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//===- RegionInfo.h - SESE region analysis ----------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Calculate a program structure tree built out of single entry single exit
// regions.
// The basic ideas are taken from "The Program Structure Tree - Richard Johnson,
// David Pearson, Keshav Pingali - 1994", however enriched with ideas from "The
// Refined Process Structure Tree - Jussi Vanhatalo, Hagen Voelyer, Jana
// Koehler - 2009".
// The algorithm to calculate these data structures however is completely
// different, as it takes advantage of existing information already available
// in (Post)dominace tree and dominance frontier passes. This leads to a simpler
// and in practice hopefully better performing algorithm. The runtime of the
// algorithms described in the papers above are both linear in graph size,
// O(V+E), whereas this algorithm is not, as the dominance frontier information
// itself is not, but in practice runtime seems to be in the order of magnitude
// of dominance tree calculation.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_REGION_INFO_H
#define LLVM_ANALYSIS_REGION_INFO_H
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/Analysis/DominanceFrontier.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/Support/Allocator.h"
#include <map>
namespace llvm {
class Region;
class RegionInfo;
class raw_ostream;
class Loop;
class LoopInfo;
/// @brief Marker class to iterate over the elements of a Region in flat mode.
///
/// The class is used to either iterate in Flat mode or by not using it to not
/// iterate in Flat mode. During a Flat mode iteration all Regions are entered
/// and the iteration returns every BasicBlock. If the Flat mode is not
/// selected for SubRegions just one RegionNode containing the subregion is
/// returned.
template <class GraphType>
class FlatIt {};
/// @brief A RegionNode represents a subregion or a BasicBlock that is part of a
/// Region.
class RegionNode {
// DO NOT IMPLEMENT
RegionNode(const RegionNode &);
// DO NOT IMPLEMENT
const RegionNode &operator=(const RegionNode &);
protected:
/// This is the entry basic block that starts this region node. If this is a
/// BasicBlock RegionNode, then entry is just the basic block, that this
/// RegionNode represents. Otherwise it is the entry of this (Sub)RegionNode.
///
/// In the BBtoRegionNode map of the parent of this node, BB will always map
/// to this node no matter which kind of node this one is.
///
/// The node can hold either a Region or a BasicBlock.
/// Use one bit to save, if this RegionNode is a subregion or BasicBlock
/// RegionNode.
PointerIntPair<BasicBlock*, 1, bool> entry;
/// @brief The parent Region of this RegionNode.
/// @see getParent()
Region* parent;
public:
/// @brief Create a RegionNode.
///
/// @param Parent The parent of this RegionNode.
/// @param Entry The entry BasicBlock of the RegionNode. If this
/// RegionNode represents a BasicBlock, this is the
/// BasicBlock itself. If it represents a subregion, this
/// is the entry BasicBlock of the subregion.
/// @param isSubRegion If this RegionNode represents a SubRegion.
inline RegionNode(Region* Parent, BasicBlock* Entry, bool isSubRegion = 0)
: entry(Entry, isSubRegion), parent(Parent) {}
/// @brief Get the parent Region of this RegionNode.
///
/// The parent Region is the Region this RegionNode belongs to. If for
/// example a BasicBlock is element of two Regions, there exist two
/// RegionNodes for this BasicBlock. Each with the getParent() function
/// pointing to the Region this RegionNode belongs to.
///
/// @return Get the parent Region of this RegionNode.
inline Region* getParent() const { return parent; }
/// @brief Get the entry BasicBlock of this RegionNode.
///
/// If this RegionNode represents a BasicBlock this is just the BasicBlock
/// itself, otherwise we return the entry BasicBlock of the Subregion
///
/// @return The entry BasicBlock of this RegionNode.
inline BasicBlock* getEntry() const { return entry.getPointer(); }
/// @brief Get the content of this RegionNode.
///
/// This can be either a BasicBlock or a subregion. Before calling getNodeAs()
/// check the type of the content with the isSubRegion() function call.
