-//===- LoopInfo.cpp - Natural Loop Calculator -------------------------------=//
+//===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// 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
// and determine the loop depth of various nodes of the CFG. Note that the
//===----------------------------------------------------------------------===//
#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/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include <algorithm>
+using namespace llvm;
-static RegisterAnalysis<LoopInfo>
-X("loops", "Natural Loop Construction", true);
+// Always verify loopinfo if expensive checking is enabled.
+#ifdef XDEBUG
+static bool VerifyLoopInfo = true;
+#else
+static bool VerifyLoopInfo = false;
+#endif
+static cl::opt<bool,true>
+VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
+ cl::desc("Verify loop info (time consuming)"));
+
+char LoopInfo::ID = 0;
+INITIALIZE_PASS(LoopInfo, "loops", "Natural Loop Information", true, true);
//===----------------------------------------------------------------------===//
// Loop implementation
//
-bool Loop::contains(const BasicBlock *BB) const {
- return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
+
+/// isLoopInvariant - Return true if the specified value is loop invariant
+///
+bool Loop::isLoopInvariant(Value *V) const {
+ if (Instruction *I = dyn_cast<Instruction>(V))
+ return !contains(I);
+ return true; // All non-instructions are loop invariant
}
-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;
+/// hasLoopInvariantOperands - Return true if all the operands of the
+/// specified instruction are loop invariant.
+bool Loop::hasLoopInvariantOperands(Instruction *I) const {
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
+ if (!isLoopInvariant(I->getOperand(i)))
+ return false;
+
+ return true;
}
-/// getNumBackEdges - Calculate the number of back edges to the loop header.
+/// makeLoopInvariant - If the given value is an instruciton inside of the
+/// loop and it can be hoisted, do so to make it trivially loop-invariant.
+/// Return true if the value after any hoisting is loop invariant. This
+/// function can be used as a slightly more aggressive replacement for
+/// isLoopInvariant.
///
-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;
+/// If InsertPt is specified, it is the point to hoist instructions to.
+/// If null, the terminator of the loop preheader is used.
+///
+bool Loop::makeLoopInvariant(Value *V, bool &Changed,
+ Instruction *InsertPt) const {
+ if (Instruction *I = dyn_cast<Instruction>(V))
+ return makeLoopInvariant(I, Changed, InsertPt);
+ return true; // All non-instructions are loop-invariant.
}
-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);
- }
+/// makeLoopInvariant - If the given instruction is inside of the
+/// loop and it can be hoisted, do so to make it trivially loop-invariant.
+/// Return true if the instruction after any hoisting is loop invariant. This
+/// function can be used as a slightly more aggressive replacement for
+/// isLoopInvariant.
+///
+/// If InsertPt is specified, it is the point to hoist instructions to.
+/// If null, the terminator of the loop preheader is used.
+///
+bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
+ Instruction *InsertPt) const {
+ // Test if the value is already loop-invariant.
+ if (isLoopInvariant(I))
+ return true;
+ if (!I->isSafeToSpeculativelyExecute())
+ return false;
+ if (I->mayReadFromMemory())
+ return false;
+ // Determine the insertion point, unless one was given.
+ if (!InsertPt) {
+ BasicBlock *Preheader = getLoopPreheader();
+ // Without a preheader, hoisting is not feasible.
+ if (!Preheader)
+ return false;
+ InsertPt = Preheader->getTerminator();
}
-
- OS << "\n";
-
- for (unsigned i = 0, e = getSubLoops().size(); i != e; ++i)
- getSubLoops()[i]->print(OS, Depth+2);
-}
-
-void Loop::dump() const {
- print(std::cerr);
+ // Don't hoist instructions with loop-variant operands.
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
+ if (!makeLoopInvariant(I->getOperand(i), Changed, InsertPt))
+ return false;
+
+ // Hoist.
+ I->moveBefore(InsertPt);
+ Changed = true;
+ return true;
}
+/// 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.
+///
+/// The IndVarSimplify pass transforms loops to have a canonical induction
+/// variable.
