X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FLoopInfo.cpp;h=156d8b1bace4092a71cc64a2b83bcb797d889911;hb=275b3017404e9d3cfe73631257121ca020f88f21;hp=410a0123828900b6436a7758eacda99d45084cfd;hpb=cf3056db0fee1db7921214b1f25cea04e959e105;p=oota-llvm.git diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp index 410a0123828..156d8b1bace 100644 --- a/lib/Analysis/LoopInfo.cpp +++ b/lib/Analysis/LoopInfo.cpp @@ -1,4 +1,11 @@ //===- 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 @@ -8,11 +15,16 @@ //===----------------------------------------------------------------------===// #include "llvm/Analysis/LoopInfo.h" +#include "llvm/Constants.h" +#include "llvm/Instructions.h" #include "llvm/Analysis/Dominators.h" -#include "llvm/Support/CFG.h" #include "llvm/Assembly/Writer.h" -#include "Support/DepthFirstIterator.h" +#include "llvm/Support/CFG.h" +#include "llvm/ADT/DepthFirstIterator.h" #include +#include + +using namespace llvm; static RegisterAnalysis X("loops", "Natural Loop Construction", true); @@ -21,7 +33,7 @@ X("loops", "Natural Loop Construction", true); // Loop implementation // bool Loop::contains(const BasicBlock *BB) const { - return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end(); + return std::find(Blocks.begin(), Blocks.end(), BB) != Blocks.end(); } bool Loop::isLoopExit(const BasicBlock *BB) const { @@ -46,6 +58,14 @@ unsigned Loop::getNumBackEdges() const { return NumBackEdges; } +/// isLoopInvariant - Return true if the specified value is loop invariant +/// +bool Loop::isLoopInvariant(Value *V) const { + if (Instruction *I = dyn_cast(V)) + return !contains(I->getParent()); + return true; // All non-instructions are loop invariant +} + void Loop::print(std::ostream &OS, unsigned Depth) const { OS << std::string(Depth*2, ' ') << "Loop Containing: "; @@ -53,18 +73,10 @@ void Loop::print(std::ostream &OS, unsigned Depth) const { 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 (unsigned i = 0, e = getSubLoops().size(); i != e; ++i) - getSubLoops()[i]->print(OS, Depth+2); + for (iterator I = begin(), E = end(); I != E; ++I) + (*I)->print(OS, Depth+2); } void Loop::dump() const { @@ -100,9 +112,6 @@ void LoopInfo::Calculate(const DominatorSet &DS) { 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 { @@ -110,14 +119,14 @@ void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const { AU.addRequired(); } -void LoopInfo::print(std::ostream &OS) const { +void LoopInfo::print(std::ostream &OS, const Module* ) 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"; + << I->second->getLoopDepth() << "\n"; #endif } @@ -144,11 +153,14 @@ Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) { 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?? + 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, @@ -235,14 +247,6 @@ Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) { } } - // 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; } @@ -282,17 +286,73 @@ void LoopInfo::InsertLoopInto(Loop *L, Loop *Parent) { 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; +} + +/// removeBlock - This method completely removes BB from all data structures, +/// including all of the Loop objects it is nested in and our mapping from +/// BasicBlocks to loops. +void LoopInfo::removeBlock(BasicBlock *BB) { + std::map::iterator I = BBMap.find(BB); + if (I != BBMap.end()) { + for (Loop *L = I->second; L; L = L->getParentLoop()) + L->removeBlockFromLoop(BB); + + BBMap.erase(I); + } +} + + +//===----------------------------------------------------------------------===// +// APIs for simple analysis of the loop. +// + +/// getExitBlocks - Return all of the successor blocks of this loop. These +/// are the blocks _outside of the current loop_ which are branched to. +/// +void Loop::getExitBlocks(std::vector &ExitBlocks) const { + for (std::vector::const_iterator BI = Blocks.begin(), + BE = Blocks.end(); BI != BE; ++BI) + for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I) + if (!contains(*I)) // Not in current loop? + ExitBlocks.push_back(*I); // It must be an exit block... +} /// 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. The "preheaders" pass can be -/// "Required" to ensure that there is always a preheader node for every loop. +/// header of the loop is the preheader node. /// -/// This method returns null if there is no preheader for the loop (either -/// because the loop is dead or because multiple blocks branch to the header -/// node of this loop). +/// 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... @@ -320,6 +380,88 @@ BasicBlock *Loop::getLoopPreheader() const { 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(); isa(I); ++I) { + PHINode *PN = cast(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 (BI->isConditional()) + 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 @@ -327,7 +469,8 @@ BasicBlock *Loop::getLoopPreheader() const { /// valid to replace the loop header with this method. /// void Loop::addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI) { - assert(LI[getHeader()] == this && "Incorrect LI specified for this loop!"); + 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!"); @@ -342,18 +485,51 @@ void Loop::addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI) { } } -/// 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. +/// 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; +} + +/// addChildLoop - Add the specified loop to be a child of this loop. /// -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); - } +void Loop::addChildLoop(Loop *NewChild) { + assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); + NewChild->ParentLoop = this; + SubLoops.push_back(NewChild); +} + +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); }