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 #define DEBUG_TYPE "lazy-value-info"
16 #include "llvm/Analysis/LazyValueInfo.h"
17 #include "llvm/Analysis/ValueTracking.h"
18 #include "llvm/Constants.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Analysis/ConstantFolding.h"
21 #include "llvm/Target/TargetData.h"
22 #include "llvm/Support/CFG.h"
23 #include "llvm/Support/ConstantRange.h"
24 #include "llvm/Support/Debug.h"
25 #include "llvm/Support/raw_ostream.h"
26 #include "llvm/Support/ValueHandle.h"
27 #include "llvm/ADT/DenseMap.h"
28 #include "llvm/ADT/DenseSet.h"
29 #include "llvm/ADT/STLExtras.h"
35 char LazyValueInfo::ID = 0;
36 INITIALIZE_PASS(LazyValueInfo, "lazy-value-info",
37 "Lazy Value Information Analysis", false, true)
40 FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
44 //===----------------------------------------------------------------------===//
46 //===----------------------------------------------------------------------===//
48 /// LVILatticeVal - This is the information tracked by LazyValueInfo for each
51 /// FIXME: This is basically just for bringup, this can be made a lot more rich
57 /// undefined - This Value has no known value yet.
60 /// constant - This Value has a specific constant value.
62 /// notconstant - This Value is known to not have the specified value.
65 /// constantrange - The Value falls within this range.
68 /// overdefined - This value is not known to be constant, and we know that
73 /// Val: This stores the current lattice value along with the Constant* for
74 /// the constant if this is a 'constant' or 'notconstant' value.
80 LVILatticeVal() : Tag(undefined), Val(0), Range(1, true) {}
82 static LVILatticeVal get(Constant *C) {
84 if (!isa<UndefValue>(C))
88 static LVILatticeVal getNot(Constant *C) {
90 if (!isa<UndefValue>(C))
91 Res.markNotConstant(C);
94 static LVILatticeVal getRange(ConstantRange CR) {
96 Res.markConstantRange(CR);
100 bool isUndefined() const { return Tag == undefined; }
101 bool isConstant() const { return Tag == constant; }
102 bool isNotConstant() const { return Tag == notconstant; }
103 bool isConstantRange() const { return Tag == constantrange; }
104 bool isOverdefined() const { return Tag == overdefined; }
106 Constant *getConstant() const {
107 assert(isConstant() && "Cannot get the constant of a non-constant!");
111 Constant *getNotConstant() const {
112 assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
116 ConstantRange getConstantRange() const {
117 assert(isConstantRange() &&
118 "Cannot get the constant-range of a non-constant-range!");
122 /// markOverdefined - Return true if this is a change in status.
123 bool markOverdefined() {
130 /// markConstant - Return true if this is a change in status.
131 bool markConstant(Constant *V) {
132 assert(V && "Marking constant with NULL");
133 if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
134 return markConstantRange(ConstantRange(CI->getValue()));
135 if (isa<UndefValue>(V))
138 assert((!isConstant() || getConstant() == V) &&
139 "Marking constant with different value");
140 assert(isUndefined());
146 /// markNotConstant - Return true if this is a change in status.
147 bool markNotConstant(Constant *V) {
148 assert(V && "Marking constant with NULL");
149 if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
150 return markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue()));
151 if (isa<UndefValue>(V))
154 assert((!isConstant() || getConstant() != V) &&
155 "Marking constant !constant with same value");
156 assert((!isNotConstant() || getNotConstant() == V) &&
157 "Marking !constant with different value");
158 assert(isUndefined() || isConstant());
164 /// markConstantRange - Return true if this is a change in status.
165 bool markConstantRange(const ConstantRange NewR) {
166 if (isConstantRange()) {
167 if (NewR.isEmptySet())
168 return markOverdefined();
170 bool changed = Range == NewR;
175 assert(isUndefined());
176 if (NewR.isEmptySet())
177 return markOverdefined();
184 /// mergeIn - Merge the specified lattice value into this one, updating this
185 /// one and returning true if anything changed.