+///
+PHINode *Loop::getCanonicalInductionVariable() const {
+ BasicBlock *H = getHeader();
-//===----------------------------------------------------------------------===//
-// LoopInfo implementation
-//
-void LoopInfo::stub() {}
-
-bool LoopInfo::runOnFunction(Function &) {
- releaseMemory();
- Calculate(getAnalysis<DominatorSet>()); // Update
- return false;
+ 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<PHINode>(I); ++I) {
+ PHINode *PN = cast<PHINode>(I);
+ if (ConstantInt *CI =
+ dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
+ if (CI->isNullValue())
+ if (Instruction *Inc =
+ dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
+ if (Inc->getOpcode() == Instruction::Add &&
+ Inc->getOperand(0) == PN)
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
+ if (CI->equalsInt(1))
+ return PN;
+ }
+ return 0;
}
-void LoopInfo::releaseMemory() {
- for (std::vector<Loop*>::iterator I = TopLevelLoops.begin(),
- E = TopLevelLoops.end(); I != E; ++I)
- delete *I; // Delete all of the loops...
+/// 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.
+///
+/// The IndVarSimplify pass transforms loops to have a form that this
+/// function easily understands.
+///
+Value *Loop::getTripCount() const {
+ // Canonical loops will end with a 'cmp ne I, V', where I is the incremented
+ // canonical induction variable and V is the trip count of the loop.
+ PHINode *IV = getCanonicalInductionVariable();
+ if (IV == 0 || IV->getNumIncomingValues() != 2) return 0;
+
+ bool P0InLoop = contains(IV->getIncomingBlock(0));
+ Value *Inc = IV->getIncomingValue(!P0InLoop);
+ BasicBlock *BackedgeBlock = IV->getIncomingBlock(!P0InLoop);
+
+ if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator()))
+ if (BI->isConditional()) {
+ if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
+ if (ICI->getOperand(0) == Inc) {
+ if (BI->getSuccessor(0) == getHeader()) {
+ if (ICI->getPredicate() == ICmpInst::ICMP_NE)
+ return ICI->getOperand(1);
+ } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) {
+ return ICI->getOperand(1);
+ }
+ }
+ }
+ }
- BBMap.clear(); // Reset internal state of analysis
- TopLevelLoops.clear();
+ return 0;
}
-
-void LoopInfo::Calculate(const DominatorSet &DS) {
- BasicBlock *RootNode = DS.getRoot();
-
- for (df_iterator<BasicBlock*> 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);
+/// getSmallConstantTripCount - Returns the trip count of this loop as a
+/// normal unsigned value, if possible. Returns 0 if the trip count is unknown
+/// of not constant. Will also return 0 if the trip count is very large
+/// (>= 2^32)
+unsigned Loop::getSmallConstantTripCount() const {
+ Value* TripCount = this->getTripCount();
+ if (TripCount) {
+ if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) {
+ // Guard against huge trip counts.
+ if (TripCountC->getValue().getActiveBits() <= 32) {
+ return (unsigned)TripCountC->getZExtValue();
+ }
+ }
+ }
+ return 0;
}
-void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesAll();
- AU.addRequired<DominatorSet>();
+/// getSmallConstantTripMultiple - Returns the largest constant divisor of the
+/// trip count of this loop as a normal unsigned value, if possible. This
+/// means that the actual trip count is always a multiple of the returned
+/// value (don't forget the trip count could very well be zero as well!).
+///
+/// Returns 1 if the trip count is unknown or not guaranteed to be the
+/// multiple of a constant (which is also the case if the trip count is simply
+/// constant, use getSmallConstantTripCount for that case), Will also return 1
+/// if the trip count is very large (>= 2^32).
