1 //===- LazyValueInfo.cpp - Value constraint analysis ------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the interface for lazy computation of value constraint
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Analysis/LazyValueInfo.h"
16 #include "llvm/ADT/DenseSet.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/Analysis/AssumptionTracker.h"
19 #include "llvm/Analysis/ConstantFolding.h"
20 #include "llvm/Analysis/ValueTracking.h"
21 #include "llvm/IR/CFG.h"
22 #include "llvm/IR/ConstantRange.h"
23 #include "llvm/IR/Constants.h"
24 #include "llvm/IR/DataLayout.h"
25 #include "llvm/IR/Dominators.h"
26 #include "llvm/IR/Instructions.h"
27 #include "llvm/IR/IntrinsicInst.h"
28 #include "llvm/IR/PatternMatch.h"
29 #include "llvm/IR/ValueHandle.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/raw_ostream.h"
32 #include "llvm/Target/TargetLibraryInfo.h"
36 using namespace PatternMatch;
38 #define DEBUG_TYPE "lazy-value-info"
40 char LazyValueInfo::ID = 0;
41 INITIALIZE_PASS_BEGIN(LazyValueInfo, "lazy-value-info",
42 "Lazy Value Information Analysis", false, true)
43 INITIALIZE_PASS_DEPENDENCY(AssumptionTracker)
44 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
45 INITIALIZE_PASS_END(LazyValueInfo, "lazy-value-info",
46 "Lazy Value Information Analysis", false, true)
49 FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
53 //===----------------------------------------------------------------------===//
55 //===----------------------------------------------------------------------===//
57 /// LVILatticeVal - This is the information tracked by LazyValueInfo for each
60 /// FIXME: This is basically just for bringup, this can be made a lot more rich
66 /// undefined - This Value has no known value yet.
69 /// constant - This Value has a specific constant value.
71 /// notconstant - This Value is known to not have the specified value.
74 /// constantrange - The Value falls within this range.
77 /// overdefined - This value is not known to be constant, and we know that
82 /// Val: This stores the current lattice value along with the Constant* for
83 /// the constant if this is a 'constant' or 'notconstant' value.
89 LVILatticeVal() : Tag(undefined), Val(nullptr), Range(1, true) {}
91 static LVILatticeVal get(Constant *C) {
93 if (!isa<UndefValue>(C))
97 static LVILatticeVal getNot(Constant *C) {
99 if (!isa<UndefValue>(C))
100 Res.markNotConstant(C);
103 static LVILatticeVal getRange(ConstantRange CR) {
105 Res.markConstantRange(CR);
109 bool isUndefined() const { return Tag == undefined; }
110 bool isConstant() const { return Tag == constant; }
111 bool isNotConstant() const { return Tag == notconstant; }
112 bool isConstantRange() const { return Tag == constantrange; }
113 bool isOverdefined() const { return Tag == overdefined; }
115 Constant *getConstant() const {
116 assert(isConstant() && "Cannot get the constant of a non-constant!");
120 Constant *getNotConstant() const {
121 assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
125 ConstantRange getConstantRange() const {
126 assert(isConstantRange() &&
127 "Cannot get the constant-range of a non-constant-range!");
131 /// markOverdefined - Return true if this is a change in status.
132 bool markOverdefined() {
139 /// markConstant - Return true if this is a change in status.
140 bool markConstant(Constant *V) {
141 assert(V && "Marking constant with NULL");
142 if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
143 return markConstantRange(ConstantRange(CI->getValue()));
144 if (isa<UndefValue>(V))
147 assert((!isConstant() || getConstant() == V) &&
148 "Marking constant with different value");
149 assert(isUndefined());
155 /// markNotConstant - Return true if this is a change in status.
156 bool markNotConstant(Constant *V) {
157 assert(V && "Marking constant with NULL");
158 if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
159 return markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue()));
160 if (isa<UndefValue>(V))
163 assert((!isConstant() || getConstant() != V) &&
164 "Marking constant !constant with same value");
165 assert((!isNotConstant() || getNotConstant() == V) &&
166 "Marking !constant with different value");
167 assert(isUndefined() || isConstant());
173 /// markConstantRange - Return true if this is a change in status.
174 bool markConstantRange(const ConstantRange NewR) {
175 if (isConstantRange()) {
176 if (NewR.isEmptySet())
177 return markOverdefined();
179 bool changed = Range != NewR;
184 assert(isUndefined());
185 if (NewR.isEmptySet())
186 return markOverdefined();
193 /// mergeIn - Merge the specified lattice value into this one, updating this
194 /// one and returning true if anything changed.
195 bool mergeIn(const LVILatticeVal &RHS) {
196 if (RHS.isUndefined() || isOverdefined()) return false;
197 if (RHS.isOverdefined()) return markOverdefined();
207 if (RHS.isConstant()) {
210 return markOverdefined();
213 if (RHS.isNotConstant()) {
215 return markOverdefined();
217 // Unless we can prove that the two Constants are different, we must
218 // move to overdefined.
