X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FLoopInfo.cpp;h=41c4b555bd14a88c930aeca7d3dc23e390d1953c;hb=4c6cb7a2b1fca93742a7751640375854bca762ae;hp=ef4b6430ba2ad4aa1b0c511569c00e25b1cb18fa;hpb=ae5d39e1bba338e41911d5e002c96c88d7618db8;p=oota-llvm.git diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp index ef4b6430ba2..41c4b555bd1 100644 --- a/lib/Analysis/LoopInfo.cpp +++ b/lib/Analysis/LoopInfo.cpp @@ -1,4 +1,11 @@ -//===- LoopInfo.cpp - Natural Loop Calculator -------------------------------=// +//===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file was developed by the LLVM research group and is distributed under +// the University of Illinois Open Source License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// // // This file defines the LoopInfo class that is used to identify natural loops // and determine the loop depth of various nodes of the CFG. Note that the @@ -14,6 +21,8 @@ #include "Support/DepthFirstIterator.h" #include +namespace llvm { + static RegisterAnalysis X("loops", "Natural Loop Construction", true); @@ -25,41 +34,53 @@ bool Loop::contains(const BasicBlock *BB) const { } bool Loop::isLoopExit(const BasicBlock *BB) const { - for (BasicBlock::succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB); + for (succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) { - if (! contains(*SI)) + if (!contains(*SI)) return true; } return false; } +/// getNumBackEdges - Calculate the number of back edges to the loop header. +/// unsigned Loop::getNumBackEdges() const { - unsigned numBackEdges = 0; - BasicBlock *header = Blocks.front(); - - for (std::vector::const_iterator I = Blocks.begin(), - E = Blocks.end(); I != E; ++I) { - for (BasicBlock::succ_iterator SI = succ_begin(*I), SE = succ_end(*I); - SI != SE; ++SI) - if (header == *SI) - ++numBackEdges; - } - return numBackEdges; + unsigned NumBackEdges = 0; + BasicBlock *H = getHeader(); + + for (pred_iterator I = pred_begin(H), E = pred_end(H); I != E; ++I) + if (contains(*I)) + ++NumBackEdges; + + return NumBackEdges; } -void Loop::print(std::ostream &OS) const { - OS << std::string(getLoopDepth()*2, ' ') << "Loop Containing: "; +void Loop::print(std::ostream &OS, unsigned Depth) const { + OS << std::string(Depth*2, ' ') << "Loop Containing: "; for (unsigned i = 0; i < getBlocks().size(); ++i) { if (i) OS << ","; - WriteAsOperand(OS, (const Value*)getBlocks()[i]); + WriteAsOperand(OS, getBlocks()[i], false); } + if (!ExitBlocks.empty()) { + OS << "\tExitBlocks: "; + for (unsigned i = 0; i < getExitBlocks().size(); ++i) { + if (i) OS << ","; + WriteAsOperand(OS, getExitBlocks()[i], false); + } + } + OS << "\n"; - for (unsigned i = 0, e = getSubLoops().size(); i != e; ++i) - getSubLoops()[i]->print(OS); + for (iterator I = begin(), E = end(); I != E; ++I) + (*I)->print(OS, Depth+2); } +void Loop::dump() const { + print(std::cerr); +} + + //===----------------------------------------------------------------------===// // LoopInfo implementation // @@ -101,6 +122,18 @@ void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const { void LoopInfo::print(std::ostream &OS) const { for (unsigned i = 0; i < TopLevelLoops.size(); ++i) TopLevelLoops[i]->print(OS); +#if 0 + for (std::map::const_iterator I = BBMap.begin(), + E = BBMap.end(); I != E; ++I) + OS << "BB '" << I->first->getName() << "' level = " + << I->second->LoopDepth << "\n"; +#endif +} + +static bool isNotAlreadyContainedIn(Loop *SubLoop, Loop *ParentLoop) { + if (SubLoop == 0) return true; + if (SubLoop == ParentLoop) return false; + return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); } Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) { @@ -109,70 +142,160 @@ Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) { std::vector TodoStack; // Scan the predecessors of BB, checking to see if BB dominates any of - // them. + // them. This identifies backedges which target this node... for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) if (DS.dominates(BB, *I)) // If BB dominates it's predecessor... TodoStack.push_back(*I); - if (TodoStack.empty()) return 0; // Doesn't dominate any predecessors... + if (TodoStack.empty()) return 0; // No backedges to this block... // Create a new loop to represent this basic