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 (DenseSet<OverDefinedPairTy>::iterator
443 I = Parent->OverDefinedCache.begin(),
444 E = Parent->OverDefinedCache.end();
446 if (I->second == getValPtr())
447 ToErase.push_back(*I);
450 for (SmallVectorImpl<OverDefinedPairTy>::iterator I = ToErase.begin(),
451 E = ToErase.end(); I != E; ++I)
452 Parent->OverDefinedCache.erase(*I);
454 // This erasure deallocates *this, so it MUST happen after we're done
455 // using any and all members of *this.
456 Parent->ValueCache.erase(*this);
459 void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
460 // Shortcut if we have never seen this block.
461 DenseSet<AssertingVH<BasicBlock> >::iterator I = SeenBlocks.find(BB);
462 if (I == SeenBlocks.end())
466 SmallVector<OverDefinedPairTy, 4> ToErase;
467 for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
468 E = OverDefinedCache.end(); I != E; ++I) {
470 ToErase.push_back(*I);
473 for (SmallVectorImpl<OverDefinedPairTy>::iterator I = ToErase.begin(),
474 E = ToErase.end(); I != E; ++I)
475 OverDefinedCache.erase(*I);
477 for (std::map<LVIValueHandle, ValueCacheEntryTy>::iterator
478 I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
482 void LazyValueInfoCache::solve() {
483 while (!BlockValueStack.empty()) {
484 std::pair<BasicBlock*, Value*> &e = BlockValueStack.top();
485 if (solveBlockValue(e.second, e.first)) {
486 assert(BlockValueStack.top() == e);
487 BlockValueStack.pop();
492 bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
493 // If already a constant, there is nothing to compute.
494 if (isa<Constant>(Val))
497 LVIValueHandle ValHandle(Val, this);
498 std::map<LVIValueHandle, ValueCacheEntryTy>::iterator I =
499 ValueCache.find(ValHandle);
500 if (I == ValueCache.end()) return false;
501 return I->second.count(BB);
504 LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
505 // If already a constant, there is nothing to compute.
506 if (Constant *VC = dyn_cast<Constant>(Val))
507 return LVILatticeVal::get(VC);
509 SeenBlocks.insert(BB);
510 return lookup(Val)[BB];
513 bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
514 if (isa<Constant>(Val))
517 ValueCacheEntryTy &Cache = lookup(Val);
518 SeenBlocks.insert(BB);
519 LVILatticeVal &BBLV = Cache[BB];
521 // OverDefinedCacheUpdater is a helper object that will update
522 // the OverDefinedCache for us when this method exits. Make sure to
523 // call markResult on it as we exit, passing a bool to indicate if the
524 // cache needs updating, i.e. if we have solved a new value or not.
525 OverDefinedCacheUpdater ODCacheUpdater(Val, BB, BBLV, this);
527 if (!BBLV.isUndefined()) {
528 DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
530 // Since we're reusing a cached value here, we don't need to update the
531 // OverDefinedCache. The cache will have been properly updated
532 // whenever the cached value was inserted.
533 ODCacheUpdater.markResult(false);
537 // Otherwise, this is the first time we're seeing this block. Reset the
538 // lattice value to overdefined, so that cycles will terminate and be
539 // conservatively correct.
540 BBLV.markOverdefined();
542 Instruction *BBI = dyn_cast<Instruction>(Val);
543 if (!BBI || BBI->getParent() != BB) {
544 return ODCacheUpdater.markResult(solveBlockValueNonLocal(BBLV, Val, BB));
547 if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
548 return ODCacheUpdater.markResult(solveBlockValuePHINode(BBLV, PN, BB));
551 if (AllocaInst *AI = dyn_cast<AllocaInst>(BBI)) {
552 BBLV = LVILatticeVal::getNot(ConstantPointerNull::get(AI->getType()));
553 return ODCacheUpdater.markResult(true);
556 // We can only analyze the definitions of certain classes of instructions
557 // (integral binops and casts at the moment), so bail if this isn't one.