219 // FIXME: use DataLayout/TargetLibraryInfo for smarter constant folding.
220 if (ConstantInt *Res = dyn_cast<ConstantInt>(
221 ConstantFoldCompareInstOperands(CmpInst::ICMP_NE,
223 RHS.getNotConstant())))
225 return markNotConstant(RHS.getNotConstant());
227 return markOverdefined();
230 // RHS is a ConstantRange, LHS is a non-integer Constant.
232 // FIXME: consider the case where RHS is a range [1, 0) and LHS is
233 // a function. The correct result is to pick up RHS.
235 return markOverdefined();
238 if (isNotConstant()) {
239 if (RHS.isConstant()) {
241 return markOverdefined();
243 // Unless we can prove that the two Constants are different, we must
244 // move to overdefined.
245 // FIXME: use DataLayout/TargetLibraryInfo for smarter constant folding.
246 if (ConstantInt *Res = dyn_cast<ConstantInt>(
247 ConstantFoldCompareInstOperands(CmpInst::ICMP_NE,
253 return markOverdefined();
256 if (RHS.isNotConstant()) {
259 return markOverdefined();
262 return markOverdefined();
265 assert(isConstantRange() && "New LVILattice type?");
266 if (!RHS.isConstantRange())
267 return markOverdefined();
269 ConstantRange NewR = Range.unionWith(RHS.getConstantRange());
270 if (NewR.isFullSet())
271 return markOverdefined();
272 return markConstantRange(NewR);
276 } // end anonymous namespace.
279 raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val)
281 raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
282 if (Val.isUndefined())
283 return OS << "undefined";
284 if (Val.isOverdefined())
285 return OS << "overdefined";
287 if (Val.isNotConstant())
288 return OS << "notconstant<" << *Val.getNotConstant() << '>';
289 else if (Val.isConstantRange())
290 return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
291 << Val.getConstantRange().getUpper() << '>';
292 return OS << "constant<" << *Val.getConstant() << '>';
296 //===----------------------------------------------------------------------===//
297 // LazyValueInfoCache Decl
298 //===----------------------------------------------------------------------===//
301 /// LVIValueHandle - A callback value handle updates the cache when
302 /// values are erased.
303 class LazyValueInfoCache;
304 struct LVIValueHandle : public CallbackVH {
305 LazyValueInfoCache *Parent;
307 LVIValueHandle(Value *V, LazyValueInfoCache *P)
308 : CallbackVH(V), Parent(P) { }
310 void deleted() override;
311 void allUsesReplacedWith(Value *V) override {
318 /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
319 /// maintains information about queries across the clients' queries.
320 class LazyValueInfoCache {
321 /// ValueCacheEntryTy - This is all of the cached block information for
322 /// exactly one Value*. The entries are sorted by the BasicBlock* of the
323 /// entries, allowing us to do a lookup with a binary search.
324 typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
326 /// ValueCache - This is all of the cached information for all values,
327 /// mapped from Value* to key information.
328 std::map<LVIValueHandle, ValueCacheEntryTy> ValueCache;
330 /// OverDefinedCache - This tracks, on a per-block basis, the set of
331 /// values that are over-defined at the end of that block. This is required
332 /// for cache updating.
333 typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
334 DenseSet<OverDefinedPairTy> OverDefinedCache;
336 /// SeenBlocks - Keep track of all blocks that we have ever seen, so we
337 /// don't spend time removing unused blocks from our caches.
338 DenseSet<AssertingVH<BasicBlock> > SeenBlocks;
340 /// BlockValueStack - This stack holds the state of the value solver
341 /// during a query. It basically emulates the callstack of the naive
342 /// recursive value lookup process.
343 std::stack<std::pair<BasicBlock*, Value*> > BlockValueStack;
345 /// A pointer to the cache of @llvm.assume calls.
346 AssumptionTracker *AT;
347 /// An optional DL pointer.
348 const DataLayout *DL;
349 /// An optional DT pointer.
352 friend struct LVIValueHandle;
354 /// OverDefinedCacheUpdater - A helper object that ensures that the
355 /// OverDefinedCache is updated whenever solveBlockValue returns.
356 struct OverDefinedCacheUpdater {
357 LazyValueInfoCache *Parent;
362 OverDefinedCacheUpdater(Value *V, BasicBlock *B, LVILatticeVal &LV,
363 LazyValueInfoCache *P)
364 : Parent(P), Val(V), BB(B), BBLV(LV) { }
366 bool markResult(bool changed) {
367 if (changed && BBLV.isOverdefined())
368 Parent->OverDefinedCache.insert(std::make_pair(BB, Val));
375 LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
376 bool getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T,
377 LVILatticeVal &Result,
378 Instruction *CxtI = nullptr);
379 bool hasBlockValue(Value *Val, BasicBlock *BB);
381 // These methods process one work item and may add more. A false value
382 // returned means that the work item was not completely processed and must
383 // be revisited after going through the new items.
