1 //===- LazyValueInfo.cpp - Value constraint analysis ----------------------===//
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/CommandLine.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/raw_ostream.h"
33 #include "llvm/Target/TargetLibraryInfo.h"
37 using namespace PatternMatch;
39 #define DEBUG_TYPE "lazy-value-info"
41 // Experimentally derived threshold for the number of basic blocks lowered for
42 // lattice value overdefined.
43 static cl::opt<unsigned>
44 OverdefinedBBThreshold("lvi-overdefined-BB-threshold",
45 cl::init(1500), cl::Hidden,
46 cl::desc("Threshold of the number of basic blocks lowered for lattice value"
49 // Experimentally derived threshold for additional lowering lattice values
50 // overdefined per block.
51 static cl::opt<unsigned>
52 OverdefinedThreshold("lvi-overdefined-threshold", cl::init(10), cl::Hidden,
53 cl::desc("Threshold of lowering lattice value 'overdefined'."));
55 char LazyValueInfo::ID = 0;
56 INITIALIZE_PASS_BEGIN(LazyValueInfo, "lazy-value-info",
57 "Lazy Value Information Analysis", false, true)
58 INITIALIZE_PASS_DEPENDENCY(AssumptionTracker)
59 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
60 INITIALIZE_PASS_END(LazyValueInfo, "lazy-value-info",
61 "Lazy Value Information Analysis", false, true)
64 FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
68 //===----------------------------------------------------------------------===//
70 //===----------------------------------------------------------------------===//
72 /// LVILatticeVal - This is the information tracked by LazyValueInfo for each
75 /// FIXME: This is basically just for bringup, this can be made a lot more rich
81 /// undefined - This Value has no known value yet.
84 /// constant - This Value has a specific constant value.
86 /// notconstant - This Value is known to not have the specified value.
89 /// constantrange - The Value falls within this range.
92 /// overdefined - This value is not known to be constant, and we know that
97 /// Val: This stores the current lattice value along with the Constant* for
98 /// the constant if this is a 'constant' or 'notconstant' value.
104 LVILatticeVal() : Tag(undefined), Val(nullptr), Range(1, true) {}
106 static LVILatticeVal get(Constant *C) {
108 if (!isa<UndefValue>(C))
112 static LVILatticeVal getNot(Constant *C) {
114 if (!isa<UndefValue>(C))
115 Res.markNotConstant(C);
118 static LVILatticeVal getRange(ConstantRange CR) {
120 Res.markConstantRange(CR);
124 bool isUndefined() const { return Tag == undefined; }
125 bool isConstant() const { return Tag == constant; }
126 bool isNotConstant() const { return Tag == notconstant; }
127 bool isConstantRange() const { return Tag == constantrange; }
128 bool isOverdefined() const { return Tag == overdefined; }
130 Constant *getConstant() const {
131 assert(isConstant() && "Cannot get the constant of a non-constant!");
135 Constant *getNotConstant() const {
136 assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
140 ConstantRange getConstantRange() const {
141 assert(isConstantRange() &&
142 "Cannot get the constant-range of a non-constant-range!");
146 /// markOverdefined - Return true if this is a change in status.
147 bool markOverdefined() {
154 /// markConstant - Return true if this is a change in status.
155 bool markConstant(Constant *V) {
156 assert(V && "Marking constant with NULL");
157 if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
158 return markConstantRange(ConstantRange(CI->getValue()));
159 if (isa<UndefValue>(V))
162 assert((!isConstant() || getConstant() == V) &&
163 "Marking constant with different value");
164 assert(isUndefined());
170 /// markNotConstant - Return true if this is a change in status.
171 bool markNotConstant(Constant *V) {
172 assert(V && "Marking constant with NULL");
173 if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
174 return markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue()));
175 if (isa<UndefValue>(V))
178 assert((!isConstant() || getConstant() != V) &&
179 "Marking constant !constant with same value");
180 assert((!isNotConstant() || getNotConstant() == V) &&
181 "Marking !constant with different value");
182 assert(isUndefined() || isConstant());
188 /// markConstantRange - Return true if this is a change in status.
189 bool markConstantRange(const ConstantRange NewR) {
190 if (isConstantRange()) {
191 if (NewR.isEmptySet())
192 return markOverdefined();
194 bool changed = Range != NewR;
199 assert(isUndefined());
200 if (NewR.isEmptySet())
201 return markOverdefined();
208 /// mergeIn - Merge the specified lattice value into this one, updating this
209 /// one and returning true if anything changed.
210 bool mergeIn(const LVILatticeVal &RHS) {
211 if (RHS.isUndefined() || isOverdefined()) return false;
212 if (RHS.isOverdefined()) return markOverdefined();
222 if (RHS.isConstant()) {
225 return markOverdefined();
228 if (RHS.isNotConstant()) {
230 return markOverdefined();
232 // Unless we can prove that the two Constants are different, we must
233 // move to overdefined.
