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