558 LVILatticeVal Result;
559 if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
560 !BBI->getType()->isIntegerTy()) {
561 DEBUG(dbgs() << " compute BB '" << BB->getName()
562 << "' - overdefined because inst def found.\n");
563 BBLV.markOverdefined();
564 return ODCacheUpdater.markResult(true);
567 // FIXME: We're currently limited to binops with a constant RHS. This should
569 BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
570 if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
571 DEBUG(dbgs() << " compute BB '" << BB->getName()
572 << "' - overdefined because inst def found.\n");
574 BBLV.markOverdefined();
575 return ODCacheUpdater.markResult(true);
578 return ODCacheUpdater.markResult(solveBlockValueConstantRange(BBLV, BBI, BB));
581 static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
582 if (LoadInst *L = dyn_cast<LoadInst>(I)) {
583 return L->getPointerAddressSpace() == 0 &&
584 GetUnderlyingObject(L->getPointerOperand()) == Ptr;
586 if (StoreInst *S = dyn_cast<StoreInst>(I)) {
587 return S->getPointerAddressSpace() == 0 &&
588 GetUnderlyingObject(S->getPointerOperand()) == Ptr;
590 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
591 if (MI->isVolatile()) return false;
593 // FIXME: check whether it has a valuerange that excludes zero?
594 ConstantInt *Len = dyn_cast<ConstantInt>(MI->getLength());
595 if (!Len || Len->isZero()) return false;
597 if (MI->getDestAddressSpace() == 0)
598 if (GetUnderlyingObject(MI->getRawDest()) == Ptr)
600 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
601 if (MTI->getSourceAddressSpace() == 0)
602 if (GetUnderlyingObject(MTI->getRawSource()) == Ptr)
608 bool LazyValueInfoCache::solveBlockValueNonLocal(LVILatticeVal &BBLV,
609 Value *Val, BasicBlock *BB) {
610 LVILatticeVal Result; // Start Undefined.
612 // If this is a pointer, and there's a load from that pointer in this BB,
613 // then we know that the pointer can't be NULL.
614 bool NotNull = false;
615 if (Val->getType()->isPointerTy()) {
616 if (isKnownNonNull(Val)) {
619 Value *UnderlyingVal = GetUnderlyingObject(Val);
620 // If 'GetUnderlyingObject' didn't converge, skip it. It won't converge
621 // inside InstructionDereferencesPointer either.
622 if (UnderlyingVal == GetUnderlyingObject(UnderlyingVal, nullptr, 1)) {
623 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
625 if (InstructionDereferencesPointer(BI, UnderlyingVal)) {
634 // If this is the entry block, we must be asking about an argument. The
635 // value is overdefined.
636 if (BB == &BB->getParent()->getEntryBlock()) {
637 assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
639 PointerType *PTy = cast<PointerType>(Val->getType());
640 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
642 Result.markOverdefined();
648 // Loop over all of our predecessors, merging what we know from them into
650 bool EdgesMissing = false;
651 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
652 LVILatticeVal EdgeResult;
653 EdgesMissing |= !getEdgeValue(Val, *PI, BB, EdgeResult);
657 Result.mergeIn(EdgeResult);
659 // If we hit overdefined, exit early. The BlockVals entry is already set
661 if (Result.isOverdefined()) {
662 DEBUG(dbgs() << " compute BB '" << BB->getName()
663 << "' - overdefined because of pred.\n");
664 // If we previously determined that this is a pointer that can't be null
665 // then return that rather than giving up entirely.
667 PointerType *PTy = cast<PointerType>(Val->getType());
668 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
678 // Return the merged value, which is more precise than 'overdefined'.