234 // FIXME: use DataLayout/TargetLibraryInfo for smarter constant folding.
235 if (ConstantInt *Res = dyn_cast<ConstantInt>(
236 ConstantFoldCompareInstOperands(CmpInst::ICMP_NE,
238 RHS.getNotConstant())))
240 return markNotConstant(RHS.getNotConstant());
242 return markOverdefined();
245 // RHS is a ConstantRange, LHS is a non-integer Constant.
247 // FIXME: consider the case where RHS is a range [1, 0) and LHS is
248 // a function. The correct result is to pick up RHS.
250 return markOverdefined();
253 if (isNotConstant()) {
254 if (RHS.isConstant()) {
256 return markOverdefined();
258 // Unless we can prove that the two Constants are different, we must
259 // move to overdefined.
260 // FIXME: use DataLayout/TargetLibraryInfo for smarter constant folding.
261 if (ConstantInt *Res = dyn_cast<ConstantInt>(
262 ConstantFoldCompareInstOperands(CmpInst::ICMP_NE,
268 return markOverdefined();
271 if (RHS.isNotConstant()) {
274 return markOverdefined();
277 return markOverdefined();
280 assert(isConstantRange() && "New LVILattice type?");
281 if (!RHS.isConstantRange())
282 return markOverdefined();
284 ConstantRange NewR = Range.unionWith(RHS.getConstantRange());
285 if (NewR.isFullSet())
286 return markOverdefined();
287 return markConstantRange(NewR);
291 } // end anonymous namespace.
294 raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val)
296 raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
297 if (Val.isUndefined())
298 return OS << "undefined";
299 if (Val.isOverdefined())
300 return OS << "overdefined";
302 if (Val.isNotConstant())
303 return OS << "notconstant<" << *Val.getNotConstant() << '>';
304 else if (Val.isConstantRange())
305 return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
306 << Val.getConstantRange().getUpper() << '>';
307 return OS << "constant<" << *Val.getConstant() << '>';
311 //===----------------------------------------------------------------------===//
312 // LazyValueInfoCache Decl
313 //===----------------------------------------------------------------------===//
316 /// LVIValueHandle - A callback value handle updates the cache when
317 /// values are erased.
318 class LazyValueInfoCache;
319 struct LVIValueHandle : public CallbackVH {
320 LazyValueInfoCache *Parent;
322 LVIValueHandle(Value *V, LazyValueInfoCache *P)
323 : CallbackVH(V), Parent(P) { }
325 void deleted() override;
326 void allUsesReplacedWith(Value *V) override {
333 /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
334 /// maintains information about queries across the clients' queries.
335 class LazyValueInfoCache {
336 /// ValueCacheEntryTy - This is all of the cached block information for
337 /// exactly one Value*. The entries are sorted by the BasicBlock* of the
338 /// entries, allowing us to do a lookup with a binary search.
339 typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
341 /// ValueCache - This is all of the cached information for all values,
342 /// mapped from Value* to key information.
343 std::map<LVIValueHandle, ValueCacheEntryTy> ValueCache;
345 /// OverDefinedCache - This tracks, on a per-block basis, the set of
346 /// values that are over-defined at the end of that block. This is required
347 /// for cache updating.
348 typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
349 DenseSet<OverDefinedPairTy> OverDefinedCache;
351 /// SeenBlocks - Keep track of all blocks that we have ever seen, so we
352 /// don't spend time removing unused blocks from our caches.
353 DenseSet<AssertingVH<BasicBlock> > SeenBlocks;
355 /// BlockValueStack - This stack holds the state of the value solver
356 /// during a query. It basically emulates the callstack of the naive
357 /// recursive value lookup process.
358 std::stack<std::pair<BasicBlock*, Value*> > BlockValueStack;
360 /// A pointer to the cache of @llvm.assume calls.
361 AssumptionTracker *AT;
362 /// An optional DL pointer.
363 const DataLayout *DL;
364 /// An optional DT pointer.
366 /// A counter to record how many times Overdefined has been tried to be
368 DenseMap<BasicBlock *, unsigned> LoweringOverdefinedTimes;
370 friend struct LVIValueHandle;
372 /// OverDefinedCacheUpdater - A helper object that ensures that the
373 /// OverDefinedCache is updated whenever solveBlockValue returns.
374 struct OverDefinedCacheUpdater {
375 LazyValueInfoCache *Parent;
380 OverDefinedCacheUpdater(Value *V, BasicBlock *B, LVILatticeVal &LV,
381 LazyValueInfoCache *P)
382 : Parent(P), Val(V), BB(B), BBLV(LV) { }
384 bool markResult(bool changed) {
385 if (changed && BBLV.isOverdefined())
386 Parent->OverDefinedCache.insert(std::make_pair(BB, Val));
393 LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
394 bool getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T,
395 LVILatticeVal &Result,
396 Instruction *CxtI = nullptr);
397 bool hasBlockValue(Value *Val, BasicBlock *BB);
399 // These methods process one work item and may add more. A false value
400 // returned means that the work item was not completely processed and must
401 // be revisited after going through the new items.
