1 //===- RegionInfo.h - SESE region analysis ----------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Calculate a program structure tree built out of single entry single exit
12 // The basic ideas are taken from "The Program Structure Tree - Richard Johnson,
13 // David Pearson, Keshav Pingali - 1994", however enriched with ideas from "The
14 // Refined Process Structure Tree - Jussi Vanhatalo, Hagen Voelyer, Jana
16 // The algorithm to calculate these data structures however is completely
17 // different, as it takes advantage of existing information already available
18 // in (Post)dominace tree and dominance frontier passes. This leads to a simpler
19 // and in practice hopefully better performing algorithm. The runtime of the
20 // algorithms described in the papers above are both linear in graph size,
21 // O(V+E), whereas this algorithm is not, as the dominance frontier information
22 // itself is not, but in practice runtime seems to be in the order of magnitude
23 // of dominance tree calculation.
25 //===----------------------------------------------------------------------===//
27 #ifndef LLVM_ANALYSIS_REGION_INFO_H
28 #define LLVM_ANALYSIS_REGION_INFO_H
30 #include "llvm/ADT/PointerIntPair.h"
31 #include "llvm/Analysis/Dominators.h"
32 #include "llvm/Analysis/PostDominators.h"
33 #include "llvm/Support/Allocator.h"
43 /// @brief Marker class to iterate over the elements of a Region in flat mode.
45 /// The class is used to either iterate in Flat mode or by not using it to not
46 /// iterate in Flat mode. During a Flat mode iteration all Regions are entered
47 /// and the iteration returns every BasicBlock. If the Flat mode is not
48 /// selected for SubRegions just one RegionNode containing the subregion is
50 template <class GraphType>
53 /// @brief A RegionNode represents a subregion or a BasicBlock that is part of a
57 RegionNode(const RegionNode &);
59 const RegionNode &operator=(const RegionNode &);
62 /// This is the entry basic block that starts this region node. If this is a
63 /// BasicBlock RegionNode, then entry is just the basic block, that this
64 /// RegionNode represents. Otherwise it is the entry of this (Sub)RegionNode.
66 /// In the BBtoRegionNode map of the parent of this node, BB will always map
67 /// to this node no matter which kind of node this one is.
69 /// The node can hold either a Region or a BasicBlock.
70 /// Use one bit to save, if this RegionNode is a subregion or BasicBlock
72 PointerIntPair<BasicBlock*, 1, bool> entry;
74 /// @brief The parent Region of this RegionNode.
79 /// @brief Create a RegionNode.
81 /// @param Parent The parent of this RegionNode.
82 /// @param Entry The entry BasicBlock of the RegionNode. If this
83 /// RegionNode represents a BasicBlock, this is the
84 /// BasicBlock itself. If it represents a subregion, this
85 /// is the entry BasicBlock of the subregion.
86 /// @param isSubRegion If this RegionNode represents a SubRegion.
87 inline RegionNode(Region* Parent, BasicBlock* Entry, bool isSubRegion = 0)
88 : entry(Entry, isSubRegion), parent(Parent) {}
90 /// @brief Get the parent Region of this RegionNode.
92 /// The parent Region is the Region this RegionNode belongs to. If for
93 /// example a BasicBlock is element of two Regions, there exist two
94 /// RegionNodes for this BasicBlock. Each with the getParent() function
95 /// pointing to the Region this RegionNode belongs to.
97 /// @return Get the parent Region of this RegionNode.
98 inline Region* getParent() const { return parent; }
100 /// @brief Get the entry BasicBlock of this RegionNode.
102 /// If this RegionNode represents a BasicBlock this is just the BasicBlock
103 /// itself, otherwise we return the entry BasicBlock of the Subregion
105 /// @return The entry BasicBlock of this RegionNode.
106 inline BasicBlock* getEntry() const { return entry.getPointer(); }
108 /// @brief Get the content of this RegionNode.
110 /// This can be either a BasicBlock or a subregion. Before calling getNodeAs()
111 /// check the type of the content with the isSubRegion() function call.
113 /// @return The content of this RegionNode.
115 inline T* getNodeAs() const;
117 /// @brief Is this RegionNode a subregion?
119 /// @return True if it contains a subregion. False if it contains a
121 inline bool isSubRegion() const {
122 return entry.getInt();
126 /// Print a RegionNode.
127 inline raw_ostream &operator<<(raw_ostream &OS, const RegionNode &Node);
130 inline BasicBlock* RegionNode::getNodeAs<BasicBlock>() const {
131 assert(!isSubRegion() && "This is not a BasicBlock RegionNode!");
136 inline Region* RegionNode::getNodeAs<Region>() const {
137 assert(isSubRegion() && "This is not a subregion RegionNode!");
138 return reinterpret_cast<Region*>(const_cast<RegionNode*>(this));
141 //===----------------------------------------------------------------------===//
142 /// @brief A single entry single exit Region.
