#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Analysis/Dominators.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;
#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 (!I->isSafeToSpeculativelyExecute())
return false;
if (I->mayReadFromMemory())
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;
}
Value *Loop::getTripCount() const {
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);
}
}
}
}
return 0;
}
unsigned Loop::getSmallConstantTripCount() const {
Value* TripCount = this->getTripCount();
if (TripCount) {
if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) {
if (TripCountC->getValue().getActiveBits() <= 32) {
return (unsigned)TripCountC->getZExtValue();
}
}
}
return 0;
}
unsigned Loop::getSmallConstantTripMultiple() const {
Value* TripCount = this->getTripCount();
ConstantInt *Result = NULL;
if (TripCount) {
Result = dyn_cast<ConstantInt>(TripCount);
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;
}
}
}
if (Result && Result->getValue().getActiveBits() <= 32) {
return (unsigned)Result->getZExtValue();
} else {
return 1;
}
}
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::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;
}
void Loop::dump() const {
print(dbgs());
}
bool LoopInfo::runOnFunction(Function &) {
releaseMemory();
LI.Calculate(getAnalysis<DominatorTree>().getBase()); return false;
}
void LoopInfo::verifyAnalysis() const {
if (!VerifyLoopInfo) return;
for (iterator I = begin(), E = end(); I != E; ++I) {
assert(!(*I)->getParentLoop() && "Top-level loop has a parent!");
(*I)->verifyLoopNest();
}
}
void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<DominatorTree>();
}
void LoopInfo::print(raw_ostream &OS, const Module*) const {
LI.print(OS);
}