block... Loop *L = new Loop(BB); BBMap[BB] = L; + BasicBlock *EntryBlock = &BB->getParent()->getEntryBlock(); + while (!TodoStack.empty()) { // Process all the nodes in the loop BasicBlock *X = TodoStack.back(); TodoStack.pop_back(); - if (!L->contains(X)) { // As of yet unprocessed?? - L->Blocks.push_back(X); + if (!L->contains(X) && // As of yet unprocessed?? + DS.dominates(EntryBlock, X)) { // X is reachable from entry block? + // Check to see if this block already belongs to a loop. If this occurs + // then we have a case where a loop that is supposed to be a child of the + // current loop was processed before the current loop. When this occurs, + // this child loop gets added to a part of the current loop, making it a + // sibling to the current loop. We have to reparent this loop. + if (Loop *SubLoop = const_cast(getLoopFor(X))) + if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)) { + // Remove the subloop from it's current parent... + assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); + Loop *SLP = SubLoop->ParentLoop; // SubLoopParent + std::vector::iterator I = + std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); + assert(I != SLP->SubLoops.end() && "SubLoop not a child of parent?"); + SLP->SubLoops.erase(I); // Remove from parent... + + // Add the subloop to THIS loop... + SubLoop->ParentLoop = L; + L->SubLoops.push_back(SubLoop); + } + // Normal case, add the block to our loop... + L->Blocks.push_back(X); + // Add all of the predecessors of X to the end of the work stack... TodoStack.insert(TodoStack.end(), pred_begin(X), pred_end(X)); } } + // If there are any loops nested within this loop, create them now! + for (std::vector::iterator I = L->Blocks.begin(), + E = L->Blocks.end(); I != E; ++I) + if (Loop *NewLoop = ConsiderForLoop(*I, DS)) { + L->SubLoops.push_back(NewLoop); + NewLoop->ParentLoop = L; + } + // Add the basic blocks that comprise this loop to the BBMap so that this - // loop can be found for them. Also check subsidary basic blocks to see if - // they start subloops of their own. + // loop can be found for them. // - for (std::vector::reverse_iterator I = L->Blocks.rbegin(), - E = L->Blocks.rend(); I != E; ++I) - - // Check to see if this block starts a new loop - if (*I != BB) - if (Loop *NewLoop = ConsiderForLoop(*I, DS)) { - L->SubLoops.push_back(NewLoop); - NewLoop->ParentLoop = L; + for (std::vector::iterator I = L->Blocks.begin(), + E = L->Blocks.end(); I != E; ++I) { + std::map::iterator BBMI = BBMap.lower_bound(*I); + if (BBMI == BBMap.end() || BBMI->first != *I) // Not in map yet... + BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level + } + + // Now that we have a list of all of the child loops of this loop, check to + // see if any of them should actually be nested inside of each other. We can + // accidentally pull loops our of their parents, so we must make sure to + // organize the loop nests correctly now. + { + std::map ContainingLoops; + for (unsigned i = 0; i != L->SubLoops.size(); ++i) { + Loop *Child = L->SubLoops[i]; + assert(Child->getParentLoop() == L && "Not proper child loop?"); + + if (Loop *ContainingLoop = ContainingLoops[Child->getHeader()]) { + // If there is already a loop which contains this loop, move this loop + // into the containing loop. + MoveSiblingLoopInto(Child, ContainingLoop); + --i; // The loop got removed from the SubLoops list. } else { - std::map::iterator BBMI = BBMap.lower_bound(*I); - if (BBMI == BBMap.end() || BBMI->first != *I) { // Not in map yet... - BBMap.insert(BBMI, std::make_pair(*I, L)); - } else { - // If this is already in the BBMap then this means that we already - // added a loop for it, but incorrectly added the loop to a higher - // level loop instead of the current loop we are creating. Fix this - // now by moving the loop into the correct subloop. - // - Loop *SubLoop = BBMI->second; - Loop *OldSubLoopParent = SubLoop->getParentLoop(); - if (OldSubLoopParent != L) { - // Remove SubLoop from OldSubLoopParent's list of subloops... - std::vector::iterator I = - std::find(OldSubLoopParent->SubLoops.begin(), - OldSubLoopParent->SubLoops.end(), SubLoop); - assert(I != OldSubLoopParent->SubLoops.end() - && "Loop parent doesn't contain loop?"); - OldSubLoopParent->SubLoops.erase(I); - SubLoop->ParentLoop = L; - L->SubLoops.push_back(SubLoop); + // This is currently considered to be a top-level loop. Check to see if + // any of the contained blocks are loop headers for subloops we have + // already processed. + for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { + Loop *&BlockLoop = ContainingLoops[Child->Blocks[b]]; + if (BlockLoop == 0) { // Child block not processed yet... + BlockLoop = Child; + } else if (BlockLoop != Child) { + Loop *SubLoop = BlockLoop; + // Reparent all of the blocks which used to belong to BlockLoops + for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) + ContainingLoops[SubLoop->Blocks[j]] = Child; + + // There is already a loop which contains this block, that means + // that we should reparent the loop which the block is currently + // considered to belong to to be a child of this loop. + MoveSiblingLoopInto(SubLoop, Child); + --i; // We just shrunk the SubLoops list. } } - } + } + } + } + + // Now that we know all of the blocks that make up this loop, see if there are + // any branches to outside of the loop... building the ExitBlocks list. + for (std::vector::iterator BI = L->Blocks.begin(), + BE = L->Blocks.end(); BI != BE; ++BI) + for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I) + if (!L->contains(*I)) // Not in current loop? + L->ExitBlocks.push_back(*I); // It must be an exit block... return L; } +/// MoveSiblingLoopInto - This method moves the NewChild loop to live inside of +/// the NewParent Loop, instead of being a sibling of it. +void LoopInfo::MoveSiblingLoopInto(Loop *NewChild, Loop *NewParent) { + Loop *OldParent = NewChild->getParentLoop(); + assert(OldParent && OldParent == NewParent->getParentLoop() && + NewChild != NewParent && "Not sibling loops!"); + + // Remove NewChild from being a child of OldParent + std::vector::iterator I = + std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), NewChild); + assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); + OldParent->SubLoops.erase(I); // Remove from parent's subloops list + NewChild->ParentLoop = 0; + + InsertLoopInto(NewChild, NewParent); +} + +/// InsertLoopInto - This inserts loop L into the specified parent loop. If the +/// parent loop contains a loop which should contain L, the loop gets inserted +/// into L instead. +void LoopInfo::InsertLoopInto(Loop *L, Loop *Parent) { + BasicBlock *LHeader = L->getHeader(); + assert(Parent->contains(LHeader) && "This loop should not be inserted here!"); + + // Check to see if it belongs in a child loop... + for (unsigned i = 0, e = Parent->SubLoops.size(); i != e; ++i) + if (Parent->SubLoops[i]->contains(LHeader)) { + InsertLoopInto(L, Parent->SubLoops[i]); + return; + } + + // If not, insert it here! + Parent->SubLoops.push_back(L); + L->ParentLoop = Parent; +} + + + /// getLoopPreheader - If there is a preheader for this loop, return it. A /// loop has a preheader if there is only one edge to the header of the loop /// from outside of the loop. If this is the case, the block branching to the @@ -196,6 +319,13 @@ BasicBlock *Loop::getLoopPreheader() const { return 0; // Multiple predecessors outside the loop Out = *PI; } + + // Make sure there is only one exit out of the preheader... + succ_iterator SI = succ_begin(Out); + ++SI; + if (SI != succ_end(Out)) + return 0; // Multiple exits from the block, must not be a preheader. + // If there is exactly one preheader, return it. If there was zero, then Out // is still null. @@ -223,3 +353,21 @@ void Loop::addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI) { L = L->getParentLoop(); } } + +/// changeExitBlock - This method is used to update loop information. All +/// instances of the specified Old basic block are removed from the exit list +/// and replaced with New. +/// +void Loop::changeExitBlock(BasicBlock *Old, BasicBlock *New) { + assert(Old != New && "Cannot changeExitBlock to the same thing!"); + assert(Old && New && "Cannot changeExitBlock to or from a null node!"); + assert(hasExitBlock(Old) && "Old exit block not found!"); + std::vector::iterator + I = std::find(ExitBlocks.begin(), ExitBlocks.end(), Old); + while (I != ExitBlocks.end()) { + *I = New; + I = std::find(I+1, ExitBlocks.end(), Old); + } +} + +} // End llvm namespace