///
/// @return The content of this RegionNode.
template<class T>
inline T* getNodeAs() const;
/// @brief Is this RegionNode a subregion?
///
/// @return True if it contains a subregion. False if it contains a
/// BasicBlock.
inline bool isSubRegion() const {
return entry.getInt();
}
};
/// Print a RegionNode.
inline raw_ostream &operator<<(raw_ostream &OS, const RegionNode &Node);
template<>
inline BasicBlock* RegionNode::getNodeAs<BasicBlock>() const {
assert(!isSubRegion() && "This is not a BasicBlock RegionNode!");
return getEntry();
}
template<>
inline Region* RegionNode::getNodeAs<Region>() const {
assert(isSubRegion() && "This is not a subregion RegionNode!");
return reinterpret_cast<Region*>(const_cast<RegionNode*>(this));
}
//===----------------------------------------------------------------------===//
/// @brief A single entry single exit Region.
///
/// A Region is a connected subgraph of a control flow graph that has exactly
/// two connections to the remaining graph. It can be used to analyze or
/// optimize parts of the control flow graph.
///
/// A <em> simple Region </em> is connected to the remaining graph by just two
/// edges. One edge entering the Region and another one leaving the Region.
///
/// An <em> extended Region </em> (or just Region) is a subgraph that can be
/// transform into a simple Region. The transformation is done by adding
/// BasicBlocks that merge several entry or exit edges so that after the merge
/// just one entry and one exit edge exists.
///
/// The \e Entry of a Region is the first BasicBlock that is passed after
/// entering the Region. It is an element of the Region. The entry BasicBlock
/// dominates all BasicBlocks in the Region.
///
/// The \e Exit of a Region is the first BasicBlock that is passed after
/// leaving the Region. It is not an element of the Region. The exit BasicBlock,
/// postdominates all BasicBlocks in the Region.
///
/// A <em> canonical Region </em> cannot be constructed by combining smaller
/// Regions.
///
/// Region A is the \e parent of Region B, if B is completely contained in A.
///
/// Two canonical Regions either do not intersect at all or one is
/// the parent of the other.
///
/// The <em> Program Structure Tree</em> is a graph (V, E) where V is the set of
/// Regions in the control flow graph and E is the \e parent relation of these
/// Regions.
///
/// Example:
///
/// \verbatim
/// A simple control flow graph, that contains two regions.
///
/// 1
/// / |
/// 2 |
/// / \ 3
/// 4 5 |
/// | | |
/// 6 7 8
/// \ | /
/// \ |/ Region A: 1 -> 9 {1,2,3,4,5,6,7,8}
/// 9 Region B: 2 -> 9 {2,4,5,6,7}
/// \endverbatim
///
/// You can obtain more examples by either calling
///
/// <tt> "opt -regions -analyze anyprogram.ll" </tt>
/// or
/// <tt> "opt -view-regions-only anyprogram.ll" </tt>
///
/// on any LLVM file you are interested in.
///
/// The first call returns a textual representation of the program structure
/// tree, the second one creates a graphical representation using graphviz.
class Region : public RegionNode {
friend class RegionInfo;
// DO NOT IMPLEMENT
Region(const Region &);
// DO NOT IMPLEMENT
const Region &operator=(const Region &);
// Information necessary to manage this Region.
RegionInfo* RI;
DominatorTree *DT;
// The exit BasicBlock of this region.
// (The entry BasicBlock is part of RegionNode)
BasicBlock *exit;
typedef std::vector<Region*> RegionSet;
// The subregions of this region.
RegionSet children;
typedef std::map<BasicBlock*, RegionNode*> BBNodeMapT;
// Save the BasicBlock RegionNodes that are element of this Region.
mutable BBNodeMapT BBNodeMap;
/// verifyBBInRegion - Check if a BB is in this Region. This check also works
/// if the region is incorrectly built. (EXPENSIVE!)
void verifyBBInRegion(BasicBlock* BB) const;
/// verifyWalk - Walk over all the BBs of the region starting from BB and
/// verify that all reachable basic blocks are elements of the region.