+unsigned Loop::getSmallConstantTripMultiple() const {
+ Value* TripCount = this->getTripCount();
+ // This will hold the ConstantInt result, if any
+ ConstantInt *Result = NULL;
+ if (TripCount) {
+ // See if the trip count is constant itself
+ Result = dyn_cast<ConstantInt>(TripCount);
+ // if not, see if it is a multiplication
+ if (!Result)
+ if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TripCount)) {
+ switch (BO->getOpcode()) {
+ case BinaryOperator::Mul:
+ Result = dyn_cast<ConstantInt>(BO->getOperand(1));
+ break;
+ case BinaryOperator::Shl:
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1)))
+ if (CI->getValue().getActiveBits() <= 5)
+ return 1u << CI->getZExtValue();
+ break;
+ default:
+ break;
+ }
+ }
+ }
+ // Guard against huge trip counts.
+ if (Result && Result->getValue().getActiveBits() <= 32) {
+ return (unsigned)Result->getZExtValue();
+ } else {
+ return 1;
+ }
}
-void LoopInfo::print(std::ostream &OS) const {
- for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
- TopLevelLoops[i]->print(OS);
-#if 0
- for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(),
- E = BBMap.end(); I != E; ++I)
- OS << "BB '" << I->first->getName() << "' level = "
- << I->second->LoopDepth << "\n";
-#endif
-}
+/// isLCSSAForm - Return true if the Loop is in LCSSA form
+bool Loop::isLCSSAForm(DominatorTree &DT) const {
+ // Sort the blocks vector so that we can use binary search to do quick
+ // lookups.
+ SmallPtrSet<BasicBlock*, 16> LoopBBs(block_begin(), block_end());
+
+ for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
+ BasicBlock *BB = *BI;
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;++I)
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
+ ++UI) {
+ User *U = *UI;
+ BasicBlock *UserBB = cast<Instruction>(U)->getParent();
+ if (PHINode *P = dyn_cast<PHINode>(U))
+ UserBB = P->getIncomingBlock(UI);
+
+ // Check the current block, as a fast-path, before checking whether
+ // the use is anywhere in the loop. Most values are used in the same
+ // block they are defined in. Also, blocks not reachable from the
+ // entry are special; uses in them don't need to go through PHIs.
+ if (UserBB != BB &&
+ !LoopBBs.count(UserBB) &&
+ DT.isReachableFromEntry(UserBB))
+ return false;
+ }
+ }
-static bool isNotAlreadyContainedIn(Loop *SubLoop, Loop *ParentLoop) {
- if (SubLoop == 0) return true;
- if (SubLoop == ParentLoop) return false;
- return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
+ return true;
}
-Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) {
- if (BBMap.find(BB) != BBMap.end()) return 0; // Haven't processed this node?
-
- std::vector<BasicBlock *> 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;
-
- 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??
- // 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<Loop*>(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<Loop*>::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<BasicBlock*>::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;
- }
+/// isLoopSimplifyForm - Return true if the Loop is in the form that
+/// the LoopSimplify form transforms loops to, which is sometimes called
+/// normal form.
+bool Loop::isLoopSimplifyForm() const {
+ // Normal-form loops have a preheader, a single backedge, and all of their
+ // exits have all their predecessors inside the loop.
+ return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
+}
- // Add the basic blocks that comprise this loop to the BBMap so that this
- // loop can be found for them.
- //
- for (std::vector<BasicBlock*>::iterator I = L->Blocks.begin(),
- E = L->Blocks.end(); I != E; ++I) {
- std::map<BasicBlock*, Loop*>::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
- }
+/// hasDedicatedExits - Return true if no exit block for the loop
+/// has a predecessor that is outside the loop.
+bool Loop::hasDedicatedExits() const {
+ // Sort the blocks vector so that we can use binary search to do quick
+ // lookups.
+ SmallPtrSet<BasicBlock *, 16> LoopBBs(block_begin(), block_end());
+ // Each predecessor of each exit block of a normal loop is contained
+ // within the loop.
+ SmallVector<BasicBlock *, 4> ExitBlocks;
+ getExitBlocks(ExitBlocks);
+ for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
+ for (pred_iterator PI = pred_begin(ExitBlocks[i]),
+ PE = pred_end(ExitBlocks[i]); PI != PE; ++PI)
+ if (!LoopBBs.count(*PI))
+ return false;
+ // All the requirements are met.
+ return true;
+}
- // 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<BasicBlock*, Loop*> 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.