402 bool solveBlockValue(Value *Val, BasicBlock *BB);
403 bool solveBlockValueNonLocal(LVILatticeVal &BBLV,
404 Value *Val, BasicBlock *BB);
405 bool solveBlockValuePHINode(LVILatticeVal &BBLV,
406 PHINode *PN, BasicBlock *BB);
407 bool solveBlockValueConstantRange(LVILatticeVal &BBLV,
408 Instruction *BBI, BasicBlock *BB);
409 void mergeAssumeBlockValueConstantRange(Value *Val, LVILatticeVal &BBLV,
414 ValueCacheEntryTy &lookup(Value *V) {
415 return ValueCache[LVIValueHandle(V, this)];
419 /// getValueInBlock - This is the query interface to determine the lattice
420 /// value for the specified Value* at the end of the specified block.
421 LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB,
422 Instruction *CxtI = nullptr);
424 /// getValueAt - This is the query interface to determine the lattice
425 /// value for the specified Value* at the specified instruction (generally
426 /// from an assume intrinsic).
427 LVILatticeVal getValueAt(Value *V, Instruction *CxtI);
429 /// getValueOnEdge - This is the query interface to determine the lattice
430 /// value for the specified Value* that is true on the specified edge.
431 LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB,
432 Instruction *CxtI = nullptr);
434 /// threadEdge - This is the update interface to inform the cache that an
435 /// edge from PredBB to OldSucc has been threaded to be from PredBB to
437 void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
439 /// eraseBlock - This is part of the update interface to inform the cache
440 /// that a block has been deleted.
441 void eraseBlock(BasicBlock *BB);
443 /// clear - Empty the cache.
447 OverDefinedCache.clear();
450 LazyValueInfoCache(AssumptionTracker *AT,
451 const DataLayout *DL = nullptr,
452 DominatorTree *DT = nullptr) : AT(AT), DL(DL), DT(DT) {}
454 } // end anonymous namespace
456 void LVIValueHandle::deleted() {
457 typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
459 SmallVector<OverDefinedPairTy, 4> ToErase;
460 for (DenseSet<OverDefinedPairTy>::iterator
461 I = Parent->OverDefinedCache.begin(),
462 E = Parent->OverDefinedCache.end();
464 if (I->second == getValPtr())
465 ToErase.push_back(*I);
468 for (SmallVectorImpl<OverDefinedPairTy>::iterator I = ToErase.begin(),
469 E = ToErase.end(); I != E; ++I)
470 Parent->OverDefinedCache.erase(*I);
472 // This erasure deallocates *this, so it MUST happen after we're done
473 // using any and all members of *this.
474 Parent->ValueCache.erase(*this);
477 void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
478 // Shortcut if we have never seen this block.
479 DenseSet<AssertingVH<BasicBlock> >::iterator I = SeenBlocks.find(BB);
480 if (I == SeenBlocks.end())
484 SmallVector<OverDefinedPairTy, 4> ToErase;
485 for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
486 E = OverDefinedCache.end(); I != E; ++I) {
488 ToErase.push_back(*I);
491 for (SmallVectorImpl<OverDefinedPairTy>::iterator I = ToErase.begin(),
492 E = ToErase.end(); I != E; ++I)
493 OverDefinedCache.erase(*I);
495 for (std::map<LVIValueHandle, ValueCacheEntryTy>::iterator
496 I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
500 void LazyValueInfoCache::solve() {
501 // Reset the counter of lowering overdefined value.
502 LoweringOverdefinedTimes.clear();
504 while (!BlockValueStack.empty()) {
505 std::pair<BasicBlock*, Value*> &e = BlockValueStack.top();
506 if (solveBlockValue(e.second, e.first)) {
507 assert(BlockValueStack.top() == e);
508 BlockValueStack.pop();
513 bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
514 // If already a constant, there is nothing to compute.
515 if (isa<Constant>(Val))
518 LVIValueHandle ValHandle(Val, this);
519 std::map<LVIValueHandle, ValueCacheEntryTy>::iterator I =
520 ValueCache.find(ValHandle);
521 if (I == ValueCache.end()) return false;
522 return I->second.count(BB);
525 LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
526 // If already a constant, there is nothing to compute.
527 if (Constant *VC = dyn_cast<Constant>(Val))
528 return LVILatticeVal::get(VC);
530 SeenBlocks.insert(BB);
531 return lookup(Val)[BB];
534 bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
535 if (isa<Constant>(Val))
538 ValueCacheEntryTy &Cache = lookup(Val);
539 SeenBlocks.insert(BB);
540 LVILatticeVal &BBLV = Cache[BB];
542 // OverDefinedCacheUpdater is a helper object that will update
543 // the OverDefinedCache for us when this method exits. Make sure to
544 // call markResult on it as we exist, passing a bool to indicate if the
545 // cache needs updating, i.e. if we have solve a new value or not.