384 bool solveBlockValue(Value *Val, BasicBlock *BB);
385 bool solveBlockValueNonLocal(LVILatticeVal &BBLV,
386 Value *Val, BasicBlock *BB);
387 bool solveBlockValuePHINode(LVILatticeVal &BBLV,
388 PHINode *PN, BasicBlock *BB);
389 bool solveBlockValueConstantRange(LVILatticeVal &BBLV,
390 Instruction *BBI, BasicBlock *BB);
391 void mergeAssumeBlockValueConstantRange(Value *Val, LVILatticeVal &BBLV,
396 ValueCacheEntryTy &lookup(Value *V) {
397 return ValueCache[LVIValueHandle(V, this)];
401 /// getValueInBlock - This is the query interface to determine the lattice
402 /// value for the specified Value* at the end of the specified block.
403 LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB,
404 Instruction *CxtI = nullptr);
406 /// getValueAt - This is the query interface to determine the lattice
407 /// value for the specified Value* at the specified instruction (generally
408 /// from an assume intrinsic).
409 LVILatticeVal getValueAt(Value *V, Instruction *CxtI);
411 /// getValueOnEdge - This is the query interface to determine the lattice
412 /// value for the specified Value* that is true on the specified edge.
413 LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB,
414 Instruction *CxtI = nullptr);
416 /// threadEdge - This is the update interface to inform the cache that an
417 /// edge from PredBB to OldSucc has been threaded to be from PredBB to
419 void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
421 /// eraseBlock - This is part of the update interface to inform the cache
422 /// that a block has been deleted.
423 void eraseBlock(BasicBlock *BB);
425 /// clear - Empty the cache.
429 OverDefinedCache.clear();
432 LazyValueInfoCache(AssumptionTracker *AT,
433 const DataLayout *DL = nullptr,
434 DominatorTree *DT = nullptr) : AT(AT), DL(DL), DT(DT) {}
436 } // end anonymous namespace
438 void LVIValueHandle::deleted() {
439 typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
441 SmallVector<OverDefinedPairTy, 4> ToErase;
442 for (const OverDefinedPairTy &P : Parent->OverDefinedCache)
443 if (P.second == getValPtr())
444 ToErase.push_back(P);
445 for (const OverDefinedPairTy &P : ToErase)
446 Parent->OverDefinedCache.erase(P);
448 // This erasure deallocates *this, so it MUST happen after we're done
449 // using any and all members of *this.
450 Parent->ValueCache.erase(*this);
453 void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
454 // Shortcut if we have never seen this block.
455 DenseSet<AssertingVH<BasicBlock> >::iterator I = SeenBlocks.find(BB);
456 if (I == SeenBlocks.end())
460 SmallVector<OverDefinedPairTy, 4> ToErase;
461 for (const OverDefinedPairTy& P : OverDefinedCache)
463 ToErase.push_back(P);
464 for (const OverDefinedPairTy &P : ToErase)
465 OverDefinedCache.erase(P);
467 for (std::map<LVIValueHandle, ValueCacheEntryTy>::iterator
468 I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
472 void LazyValueInfoCache::solve() {
473 while (!BlockValueStack.empty()) {
474 std::pair<BasicBlock*, Value*> &e = BlockValueStack.top();
475 if (solveBlockValue(e.second, e.first)) {
476 assert(BlockValueStack.top() == e);
477 BlockValueStack.pop();
482 bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
483 // If already a constant, there is nothing to compute.
484 if (isa<Constant>(Val))
487 LVIValueHandle ValHandle(Val, this);
488 std::map<LVIValueHandle, ValueCacheEntryTy>::iterator I =
489 ValueCache.find(ValHandle);
490 if (I == ValueCache.end()) return false;
491 return I->second.count(BB);
494 LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
495 // If already a constant, there is nothing to compute.
496 if (Constant *VC = dyn_cast<Constant>(Val))
497 return LVILatticeVal::get(VC);
499 SeenBlocks.insert(BB);
500 return lookup(Val)[BB];
503 bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
504 if (isa<Constant>(Val))
507 ValueCacheEntryTy &Cache = lookup(Val);
508 SeenBlocks.insert(BB);
509 LVILatticeVal &BBLV = Cache[BB];
511 // OverDefinedCacheUpdater is a helper object that will update
512 // the OverDefinedCache for us when this method exits. Make sure to
513 // call markResult on it as we exit, passing a bool to indicate if the
514 // cache needs updating, i.e. if we have solved a new value or not.
515 OverDefinedCacheUpdater ODCacheUpdater(Val, BB, BBLV, this);
517 if (!BBLV.isUndefined()) {
518 DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
520 // Since we're reusing a cached value here, we don't need to update the
521 // OverDefinedCache. The cache will have been properly updated
522 // whenever the cached value was inserted.
