X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FLoopInfo.cpp;h=275331b03a58f952f0298d7dde3fc7ec54fb4559;hb=b169426272b85ce28a9a56d13154e61b158fc47a;hp=38b9c6699992e7c1f61823ef819d94cee0b037a4;hpb=24199db80ebd43398318b21d3e8d13e9bf72981d;p=oota-llvm.git diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp index 38b9c669999..275331b03a5 100644 --- a/lib/Analysis/LoopInfo.cpp +++ b/lib/Analysis/LoopInfo.cpp @@ -1,10 +1,10 @@ //===- 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 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 @@ -20,533 +20,31 @@ #include "llvm/Analysis/Dominators.h" #include "llvm/Assembly/Writer.h" #include "llvm/Support/CFG.h" -#include "Support/DepthFirstIterator.h" +#include "llvm/Support/Streams.h" +#include "llvm/ADT/DepthFirstIterator.h" +#include "llvm/ADT/SmallPtrSet.h" #include +#include using namespace llvm; -static RegisterAnalysis -X("loops", "Natural Loop Construction", true); +char LoopInfo::ID = 0; +static RegisterPass +X("loops", "Natural Loop Construction", true, true); //===----------------------------------------------------------------------===// // Loop implementation // -bool Loop::contains(const BasicBlock *BB) const { - return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end(); -} - -bool Loop::isLoopExit(const BasicBlock *BB) const { - for (succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB); - SI != SE; ++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 *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, unsigned Depth) const { - OS << std::string(Depth*2, ' ') << "Loop Containing: "; - - for (unsigned i = 0; i < getBlocks().size(); ++i) { - if (i) OS << ","; - 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 (iterator I = begin(), E = end(); I != E; ++I) - (*I)->print(OS, Depth+2); -} - -void Loop::dump() const { - print(std::cerr); -} - //===----------------------------------------------------------------------===// // LoopInfo implementation // -void LoopInfo::stub() {} - bool LoopInfo::runOnFunction(Function &) { releaseMemory(); - Calculate(getAnalysis()); // Update + LI->Calculate(getAnalysis().getBase()); // Update return false; } -void LoopInfo::releaseMemory() { - for (std::vector::iterator I = TopLevelLoops.begin(), - E = TopLevelLoops.end(); I != E; ++I) - delete *I; // Delete all of the loops... - - BBMap.clear(); // Reset internal state of analysis - TopLevelLoops.clear(); -} - - -void LoopInfo::Calculate(const DominatorSet &DS) { - BasicBlock *RootNode = DS.getRoot(); - - for (df_iterator NI = df_begin(RootNode), - NE = df_end(RootNode); NI != NE; ++NI) - if (Loop *L = ConsiderForLoop(*NI, DS)) - TopLevelLoops.push_back(L); - - for (unsigned i = 0; i < TopLevelLoops.size(); ++i) - TopLevelLoops[i]->setLoopDepth(1); -} - void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesAll(); - AU.addRequired(); -} - -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) { - if (BBMap.find(BB) != BBMap.end()) return 0; // Haven't processed this node? - - std::vector TodoStack; - - // Scan the predecessors of BB, checking to see if BB dominates any of - // 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; // 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?? - 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. - // - 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 { - // 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; -} - -/// changeLoopFor - Change the top-level loop that contains BB to the -/// specified loop. This should be used by transformations that restructure -/// the loop hierarchy tree. -void LoopInfo::changeLoopFor(BasicBlock *BB, Loop *L) { - Loop *&OldLoop = BBMap[BB]; - assert(OldLoop && "Block not in a loop yet!"); - OldLoop = L; -} - -/// changeTopLevelLoop - Replace the specified loop in the top-level loops -/// list with the indicated loop. -void LoopInfo::changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { - std::vector::iterator I = std::find(TopLevelLoops.begin(), - TopLevelLoops.end(), OldLoop); - assert(I != TopLevelLoops.end() && "Old loop not at top level!"); - *I = NewLoop; - assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && - "Loops already embedded into a subloop!"); -} - -/// removeLoop - This removes the specified top-level loop from this loop info -/// object. The loop is not deleted, as it will presumably be inserted into -/// another loop. -Loop *LoopInfo::removeLoop(iterator I) { - assert(I != end() && "Cannot remove end iterator!"); - Loop *L = *I; - assert(L->getParentLoop() == 0 && "Not a top-level loop!"); - TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); - return L; -} - - - -//===----------------------------------------------------------------------===// -// APIs for simple analysis of the loop. -// - -/// 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 -/// header of the loop is the preheader node. -/// -/// This method returns null if there is no preheader for the loop. -/// -BasicBlock *Loop::getLoopPreheader() const { - // Keep track of nodes outside the loop branching to the header... - BasicBlock *Out = 0; - - // Loop over the predecessors of the header node... - BasicBlock *Header = getHeader(); - for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header); - PI != PE; ++PI) - if (!contains(*PI)) { // If the block is not in the loop... - if (Out && Out != *PI) - 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. - return Out; -} - -/// getCanonicalInductionVariable - Check to see if the loop has a canonical -/// induction variable: an integer recurrence that starts at 0 and increments by -/// one each time through the loop. If so, return the phi node that corresponds -/// to it. -/// -PHINode *Loop::getCanonicalInductionVariable() const { - BasicBlock *H = getHeader(); - - BasicBlock *Incoming = 0, *Backedge = 0; - pred_iterator PI = pred_begin(H); - assert(PI != pred_end(H) && "Loop must have at least one backedge!"); - Backedge = *PI++; - if (PI == pred_end(H)) return 0; // dead loop - Incoming = *PI++; - if (PI != pred_end(H)) return 0; // multiple backedges? - - if (contains(Incoming)) { - if (contains(Backedge)) - return 0; - std::swap(Incoming, Backedge); - } else if (!contains(Backedge)) - return 0; - - // Loop over all of the PHI nodes, looking for a canonical indvar. - for (BasicBlock::iterator I = H->begin(); - PHINode *PN = dyn_cast(I); ++I) - if (Instruction *Inc = - dyn_cast(PN->getIncomingValueForBlock(Backedge))) - if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(0) == PN) - if (ConstantInt *CI = dyn_cast(Inc->getOperand(1))) - if (CI->equalsInt(1)) - return PN; - - return 0; -} - -/// getCanonicalInductionVariableIncrement - Return the LLVM value that holds -/// the canonical induction variable value for the "next" iteration of the loop. -/// This always succeeds if getCanonicalInductionVariable succeeds. -/// -Instruction *Loop::getCanonicalInductionVariableIncrement() const { - if (PHINode *PN = getCanonicalInductionVariable()) { - bool P1InLoop = contains(PN->getIncomingBlock(1)); - return cast(PN->getIncomingValue(P1InLoop)); - } - return 0; -} - -/// getTripCount - Return a loop-invariant LLVM value indicating the number of -/// times the loop will be executed. Note that this means that the backedge of -/// the loop executes N-1 times. If the trip-count cannot be determined, this -/// returns null. -/// -Value *Loop::getTripCount() const { - // Canonical loops will end with a 'setne I, V', where I is the incremented - // canonical induction variable and V is the trip count of the loop. - Instruction *Inc = getCanonicalInductionVariableIncrement(); - if (Inc == 0) return 0; - PHINode *IV = cast(Inc->getOperand(0)); - - BasicBlock *BackedgeBlock = - IV->getIncomingBlock(contains(IV->getIncomingBlock(1))); - - if (BranchInst *BI = dyn_cast(BackedgeBlock->getTerminator())) - if (SetCondInst *SCI = dyn_cast(BI->getCondition())) - if (SCI->getOperand(0) == Inc) - if (BI->getSuccessor(0) == getHeader()) { - if (SCI->getOpcode() == Instruction::SetNE) - return SCI->getOperand(1); - } else if (SCI->getOpcode() == Instruction::SetEQ) { - return SCI->getOperand(1); - } - - return 0; -} - - -//===-------------------------------------------------------------------===// -// APIs for updating loop information after changing the CFG -// - -/// addBasicBlockToLoop - This function is used by other analyses to update loop -/// information. NewBB is set to be a new member of the current loop. Because -/// of this, it is added as a member of all parent loops, and is added to the -/// specified LoopInfo object as being in the current basic block. It is not -/// valid to replace the loop header with this method. -/// -void Loop::addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI) { - assert((Blocks.empty() || LI[getHeader()] == this) && - "Incorrect LI specified for this loop!"); - assert(NewBB && "Cannot add a null basic block to the loop!"); - assert(LI[NewBB] == 0 && "BasicBlock already in the loop!"); - - // Add the loop mapping to the LoopInfo object... - LI.BBMap[NewBB] = this; - - // Add the basic block to this loop and all parent loops... - Loop *L = this; - while (L) { - L->Blocks.push_back(NewBB); - 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); - } -} - -/// replaceChildLoopWith - This is used when splitting loops up. It replaces -/// the OldChild entry in our children list with NewChild, and updates the -/// parent pointers of the two loops as appropriate. -void Loop::replaceChildLoopWith(Loop *OldChild, Loop *NewChild) { - assert(OldChild->ParentLoop == this && "This loop is already broken!"); - assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); - std::vector::iterator I = std::find(SubLoops.begin(), SubLoops.end(), - OldChild); - assert(I != SubLoops.end() && "OldChild not in loop!"); - *I = NewChild; - OldChild->ParentLoop = 0; - NewChild->ParentLoop = this; - - // Update the loop depth of the new child. - NewChild->setLoopDepth(LoopDepth+1); -} - -/// addChildLoop - Add the specified loop to be a child of this loop. -/// -void Loop::addChildLoop(Loop *NewChild) { - assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); - NewChild->ParentLoop = this; - SubLoops.push_back(NewChild); - - // Update the loop depth of the new child. - NewChild->setLoopDepth(LoopDepth+1); -} - -template -static void RemoveFromVector(std::vector &V, T *N) { - typename std::vector::iterator I = std::find(V.begin(), V.end(), N); - assert(I != V.end() && "N is not in this list!"); - V.erase(I); -} - -/// removeChildLoop - This removes the specified child from being a subloop of -/// this loop. The loop is not deleted, as it will presumably be inserted -/// into another loop. -Loop *Loop::removeChildLoop(iterator I) { - assert(I != SubLoops.end() && "Cannot remove end iterator!"); - Loop *Child = *I; - assert(Child->ParentLoop == this && "Child is not a child of this loop!"); - SubLoops.erase(SubLoops.begin()+(I-begin())); - Child->ParentLoop = 0; - return Child; -} - - -/// removeBlockFromLoop - This removes the specified basic block from the -/// current loop, updating the Blocks and ExitBlocks lists as appropriate. This -/// does not update the mapping in the LoopInfo class. -void Loop::removeBlockFromLoop(BasicBlock *BB) { - RemoveFromVector(Blocks, BB); - - // If this block branched out of this loop, remove any exit blocks entries due - // to it. - for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) - if (!contains(*SI) && *SI != BB) - RemoveFromVector(ExitBlocks, *SI); - - // If any blocks in this loop branch to BB, add it to the exit blocks set. - for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) - if (contains(*PI)) - ExitBlocks.push_back(BB); + AU.addRequired(); }