186 bool mergeIn(const LVILatticeVal &RHS) {
187 if (RHS.isUndefined() || isOverdefined()) return false;
188 if (RHS.isOverdefined()) return markOverdefined();
198 if (RHS.isConstant()) {
201 return markOverdefined();
204 if (RHS.isNotConstant()) {
206 return markOverdefined();
208 // Unless we can prove that the two Constants are different, we must
209 // move to overdefined.
210 // FIXME: use TargetData for smarter constant folding.
211 if (ConstantInt *Res = dyn_cast<ConstantInt>(
212 ConstantFoldCompareInstOperands(CmpInst::ICMP_NE,
214 RHS.getNotConstant())))
216 return markNotConstant(RHS.getNotConstant());
218 return markOverdefined();
221 // RHS is a ConstantRange, LHS is a non-integer Constant.
223 // FIXME: consider the case where RHS is a range [1, 0) and LHS is
224 // a function. The correct result is to pick up RHS.
226 return markOverdefined();
229 if (isNotConstant()) {
230 if (RHS.isConstant()) {
232 return markOverdefined();
234 // Unless we can prove that the two Constants are different, we must
235 // move to overdefined.
236 // FIXME: use TargetData for smarter constant folding.
237 if (ConstantInt *Res = dyn_cast<ConstantInt>(
238 ConstantFoldCompareInstOperands(CmpInst::ICMP_NE,
244 return markOverdefined();
247 if (RHS.isNotConstant()) {
250 return markOverdefined();
253 return markOverdefined();
256 assert(isConstantRange() && "New LVILattice type?");
257 if (!RHS.isConstantRange())
258 return markOverdefined();
260 ConstantRange NewR = Range.unionWith(RHS.getConstantRange());
261 if (NewR.isFullSet())
262 return markOverdefined();
263 return markConstantRange(NewR);
267 } // end anonymous namespace.
270 raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
271 if (Val.isUndefined())
272 return OS << "undefined";
273 if (Val.isOverdefined())
274 return OS << "overdefined";
276 if (Val.isNotConstant())
277 return OS << "notconstant<" << *Val.getNotConstant() << '>';
278 else if (Val.isConstantRange())
279 return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
280 << Val.getConstantRange().getUpper() << '>';
281 return OS << "constant<" << *Val.getConstant() << '>';
285 //===----------------------------------------------------------------------===//
286 // LazyValueInfoCache Decl
287 //===----------------------------------------------------------------------===//
290 /// LVIValueHandle - A callback value handle update the cache when
291 /// values are erased.
292 class LazyValueInfoCache;
293 struct LVIValueHandle : public CallbackVH {
294 LazyValueInfoCache *Parent;
296 LVIValueHandle(Value *V, LazyValueInfoCache *P)
297 : CallbackVH(V), Parent(P) { }
300 void allUsesReplacedWith(Value *V) {
308 struct DenseMapInfo<LVIValueHandle> {
309 typedef DenseMapInfo<Value*> PointerInfo;
310 static inline LVIValueHandle getEmptyKey() {
311 return LVIValueHandle(PointerInfo::getEmptyKey(),
312 static_cast<LazyValueInfoCache*>(0));
314 static inline LVIValueHandle getTombstoneKey() {
315 return LVIValueHandle(PointerInfo::getTombstoneKey(),
316 static_cast<LazyValueInfoCache*>(0));
318 static unsigned getHashValue(const LVIValueHandle &Val) {
319 return PointerInfo::getHashValue(Val);
321 static bool isEqual(const LVIValueHandle &LHS, const LVIValueHandle &RHS) {
327 struct DenseMapInfo<std::pair<AssertingVH<BasicBlock>, Value*> > {
328 typedef std::pair<AssertingVH<BasicBlock>, Value*> PairTy;
329 typedef DenseMapInfo<AssertingVH<BasicBlock> > APointerInfo;
330 typedef DenseMapInfo<Value*> BPointerInfo;
331 static inline PairTy getEmptyKey() {
332 return std::make_pair(APointerInfo::getEmptyKey(),
333 BPointerInfo::getEmptyKey());
335 static inline PairTy getTombstoneKey() {
336 return std::make_pair(APointerInfo::getTombstoneKey(),
337 BPointerInfo::getTombstoneKey());
339 static unsigned getHashValue( const PairTy &Val) {
340 return APointerInfo::getHashValue(Val.first) ^
341 BPointerInfo::getHashValue(Val.second);
343 static bool isEqual(const PairTy &LHS, const PairTy &RHS) {
344 return APointerInfo::isEqual(LHS.first, RHS.first) &&
345 BPointerInfo::isEqual(LHS.second, RHS.second);
351 /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
352 /// maintains information about queries across the clients' queries.