- }
- }
- }
+/// getUniqueExitBlocks - Return all unique successor blocks of this loop.
+/// These are the blocks _outside of the current loop_ which are branched to.
+/// This assumes that loop exits are in canonical form.
+///
+void
+Loop::getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const {
+ assert(hasDedicatedExits() &&
+ "getUniqueExitBlocks assumes the loop has canonical form exits!");
+
+ // Sort the blocks vector so that we can use binary search to do quick
+ // lookups.
+ SmallVector<BasicBlock *, 128> LoopBBs(block_begin(), block_end());
+ std::sort(LoopBBs.begin(), LoopBBs.end());
+
+ SmallVector<BasicBlock *, 32> switchExitBlocks;
+
+ for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) {
+
+ BasicBlock *current = *BI;
+ switchExitBlocks.clear();
+
+ for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I) {
+ // If block is inside the loop then it is not a exit block.
+ if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
+ continue;
+
+ pred_iterator PI = pred_begin(*I);
+ BasicBlock *firstPred = *PI;
+
+ // If current basic block is this exit block's first predecessor
+ // then only insert exit block in to the output ExitBlocks vector.
+ // This ensures that same exit block is not inserted twice into
+ // ExitBlocks vector.
+ if (current != firstPred)
+ continue;
+
+ // If a terminator has more then two successors, for example SwitchInst,
+ // then it is possible that there are multiple edges from current block
+ // to one exit block.
+ if (std::distance(succ_begin(current), succ_end(current)) <= 2) {
+ ExitBlocks.push_back(*I);
+ continue;
+ }
+
+ // In case of multiple edges from current block to exit block, collect
+ // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
+ // duplicate edges.
+ if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I)
+ == switchExitBlocks.end()) {
+ switchExitBlocks.push_back(*I);
+ ExitBlocks.push_back(*I);
+ }
}
}
+}
- // 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<BasicBlock*>::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;
+/// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
+/// block, return that block. Otherwise return null.
+BasicBlock *Loop::getUniqueExitBlock() const {
+ SmallVector<BasicBlock *, 8> UniqueExitBlocks;
+ getUniqueExitBlocks(UniqueExitBlocks);
+ if (UniqueExitBlocks.size() == 1)
+ return UniqueExitBlocks[0];
+ return 0;
}
-/// 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<Loop*>::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);
+void Loop::dump() const {
+ print(dbgs());
}
-/// 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;
+//===----------------------------------------------------------------------===//
+// LoopInfo implementation
+//
+bool LoopInfo::runOnFunction(Function &) {
+ releaseMemory();
+ LI.Calculate(getAnalysis<DominatorTree>().getBase()); // Update
+ return false;
}
+void LoopInfo::verifyAnalysis() const {
+ // LoopInfo is a FunctionPass, but verifying every loop in the function
+ // each time verifyAnalysis is called is very expensive. The
+ // -verify-loop-info option can enable this. In order to perform some
+ // checking by default, LoopPass has been taught to call verifyLoop
+ // manually during loop pass sequences.
+ if (!VerifyLoopInfo) return;
-/// 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.
-///
-/// 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).
-///
-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.
-
+ for (iterator I = begin(), E = end(); I != E; ++I) {
+ assert(!(*I)->getParentLoop() && "Top-level loop has a parent!");
+ (*I)->verifyLoopNest();
+ }
- // If there is exactly one preheader, return it. If there was zero, then Out
- // is still null.
- return Out;
+ // TODO: check BBMap consistency.
}
-/// 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(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();
- }
+void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesAll();
+ AU.addRequired<DominatorTree>();
}
-/// 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<BasicBlock*>::iterator
- I = std::find(ExitBlocks.begin(), ExitBlocks.end(), Old);
- while (I != ExitBlocks.end()) {
- *I = New;
- I = std::find(I+1, ExitBlocks.end(), Old);
- }
+void LoopInfo::print(raw_ostream &OS, const Module*) const {
+ LI.print(OS);
}
+
projects / oota-llvm.git / blobdiff