679 assert(!Result.isOverdefined());
684 bool LazyValueInfoCache::solveBlockValuePHINode(LVILatticeVal &BBLV,
685 PHINode *PN, BasicBlock *BB) {
686 LVILatticeVal Result; // Start Undefined.
688 // Loop over all of our predecessors, merging what we know from them into
690 bool EdgesMissing = false;
691 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
692 BasicBlock *PhiBB = PN->getIncomingBlock(i);
693 Value *PhiVal = PN->getIncomingValue(i);
694 LVILatticeVal EdgeResult;
695 // Note that we can provide PN as the context value to getEdgeValue, even
696 // though the results will be cached, because PN is the value being used as
697 // the cache key in the caller.
698 EdgesMissing |= !getEdgeValue(PhiVal, PhiBB, BB, EdgeResult, PN);
702 Result.mergeIn(EdgeResult);
704 // If we hit overdefined, exit early. The BlockVals entry is already set
706 if (Result.isOverdefined()) {
707 DEBUG(dbgs() << " compute BB '" << BB->getName()
708 << "' - overdefined because of pred.\n");
717 // Return the merged value, which is more precise than 'overdefined'.
718 assert(!Result.isOverdefined() && "Possible PHI in entry block?");
723 static bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
724 LVILatticeVal &Result,
725 bool isTrueDest = true);
727 // If we can determine a constant range for the value Val in the context
728 // provided by the instruction BBI, then merge it into BBLV. If we did find a
729 // constant range, return true.
730 void LazyValueInfoCache::mergeAssumeBlockValueConstantRange(Value *Val,
733 BBI = BBI ? BBI : dyn_cast<Instruction>(Val);
737 for (auto &I : AT->assumptions(BBI->getParent()->getParent())) {
738 if (!isValidAssumeForContext(I, BBI, DL, DT))
741 Value *C = I->getArgOperand(0);
742 if (ICmpInst *ICI = dyn_cast<ICmpInst>(C)) {
743 LVILatticeVal Result;
744 if (getValueFromFromCondition(Val, ICI, Result)) {
745 if (BBLV.isOverdefined())
748 BBLV.mergeIn(Result);
754 bool LazyValueInfoCache::solveBlockValueConstantRange(LVILatticeVal &BBLV,
757 // Figure out the range of the LHS. If that fails, bail.
758 if (!hasBlockValue(BBI->getOperand(0), BB)) {
759 BlockValueStack.push(std::make_pair(BB, BBI->getOperand(0)));
763 LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
764 mergeAssumeBlockValueConstantRange(BBI->getOperand(0), LHSVal, BBI);
765 if (!LHSVal.isConstantRange()) {
766 BBLV.markOverdefined();
770 ConstantRange LHSRange = LHSVal.getConstantRange();
771 ConstantRange RHSRange(1);
772 IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
773 if (isa<BinaryOperator>(BBI)) {
774 if (ConstantInt *RHS = dyn_cast<ConstantInt>(BBI->getOperand(1))) {
775 RHSRange = ConstantRange(RHS->getValue());
777 BBLV.markOverdefined();
782 // NOTE: We're currently limited by the set of operations that ConstantRange
783 // can evaluate symbolically. Enhancing that set will allows us to analyze
785 LVILatticeVal Result;
786 switch (BBI->getOpcode()) {
787 case Instruction::Add:
788 Result.markConstantRange(LHSRange.add(RHSRange));
790 case Instruction::Sub:
791 Result.markConstantRange(LHSRange.sub(RHSRange));
793 case Instruction::Mul:
794 Result.markConstantRange(LHSRange.multiply(RHSRange));
796 case Instruction::UDiv:
797 Result.markConstantRange(LHSRange.udiv(RHSRange));
799 case Instruction::Shl:
800 Result.markConstantRange(LHSRange.shl(RHSRange));
802 case Instruction::LShr:
803 Result.markConstantRange(LHSRange.lshr(RHSRange));
805 case Instruction::Trunc:
806 Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
808 case Instruction::SExt:
809 Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
811 case Instruction::ZExt:
812 Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
814 case Instruction::BitCast:
815 Result.markConstantRange(LHSRange);
817 case Instruction::And:
818 Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
820 case Instruction::Or:
821 Result.markConstantRange(LHSRange.binaryOr(RHSRange));
824 // Unhandled instructions are overdefined.