353 class LazyValueInfoCache {
355 /// ValueCacheEntryTy - This is all of the cached block information for
356 /// exactly one Value*. The entries are sorted by the BasicBlock* of the
357 /// entries, allowing us to do a lookup with a binary search.
358 typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
361 friend struct LVIValueHandle;
363 /// OverDefinedCacheUpdater - A helper object that ensures that the
364 /// OverDefinedCache is updated whenever solveBlockValue returns.
365 struct OverDefinedCacheUpdater {
366 LazyValueInfoCache *Parent;
371 OverDefinedCacheUpdater(Value *V, BasicBlock *B, LVILatticeVal &LV,
372 LazyValueInfoCache *P)
373 : Parent(P), Val(V), BB(B), BBLV(LV) { }
375 bool markResult(bool changed) {
376 if (changed && BBLV.isOverdefined())
377 Parent->OverDefinedCache.insert(std::make_pair(BB, Val));
382 /// ValueCache - This is all of the cached information for all values,
383 /// mapped from Value* to key information.
384 DenseMap<LVIValueHandle, ValueCacheEntryTy> ValueCache;
386 /// OverDefinedCache - This tracks, on a per-block basis, the set of
387 /// values that are over-defined at the end of that block. This is required
388 /// for cache updating.
389 typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
390 DenseSet<OverDefinedPairTy> OverDefinedCache;
392 LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
393 bool getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T,
394 LVILatticeVal &Result);
395 bool hasBlockValue(Value *Val, BasicBlock *BB);
397 // These methods process one work item and may add more. A false value
398 // returned means that the work item was not completely processed and must
399 // be revisited after going through the new items.
400 bool solveBlockValue(Value *Val, BasicBlock *BB);
401 bool solveBlockValueNonLocal(LVILatticeVal &BBLV,
402 Value *Val, BasicBlock *BB);
403 bool solveBlockValuePHINode(LVILatticeVal &BBLV,
404 PHINode *PN, BasicBlock *BB);
405 bool solveBlockValueConstantRange(LVILatticeVal &BBLV,
406 Instruction *BBI, BasicBlock *BB);
410 ValueCacheEntryTy &lookup(Value *V) {
411 return ValueCache[LVIValueHandle(V, this)];
414 std::stack<std::pair<BasicBlock*, Value*> > block_value_stack;
417 /// getValueInBlock - This is the query interface to determine the lattice
418 /// value for the specified Value* at the end of the specified block.
419 LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB);
421 /// getValueOnEdge - This is the query interface to determine the lattice
422 /// value for the specified Value* that is true on the specified edge.
423 LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB);
425 /// threadEdge - This is the update interface to inform the cache that an
426 /// edge from PredBB to OldSucc has been threaded to be from PredBB to
428 void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
430 /// eraseBlock - This is part of the update interface to inform the cache
431 /// that a block has been deleted.