/// (EXPENSIVE!)
void verifyWalk(BasicBlock* BB, std::set<BasicBlock*>* visitedBB) const;
/// verifyRegionNest - Verify if the region and its children are valid
/// regions (EXPENSIVE!)
void verifyRegionNest() const;
public:
/// @brief Create a new region.
///
/// @param Entry The entry basic block of the region.
/// @param Exit The exit basic block of the region.
/// @param RI The region info object that is managing this region.
/// @param DT The dominator tree of the current function.
/// @param Parent The surrounding region or NULL if this is a top level
/// region.
Region(BasicBlock *Entry, BasicBlock *Exit, RegionInfo* RI,
DominatorTree *DT, Region *Parent = 0);
/// Delete the Region and all its subregions.
~Region();
/// @brief Get the entry BasicBlock of the Region.
/// @return The entry BasicBlock of the region.
BasicBlock *getEntry() const { return RegionNode::getEntry(); }
/// @brief Replace the entry basic block of the region with the new basic
/// block.
///
/// @param BB The new entry basic block of the region.
void replaceEntry(BasicBlock *BB);
/// @brief Replace the exit basic block of the region with the new basic
/// block.
///
/// @param BB The new exit basic block of the region.
void replaceExit(BasicBlock *BB);
/// @brief Get the exit BasicBlock of the Region.
/// @return The exit BasicBlock of the Region, NULL if this is the TopLevel
/// Region.
BasicBlock *getExit() const { return exit; }
/// @brief Get the parent of the Region.
/// @return The parent of the Region or NULL if this is a top level
/// Region.
Region *getParent() const { return RegionNode::getParent(); }
/// @brief Get the RegionNode representing the current Region.
/// @return The RegionNode representing the current Region.
RegionNode* getNode() const {
return const_cast<RegionNode*>(reinterpret_cast<const RegionNode*>(this));
}
/// @brief Get the nesting level of this Region.
///
/// An toplevel Region has depth 0.
///
/// @return The depth of the region.
unsigned getDepth() const;
/// @brief Check if a Region is the TopLevel region.
///
/// The toplevel region represents the whole function.
bool isTopLevelRegion() const { return exit == NULL; }
/// @brief Return a new (non canonical) region, that is obtained by joining
/// this region with its predecessors.
///
/// @return A region also starting at getEntry(), but reaching to the next
/// basic block that forms with getEntry() a (non canonical) region.
/// NULL if such a basic block does not exist.
Region *getExpandedRegion() const;
/// @brief Return the first block of this region's single entry edge,
/// if existing.
///
/// @return The BasicBlock starting this region's single entry edge,
/// else NULL.
BasicBlock *getEnteringBlock() const;
/// @brief Return the first block of this region's single exit edge,
/// if existing.
///
/// @return The BasicBlock starting this region's single exit edge,
/// else NULL.
BasicBlock *getExitingBlock() const;
/// @brief Is this a simple region?
///
/// A region is simple if it has exactly one exit and one entry edge.
///
/// @return True if the Region is simple.
bool isSimple() const;
/// @brief Returns the name of the Region.
/// @return The Name of the Region.
std::string getNameStr() const;
/// @brief Return the RegionInfo object, that belongs to this Region.
RegionInfo *getRegionInfo() const {
return RI;
}
/// PrintStyle - Print region in difference ways.
enum PrintStyle { PrintNone, PrintBB, PrintRN };
/// @brief Print the region.
///
/// @param OS The output stream the Region is printed to.
/// @param printTree Print also the tree of subregions.
/// @param level The indentation level used for printing.
void print(raw_ostream& OS, bool printTree = true, unsigned level = 0,
enum PrintStyle Style = PrintNone) const;
/// @brief Print the region to stderr.
void dump() const;
/// @brief Check if the region contains a BasicBlock.