523 ODCacheUpdater.markResult(false);
527 // Otherwise, this is the first time we're seeing this block. Reset the
528 // lattice value to overdefined, so that cycles will terminate and be
529 // conservatively correct.
530 BBLV.markOverdefined();
532 Instruction *BBI = dyn_cast<Instruction>(Val);
533 if (!BBI || BBI->getParent() != BB) {
534 return ODCacheUpdater.markResult(solveBlockValueNonLocal(BBLV, Val, BB));
537 if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
538 return ODCacheUpdater.markResult(solveBlockValuePHINode(BBLV, PN, BB));
541 if (AllocaInst *AI = dyn_cast<AllocaInst>(BBI)) {
542 BBLV = LVILatticeVal::getNot(ConstantPointerNull::get(AI->getType()));
543 return ODCacheUpdater.markResult(true);
546 // We can only analyze the definitions of certain classes of instructions
547 // (integral binops and casts at the moment), so bail if this isn't one.
548 LVILatticeVal Result;
549 if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
550 !BBI->getType()->isIntegerTy()) {
551 DEBUG(dbgs() << " compute BB '" << BB->getName()
552 << "' - overdefined because inst def found.\n");
553 BBLV.markOverdefined();
554 return ODCacheUpdater.markResult(true);
557 // FIXME: We're currently limited to binops with a constant RHS. This should
559 BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
560 if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
561 DEBUG(dbgs() << " compute BB '" << BB->getName()
562 << "' - overdefined because inst def found.\n");
564 BBLV.markOverdefined();
565 return ODCacheUpdater.markResult(true);
568 return ODCacheUpdater.markResult(solveBlockValueConstantRange(BBLV, BBI, BB));
571 static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
572 if (LoadInst *L = dyn_cast<LoadInst>(I)) {
573 return L->getPointerAddressSpace() == 0 &&
574 GetUnderlyingObject(L->getPointerOperand()) == Ptr;
576 if (StoreInst *S = dyn_cast<StoreInst>(I)) {
577 return S->getPointerAddressSpace() == 0 &&
578 GetUnderlyingObject(S->getPointerOperand()) == Ptr;
580 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
581 if (MI->isVolatile()) return false;
583 // FIXME: check whether it has a valuerange that excludes zero?
584 ConstantInt *Len = dyn_cast<ConstantInt>(MI->getLength());
585 if (!Len || Len->isZero()) return false;
587 if (MI->getDestAddressSpace() == 0)
588 if (GetUnderlyingObject(MI->getRawDest()) == Ptr)
590 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
591 if (MTI->getSourceAddressSpace() == 0)
592 if (GetUnderlyingObject(MTI->getRawSource()) == Ptr)
598 bool LazyValueInfoCache::solveBlockValueNonLocal(LVILatticeVal &BBLV,
599 Value *Val, BasicBlock *BB) {
600 LVILatticeVal Result; // Start Undefined.
602 // If this is a pointer, and there's a load from that pointer in this BB,
603 // then we know that the pointer can't be NULL.
604 bool NotNull = false;
605 if (Val->getType()->isPointerTy()) {
606 if (isKnownNonNull(Val)) {
609 Value *UnderlyingVal = GetUnderlyingObject(Val);
610 // If 'GetUnderlyingObject' didn't converge, skip it. It won't converge
611 // inside InstructionDereferencesPointer either.
612 if (UnderlyingVal == GetUnderlyingObject(UnderlyingVal, nullptr, 1)) {
613 for (Instruction &I : *BB) {
614 if (InstructionDereferencesPointer(&I, UnderlyingVal)) {
623 // If this is the entry block, we must be asking about an argument. The
624 // value is overdefined.
625 if (BB == &BB->getParent()->getEntryBlock()) {
626 assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
628 PointerType *PTy = cast<PointerType>(Val->getType());
629 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
631 Result.markOverdefined();
637 // Loop over all of our predecessors, merging what we know from them into
639 bool EdgesMissing = false;
640 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
641 LVILatticeVal EdgeResult;
642 EdgesMissing |= !getEdgeValue(Val, *PI, BB, EdgeResult);
646 Result.mergeIn(EdgeResult);
648 // If we hit overdefined, exit early. The BlockVals entry is already set
650 if (Result.isOverdefined()) {
651 DEBUG(dbgs() << " compute BB '" << BB->getName()
652 << "' - overdefined because of pred.\n");
653 // If we previously determined that this is a pointer that can't be null
654 // then return that rather than giving up entirely.
656 PointerType *PTy = cast<PointerType>(Val->getType());
657 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
667 // Return the merged value, which is more precise than 'overdefined'.