432 void eraseBlock(BasicBlock *BB);
434 /// clear - Empty the cache.
437 OverDefinedCache.clear();
440 } // end anonymous namespace
442 void LVIValueHandle::deleted() {
443 typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
445 SmallVector<OverDefinedPairTy, 4> ToErase;
446 for (DenseSet<OverDefinedPairTy>::iterator
447 I = Parent->OverDefinedCache.begin(),
448 E = Parent->OverDefinedCache.end();
450 if (I->second == getValPtr())
451 ToErase.push_back(*I);
454 for (SmallVector<OverDefinedPairTy, 4>::iterator I = ToErase.begin(),
455 E = ToErase.end(); I != E; ++I)
456 Parent->OverDefinedCache.erase(*I);
458 // This erasure deallocates *this, so it MUST happen after we're done
459 // using any and all members of *this.
460 Parent->ValueCache.erase(*this);
463 void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
464 SmallVector<OverDefinedPairTy, 4> ToErase;
465 for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
466 E = OverDefinedCache.end(); I != E; ++I) {
468 ToErase.push_back(*I);
471 for (SmallVector<OverDefinedPairTy, 4>::iterator I = ToErase.begin(),
472 E = ToErase.end(); I != E; ++I)
473 OverDefinedCache.erase(*I);
475 for (DenseMap<LVIValueHandle, ValueCacheEntryTy>::iterator
476 I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
480 void LazyValueInfoCache::solve() {
481 while (!block_value_stack.empty()) {
482 std::pair<BasicBlock*, Value*> &e = block_value_stack.top();
483 if (solveBlockValue(e.second, e.first))
484 block_value_stack.pop();
488 bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
489 // If already a constant, there is nothing to compute.
490 if (isa<Constant>(Val))
493 LVIValueHandle ValHandle(Val, this);
494 if (!ValueCache.count(ValHandle)) return false;
495 return ValueCache[ValHandle].count(BB);
498 LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
499 // If already a constant, there is nothing to compute.
500 if (Constant *VC = dyn_cast<Constant>(Val))
501 return LVILatticeVal::get(VC);
503 return lookup(Val)[BB];
506 bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
507 if (isa<Constant>(Val))
510 ValueCacheEntryTy &Cache = lookup(Val);
511 LVILatticeVal &BBLV = Cache[BB];
513 // OverDefinedCacheUpdater is a helper object that will update
514 // the OverDefinedCache for us when this method exits. Make sure to
515 // call markResult on it as we exist, passing a bool to indicate if the
516 // cache needs updating, i.e. if we have solve a new value or not.
517 OverDefinedCacheUpdater ODCacheUpdater(Val, BB, BBLV, this);
519 // If we've already computed this block's value, return it.
520 if (!BBLV.isUndefined()) {
521 DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
523 // Since we're reusing a cached value here, we don't need to update the
524 // OverDefinedCahce. The cache will have been properly updated
525 // whenever the cached value was inserted.
526 ODCacheUpdater.markResult(false);
530 // Otherwise, this is the first time we're seeing this block. Reset the
531 // lattice value to overdefined, so that cycles will terminate and be
532 // conservatively correct.
533 BBLV.markOverdefined();
535 Instruction *BBI = dyn_cast<Instruction>(Val);
536 if (BBI == 0 || BBI->getParent() != BB) {
537 return ODCacheUpdater.markResult(solveBlockValueNonLocal(BBLV, Val, BB));
540 if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
541 return ODCacheUpdater.markResult(solveBlockValuePHINode(BBLV, PN, BB));
544 // We can only analyze the definitions of certain classes of instructions
545 // (integral binops and casts at the moment), so bail if this isn't one.