546 OverDefinedCacheUpdater ODCacheUpdater(Val, BB, BBLV, this);
548 if (!BBLV.isUndefined()) {
549 DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
551 // Since we're reusing a cached value here, we don't need to update the
552 // OverDefinedCahce. The cache will have been properly updated
553 // whenever the cached value was inserted.
554 ODCacheUpdater.markResult(false);
558 // Otherwise, this is the first time we're seeing this block. Reset the
559 // lattice value to overdefined, so that cycles will terminate and be
560 // conservatively correct.
561 BBLV.markOverdefined();
562 ++LoweringOverdefinedTimes[BB];
564 Instruction *BBI = dyn_cast<Instruction>(Val);
565 if (!BBI || BBI->getParent() != BB) {
566 return ODCacheUpdater.markResult(solveBlockValueNonLocal(BBLV, Val, BB));
569 if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
570 return ODCacheUpdater.markResult(solveBlockValuePHINode(BBLV, PN, BB));
573 if (AllocaInst *AI = dyn_cast<AllocaInst>(BBI)) {
574 BBLV = LVILatticeVal::getNot(ConstantPointerNull::get(AI->getType()));
575 return ODCacheUpdater.markResult(true);
578 // We can only analyze the definitions of certain classes of instructions
579 // (integral binops and casts at the moment), so bail if this isn't one.
580 LVILatticeVal Result;
581 if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
582 !BBI->getType()->isIntegerTy()) {
583 DEBUG(dbgs() << " compute BB '" << BB->getName()
584 << "' - overdefined because inst def found.\n");
585 BBLV.markOverdefined();
586 return ODCacheUpdater.markResult(true);
589 // FIXME: We're currently limited to binops with a constant RHS. This should
591 BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
592 if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
593 DEBUG(dbgs() << " compute BB '" << BB->getName()
594 << "' - overdefined because inst def found.\n");
596 BBLV.markOverdefined();
597 return ODCacheUpdater.markResult(true);
600 return ODCacheUpdater.markResult(solveBlockValueConstantRange(BBLV, BBI, BB));
603 static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
604 if (LoadInst *L = dyn_cast<LoadInst>(I)) {
605 return L->getPointerAddressSpace() == 0 &&
606 GetUnderlyingObject(L->getPointerOperand()) == Ptr;
608 if (StoreInst *S = dyn_cast<StoreInst>(I)) {
609 return S->getPointerAddressSpace() == 0 &&
610 GetUnderlyingObject(S->getPointerOperand()) == Ptr;
612 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
613 if (MI->isVolatile()) return false;
615 // FIXME: check whether it has a valuerange that excludes zero?
616 ConstantInt *Len = dyn_cast<ConstantInt>(MI->getLength());
617 if (!Len || Len->isZero()) return false;
619 if (MI->getDestAddressSpace() == 0)
620 if (GetUnderlyingObject(MI->getRawDest()) == Ptr)
622 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
623 if (MTI->getSourceAddressSpace() == 0)
624 if (GetUnderlyingObject(MTI->getRawSource()) == Ptr)
630 bool LazyValueInfoCache::solveBlockValueNonLocal(LVILatticeVal &BBLV,
631 Value *Val, BasicBlock *BB) {
632 LVILatticeVal Result; // Start Undefined.
634 // If this is a pointer, and there's a load from that pointer in this BB,
635 // then we know that the pointer can't be NULL.
636 bool NotNull = false;
637 if (Val->getType()->isPointerTy()) {
638 if (isKnownNonNull(Val)) {
641 Value *UnderlyingVal = GetUnderlyingObject(Val);
642 // If 'GetUnderlyingObject' didn't converge, skip it. It won't converge
643 // inside InstructionDereferencesPointer either.
644 if (UnderlyingVal == GetUnderlyingObject(UnderlyingVal, nullptr, 1)) {
645 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
647 if (InstructionDereferencesPointer(BI, UnderlyingVal)) {
656 // If this is the entry block, we must be asking about an argument. The
657 // value is overdefined.
658 if (BB == &BB->getParent()->getEntryBlock()) {
659 assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
661 PointerType *PTy = cast<PointerType>(Val->getType());
662 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
664 Result.markOverdefined();
670 // Loop over all of our predecessors, merging what we know from them into
672 bool EdgesMissing = false;
673 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
674 LVILatticeVal EdgeResult;
675 EdgesMissing |= !getEdgeValue(Val, *PI, BB, EdgeResult);
679 Result.mergeIn(EdgeResult);
681 // If we hit overdefined, exit early. The BlockVals entry is already set
683 if (Result.isOverdefined()) {
684 DEBUG(dbgs() << " compute BB '" << BB->getName()
685 << "' - overdefined because of pred.\n");
686 // If we previously determined that this is a pointer that can't be null
687 // then return that rather than giving up entirely.