///
/// @param BB The BasicBlock that might be contained in this Region.
/// @return True if the block is contained in the region otherwise false.
bool contains(const BasicBlock *BB) const;
/// @brief Check if the region contains another region.
///
/// @param SubRegion The region that might be contained in this Region.
/// @return True if SubRegion is contained in the region otherwise false.
bool contains(const Region *SubRegion) const {
// Toplevel Region.
if (!getExit())
return true;
return contains(SubRegion->getEntry())
&& (contains(SubRegion->getExit()) || SubRegion->getExit() == getExit());
}
/// @brief Check if the region contains an Instruction.
///
/// @param Inst The Instruction that might be contained in this region.
/// @return True if the Instruction is contained in the region otherwise false.
bool contains(const Instruction *Inst) const {
return contains(Inst->getParent());
}
/// @brief Check if the region contains a loop.
///
/// @param L The loop that might be contained in this region.
/// @return True if the loop is contained in the region otherwise false.
/// In case a NULL pointer is passed to this function the result
/// is false, except for the region that describes the whole function.
/// In that case true is returned.
bool contains(const Loop *L) const;
/// @brief Get the outermost loop in the region that contains a loop.
///
/// Find for a Loop L the outermost loop OuterL that is a parent loop of L
/// and is itself contained in the region.
///
/// @param L The loop the lookup is started.
/// @return The outermost loop in the region, NULL if such a loop does not
/// exist or if the region describes the whole function.
Loop *outermostLoopInRegion(Loop *L) const;
/// @brief Get the outermost loop in the region that contains a basic block.
///
/// Find for a basic block BB the outermost loop L that contains BB and is
/// itself contained in the region.
///
/// @param LI A pointer to a LoopInfo analysis.
/// @param BB The basic block surrounded by the loop.
/// @return The outermost loop in the region, NULL if such a loop does not
/// exist or if the region describes the whole function.
Loop *outermostLoopInRegion(LoopInfo *LI, BasicBlock* BB) const;
/// @brief Get the subregion that starts at a BasicBlock
///
/// @param BB The BasicBlock the subregion should start.
/// @return The Subregion if available, otherwise NULL.
Region* getSubRegionNode(BasicBlock *BB) const;
/// @brief Get the RegionNode for a BasicBlock
///
/// @param BB The BasicBlock at which the RegionNode should start.
/// @return If available, the RegionNode that represents the subregion
/// starting at BB. If no subregion starts at BB, the RegionNode
/// representing BB.
RegionNode* getNode(BasicBlock *BB) const;
/// @brief Get the BasicBlock RegionNode for a BasicBlock
///
/// @param BB The BasicBlock for which the RegionNode is requested.
/// @return The RegionNode representing the BB.
RegionNode* getBBNode(BasicBlock *BB) const;
/// @brief Add a new subregion to this Region.
///
/// @param SubRegion The new subregion that will be added.
/// @param moveChildren Move the children of this region, that are also
/// contained in SubRegion into SubRegion.
void addSubRegion(Region *SubRegion, bool moveChildren = false);
/// @brief Remove a subregion from this Region.
///
/// The subregion is not deleted, as it will probably be inserted into another
/// region.
/// @param SubRegion The SubRegion that will be removed.
Region *removeSubRegion(Region *SubRegion);
/// @brief Move all direct child nodes of this Region to another Region.
///
/// @param To The Region the child nodes will be transferred to.
void transferChildrenTo(Region *To);
/// @brief Verify if the region is a correct region.
///
/// Check if this is a correctly build Region. This is an expensive check, as
/// the complete CFG of the Region will be walked.
void verifyRegion() const;
/// @brief Clear the cache for BB RegionNodes.
///
/// After calling this function the BasicBlock RegionNodes will be stored at
/// different memory locations. RegionNodes obtained before this function is
/// called are therefore not comparable to RegionNodes abtained afterwords.
void clearNodeCache();
/// @name Subregion Iterators
///
/// These iterators iterator over all subregions of this Region.