546 LVILatticeVal Result;
547 if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
548 !BBI->getType()->isIntegerTy()) {
549 DEBUG(dbgs() << " compute BB '" << BB->getName()
550 << "' - overdefined because inst def found.\n");
551 BBLV.markOverdefined();
552 return ODCacheUpdater.markResult(true);
555 // FIXME: We're currently limited to binops with a constant RHS. This should
557 BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
558 if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
559 DEBUG(dbgs() << " compute BB '" << BB->getName()
560 << "' - overdefined because inst def found.\n");
562 BBLV.markOverdefined();
563 return ODCacheUpdater.markResult(true);
566 return ODCacheUpdater.markResult(solveBlockValueConstantRange(BBLV, BBI, BB));
569 static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
570 if (LoadInst *L = dyn_cast<LoadInst>(I)) {
571 return L->getPointerAddressSpace() == 0 &&
572 GetUnderlyingObject(L->getPointerOperand()) ==
573 GetUnderlyingObject(Ptr);
575 if (StoreInst *S = dyn_cast<StoreInst>(I)) {
576 return S->getPointerAddressSpace() == 0 &&
577 GetUnderlyingObject(S->getPointerOperand()) ==
578 GetUnderlyingObject(Ptr);
580 // FIXME: llvm.memset, etc.
584 bool LazyValueInfoCache::solveBlockValueNonLocal(LVILatticeVal &BBLV,
585 Value *Val, BasicBlock *BB) {
586 LVILatticeVal Result; // Start Undefined.
588 // If this is a pointer, and there's a load from that pointer in this BB,
589 // then we know that the pointer can't be NULL.
590 bool NotNull = false;
591 if (Val->getType()->isPointerTy()) {
592 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){
593 if (InstructionDereferencesPointer(BI, Val)) {
600 // If this is the entry block, we must be asking about an argument. The
601 // value is overdefined.
602 if (BB == &BB->getParent()->getEntryBlock()) {
603 assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
605 const PointerType *PTy = cast<PointerType>(Val->getType());
606 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
608 Result.markOverdefined();
614 // Loop over all of our predecessors, merging what we know from them into
616 bool EdgesMissing = false;
617 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
618 LVILatticeVal EdgeResult;
619 EdgesMissing |= !getEdgeValue(Val, *PI, BB, EdgeResult);
623 Result.mergeIn(EdgeResult);
625 // If we hit overdefined, exit early. The BlockVals entry is already set
627 if (Result.isOverdefined()) {
628 DEBUG(dbgs() << " compute BB '" << BB->getName()
629 << "' - overdefined because of pred.\n");
630 // If we previously determined that this is a pointer that can't be null
631 // then return that rather than giving up entirely.
633 const PointerType *PTy = cast<PointerType>(Val->getType());
634 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
644 // Return the merged value, which is more precise than 'overdefined'.
645 assert(!Result.isOverdefined());
650 bool LazyValueInfoCache::solveBlockValuePHINode(LVILatticeVal &BBLV,
651 PHINode *PN, BasicBlock *BB) {
652 LVILatticeVal Result; // Start Undefined.
654 // Loop over all of our predecessors, merging what we know from them into
656 bool EdgesMissing = false;
657 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
658 BasicBlock *PhiBB = PN->getIncomingBlock(i);
659 Value *PhiVal = PN->getIncomingValue(i);
660 LVILatticeVal EdgeResult;
661 EdgesMissing |= !getEdgeValue(PhiVal, PhiBB, BB, EdgeResult);
665 Result.mergeIn(EdgeResult);
667 // If we hit overdefined, exit early. The BlockVals entry is already set
669 if (Result.isOverdefined()) {
670 DEBUG(dbgs() << " compute BB '" << BB->getName()
671 << "' - overdefined because of pred.\n");
680 // Return the merged value, which is more precise than 'overdefined'.
681 assert(!Result.isOverdefined() && "Possible PHI in entry block?");
686 bool LazyValueInfoCache::solveBlockValueConstantRange(LVILatticeVal &BBLV,
689 // Figure out the range of the LHS. If that fails, bail.