826 DEBUG(dbgs() << " compute BB '" << BB->getName()
827 << "' - overdefined because inst def found.\n");
828 Result.markOverdefined();
836 bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
837 LVILatticeVal &Result, bool isTrueDest) {
838 if (ICI && isa<Constant>(ICI->getOperand(1))) {
839 if (ICI->isEquality() && ICI->getOperand(0) == Val) {
840 // We know that V has the RHS constant if this is a true SETEQ or
842 if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
843 Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
845 Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
849 // Recognize the range checking idiom that InstCombine produces.
850 // (X-C1) u< C2 --> [C1, C1+C2)
851 ConstantInt *NegOffset = nullptr;
852 if (ICI->getPredicate() == ICmpInst::ICMP_ULT)
853 match(ICI->getOperand(0), m_Add(m_Specific(Val),
854 m_ConstantInt(NegOffset)));
856 ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1));
857 if (CI && (ICI->getOperand(0) == Val || NegOffset)) {
858 // Calculate the range of values that would satisfy the comparison.
859 ConstantRange CmpRange(CI->getValue());
860 ConstantRange TrueValues =
861 ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
863 if (NegOffset) // Apply the offset from above.
864 TrueValues = TrueValues.subtract(NegOffset->getValue());
866 // If we're interested in the false dest, invert the condition.
867 if (!isTrueDest) TrueValues = TrueValues.inverse();
869 Result = LVILatticeVal::getRange(TrueValues);
877 /// \brief Compute the value of Val on the edge BBFrom -> BBTo. Returns false if
878 /// Val is not constrained on the edge.
879 static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
880 BasicBlock *BBTo, LVILatticeVal &Result) {
881 // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
883 if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
884 // If this is a conditional branch and only one successor goes to BBTo, then
885 // we maybe able to infer something from the condition.
886 if (BI->isConditional() &&
887 BI->getSuccessor(0) != BI->getSuccessor(1)) {
888 bool isTrueDest = BI->getSuccessor(0) == BBTo;
889 assert(BI->getSuccessor(!isTrueDest) == BBTo &&
890 "BBTo isn't a successor of BBFrom");
892 // If V is the condition of the branch itself, then we know exactly what
894 if (BI->getCondition() == Val) {
895 Result = LVILatticeVal::get(ConstantInt::get(
896 Type::getInt1Ty(Val->getContext()), isTrueDest));
900 // If the condition of the branch is an equality comparison, we may be
901 // able to infer the value.
902 ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
903 if (getValueFromFromCondition(Val, ICI, Result, isTrueDest))
908 // If the edge was formed by a switch on the value, then we may know exactly
910 if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
911 if (SI->getCondition() != Val)
914 bool DefaultCase = SI->getDefaultDest() == BBTo;
915 unsigned BitWidth = Val->getType()->getIntegerBitWidth();
916 ConstantRange EdgesVals(BitWidth, DefaultCase/*isFullSet*/);
918 for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
920 ConstantRange EdgeVal(i.getCaseValue()->getValue());
922 // It is possible that the default destination is the destination of
923 // some cases. There is no need to perform difference for those cases.
924 if (i.getCaseSuccessor() != BBTo)
925 EdgesVals = EdgesVals.difference(EdgeVal);
926 } else if (i.getCaseSuccessor() == BBTo)
927 EdgesVals = EdgesVals.unionWith(EdgeVal);
929 Result = LVILatticeVal::getRange(EdgesVals);
935 /// \brief Compute the value of Val on the edge BBFrom -> BBTo, or the value at
936 /// the basic block if the edge does not constraint Val.
937 bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom,
938 BasicBlock *BBTo, LVILatticeVal &Result,
940 // If already a constant, there is nothing to compute.