689 PointerType *PTy = cast<PointerType>(Val->getType());
690 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
700 // Return the merged value, which is more precise than 'overdefined'.
701 assert(!Result.isOverdefined());
706 bool LazyValueInfoCache::solveBlockValuePHINode(LVILatticeVal &BBLV,
707 PHINode *PN, BasicBlock *BB) {
708 LVILatticeVal Result; // Start Undefined.
710 // Loop over all of our predecessors, merging what we know from them into
712 bool EdgesMissing = false;
713 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
714 BasicBlock *PhiBB = PN->getIncomingBlock(i);
715 Value *PhiVal = PN->getIncomingValue(i);
716 LVILatticeVal EdgeResult;
717 EdgesMissing |= !getEdgeValue(PhiVal, PhiBB, BB, EdgeResult, PN);
721 Result.mergeIn(EdgeResult);
723 // If we hit overdefined, exit early. The BlockVals entry is already set
725 if (Result.isOverdefined()) {
726 DEBUG(dbgs() << " compute BB '" << BB->getName()
727 << "' - overdefined because of pred.\n");
736 // Return the merged value, which is more precise than 'overdefined'.
737 assert(!Result.isOverdefined() && "Possible PHI in entry block?");
742 static bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
743 LVILatticeVal &Result,
744 bool isTrueDest = true);
746 // If we can determine a constant range for the value Val at the context
747 // provided by the instruction BBI, then merge it into BBLV. If we did find a
748 // constant range, return true.
749 void LazyValueInfoCache::mergeAssumeBlockValueConstantRange(
750 Value *Val, LVILatticeVal &BBLV, Instruction *BBI) {
751 BBI = BBI ? BBI : dyn_cast<Instruction>(Val);
755 for (auto &I : AT->assumptions(BBI->getParent()->getParent())) {
756 if (!isValidAssumeForContext(I, BBI, DL, DT))
759 Value *C = I->getArgOperand(0);
760 if (ICmpInst *ICI = dyn_cast<ICmpInst>(C)) {
761 LVILatticeVal Result;
762 if (getValueFromFromCondition(Val, ICI, Result)) {
763 if (BBLV.isOverdefined())
766 BBLV.mergeIn(Result);
772 bool LazyValueInfoCache::solveBlockValueConstantRange(LVILatticeVal &BBLV,
775 // Figure out the range of the LHS. If that fails, bail.
776 if (!hasBlockValue(BBI->getOperand(0), BB)) {
777 BlockValueStack.push(std::make_pair(BB, BBI->getOperand(0)));
781 LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
782 mergeAssumeBlockValueConstantRange(BBI->getOperand(0), LHSVal, BBI);
783 if (!LHSVal.isConstantRange()) {
784 BBLV.markOverdefined();
788 ConstantRange LHSRange = LHSVal.getConstantRange();
789 ConstantRange RHSRange(1);
790 IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
791 if (isa<BinaryOperator>(BBI)) {
792 if (ConstantInt *RHS = dyn_cast<ConstantInt>(BBI->getOperand(1))) {
793 RHSRange = ConstantRange(RHS->getValue());
795 BBLV.markOverdefined();
800 // NOTE: We're currently limited by the set of operations that ConstantRange
801 // can evaluate symbolically. Enhancing that set will allows us to analyze
803 LVILatticeVal Result;
804 switch (BBI->getOpcode()) {
805 case Instruction::Add:
806 Result.markConstantRange(LHSRange.add(RHSRange));
808 case Instruction::Sub:
809 Result.markConstantRange(LHSRange.sub(RHSRange));
811 case Instruction::Mul:
812 Result.markConstantRange(LHSRange.multiply(RHSRange));
814 case Instruction::UDiv:
815 Result.markConstantRange(LHSRange.udiv(RHSRange));
817 case Instruction::Shl:
818 Result.markConstantRange(LHSRange.shl(RHSRange));
820 case Instruction::LShr:
821 Result.markConstantRange(LHSRange.lshr(RHSRange));
823 case Instruction::Trunc:
824 Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
826 case Instruction::SExt:
827 Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
829 case Instruction::ZExt:
830 Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
832 case Instruction::BitCast:
833 Result.markConstantRange(LHSRange);
835 case Instruction::And:
836 Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
838 case Instruction::Or:
839 Result.markConstantRange(LHSRange.binaryOr(RHSRange));
842 // Unhandled instructions are overdefined.
844 DEBUG(dbgs() << " compute BB '" << BB->getName()
845 << "' - overdefined because inst def found.\n");
846 Result.markOverdefined();
854 bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
855 LVILatticeVal &Result, bool isTrueDest) {
856 if (ICI && isa<Constant>(ICI->getOperand(1))) {
857 if (ICI->isEquality() && ICI->getOperand(0) == Val) {
858 // We know that V has the RHS constant if this is a true SETEQ or
860 if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
861 Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
863 Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
867 // Recognize the range checking idiom that InstCombine produces.