144 /// A Region is a connected subgraph of a control flow graph that has exactly
145 /// two connections to the remaining graph. It can be used to analyze or
146 /// optimize parts of the control flow graph.
148 /// A <em> simple Region </em> is connected to the remaing graph by just two
149 /// edges. One edge entering the Region and another one leaving the Region.
151 /// An <em> extended Region </em> (or just Region) is a subgraph that can be
152 /// transform into a simple Region. The transformation is done by adding
153 /// BasicBlocks that merge several entry or exit edges so that after the merge
154 /// just one entry and one exit edge exists.
156 /// The \e Entry of a Region is the first BasicBlock that is passed after
157 /// entering the Region. It is an element of the Region. The entry BasicBlock
158 /// dominates all BasicBlocks in the Region.
160 /// The \e Exit of a Region is the first BasicBlock that is passed after
161 /// leaving the Region. It is not an element of the Region. The exit BasicBlock,
162 /// postdominates all BasicBlocks in the Region.
164 /// A <em> canonical Region </em> cannot be constructed by combining smaller
167 /// Region A is the \e parent of Region B, if B is completely contained in A.
169 /// Two canonical Regions either do not intersect at all or one is
170 /// the parent of the other.
172 /// The <em> Program Structure Tree</em> is a graph (V, E) where V is the set of
173 /// Regions in the control flow graph and E is the \e parent relation of these
179 /// A simple control flow graph, that contains two regions.
189 /// \ |/ Region A: 1 -> 9 {1,2,3,4,5,6,7,8}
190 /// 9 Region B: 2 -> 9 {2,4,5,6,7}
193 /// You can obtain more examples by either calling
195 /// <tt> "opt -regions -analyze anyprogram.ll" </tt>
197 /// <tt> "opt -view-regions-only anyprogram.ll" </tt>
199 /// on any LLVM file you are interested in.
201 /// The first call returns a textual representation of the program structure
202 /// tree, the second one creates a graphical representation using graphviz.
203 class Region : public RegionNode {
204 friend class RegionInfo;
206 Region(const Region &);
208 const Region &operator=(const Region &);
210 // Information necessary to manage this Region.
214 // The exit BasicBlock of this region.
215 // (The entry BasicBlock is part of RegionNode)
218 typedef std::vector<Region*> RegionSet;
220 // The subregions of this region.
223 typedef std::map<BasicBlock*, RegionNode*> BBNodeMapT;
225 // Save the BasicBlock RegionNodes that are element of this Region.
226 mutable BBNodeMapT BBNodeMap;
228 /// verifyBBInRegion - Check if a BB is in this Region. This check also works
229 /// if the region is incorrectly built. (EXPENSIVE!)
230 void verifyBBInRegion(BasicBlock* BB) const;
232 /// verifyWalk - Walk over all the BBs of the region starting from BB and
233 /// verify that all reachable basic blocks are elements of the region.
235 void verifyWalk(BasicBlock* BB, std::set<BasicBlock*>* visitedBB) const;
237 /// verifyRegionNest - Verify if the region and its children are valid
238 /// regions (EXPENSIVE!)
239 void verifyRegionNest() const;
242 /// @brief Create a new region.
244 /// @param Entry The entry basic block of the region.
245 /// @param Exit The exit basic block of the region.
246 /// @param RI The region info object that is managing this region.
247 /// @param DT The dominator tree of the current function.
248 /// @param Parent The surrounding region or NULL if this is a top level
250 Region(BasicBlock *Entry, BasicBlock *Exit, RegionInfo* RI,
251 DominatorTree *DT, Region *Parent = 0);
253 /// Delete the Region and all its subregions.
256 /// @brief Get the entry BasicBlock of the Region.
257 /// @return The entry BasicBlock of the region.
258 BasicBlock *getEntry() const { return RegionNode::getEntry(); }
260 /// @brief Replace the entry basic block of the region with the new basic
263 /// @param BB The new entry basic block of the region.
264 void replaceEntry(BasicBlock *BB);
266 /// @brief Replace the exit basic block of the region with the new basic
269 /// @param BB The new exit basic block of the region.
270 void replaceExit(BasicBlock *BB);
272 /// @brief Get the exit BasicBlock of the Region.
273 /// @return The exit BasicBlock of the Region, NULL if this is the TopLevel
275 BasicBlock *getExit() const { return exit; }
277 /// @brief Get the parent of the Region.