//@{
typedef RegionSet::iterator iterator;
typedef RegionSet::const_iterator const_iterator;
iterator begin() { return children.begin(); }
iterator end() { return children.end(); }
const_iterator begin() const { return children.begin(); }
const_iterator end() const { return children.end(); }
//@}
/// @name BasicBlock Iterators
///
/// These iterators iterate over all BasicBlock RegionNodes that are
/// contained in this Region. The iterator also iterates over BasicBlocks
/// that are elements of a subregion of this Region. It is therefore called a
/// flat iterator.
//@{
typedef df_iterator<RegionNode*, SmallPtrSet<RegionNode*, 8>, false,
GraphTraits<FlatIt<RegionNode*> > > block_iterator;
typedef df_iterator<const RegionNode*, SmallPtrSet<const RegionNode*, 8>,
false, GraphTraits<FlatIt<const RegionNode*> > >
const_block_iterator;
block_iterator block_begin();
block_iterator block_end();
const_block_iterator block_begin() const;
const_block_iterator block_end() const;
//@}
/// @name Element Iterators
///
/// These iterators iterate over all BasicBlock and subregion RegionNodes that
/// are direct children of this Region. It does not iterate over any
/// RegionNodes that are also element of a subregion of this Region.
//@{
typedef df_iterator<RegionNode*, SmallPtrSet<RegionNode*, 8>, false,
GraphTraits<RegionNode*> > element_iterator;
typedef df_iterator<const RegionNode*, SmallPtrSet<const RegionNode*, 8>,
false, GraphTraits<const RegionNode*> >
const_element_iterator;
element_iterator element_begin();
element_iterator element_end();
const_element_iterator element_begin() const;
const_element_iterator element_end() const;
//@}
};
//===----------------------------------------------------------------------===//
/// @brief Analysis that detects all canonical Regions.
///
/// The RegionInfo pass detects all canonical regions in a function. The Regions
/// are connected using the parent relation. This builds a Program Structure
/// Tree.
class RegionInfo : public FunctionPass {
typedef DenseMap<BasicBlock*,BasicBlock*> BBtoBBMap;
typedef DenseMap<BasicBlock*, Region*> BBtoRegionMap;
typedef SmallPtrSet<Region*, 4> RegionSet;
// DO NOT IMPLEMENT
RegionInfo(const RegionInfo &);
// DO NOT IMPLEMENT
const RegionInfo &operator=(const RegionInfo &);
DominatorTree *DT;
PostDominatorTree *PDT;
DominanceFrontier *DF;
/// The top level region.
Region *TopLevelRegion;
/// Map every BB to the smallest region, that contains BB.
BBtoRegionMap BBtoRegion;
// isCommonDomFrontier - Returns true if BB is in the dominance frontier of
// entry, because it was inherited from exit. In the other case there is an
// edge going from entry to BB without passing exit.
bool isCommonDomFrontier(BasicBlock* BB, BasicBlock* entry,
BasicBlock* exit) const;
// isRegion - Check if entry and exit surround a valid region, based on
// dominance tree and dominance frontier.
bool isRegion(BasicBlock* entry, BasicBlock* exit) const;
// insertShortCut - Saves a shortcut pointing from entry to exit.
// This function may extend this shortcut if possible.
void insertShortCut(BasicBlock* entry, BasicBlock* exit,
BBtoBBMap* ShortCut) const;
// getNextPostDom - Returns the next BB that postdominates N, while skipping
// all post dominators that cannot finish a canonical region.
DomTreeNode *getNextPostDom(DomTreeNode* N, BBtoBBMap *ShortCut) const;
// isTrivialRegion - A region is trivial, if it contains only one BB.
bool isTrivialRegion(BasicBlock *entry, BasicBlock *exit) const;
// createRegion - Creates a single entry single exit region.