868 // (X-C1) u< C2 --> [C1, C1+C2)
869 ConstantInt *NegOffset = nullptr;
870 if (ICI->getPredicate() == ICmpInst::ICMP_ULT)
871 match(ICI->getOperand(0), m_Add(m_Specific(Val),
872 m_ConstantInt(NegOffset)));
874 ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1));
875 if (CI && (ICI->getOperand(0) == Val || NegOffset)) {
876 // Calculate the range of values that would satisfy the comparison.
877 ConstantRange CmpRange(CI->getValue());
878 ConstantRange TrueValues =
879 ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
881 if (NegOffset) // Apply the offset from above.
882 TrueValues = TrueValues.subtract(NegOffset->getValue());
884 // If we're interested in the false dest, invert the condition.
885 if (!isTrueDest) TrueValues = TrueValues.inverse();
887 Result = LVILatticeVal::getRange(TrueValues);
895 /// \brief Compute the value of Val on the edge BBFrom -> BBTo. Returns false if
896 /// Val is not constrained on the edge.
897 static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
898 BasicBlock *BBTo, LVILatticeVal &Result) {
899 // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
901 if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
902 // If this is a conditional branch and only one successor goes to BBTo, then
903 // we maybe able to infer something from the condition.
904 if (BI->isConditional() &&
905 BI->getSuccessor(0) != BI->getSuccessor(1)) {
906 bool isTrueDest = BI->getSuccessor(0) == BBTo;
907 assert(BI->getSuccessor(!isTrueDest) == BBTo &&
908 "BBTo isn't a successor of BBFrom");
910 // If V is the condition of the branch itself, then we know exactly what
912 if (BI->getCondition() == Val) {
913 Result = LVILatticeVal::get(ConstantInt::get(
914 Type::getInt1Ty(Val->getContext()), isTrueDest));
918 // If the condition of the branch is an equality comparison, we may be
919 // able to infer the value.
920 ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
921 if (getValueFromFromCondition(Val, ICI, Result, isTrueDest))
926 // If the edge was formed by a switch on the value, then we may know exactly
928 if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
929 if (SI->getCondition() != Val)
932 bool DefaultCase = SI->getDefaultDest() == BBTo;
933 unsigned BitWidth = Val->getType()->getIntegerBitWidth();
934 ConstantRange EdgesVals(BitWidth, DefaultCase/*isFullSet*/);
936 for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
938 ConstantRange EdgeVal(i.getCaseValue()->getValue());
940 // It is possible that the default destination is the destination of
941 // some cases. There is no need to perform difference for those cases.
942 if (i.getCaseSuccessor() != BBTo)
943 EdgesVals = EdgesVals.difference(EdgeVal);
944 } else if (i.getCaseSuccessor() == BBTo)
945 EdgesVals = EdgesVals.unionWith(EdgeVal);
947 Result = LVILatticeVal::getRange(EdgesVals);
953 /// \brief Compute the value of Val on the edge BBFrom -> BBTo, or the value at
954 /// the basic block if the edge does not constraint Val.
955 bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom,
956 BasicBlock *BBTo, LVILatticeVal &Result,
958 // If already a constant, there is nothing to compute.
959 if (Constant *VC = dyn_cast<Constant>(Val)) {
960 Result = LVILatticeVal::get(VC);
964 if (getEdgeValueLocal(Val, BBFrom, BBTo, Result)) {
965 if (!Result.isConstantRange() ||
966 Result.getConstantRange().getSingleElement())
969 // FIXME: this check should be moved to the beginning of the function when
970 // LVI better supports recursive values. Even for the single value case, we
971 // can intersect to detect dead code (an empty range).
972 if (!hasBlockValue(Val, BBFrom)) {
973 BlockValueStack.push(std::make_pair(BBFrom, Val));
977 // Try to intersect ranges of the BB and the constraint on the edge.
