+ /// 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);
}
- ~Loop() {
- for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
- delete SubLoops[i];
+
+ /// 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;
+ }
+ }
}
-
- void setLoopDepth(unsigned Level) {
- LoopDepth = Level;
- for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
- SubLoops[i]->setLoopDepth(Level+1);
+
+ /// 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);
}
};
public:
~LoopInfo() { releaseMemory(); }
- const std::vector<Loop*> &getTopLevelLoops() const { return TopLevelLoops; }
+ /// 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);
+ 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...
///
- inline const Loop *operator[](const BasicBlock *BB) const {
+ const Loop *operator[](const BasicBlock *BB) const {
return getLoopFor(BB);
}
// isLoopHeader - True if the block is a loop header node
bool isLoopHeader(BasicBlock *BB) const {
- return getLoopFor(BB)->getHeader() == BB;
+ 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;
+ 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);
+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
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