941 if (Constant *VC = dyn_cast<Constant>(Val)) {
942 Result = LVILatticeVal::get(VC);
946 if (getEdgeValueLocal(Val, BBFrom, BBTo, Result)) {
947 if (!Result.isConstantRange() ||
948 Result.getConstantRange().getSingleElement())
951 // FIXME: this check should be moved to the beginning of the function when
952 // LVI better supports recursive values. Even for the single value case, we
953 // can intersect to detect dead code (an empty range).
954 if (!hasBlockValue(Val, BBFrom)) {
955 BlockValueStack.push(std::make_pair(BBFrom, Val));
959 // Try to intersect ranges of the BB and the constraint on the edge.
960 LVILatticeVal InBlock = getBlockValue(Val, BBFrom);
961 mergeAssumeBlockValueConstantRange(Val, InBlock, BBFrom->getTerminator());
962 // See note on the use of the CxtI with mergeAssumeBlockValueConstantRange,
963 // and caching, below.
964 mergeAssumeBlockValueConstantRange(Val, InBlock, CxtI);
965 if (!InBlock.isConstantRange())
968 ConstantRange Range =
969 Result.getConstantRange().intersectWith(InBlock.getConstantRange());
970 Result = LVILatticeVal::getRange(Range);
974 if (!hasBlockValue(Val, BBFrom)) {
975 BlockValueStack.push(std::make_pair(BBFrom, Val));
979 // If we couldn't compute the value on the edge, use the value from the BB.
980 Result = getBlockValue(Val, BBFrom);
981 mergeAssumeBlockValueConstantRange(Val, Result, BBFrom->getTerminator());
982 // We can use the context instruction (generically the ultimate instruction
983 // the calling pass is trying to simplify) here, even though the result of
984 // this function is generally cached when called from the solve* functions
985 // (and that cached result might be used with queries using a different
986 // context instruction), because when this function is called from the solve*
987 // functions, the context instruction is not provided. When called from
988 // LazyValueInfoCache::getValueOnEdge, the context instruction is provided,
989 // but then the result is not cached.
990 mergeAssumeBlockValueConstantRange(Val, Result, CxtI);
994 LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB,
996 DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
997 << BB->getName() << "'\n");
999 BlockValueStack.push(std::make_pair(BB, V));
1001 LVILatticeVal Result = getBlockValue(V, BB);
1002 mergeAssumeBlockValueConstantRange(V, Result, CxtI);
1004 DEBUG(dbgs() << " Result = " << Result << "\n");
1008 LVILatticeVal LazyValueInfoCache::getValueAt(Value *V, Instruction *CxtI) {
1009 DEBUG(dbgs() << "LVI Getting value " << *V << " at '"
1010 << CxtI->getName() << "'\n");
1012 LVILatticeVal Result;
1013 mergeAssumeBlockValueConstantRange(V, Result, CxtI);
1015 DEBUG(dbgs() << " Result = " << Result << "\n");
1019 LVILatticeVal LazyValueInfoCache::
1020 getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB,
1021 Instruction *CxtI) {
1022 DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
1023 << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
1025 LVILatticeVal Result;
1026 if (!getEdgeValue(V, FromBB, ToBB, Result, CxtI)) {
1028 bool WasFastQuery = getEdgeValue(V, FromBB, ToBB, Result, CxtI);
1030 assert(WasFastQuery && "More work to do after problem solved?");
1033 DEBUG(dbgs() << " Result = " << Result << "\n");
1037 void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
1038 BasicBlock *NewSucc) {
1039 // When an edge in the graph has been threaded, values that we could not
1040 // determine a value for before (i.e. were marked overdefined) may be possible
1041 // to solve now. We do NOT try to proactively update these values. Instead,
1042 // we clear their entries from the cache, and allow lazy updating to recompute
1043 // them when needed.
1045 // The updating process is fairly simple: we need to drop cached info
1046 // for all values that were marked overdefined in OldSucc, and for those same
1047 // values in any successor of OldSucc (except NewSucc) in which they were
1048 // also marked overdefined.