668 assert(!Result.isOverdefined());
673 bool LazyValueInfoCache::solveBlockValuePHINode(LVILatticeVal &BBLV,
674 PHINode *PN, BasicBlock *BB) {
675 LVILatticeVal Result; // Start Undefined.
677 // Loop over all of our predecessors, merging what we know from them into
679 bool EdgesMissing = false;
680 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
681 BasicBlock *PhiBB = PN->getIncomingBlock(i);
682 Value *PhiVal = PN->getIncomingValue(i);
683 LVILatticeVal EdgeResult;
684 // Note that we can provide PN as the context value to getEdgeValue, even
685 // though the results will be cached, because PN is the value being used as
686 // the cache key in the caller.
687 EdgesMissing |= !getEdgeValue(PhiVal, PhiBB, BB, EdgeResult, PN);
691 Result.mergeIn(EdgeResult);
693 // If we hit overdefined, exit early. The BlockVals entry is already set
695 if (Result.isOverdefined()) {
696 DEBUG(dbgs() << " compute BB '" << BB->getName()
697 << "' - overdefined because of pred.\n");
706 // Return the merged value, which is more precise than 'overdefined'.
707 assert(!Result.isOverdefined() && "Possible PHI in entry block?");
712 static bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
713 LVILatticeVal &Result,
714 bool isTrueDest = true);
716 // If we can determine a constant range for the value Val in the context
717 // provided by the instruction BBI, then merge it into BBLV. If we did find a
718 // constant range, return true.
719 void LazyValueInfoCache::mergeAssumeBlockValueConstantRange(Value *Val,
722 BBI = BBI ? BBI : dyn_cast<Instruction>(Val);
726 for (auto &I : AT->assumptions(BBI->getParent()->getParent())) {
727 if (!isValidAssumeForContext(I, BBI, DL, DT))
730 Value *C = I->getArgOperand(0);
731 if (ICmpInst *ICI = dyn_cast<ICmpInst>(C)) {
732 LVILatticeVal Result;
733 if (getValueFromFromCondition(Val, ICI, Result)) {
734 if (BBLV.isOverdefined())
737 BBLV.mergeIn(Result);
743 bool LazyValueInfoCache::solveBlockValueConstantRange(LVILatticeVal &BBLV,
746 // Figure out the range of the LHS. If that fails, bail.
747 if (!hasBlockValue(BBI->getOperand(0), BB)) {
748 BlockValueStack.push(std::make_pair(BB, BBI->getOperand(0)));
752 LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
753 mergeAssumeBlockValueConstantRange(BBI->getOperand(0), LHSVal, BBI);
754 if (!LHSVal.isConstantRange()) {
755 BBLV.markOverdefined();
759 ConstantRange LHSRange = LHSVal.getConstantRange();
760 ConstantRange RHSRange(1);
761 IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
762 if (isa<BinaryOperator>(BBI)) {
763 if (ConstantInt *RHS = dyn_cast<ConstantInt>(BBI->getOperand(1))) {
764 RHSRange = ConstantRange(RHS->getValue());
766 BBLV.markOverdefined();
771 // NOTE: We're currently limited by the set of operations that ConstantRange
772 // can evaluate symbolically. Enhancing that set will allows us to analyze
774 LVILatticeVal Result;
775 switch (BBI->getOpcode()) {
776 case Instruction::Add:
777 Result.markConstantRange(LHSRange.add(RHSRange));
779 case Instruction::Sub:
780 Result.markConstantRange(LHSRange.sub(RHSRange));
782 case Instruction::Mul:
783 Result.markConstantRange(LHSRange.multiply(RHSRange));
785 case Instruction::UDiv:
786 Result.markConstantRange(LHSRange.udiv(RHSRange));
788 case Instruction::Shl:
789 Result.markConstantRange(LHSRange.shl(RHSRange));
791 case Instruction::LShr:
792 Result.markConstantRange(LHSRange.lshr(RHSRange));
794 case Instruction::Trunc:
795 Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
797 case Instruction::SExt:
798 Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
800 case Instruction::ZExt:
801 Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
803 case Instruction::BitCast:
804 Result.markConstantRange(LHSRange);
806 case Instruction::And:
807 Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
809 case Instruction::Or:
810 Result.markConstantRange(LHSRange.binaryOr(RHSRange));
813 // Unhandled instructions are overdefined.
815 DEBUG(dbgs() << " compute BB '" << BB->getName()
816 << "' - overdefined because inst def found.\n");
817 Result.markOverdefined();
825 bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
826 LVILatticeVal &Result, bool isTrueDest) {
827 if (ICI && isa<Constant>(ICI->getOperand(1))) {
828 if (ICI->isEquality() && ICI->getOperand(0) == Val) {
829 // We know that V has the RHS constant if this is a true SETEQ or
831 if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
832 Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
834 Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
838 // Recognize the range checking idiom that InstCombine produces.
839 // (X-C1) u< C2 --> [C1, C1+C2)
840 ConstantInt *NegOffset = nullptr;
841 if (ICI->getPredicate() == ICmpInst::ICMP_ULT)
842 match(ICI->getOperand(0), m_Add(m_Specific(Val),
843 m_ConstantInt(NegOffset)));
845 ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1));
846 if (CI && (ICI->getOperand(0) == Val || NegOffset)) {
847 // Calculate the range of values that would satisfy the comparison.