978 LVILatticeVal InBlock = getBlockValue(Val, BBFrom);
979 mergeAssumeBlockValueConstantRange(Val, InBlock, CxtI);
980 if (!InBlock.isConstantRange())
983 ConstantRange Range =
984 Result.getConstantRange().intersectWith(InBlock.getConstantRange());
985 Result = LVILatticeVal::getRange(Range);
989 if (!hasBlockValue(Val, BBFrom)) {
990 BlockValueStack.push(std::make_pair(BBFrom, Val));
994 // if we couldn't compute the value on the edge, use the value from the BB
995 Result = getBlockValue(Val, BBFrom);
996 mergeAssumeBlockValueConstantRange(Val, Result, CxtI);
1000 LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB,
1001 Instruction *CxtI) {
1002 DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
1003 << BB->getName() << "'\n");
1005 BlockValueStack.push(std::make_pair(BB, V));
1007 LVILatticeVal Result = getBlockValue(V, BB);
1008 mergeAssumeBlockValueConstantRange(V, Result, CxtI);
1010 DEBUG(dbgs() << " Result = " << Result << "\n");
1014 LVILatticeVal LazyValueInfoCache::getValueAt(Value *V, Instruction *CxtI) {
1015 DEBUG(dbgs() << "LVI Getting value " << *V << " at '"
1016 << CxtI->getName() << "'\n");
1018 LVILatticeVal Result;
1019 mergeAssumeBlockValueConstantRange(V, Result, CxtI);
1021 DEBUG(dbgs() << " Result = " << Result << "\n");
1025 LVILatticeVal LazyValueInfoCache::
1026 getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB,
1027 Instruction *CxtI) {
1028 DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
1029 << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
1031 LVILatticeVal Result;
1032 if (!getEdgeValue(V, FromBB, ToBB, Result, CxtI)) {
1034 bool WasFastQuery = getEdgeValue(V, FromBB, ToBB, Result, CxtI);
1036 assert(WasFastQuery && "More work to do after problem solved?");
1039 DEBUG(dbgs() << " Result = " << Result << "\n");
1043 void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
1044 BasicBlock *NewSucc) {
1045 // When an edge in the graph has been threaded, values that we could not
1046 // determine a value for before (i.e. were marked overdefined) may be possible
1047 // to solve now. We do NOT try to proactively update these values. Instead,
1048 // we clear their entries from the cache, and allow lazy updating to recompute
1049 // them when needed.
1051 // The updating process is fairly simple: we need to dropped cached info
1052 // for all values that were marked overdefined in OldSucc, and for those same
1053 // values in any successor of OldSucc (except NewSucc) in which they were
1054 // also marked overdefined.
1055 std::vector<BasicBlock*> worklist;
1056 worklist.push_back(OldSucc);
1058 DenseSet<Value*> ClearSet;
1059 for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
1060 E = OverDefinedCache.end(); I != E; ++I) {
1061 if (I->first == OldSucc)
1062 ClearSet.insert(I->second);
1065 // Use a worklist to perform a depth-first search of OldSucc's successors.
1066 // NOTE: We do not need a visited list since any blocks we have already
1067 // visited will have had their overdefined markers cleared already, and we
1068 // thus won't loop to their successors.
1069 while (!worklist.empty()) {
1070 BasicBlock *ToUpdate = worklist.back();
1071 worklist.pop_back();
1073 // Skip blocks only accessible through NewSucc.
1074 if (ToUpdate == NewSucc) continue;
1076 bool changed = false;
1077 for (DenseSet<Value*>::iterator I = ClearSet.begin(), E = ClearSet.end();
1079 // If a value was marked overdefined in OldSucc, and is here too...
1080 DenseSet<OverDefinedPairTy>::iterator OI =
1081 OverDefinedCache.find(std::make_pair(ToUpdate, *I));
1082 if (OI == OverDefinedCache.end()) continue;
1084 // Remove it from the caches.
1085 ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
1086 ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
1088 assert(CI != Entry.end() && "Couldn't find entry to update?");
1090 OverDefinedCache.erase(OI);
1092 // If we removed anything, then we potentially need to update
1093 // blocks successors too.
1097 if (!changed) continue;
1099 worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
1103 //===----------------------------------------------------------------------===//
1104 // LazyValueInfo Impl
1105 //===----------------------------------------------------------------------===//
1107 /// getCache - This lazily constructs the LazyValueInfoCache.
1108 static LazyValueInfoCache &getCache(void *&PImpl,
1109 AssumptionTracker *AT,
1110 const DataLayout *DL = nullptr,
1111 DominatorTree *DT = nullptr) {
1113 PImpl = new LazyValueInfoCache(AT, DL, DT);
1114 return *static_cast<LazyValueInfoCache*>(PImpl);
1117 bool LazyValueInfo::runOnFunction(Function &F) {
1118 AT = &getAnalysis<AssumptionTracker>();
1120 DominatorTreeWrapperPass *DTWP =
1121 getAnalysisIfAvailable<DominatorTreeWrapperPass>();
1122 DT = DTWP ? &DTWP->getDomTree() : nullptr;
1124 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
1125 DL = DLP ? &DLP->getDataLayout() : nullptr;
1126 TLI = &getAnalysis<TargetLibraryInfo>();
1129 getCache(PImpl, AT, DL, DT).clear();
1135 void LazyValueInfo::getAnalysisUsage(AnalysisUsage &AU) const {
1136 AU.setPreservesAll();
1137 AU.addRequired<AssumptionTracker>();
1138 AU.addRequired<TargetLibraryInfo>();
1141 void LazyValueInfo::releaseMemory() {
1142 // If the cache was allocated, free it.