1049 std::vector<BasicBlock*> worklist;
1050 worklist.push_back(OldSucc);
1052 DenseSet<Value*> ClearSet;
1053 for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
1054 E = OverDefinedCache.end(); I != E; ++I) {
1055 if (I->first == OldSucc)
1056 ClearSet.insert(I->second);
1059 // Use a worklist to perform a depth-first search of OldSucc's successors.
1060 // NOTE: We do not need a visited list since any blocks we have already
1061 // visited will have had their overdefined markers cleared already, and we
1062 // thus won't loop to their successors.
1063 while (!worklist.empty()) {
1064 BasicBlock *ToUpdate = worklist.back();
1065 worklist.pop_back();
1067 // Skip blocks only accessible through NewSucc.
1068 if (ToUpdate == NewSucc) continue;
1070 bool changed = false;
1071 for (DenseSet<Value*>::iterator I = ClearSet.begin(), E = ClearSet.end();
1073 // If a value was marked overdefined in OldSucc, and is here too...
1074 DenseSet<OverDefinedPairTy>::iterator OI =
1075 OverDefinedCache.find(std::make_pair(ToUpdate, *I));
1076 if (OI == OverDefinedCache.end()) continue;
1078 // Remove it from the caches.
1079 ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
1080 ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
1082 assert(CI != Entry.end() && "Couldn't find entry to update?");
1084 OverDefinedCache.erase(OI);
1086 // If we removed anything, then we potentially need to update
1087 // blocks successors too.
1091 if (!changed) continue;
1093 worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
1097 //===----------------------------------------------------------------------===//
1098 // LazyValueInfo Impl
1099 //===----------------------------------------------------------------------===//
1101 /// getCache - This lazily constructs the LazyValueInfoCache.
1102 static LazyValueInfoCache &getCache(void *&PImpl,
1103 AssumptionTracker *AT,
1104 const DataLayout *DL = nullptr,
1105 DominatorTree *DT = nullptr) {
1107 PImpl = new LazyValueInfoCache(AT, DL, DT);
1108 return *static_cast<LazyValueInfoCache*>(PImpl);
1111 bool LazyValueInfo::runOnFunction(Function &F) {
1112 AT = &getAnalysis<AssumptionTracker>();
1114 DominatorTreeWrapperPass *DTWP =
1115 getAnalysisIfAvailable<DominatorTreeWrapperPass>();
1116 DT = DTWP ? &DTWP->getDomTree() : nullptr;
1118 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
1119 DL = DLP ? &DLP->getDataLayout() : nullptr;
1121 TLI = &getAnalysis<TargetLibraryInfo>();
1124 getCache(PImpl, AT, DL, DT).clear();
1130 void LazyValueInfo::getAnalysisUsage(AnalysisUsage &AU) const {
1131 AU.setPreservesAll();
1132 AU.addRequired<AssumptionTracker>();
1133 AU.addRequired<TargetLibraryInfo>();
1136 void LazyValueInfo::releaseMemory() {
1137 // If the cache was allocated, free it.
1139 delete &getCache(PImpl, AT);
1144 Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB,
1145 Instruction *CxtI) {
1146 LVILatticeVal Result =
1147 getCache(PImpl, AT, DL, DT).getValueInBlock(V, BB, CxtI);
1149 if (Result.isConstant())
1150 return Result.getConstant();
1151 if (Result.isConstantRange()) {
1152 ConstantRange CR = Result.getConstantRange();
1153 if (const APInt *SingleVal = CR.getSingleElement())
1154 return ConstantInt::get(V->getContext(), *SingleVal);
1159 /// getConstantOnEdge - Determine whether the specified value is known to be a
1160 /// constant on the specified edge. Return null if not.