278 /// @return The parent of the Region or NULL if this is a top level
280 Region *getParent() const { return RegionNode::getParent(); }
282 /// @brief Get the RegionNode representing the current Region.
283 /// @return The RegionNode representing the current Region.
284 RegionNode* getNode() const {
285 return const_cast<RegionNode*>(reinterpret_cast<const RegionNode*>(this));
288 /// @brief Get the nesting level of this Region.
290 /// An toplevel Region has depth 0.
292 /// @return The depth of the region.
293 unsigned getDepth() const;
295 /// @brief Return a new (non canonical) region, that is obtained by joining
296 /// this region with its predecessors.
298 /// @return A region also starting at getEntry(), but reaching to the next
299 /// basic block that forms with getEntry() a (non canonical) region.
300 /// NULL if such a basic block does not exist.
301 Region *getExpandedRegion() const;
303 /// @brief Is this a simple region?
305 /// A region is simple if it has exactly one exit and one entry edge.
307 /// @return True if the Region is simple.
308 bool isSimple() const;
310 /// @brief Returns the name of the Region.
311 /// @return The Name of the Region.
312 std::string getNameStr() const;
314 /// @brief Return the RegionInfo object, that belongs to this Region.
315 RegionInfo *getRegionInfo() const {
319 /// @brief Print the region.
321 /// @param OS The output stream the Region is printed to.
322 /// @param printTree Print also the tree of subregions.
323 /// @param level The indentation level used for printing.
324 void print(raw_ostream& OS, bool printTree = true, unsigned level = 0) const;
326 /// @brief Print the region to stderr.
329 /// @brief Check if the region contains a BasicBlock.
331 /// @param BB The BasicBlock that might be contained in this Region.
332 /// @return True if the block is contained in the region otherwise false.
333 bool contains(const BasicBlock *BB) const;
335 /// @brief Check if the region contains another region.
337 /// @param SubRegion The region that might be contained in this Region.
338 /// @return True if SubRegion is contained in the region otherwise false.
339 bool contains(const Region *SubRegion) const {
344 return contains(SubRegion->getEntry())
345 && (contains(SubRegion->getExit()) || SubRegion->getExit() == getExit());
348 /// @brief Check if the region contains an Instruction.
350 /// @param Inst The Instruction that might be contained in this region.
351 /// @return True if the Instruction is contained in the region otherwise false.
352 bool contains(const Instruction *Inst) const {
353 return contains(Inst->getParent());
356 /// @brief Check if the region contains a loop.
358 /// @param L The loop that might be contained in this region.
359 /// @return True if the loop is contained in the region otherwise false.
360 /// In case a NULL pointer is passed to this function the result
361 /// is false, except for the region that describes the whole function.
362 /// In that case true is returned.
363 bool contains(const Loop *L) const;
365 /// @brief Get the outermost loop in the region that contains a loop.
367 /// Find for a Loop L the outermost loop OuterL that is a parent loop of L
368 /// and is itself contained in the region.
370 /// @param L The loop the lookup is started.
371 /// @return The outermost loop in the region, NULL if such a loop does not
372 /// exist or if the region describes the whole function.
373 Loop *outermostLoopInRegion(Loop *L) const;
375 /// @brief Get the outermost loop in the region that contains a basic block.
377 /// Find for a basic block BB the outermost loop L that contains BB and is
378 /// itself contained in the region.
380 /// @param LI A pointer to a LoopInfo analysis.
381 /// @param BB The basic block surrounded by the loop.
382 /// @return The outermost loop in the region, NULL if such a loop does not
383 /// exist or if the region describes the whole function.
384 Loop *outermostLoopInRegion(LoopInfo *LI, BasicBlock* BB) const;
386 /// @brief Get the subregion that starts at a BasicBlock
388 /// @param BB The BasicBlock the subregion should start.
389 /// @return The Subregion if available, otherwise NULL.
390 Region* getSubRegionNode(BasicBlock *BB) const;
392 /// @brief Get the RegionNode for a BasicBlock
394 /// @param BB The BasicBlock at which the RegionNode should start.
395 /// @return If available, the RegionNode that represents the subregion
396 /// starting at BB. If no subregion starts at BB, the RegionNode
398 RegionNode* getNode(BasicBlock *BB) const;
400 /// @brief Get the BasicBlock RegionNode for a BasicBlock
402 /// @param BB The BasicBlock for which the RegionNode is requested.
403 /// @return The RegionNode representing the BB.
404 RegionNode* getBBNode(BasicBlock *BB) const;
406 /// @brief Add a new subregion to this Region.
