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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23314 91177308-0d34-0410-b5e6-96231b3b80d8
343 lines
12 KiB
C++
343 lines
12 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 loop and the basic blocks the make up the loop.
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//
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// It can calculate on the fly various bits of information, for example:
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//
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// * whether there is a preheader for the loop
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// * the number of back edges to the header
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// * whether or not a particular block branches out of the loop
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// * the successor blocks of the loop
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// * the loop depth
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// * the trip count
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// * etc...
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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 "llvm/ADT/GraphTraits.h"
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namespace llvm {
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struct DominatorSet;
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class LoopInfo;
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class PHINode;
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class Instruction;
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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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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) {}
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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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unsigned getLoopDepth() const {
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unsigned D = 0;
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for (const Loop *CurLoop = this; CurLoop; CurLoop = CurLoop->ParentLoop)
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++D;
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return D;
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}
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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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const std::vector<Loop*> &getSubLoops() const { return SubLoops; }
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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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typedef std::vector<BasicBlock*>::const_iterator block_iterator;
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block_iterator block_begin() const { return Blocks.begin(); }
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block_iterator block_end() const { return Blocks.end(); }
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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.
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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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/// isLoopInvariant - Return true if the specified value is loop invariant
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///
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bool isLoopInvariant(Value *V) const;
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//===--------------------------------------------------------------------===//
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// APIs for simple analysis of the loop.
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//
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// Note that all of these methods can fail on general loops (ie, there may not
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// be a preheader, etc). For best success, the loop simplification and
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// induction variable canonicalization pass should be used to normalize loops
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// for easy analysis. These methods assume canonical loops.
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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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void getExitBlocks(std::vector<BasicBlock*> &Blocks) const;
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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.
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///
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/// This method returns null if there is no preheader for the loop.
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///
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BasicBlock *getLoopPreheader() const;
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/// getLoopLatch - If there is a latch block for this loop, return it. A
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/// latch block is the canonical backedge for a loop. A loop header in normal
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/// form has two edges into it: one from a preheader and one from a latch
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/// block.
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BasicBlock *getLoopLatch() const;
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/// getCanonicalInductionVariable - Check to see if the loop has a canonical
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/// induction variable: an integer recurrence that starts at 0 and increments
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/// by one each time through the loop. If so, return the phi node that
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/// corresponds to it.
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///
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PHINode *getCanonicalInductionVariable() const;
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/// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
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/// the canonical induction variable value for the "next" iteration of the
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/// loop. This always succeeds if getCanonicalInductionVariable succeeds.
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///
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Instruction *getCanonicalInductionVariableIncrement() const;
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/// getTripCount - Return a loop-invariant LLVM value indicating the number of
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/// times the loop will be executed. Note that this means that the backedge
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/// of the loop executes N-1 times. If the trip-count cannot be determined,
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/// this returns null.
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///
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Value *getTripCount() const;
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//===--------------------------------------------------------------------===//
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// APIs for updating loop information after changing the CFG
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//
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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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/// 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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/// 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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/// moveToHeader - This method is used to move BB (which must be part of this
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/// loop) to be the loop header of the loop (the block that dominates all
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/// others).
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void moveToHeader(BasicBlock *BB) {
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if (Blocks[0] == BB) return;
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for (unsigned i = 0; ; ++i) {
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assert(i != Blocks.size() && "Loop does not contain BB!");
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if (Blocks[i] == BB) {
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Blocks[i] = Blocks[0];
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Blocks[0] = BB;
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return;
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}
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}
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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 as appropriate. This does not update
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/// 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);
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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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Loop *getLoopFor(const BasicBlock *BB) const {
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std::map<BasicBlock *, Loop*>::const_iterator I=
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BBMap.find(const_cast<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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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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const Loop *L = getLoopFor(BB);
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return L && L->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 Module* = 0) 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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/// removeLoop - This removes the specified top-level loop from this loop info
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/// object. The loop is not deleted, as it will presumably be inserted into
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/// another loop.
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Loop *removeLoop(iterator I);
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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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/// addTopLevelLoop - This adds the specified loop to the collection of
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/// top-level loops.
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void addTopLevelLoop(Loop *New) {
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assert(New->getParentLoop() == 0 && "Loop already in subloop!");
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TopLevelLoops.push_back(New);
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}
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/// removeBlock - This method completely removes BB from all data structures,
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/// including all of the Loop objects it is nested in and our mapping from
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/// BasicBlocks to loops.
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void removeBlock(BasicBlock *BB);
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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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