1161 Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
1163 Instruction *CxtI) {
1164 LVILatticeVal Result =
1165 getCache(PImpl, AT, DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);
1167 if (Result.isConstant())
1168 return Result.getConstant();
1169 if (Result.isConstantRange()) {
1170 ConstantRange CR = Result.getConstantRange();
1171 if (const APInt *SingleVal = CR.getSingleElement())
1172 return ConstantInt::get(V->getContext(), *SingleVal);
1177 static LazyValueInfo::Tristate
1178 getPredicateResult(unsigned Pred, Constant *C, LVILatticeVal &Result,
1179 const DataLayout *DL, TargetLibraryInfo *TLI) {
1181 // If we know the value is a constant, evaluate the conditional.
1182 Constant *Res = nullptr;
1183 if (Result.isConstant()) {
1184 Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, DL,
1186 if (ConstantInt *ResCI = dyn_cast<ConstantInt>(Res))
1187 return ResCI->isZero() ? LazyValueInfo::False : LazyValueInfo::True;
1188 return LazyValueInfo::Unknown;
1191 if (Result.isConstantRange()) {
1192 ConstantInt *CI = dyn_cast<ConstantInt>(C);
1193 if (!CI) return LazyValueInfo::Unknown;
1195 ConstantRange CR = Result.getConstantRange();
1196 if (Pred == ICmpInst::ICMP_EQ) {
1197 if (!CR.contains(CI->getValue()))
1198 return LazyValueInfo::False;
1200 if (CR.isSingleElement() && CR.contains(CI->getValue()))
1201 return LazyValueInfo::True;
1202 } else if (Pred == ICmpInst::ICMP_NE) {
1203 if (!CR.contains(CI->getValue()))
1204 return LazyValueInfo::True;
1206 if (CR.isSingleElement() && CR.contains(CI->getValue()))
1207 return LazyValueInfo::False;
1210 // Handle more complex predicates.
1211 ConstantRange TrueValues =
1212 ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
1213 if (TrueValues.contains(CR))
1214 return LazyValueInfo::True;
1215 if (TrueValues.inverse().contains(CR))
1216 return LazyValueInfo::False;
1217 return LazyValueInfo::Unknown;
1220 if (Result.isNotConstant()) {
1221 // If this is an equality comparison, we can try to fold it knowing that
1223 if (Pred == ICmpInst::ICMP_EQ) {
1224 // !C1 == C -> false iff C1 == C.
1225 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
1226 Result.getNotConstant(), C, DL,
1228 if (Res->isNullValue())
1229 return LazyValueInfo::False;
1230 } else if (Pred == ICmpInst::ICMP_NE) {
1231 // !C1 != C -> true iff C1 == C.
1232 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
1233 Result.getNotConstant(), C, DL,
1235 if (Res->isNullValue())
1236 return LazyValueInfo::True;
1238 return LazyValueInfo::Unknown;
1241 return LazyValueInfo::Unknown;
1244 /// getPredicateOnEdge - Determine whether the specified value comparison
1245 /// with a constant is known to be true or false on the specified CFG edge.
1246 /// Pred is a CmpInst predicate.
1247 LazyValueInfo::Tristate
1248 LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
1249 BasicBlock *FromBB, BasicBlock *ToBB,
1250 Instruction *CxtI) {
1251 LVILatticeVal Result =
1252 getCache(PImpl, AT, DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);
1254 return getPredicateResult(Pred, C, Result, DL, TLI);
1257 LazyValueInfo::Tristate
1258 LazyValueInfo::getPredicateAt(unsigned Pred, Value *V, Constant *C,
1259 Instruction *CxtI) {
1260 LVILatticeVal Result =
1261 getCache(PImpl, AT, DL, DT).getValueAt(V, CxtI);
1263 return getPredicateResult(Pred, C, Result, DL, TLI);
1266 void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
1267 BasicBlock *NewSucc) {
1268 if (PImpl) getCache(PImpl, AT, DL, DT).threadEdge(PredBB, OldSucc, NewSucc);
1271 void LazyValueInfo::eraseBlock(BasicBlock *BB) {
1272 if (PImpl) getCache(PImpl, AT, DL, DT).eraseBlock(BB);