Region *createRegion(BasicBlock *entry, BasicBlock *exit);
// findRegionsWithEntry - Detect all regions starting with bb 'entry'.
void findRegionsWithEntry(BasicBlock *entry, BBtoBBMap *ShortCut);
// scanForRegions - Detects regions in F.
void scanForRegions(Function &F, BBtoBBMap *ShortCut);
// getTopMostParent - Get the top most parent with the same entry block.
Region *getTopMostParent(Region *region);
// buildRegionsTree - build the region hierarchy after all region detected.
void buildRegionsTree(DomTreeNode *N, Region *region);
// Calculate - detecte all regions in function and build the region tree.
void Calculate(Function& F);
void releaseMemory();
// updateStatistics - Update statistic about created regions.
void updateStatistics(Region *R);
// isSimple - Check if a region is a simple region with exactly one entry
// edge and exactly one exit edge.
bool isSimple(Region* R) const;
public:
static char ID;
explicit RegionInfo();
~RegionInfo();
/// @name FunctionPass interface
//@{
virtual bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
virtual void print(raw_ostream &OS, const Module *) const;
virtual void verifyAnalysis() const;
//@}
/// @brief Get the smallest region that contains a BasicBlock.
///
/// @param BB The basic block.
/// @return The smallest region, that contains BB or NULL, if there is no
/// region containing BB.
Region *getRegionFor(BasicBlock *BB) const;
/// @brief Set the smallest region that surrounds a basic block.
///
/// @param BB The basic block surrounded by a region.
/// @param R The smallest region that surrounds BB.
void setRegionFor(BasicBlock *BB, Region *R);
/// @brief A shortcut for getRegionFor().
///
/// @param BB The basic block.
/// @return The smallest region, that contains BB or NULL, if there is no
/// region containing BB.
Region *operator[](BasicBlock *BB) const;
/// @brief Return the exit of the maximal refined region, that starts at a
/// BasicBlock.
///
/// @param BB The BasicBlock the refined region starts.
BasicBlock *getMaxRegionExit(BasicBlock *BB) const;
/// @brief Find the smallest region that contains two regions.
///
/// @param A The first region.
/// @param B The second region.
/// @return The smallest region containing A and B.
Region *getCommonRegion(Region* A, Region *B) const;
/// @brief Find the smallest region that contains two basic blocks.
///
/// @param A The first basic block.
/// @param B The second basic block.
/// @return The smallest region that contains A and B.
Region* getCommonRegion(BasicBlock* A, BasicBlock *B) const {
return getCommonRegion(getRegionFor(A), getRegionFor(B));
}
/// @brief Find the smallest region that contains a set of regions.
///
/// @param Regions A vector of regions.
/// @return The smallest region that contains all regions in Regions.
Region* getCommonRegion(SmallVectorImpl<Region*> &Regions) const;
/// @brief Find the smallest region that contains a set of basic blocks.
///
/// @param BBs A vector of basic blocks.
/// @return The smallest region that contains all basic blocks in BBS.
Region* getCommonRegion(SmallVectorImpl<BasicBlock*> &BBs) const;
Region *getTopLevelRegion() const {
return TopLevelRegion;
}
/// @brief Update RegionInfo after a basic block was split.
///
/// @param NewBB The basic block that was created before OldBB.
/// @param OldBB The old basic block.
void splitBlock(BasicBlock* NewBB, BasicBlock *OldBB);
/// @brief Clear the Node Cache for all Regions.
///
/// @see Region::clearNodeCache()
void clearNodeCache() {
if (TopLevelRegion)
TopLevelRegion->clearNodeCache();
}
};
inline raw_ostream &operator<<(raw_ostream &OS, const RegionNode &Node) {
if (Node.isSubRegion())
return OS << Node.getNodeAs<Region>()->getNameStr();
else
return OS << Node.getNodeAs<BasicBlock>()->getName();
}
} // End llvm namespace
#endif