#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopInfoImpl.h"
#include "llvm/Analysis/LoopIterator.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Assembly/Writer.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;
template class llvm::LoopBase<BasicBlock, Loop>;
template class llvm::LoopInfoBase<BasicBlock, Loop>;
#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_BEGIN(LoopInfo, "loops", "Natural Loop Information", true, true)
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
INITIALIZE_PASS_END(LoopInfo, "loops", "Natural Loop Information", true, true)
bool Loop::isLoopInvariant(Value *V) const {
if (Instruction *I = dyn_cast<Instruction>(V))
return !contains(I);
return true; }
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;
}
bool Loop::makeLoopInvariant(Value *V, bool &Changed,
Instruction *InsertPt) const {
if (Instruction *I = dyn_cast<Instruction>(V))
return makeLoopInvariant(I, Changed, InsertPt);
return true; }
bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
Instruction *InsertPt) const {
if (isLoopInvariant(I))
return true;
if (!isSafeToSpeculativelyExecute(I))
return false;
if (I->mayReadFromMemory())
return false;
if (isa<LandingPadInst>(I))
return false;
if (!InsertPt) {
BasicBlock *Preheader = getLoopPreheader();
if (!Preheader)
return false;
InsertPt = Preheader->getTerminator();
}
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (!makeLoopInvariant(I->getOperand(i), Changed, InsertPt))
return false;
I->moveBefore(InsertPt);
Changed = true;
return true;
}
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; Incoming = *PI++;
if (PI != pred_end(H)) return 0;
if (contains(Incoming)) {
if (contains(Backedge))
return 0;
std::swap(Incoming, Backedge);
} else if (!contains(Backedge))
return 0;
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;
}
bool Loop::isLCSSAForm(DominatorTree &DT) const {
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);
if (UserBB != BB &&
!LoopBBs.count(UserBB) &&
DT.isReachableFromEntry(UserBB))
return false;
}
}
return true;
}
bool Loop::isLoopSimplifyForm() const {
return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
}
bool Loop::isSafeToClone() const {
for (Loop::block_iterator I = block_begin(), E = block_end(); I != E; ++I) {
if (isa<IndirectBrInst>((*I)->getTerminator()))
return false;
}
return true;
}
bool Loop::hasDedicatedExits() const {
SmallPtrSet<BasicBlock *, 16> LoopBBs(block_begin(), block_end());
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;
return true;
}
void
Loop::getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const {
assert(hasDedicatedExits() &&
"getUniqueExitBlocks assumes the loop has canonical form exits!");
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 (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
continue;
pred_iterator PI = pred_begin(*I);
BasicBlock *firstPred = *PI;
if (current != firstPred)
continue;
if (std::distance(succ_begin(current), succ_end(current)) <= 2) {
ExitBlocks.push_back(*I);
continue;
}
if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I)
== switchExitBlocks.end()) {
switchExitBlocks.push_back(*I);
ExitBlocks.push_back(*I);
}
}
}
}
BasicBlock *Loop::getUniqueExitBlock() const {
SmallVector<BasicBlock *, 8> UniqueExitBlocks;
getUniqueExitBlocks(UniqueExitBlocks);
if (UniqueExitBlocks.size() == 1)
return UniqueExitBlocks[0];
return 0;
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void Loop::dump() const {
print(dbgs());
}
#endif
namespace {
class UnloopUpdater {
Loop *Unloop;
LoopInfo *LI;
LoopBlocksDFS DFS;
DenseMap<Loop*, Loop*> SubloopParents;
bool FoundIB;
public:
UnloopUpdater(Loop *UL, LoopInfo *LInfo) :
Unloop(UL), LI(LInfo), DFS(UL), FoundIB(false) {}
void updateBlockParents();
void removeBlocksFromAncestors();
void updateSubloopParents();
protected:
Loop *getNearestLoop(BasicBlock *BB, Loop *BBLoop);
};
}
void UnloopUpdater::updateBlockParents() {
if (Unloop->getNumBlocks()) {
LoopBlocksTraversal Traversal(DFS, LI);
for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
POE = Traversal.end(); POI != POE; ++POI) {
Loop *L = LI->getLoopFor(*POI);
Loop *NL = getNearestLoop(*POI, L);
if (NL != L) {
assert((NL != Unloop && (!NL || NL->contains(Unloop))) &&
"uninitialized successor");
LI->changeLoopFor(*POI, NL);
}
else {
assert((FoundIB || Unloop->contains(L)) && "uninitialized successor");
}
}