408 /// @param SubRegion The new subregion that will be added.
409 /// @param moveChildren Move the children of this region, that are also
410 /// contained in SubRegion into SubRegion.
411 void addSubRegion(Region *SubRegion, bool moveChildren = false);
413 /// @brief Remove a subregion from this Region.
415 /// The subregion is not deleted, as it will probably be inserted into another
417 /// @param SubRegion The SubRegion that will be removed.
418 Region *removeSubRegion(Region *SubRegion);
420 /// @brief Move all direct child nodes of this Region to another Region.
422 /// @param To The Region the child nodes will be transfered to.
423 void transferChildrenTo(Region *To);
425 /// @brief Verify if the region is a correct region.
427 /// Check if this is a correctly build Region. This is an expensive check, as
428 /// the complete CFG of the Region will be walked.
429 void verifyRegion() const;
431 /// @brief Clear the cache for BB RegionNodes.
433 /// After calling this function the BasicBlock RegionNodes will be stored at
434 /// different memory locations. RegionNodes obtained before this function is
435 /// called are therefore not comparable to RegionNodes abtained afterwords.
436 void clearNodeCache();
438 /// @name Subregion Iterators
440 /// These iterators iterator over all subregions of this Region.
442 typedef RegionSet::iterator iterator;
443 typedef RegionSet::const_iterator const_iterator;
445 iterator begin() { return children.begin(); }
446 iterator end() { return children.end(); }
448 const_iterator begin() const { return children.begin(); }
449 const_iterator end() const { return children.end(); }
452 /// @name BasicBlock Iterators
454 /// These iterators iterate over all BasicBlock RegionNodes that are
455 /// contained in this Region. The iterator also iterates over BasicBlocks
456 /// that are elements of a subregion of this Region. It is therefore called a
459 typedef df_iterator<RegionNode*, SmallPtrSet<RegionNode*, 8>, false,
460 GraphTraits<FlatIt<RegionNode*> > > block_iterator;
462 typedef df_iterator<const RegionNode*, SmallPtrSet<const RegionNode*, 8>,
463 false, GraphTraits<FlatIt<const RegionNode*> > >
464 const_block_iterator;
466 block_iterator block_begin();
467 block_iterator block_end();
469 const_block_iterator block_begin() const;
470 const_block_iterator block_end() const;
473 /// @name Element Iterators
475 /// These iterators iterate over all BasicBlock and subregion RegionNodes that
476 /// are direct children of this Region. It does not iterate over any
477 /// RegionNodes that are also element of a subregion of this Region.
479 typedef df_iterator<RegionNode*, SmallPtrSet<RegionNode*, 8>, false,
480 GraphTraits<RegionNode*> > element_iterator;
482 typedef df_iterator<const RegionNode*, SmallPtrSet<const RegionNode*, 8>,
483 false, GraphTraits<const RegionNode*> >
484 const_element_iterator;
486 element_iterator element_begin();
487 element_iterator element_end();
489 const_element_iterator element_begin() const;
490 const_element_iterator element_end() const;
494 //===----------------------------------------------------------------------===//
495 /// @brief Analysis that detects all canonical Regions.
497 /// The RegionInfo pass detects all canonical regions in a function. The Regions
498 /// are connected using the parent relation. This builds a Program Structure
500 class RegionInfo : public FunctionPass {
501 typedef DenseMap<BasicBlock*,BasicBlock*> BBtoBBMap;
502 typedef DenseMap<BasicBlock*, Region*> BBtoRegionMap;
503 typedef SmallPtrSet<Region*, 4> RegionSet;
506 RegionInfo(const RegionInfo &);
508 const RegionInfo &operator=(const RegionInfo &);
511 PostDominatorTree *PDT;
512 DominanceFrontier *DF;
514 /// The top level region.
515 Region *TopLevelRegion;
517 /// Map every BB to the smallest region, that contains BB.
518 BBtoRegionMap BBtoRegion;
520 // isCommonDomFrontier - Returns true if BB is in the dominance frontier of
521 // entry, because it was inherited from exit. In the other case there is an
522 // edge going from entry to BB without passing exit.
523 bool isCommonDomFrontier(BasicBlock* BB, BasicBlock* entry,
524 BasicBlock* exit) const;
526 // isRegion - Check if entry and exit surround a valid region, based on
527 // dominance tree and dominance frontier.
528 bool isRegion(BasicBlock* entry, BasicBlock* exit) const;
530 // insertShortCut - Saves a shortcut pointing from entry to exit.
531 // This function may extend this shortcut if possible.