848 ConstantRange CmpRange(CI->getValue());
849 ConstantRange TrueValues =
850 ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
852 if (NegOffset) // Apply the offset from above.
853 TrueValues = TrueValues.subtract(NegOffset->getValue());
855 // If we're interested in the false dest, invert the condition.
856 if (!isTrueDest) TrueValues = TrueValues.inverse();
858 Result = LVILatticeVal::getRange(TrueValues);
866 /// \brief Compute the value of Val on the edge BBFrom -> BBTo. Returns false if
867 /// Val is not constrained on the edge.
868 static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
869 BasicBlock *BBTo, LVILatticeVal &Result) {
870 // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
872 if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
873 // If this is a conditional branch and only one successor goes to BBTo, then
874 // we maybe able to infer something from the condition.
875 if (BI->isConditional() &&
876 BI->getSuccessor(0) != BI->getSuccessor(1)) {
877 bool isTrueDest = BI->getSuccessor(0) == BBTo;
878 assert(BI->getSuccessor(!isTrueDest) == BBTo &&
879 "BBTo isn't a successor of BBFrom");
881 // If V is the condition of the branch itself, then we know exactly what
883 if (BI->getCondition() == Val) {
884 Result = LVILatticeVal::get(ConstantInt::get(
885 Type::getInt1Ty(Val->getContext()), isTrueDest));
889 // If the condition of the branch is an equality comparison, we may be
890 // able to infer the value.
891 ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
892 if (getValueFromFromCondition(Val, ICI, Result, isTrueDest))
897 // If the edge was formed by a switch on the value, then we may know exactly
899 if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
900 if (SI->getCondition() != Val)
903 bool DefaultCase = SI->getDefaultDest() == BBTo;
904 unsigned BitWidth = Val->getType()->getIntegerBitWidth();
905 ConstantRange EdgesVals(BitWidth, DefaultCase/*isFullSet*/);
907 for (SwitchInst::CaseIt i : SI->cases()) {
908 ConstantRange EdgeVal(i.getCaseValue()->getValue());
910 // It is possible that the default destination is the destination of
911 // some cases. There is no need to perform difference for those cases.
912 if (i.getCaseSuccessor() != BBTo)
913 EdgesVals = EdgesVals.difference(EdgeVal);
914 } else if (i.getCaseSuccessor() == BBTo)
915 EdgesVals = EdgesVals.unionWith(EdgeVal);
917 Result = LVILatticeVal::getRange(EdgesVals);
923 /// \brief Compute the value of Val on the edge BBFrom -> BBTo, or the value at
924 /// the basic block if the edge does not constraint Val.
925 bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom,
926 BasicBlock *BBTo, LVILatticeVal &Result,
928 // If already a constant, there is nothing to compute.
929 if (Constant *VC = dyn_cast<Constant>(Val)) {
930 Result = LVILatticeVal::get(VC);
934 if (getEdgeValueLocal(Val, BBFrom, BBTo, Result)) {
935 if (!Result.isConstantRange() ||
936 Result.getConstantRange().getSingleElement())
939 // FIXME: this check should be moved to the beginning of the function when
940 // LVI better supports recursive values. Even for the single value case, we
941 // can intersect to detect dead code (an empty range).
942 if (!hasBlockValue(Val, BBFrom)) {
943 BlockValueStack.push(std::make_pair(BBFrom, Val));
947 // Try to intersect ranges of the BB and the constraint on the edge.
948 LVILatticeVal InBlock = getBlockValue(Val, BBFrom);
949 mergeAssumeBlockValueConstantRange(Val, InBlock, BBFrom->getTerminator());
950 // See note on the use of the CxtI with mergeAssumeBlockValueConstantRange,
951 // and caching, below.
952 mergeAssumeBlockValueConstantRange(Val, InBlock, CxtI);
953 if (!InBlock.isConstantRange())
956 ConstantRange Range =
957 Result.getConstantRange().intersectWith(InBlock.getConstantRange());
958 Result = LVILatticeVal::getRange(Range);
962 if (!hasBlockValue(Val, BBFrom)) {
963 BlockValueStack.push(std::make_pair(BBFrom, Val));
967 // If we couldn't compute the value on the edge, use the value from the BB.
968 Result = getBlockValue(Val, BBFrom);
969 mergeAssumeBlockValueConstantRange(Val, Result, BBFrom->getTerminator());
970 // We can use the context instruction (generically the ultimate instruction
971 // the calling pass is trying to simplify) here, even though the result of
972 // this function is generally cached when called from the solve* functions
973 // (and that cached result might be used with queries using a different
974 // context instruction), because when this function is called from the solve*
975 // functions, the context instruction is not provided. When called from
976 // LazyValueInfoCache::getValueOnEdge, the context instruction is provided,
977 // but then the result is not cached.