}
bool Changed = FoundIB;
for (unsigned NIters = 0; Changed; ++NIters) {
assert(NIters < Unloop->getNumBlocks() && "runaway iterative algorithm");
Changed = false;
for (LoopBlocksDFS::POIterator POI = DFS.beginPostorder(),
POE = DFS.endPostorder(); POI != POE; ++POI) {
Loop *L = LI->getLoopFor(*POI);
Loop *NL = getNearestLoop(*POI, L);
if (NL != L) {
assert(NL != Unloop && (!NL || NL->contains(Unloop)) &&
"uninitialized successor");
LI->changeLoopFor(*POI, NL);
Changed = true;
}
}
}
}
void UnloopUpdater::removeBlocksFromAncestors() {
for (Loop::block_iterator BI = Unloop->block_begin(),
BE = Unloop->block_end(); BI != BE; ++BI) {
Loop *OuterParent = LI->getLoopFor(*BI);
if (Unloop->contains(OuterParent)) {
while (OuterParent->getParentLoop() != Unloop)
OuterParent = OuterParent->getParentLoop();
OuterParent = SubloopParents[OuterParent];
}
for (Loop *OldParent = Unloop->getParentLoop(); OldParent != OuterParent;
OldParent = OldParent->getParentLoop()) {
assert(OldParent && "new loop is not an ancestor of the original");
OldParent->removeBlockFromLoop(*BI);
}
}
}
void UnloopUpdater::updateSubloopParents() {
while (!Unloop->empty()) {
Loop *Subloop = *llvm::prior(Unloop->end());
Unloop->removeChildLoop(llvm::prior(Unloop->end()));
assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop");
if (Loop *Parent = SubloopParents[Subloop])
Parent->addChildLoop(Subloop);
else
LI->addTopLevelLoop(Subloop);
}
}
Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) {
Loop *NearLoop = BBLoop;
Loop *Subloop = 0;
if (NearLoop != Unloop && Unloop->contains(NearLoop)) {
Subloop = NearLoop;
while (Subloop->getParentLoop() != Unloop) {
Subloop = Subloop->getParentLoop();
assert(Subloop && "subloop is not an ancestor of the original loop");
}
NearLoop =
SubloopParents.insert(std::make_pair(Subloop, Unloop)).first->second;
}
succ_iterator I = succ_begin(BB), E = succ_end(BB);
if (I == E) {
assert(!Subloop && "subloop blocks must have a successor");
NearLoop = 0; }
for (; I != E; ++I) {
if (*I == BB)
continue;
Loop *L = LI->getLoopFor(*I);
if (L == Unloop) {
assert((FoundIB || !DFS.hasPostorder(*I)) && "should have seen IB");
FoundIB = true;
}
if (L != Unloop && Unloop->contains(L)) {
if (Subloop)
continue;
assert(L->getParentLoop() == Unloop && "cannot skip into nested loops");
L = SubloopParents[L];
}
if (L == Unloop) {
continue;
}
if (L && !L->contains(Unloop)) {
L = L->getParentLoop();
}
if (NearLoop == Unloop || !NearLoop || NearLoop->contains(L))
NearLoop = L;
}
if (Subloop) {
SubloopParents[Subloop] = NearLoop;
return BBLoop;
}
return NearLoop;
}
bool LoopInfo::runOnFunction(Function &) {
releaseMemory();
LI.Analyze(getAnalysis<DominatorTree>().getBase());
return false;
}
void LoopInfo::updateUnloop(Loop *Unloop) {
if (!Unloop->getParentLoop()) {
for (Loop::block_iterator I = Unloop->block_begin(),
E = Unloop->block_end(); I != E; ++I) {
if (getLoopFor(*I) != Unloop)
continue;
LI.changeLoopFor(*I, 0);
}
for (LoopInfo::iterator I = LI.begin();; ++I) {
assert(I != LI.end() && "Couldn't find loop");
if (*I == Unloop) {
LI.removeLoop(I);
break;
}
}
while (!Unloop->empty())
LI.addTopLevelLoop(Unloop->removeChildLoop(llvm::prior(Unloop->end())));
return;
}
UnloopUpdater Updater(Unloop, this);
Updater.updateBlockParents();
Updater.removeBlocksFromAncestors();
Updater.updateSubloopParents();
Loop *ParentLoop = Unloop->getParentLoop();
for (Loop::iterator I = ParentLoop->begin();; ++I) {
assert(I != ParentLoop->end() && "Couldn't find loop");
if (*I == Unloop) {
ParentLoop->removeChildLoop(I);
break;
}
}
}
void LoopInfo::verifyAnalysis() const {
if (!VerifyLoopInfo) return;
DenseSet<const Loop*> Loops;
for (iterator I = begin(), E = end(); I != E; ++I) {
assert(!(*I)->getParentLoop() && "Top-level loop has a parent!");
(*I)->verifyLoopNest(&Loops);
}
for (DenseMap<BasicBlock*, Loop*>::const_iterator I = LI.BBMap.begin(),
E = LI.BBMap.end(); I != E; ++I) {
assert(Loops.count(I->second) && "orphaned loop");
assert(I->second->contains(I->first) && "orphaned block");
}
}
void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<DominatorTree>();
}
void LoopInfo::print(raw_ostream &OS, const Module*) const {
LI.print(OS);
}
void LoopBlocksDFS::perform(LoopInfo *LI) {
LoopBlocksTraversal Traversal(*this, LI);
for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
POE = Traversal.end(); POI != POE; ++POI) ;
}