1144 delete &getCache(PImpl, AT);
1149 Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB,
1150 Instruction *CxtI) {
1151 LVILatticeVal Result =
1152 getCache(PImpl, AT, DL, DT).getValueInBlock(V, BB, CxtI);
1154 if (Result.isConstant())
1155 return Result.getConstant();
1156 if (Result.isConstantRange()) {
1157 ConstantRange CR = Result.getConstantRange();
1158 if (const APInt *SingleVal = CR.getSingleElement())
1159 return ConstantInt::get(V->getContext(), *SingleVal);
1164 /// getConstantOnEdge - Determine whether the specified value is known to be a
1165 /// constant on the specified edge. Return null if not.
1166 Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
1168 Instruction *CxtI) {
1169 LVILatticeVal Result =
1170 getCache(PImpl, AT, DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);
1172 if (Result.isConstant())
1173 return Result.getConstant();
1174 if (Result.isConstantRange()) {
1175 ConstantRange CR = Result.getConstantRange();
1176 if (const APInt *SingleVal = CR.getSingleElement())
1177 return ConstantInt::get(V->getContext(), *SingleVal);
1182 static LazyValueInfo::Tristate
1183 getPredicateResult(unsigned Pred, Constant *C, LVILatticeVal &Result,
1184 const DataLayout *DL, TargetLibraryInfo *TLI) {
1186 // If we know the value is a constant, evaluate the conditional.
1187 Constant *Res = nullptr;
1188 if (Result.isConstant()) {
1189 Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, DL,
1191 if (ConstantInt *ResCI = dyn_cast<ConstantInt>(Res))
1192 return ResCI->isZero() ? LazyValueInfo::False : LazyValueInfo::True;
1193 return LazyValueInfo::Unknown;
1196 if (Result.isConstantRange()) {
1197 ConstantInt *CI = dyn_cast<ConstantInt>(C);
1198 if (!CI) return LazyValueInfo::Unknown;
1200 ConstantRange CR = Result.getConstantRange();
1201 if (Pred == ICmpInst::ICMP_EQ) {
1202 if (!CR.contains(CI->getValue()))
1203 return LazyValueInfo::False;
1205 if (CR.isSingleElement() && CR.contains(CI->getValue()))
1206 return LazyValueInfo::True;
1207 } else if (Pred == ICmpInst::ICMP_NE) {
1208 if (!CR.contains(CI->getValue()))
1209 return LazyValueInfo::True;
1211 if (CR.isSingleElement() && CR.contains(CI->getValue()))
1212 return LazyValueInfo::False;
1215 // Handle more complex predicates.
1216 ConstantRange TrueValues =
1217 ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
1218 if (TrueValues.contains(CR))
1219 return LazyValueInfo::True;
1220 if (TrueValues.inverse().contains(CR))
1221 return LazyValueInfo::False;
1222 return LazyValueInfo::Unknown;
1225 if (Result.isNotConstant()) {
1226 // If this is an equality comparison, we can try to fold it knowing that
1228 if (Pred == ICmpInst::ICMP_EQ) {
1229 // !C1 == C -> false iff C1 == C.
1230 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
1231 Result.getNotConstant(), C, DL,
1233 if (Res->isNullValue())
1234 return LazyValueInfo::False;
1235 } else if (Pred == ICmpInst::ICMP_NE) {
1236 // !C1 != C -> true iff C1 == C.
1237 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
1238 Result.getNotConstant(), C, DL,
1240 if (Res->isNullValue())
1241 return LazyValueInfo::True;
1243 return LazyValueInfo::Unknown;
1246 return LazyValueInfo::Unknown;
1249 /// getPredicateOnEdge - Determine whether the specified value comparison
1250 /// with a constant is known to be true or false on the specified CFG edge.
1251 /// Pred is a CmpInst predicate.
1252 LazyValueInfo::Tristate
1253 LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
1254 BasicBlock *FromBB, BasicBlock *ToBB,
1255 Instruction *CxtI) {
1256 LVILatticeVal Result =
1257 getCache(PImpl, AT, DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);
1259 return getPredicateResult(Pred, C, Result, DL, TLI);
1262 LazyValueInfo::Tristate
1263 LazyValueInfo::getPredicateAt(unsigned Pred, Value *V, Constant *C,
1264 Instruction *CxtI) {
1265 LVILatticeVal Result =
1266 getCache(PImpl, AT, DL, DT).getValueAt(V, CxtI);
1268 return getPredicateResult(Pred, C, Result, DL, TLI);
1271 void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
1272 BasicBlock *NewSucc) {
1273 if (PImpl) getCache(PImpl, AT, DL, DT).threadEdge(PredBB, OldSucc, NewSucc);
1276 void LazyValueInfo::eraseBlock(BasicBlock *BB) {
1277 if (PImpl) getCache(PImpl, AT, DL, DT).eraseBlock(BB);