978 mergeAssumeBlockValueConstantRange(Val, Result, CxtI);
982 LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB,
984 DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
985 << BB->getName() << "'\n");
987 BlockValueStack.push(std::make_pair(BB, V));
989 LVILatticeVal Result = getBlockValue(V, BB);
990 mergeAssumeBlockValueConstantRange(V, Result, CxtI);
992 DEBUG(dbgs() << " Result = " << Result << "\n");
996 LVILatticeVal LazyValueInfoCache::getValueAt(Value *V, Instruction *CxtI) {
997 DEBUG(dbgs() << "LVI Getting value " << *V << " at '"
998 << CxtI->getName() << "'\n");
1000 LVILatticeVal Result;
1001 mergeAssumeBlockValueConstantRange(V, Result, CxtI);
1003 DEBUG(dbgs() << " Result = " << Result << "\n");
1007 LVILatticeVal LazyValueInfoCache::
1008 getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB,
1009 Instruction *CxtI) {
1010 DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
1011 << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
1013 LVILatticeVal Result;
1014 if (!getEdgeValue(V, FromBB, ToBB, Result, CxtI)) {
1016 bool WasFastQuery = getEdgeValue(V, FromBB, ToBB, Result, CxtI);
1018 assert(WasFastQuery && "More work to do after problem solved?");
1021 DEBUG(dbgs() << " Result = " << Result << "\n");
1025 void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
1026 BasicBlock *NewSucc) {
1027 // When an edge in the graph has been threaded, values that we could not
1028 // determine a value for before (i.e. were marked overdefined) may be possible
1029 // to solve now. We do NOT try to proactively update these values. Instead,
1030 // we clear their entries from the cache, and allow lazy updating to recompute
1031 // them when needed.
1033 // The updating process is fairly simple: we need to drop cached info
1034 // for all values that were marked overdefined in OldSucc, and for those same
1035 // values in any successor of OldSucc (except NewSucc) in which they were
1036 // also marked overdefined.
1037 std::vector<BasicBlock*> worklist;
1038 worklist.push_back(OldSucc);
1040 DenseSet<Value*> ClearSet;
1041 for (OverDefinedPairTy &P : OverDefinedCache)
1042 if (P.first == OldSucc)
1043 ClearSet.insert(P.second);
1045 // Use a worklist to perform a depth-first search of OldSucc's successors.
1046 // NOTE: We do not need a visited list since any blocks we have already
1047 // visited will have had their overdefined markers cleared already, and we
1048 // thus won't loop to their successors.
1049 while (!worklist.empty()) {
1050 BasicBlock *ToUpdate = worklist.back();
1051 worklist.pop_back();
1053 // Skip blocks only accessible through NewSucc.
1054 if (ToUpdate == NewSucc) continue;
1056 bool changed = false;
1057 for (Value *V : ClearSet) {
1058 // If a value was marked overdefined in OldSucc, and is here too...
1059 DenseSet<OverDefinedPairTy>::iterator OI =
1060 OverDefinedCache.find(std::make_pair(ToUpdate, V));
1061 if (OI == OverDefinedCache.end()) continue;
1063 // Remove it from the caches.
1064 ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(V, this)];
1065 ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
1067 assert(CI != Entry.end() && "Couldn't find entry to update?");
1069 OverDefinedCache.erase(OI);
1071 // If we removed anything, then we potentially need to update
1072 // blocks successors too.
1076 if (!changed) continue;
1078 worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
1082 //===----------------------------------------------------------------------===//
1083 // LazyValueInfo Impl
1084 //===----------------------------------------------------------------------===//
1086 /// getCache - This lazily constructs the LazyValueInfoCache.
1087 static LazyValueInfoCache &getCache(void *&PImpl,
1088 AssumptionTracker *AT,
1089 const DataLayout *DL = nullptr,
1090 DominatorTree *DT = nullptr) {
1092 PImpl = new LazyValueInfoCache(AT, DL, DT);
1093 return *static_cast<LazyValueInfoCache*>(PImpl);
1096 bool LazyValueInfo::runOnFunction(Function &F) {
1097 AT = &getAnalysis<AssumptionTracker>();
1099 DominatorTreeWrapperPass *DTWP =
1100 getAnalysisIfAvailable<DominatorTreeWrapperPass>();
1101 DT = DTWP ? &DTWP->getDomTree() : nullptr;
1103 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
1104 DL = DLP ? &DLP->getDataLayout() : nullptr;
1106 TLI = &getAnalysis<TargetLibraryInfo>();
1109 getCache(PImpl, AT, DL, DT).clear();
1115 void LazyValueInfo::getAnalysisUsage(AnalysisUsage &AU) const {
1116 AU.setPreservesAll();
1117 AU.addRequired<AssumptionTracker>();
1118 AU.addRequired<TargetLibraryInfo>();
1121 void LazyValueInfo::releaseMemory() {
1122 // If the cache was allocated, free it.
