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