532 void insertShortCut(BasicBlock* entry, BasicBlock* exit,
533 BBtoBBMap* ShortCut) const;
535 // getNextPostDom - Returns the next BB that postdominates N, while skipping
536 // all post dominators that cannot finish a canonical region.
537 DomTreeNode *getNextPostDom(DomTreeNode* N, BBtoBBMap *ShortCut) const;
539 // isTrivialRegion - A region is trivial, if it contains only one BB.
540 bool isTrivialRegion(BasicBlock *entry, BasicBlock *exit) const;
542 // createRegion - Creates a single entry single exit region.
543 Region *createRegion(BasicBlock *entry, BasicBlock *exit);
545 // findRegionsWithEntry - Detect all regions starting with bb 'entry'.
546 void findRegionsWithEntry(BasicBlock *entry, BBtoBBMap *ShortCut);
548 // scanForRegions - Detects regions in F.
549 void scanForRegions(Function &F, BBtoBBMap *ShortCut);
551 // getTopMostParent - Get the top most parent with the same entry block.
552 Region *getTopMostParent(Region *region);
554 // buildRegionsTree - build the region hierarchy after all region detected.
555 void buildRegionsTree(DomTreeNode *N, Region *region);
557 // Calculate - detecte all regions in function and build the region tree.
558 void Calculate(Function& F);
560 void releaseMemory();
562 // updateStatistics - Update statistic about created regions.
563 void updateStatistics(Region *R);
565 // isSimple - Check if a region is a simple region with exactly one entry
566 // edge and exactly one exit edge.
567 bool isSimple(Region* R) const;
571 explicit RegionInfo();
575 /// @name FunctionPass interface
577 virtual bool runOnFunction(Function &F);
578 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
579 virtual void print(raw_ostream &OS, const Module *) const;
580 virtual void verifyAnalysis() const;
583 /// @brief Get the smallest region that contains a BasicBlock.
585 /// @param BB The basic block.
586 /// @return The smallest region, that contains BB or NULL, if there is no
587 /// region containing BB.
588 Region *getRegionFor(BasicBlock *BB) const;
590 /// @brief Set the smallest region that surrounds a basic block.
592 /// @param BB The basic block surrounded by a region.
593 /// @param R The smallest region that surrounds BB.
594 void setRegionFor(BasicBlock *BB, Region *R);
596 /// @brief A shortcut for getRegionFor().
598 /// @param BB The basic block.
599 /// @return The smallest region, that contains BB or NULL, if there is no
600 /// region containing BB.
601 Region *operator[](BasicBlock *BB) const;
603 /// @brief Return the exit of the maximal refined region, that starts at a
606 /// @param BB The BasicBlock the refined region starts.
607 BasicBlock *getMaxRegionExit(BasicBlock *BB) const;
609 /// @brief Find the smallest region that contains two regions.
611 /// @param A The first region.
612 /// @param B The second region.
613 /// @return The smallest region containing A and B.
614 Region *getCommonRegion(Region* A, Region *B) const;
616 /// @brief Find the smallest region that contains two basic blocks.
618 /// @param A The first basic block.
619 /// @param B The second basic block.
620 /// @return The smallest region that contains A and B.
621 Region* getCommonRegion(BasicBlock* A, BasicBlock *B) const {
622 return getCommonRegion(getRegionFor(A), getRegionFor(B));
625 /// @brief Find the smallest region that contains a set of regions.
627 /// @param Regions A vector of regions.
628 /// @return The smallest region that contains all regions in Regions.
629 Region* getCommonRegion(SmallVectorImpl<Region*> &Regions) const;
631 /// @brief Find the smallest region that contains a set of basic blocks.
633 /// @param BBs A vector of basic blocks.
634 /// @return The smallest region that contains all basic blocks in BBS.
635 Region* getCommonRegion(SmallVectorImpl<BasicBlock*> &BBs) const;
637 Region *getTopLevelRegion() const {
638 return TopLevelRegion;
641 /// @brief Update RegionInfo after a basic block was split.
643 /// @param NewBB The basic block that was created before OldBB.
644 /// @param OldBB The old basic block.
645 void splitBlock(BasicBlock* NewBB, BasicBlock *OldBB);
647 /// @brief Clear the Node Cache for all Regions.
649 /// @see Region::clearNodeCache()
650 void clearNodeCache() {
652 TopLevelRegion->clearNodeCache();
656 inline raw_ostream &operator<<(raw_ostream &OS, const RegionNode &Node) {
657 if (Node.isSubRegion())
658 return OS << Node.getNodeAs<Region>()->getNameStr();
660 return OS << Node.getNodeAs<BasicBlock>()->getNameStr();
662 } // End llvm namespace