1124 delete &getCache(PImpl, AT);
1129 Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB,
1130 Instruction *CxtI) {
1131 LVILatticeVal Result =
1132 getCache(PImpl, AT, DL, DT).getValueInBlock(V, BB, CxtI);
1134 if (Result.isConstant())
1135 return Result.getConstant();
1136 if (Result.isConstantRange()) {
1137 ConstantRange CR = Result.getConstantRange();
1138 if (const APInt *SingleVal = CR.getSingleElement())
1139 return ConstantInt::get(V->getContext(), *SingleVal);
1144 /// getConstantOnEdge - Determine whether the specified value is known to be a
1145 /// constant on the specified edge. Return null if not.
1146 Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
1148 Instruction *CxtI) {
1149 LVILatticeVal Result =
1150 getCache(PImpl, AT, DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);
1152 if (Result.isConstant())
1153 return Result.getConstant();
1154 if (Result.isConstantRange()) {
1155 ConstantRange CR = Result.getConstantRange();
1156 if (const APInt *SingleVal = CR.getSingleElement())
1157 return ConstantInt::get(V->getContext(), *SingleVal);
1162 static LazyValueInfo::Tristate
1163 getPredicateResult(unsigned Pred, Constant *C, LVILatticeVal &Result,
1164 const DataLayout *DL, TargetLibraryInfo *TLI) {
1166 // If we know the value is a constant, evaluate the conditional.
1167 Constant *Res = nullptr;
1168 if (Result.isConstant()) {
1169 Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, DL,
1171 if (ConstantInt *ResCI = dyn_cast<ConstantInt>(Res))
1172 return ResCI->isZero() ? LazyValueInfo::False : LazyValueInfo::True;
1173 return LazyValueInfo::Unknown;
1176 if (Result.isConstantRange()) {
1177 ConstantInt *CI = dyn_cast<ConstantInt>(C);
1178 if (!CI) return LazyValueInfo::Unknown;
1180 ConstantRange CR = Result.getConstantRange();
1181 if (Pred == ICmpInst::ICMP_EQ) {
1182 if (!CR.contains(CI->getValue()))
1183 return LazyValueInfo::False;
1185 if (CR.isSingleElement() && CR.contains(CI->getValue()))
1186 return LazyValueInfo::True;
1187 } else if (Pred == ICmpInst::ICMP_NE) {
1188 if (!CR.contains(CI->getValue()))
1189 return LazyValueInfo::True;
1191 if (CR.isSingleElement() && CR.contains(CI->getValue()))
1192 return LazyValueInfo::False;
1195 // Handle more complex predicates.
1196 ConstantRange TrueValues =
1197 ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
1198 if (TrueValues.contains(CR))
1199 return LazyValueInfo::True;
1200 if (TrueValues.inverse().contains(CR))
1201 return LazyValueInfo::False;
1202 return LazyValueInfo::Unknown;
1205 if (Result.isNotConstant()) {
1206 // If this is an equality comparison, we can try to fold it knowing that
1208 if (Pred == ICmpInst::ICMP_EQ) {
1209 // !C1 == C -> false iff C1 == C.
1210 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
1211 Result.getNotConstant(), C, DL,
1213 if (Res->isNullValue())
1214 return LazyValueInfo::False;
1215 } else if (Pred == ICmpInst::ICMP_NE) {
1216 // !C1 != C -> true iff C1 == C.
1217 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
1218 Result.getNotConstant(), C, DL,
1220 if (Res->isNullValue())
1221 return LazyValueInfo::True;
1223 return LazyValueInfo::Unknown;
1226 return LazyValueInfo::Unknown;
1229 /// getPredicateOnEdge - Determine whether the specified value comparison
1230 /// with a constant is known to be true or false on the specified CFG edge.
1231 /// Pred is a CmpInst predicate.
1232 LazyValueInfo::Tristate
1233 LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
1234 BasicBlock *FromBB, BasicBlock *ToBB,
1235 Instruction *CxtI) {
1236 LVILatticeVal Result =
1237 getCache(PImpl, AT, DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);
1239 return getPredicateResult(Pred, C, Result, DL, TLI);
1242 LazyValueInfo::Tristate
1243 LazyValueInfo::getPredicateAt(unsigned Pred, Value *V, Constant *C,
1244 Instruction *CxtI) {
1245 LVILatticeVal Result =
1246 getCache(PImpl, AT, DL, DT).getValueAt(V, CxtI);
1248 return getPredicateResult(Pred, C, Result, DL, TLI);
1251 void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
1252 BasicBlock *NewSucc) {
1253 if (PImpl) getCache(PImpl, AT, DL, DT).threadEdge(PredBB, OldSucc, NewSucc);
1256 void LazyValueInfo::eraseBlock(BasicBlock *BB) {
1257 if (PImpl) getCache(PImpl, AT, DL, DT).eraseBlock(BB);