690 if (!hasBlockValue(BBI->getOperand(0), BB)) {
691 block_value_stack.push(std::make_pair(BB, BBI->getOperand(0)));
695 LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
696 if (!LHSVal.isConstantRange()) {
697 BBLV.markOverdefined();
701 ConstantRange LHSRange = LHSVal.getConstantRange();
702 ConstantRange RHSRange(1);
703 const IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
704 if (isa<BinaryOperator>(BBI)) {
705 if (ConstantInt *RHS = dyn_cast<ConstantInt>(BBI->getOperand(1))) {
706 RHSRange = ConstantRange(RHS->getValue());
708 BBLV.markOverdefined();
713 // NOTE: We're currently limited by the set of operations that ConstantRange
714 // can evaluate symbolically. Enhancing that set will allows us to analyze
716 LVILatticeVal Result;
717 switch (BBI->getOpcode()) {
718 case Instruction::Add:
719 Result.markConstantRange(LHSRange.add(RHSRange));
721 case Instruction::Sub:
722 Result.markConstantRange(LHSRange.sub(RHSRange));
724 case Instruction::Mul:
725 Result.markConstantRange(LHSRange.multiply(RHSRange));
727 case Instruction::UDiv:
728 Result.markConstantRange(LHSRange.udiv(RHSRange));
730 case Instruction::Shl:
731 Result.markConstantRange(LHSRange.shl(RHSRange));
733 case Instruction::LShr:
734 Result.markConstantRange(LHSRange.lshr(RHSRange));
736 case Instruction::Trunc:
737 Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
739 case Instruction::SExt:
740 Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
742 case Instruction::ZExt:
743 Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
745 case Instruction::BitCast:
746 Result.markConstantRange(LHSRange);
748 case Instruction::And:
749 Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
751 case Instruction::Or:
752 Result.markConstantRange(LHSRange.binaryOr(RHSRange));
755 // Unhandled instructions are overdefined.
757 DEBUG(dbgs() << " compute BB '" << BB->getName()
758 << "' - overdefined because inst def found.\n");
759 Result.markOverdefined();
767 /// getEdgeValue - This method attempts to infer more complex
768 bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom,
769 BasicBlock *BBTo, LVILatticeVal &Result) {
770 // If already a constant, there is nothing to compute.
771 if (Constant *VC = dyn_cast<Constant>(Val)) {
772 Result = LVILatticeVal::get(VC);
776 // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
778 if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
779 // If this is a conditional branch and only one successor goes to BBTo, then
780 // we maybe able to infer something from the condition.
781 if (BI->isConditional() &&
782 BI->getSuccessor(0) != BI->getSuccessor(1)) {
783 bool isTrueDest = BI->getSuccessor(0) == BBTo;
784 assert(BI->getSuccessor(!isTrueDest) == BBTo &&
785 "BBTo isn't a successor of BBFrom");
787 // If V is the condition of the branch itself, then we know exactly what
789 if (BI->getCondition() == Val) {
790 Result = LVILatticeVal::get(ConstantInt::get(
791 Type::getInt1Ty(Val->getContext()), isTrueDest));
795 // If the condition of the branch is an equality comparison, we may be
796 // able to infer the value.
797 ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
798 if (ICI && ICI->getOperand(0) == Val &&
799 isa<Constant>(ICI->getOperand(1))) {
800 if (ICI->isEquality()) {
801 // We know that V has the RHS constant if this is a true SETEQ or
803 if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
804 Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
806 Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
810 if (ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
811 // Calculate the range of values that would satisfy the comparison.
812 ConstantRange CmpRange(CI->getValue(), CI->getValue()+1);
813 ConstantRange TrueValues =
814 ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
816 // If we're interested in the false dest, invert the condition.
817 if (!isTrueDest) TrueValues = TrueValues.inverse();
819 // Figure out the possible values of the query BEFORE this branch.
820 LVILatticeVal InBlock = getBlockValue(Val, BBFrom);
821 if (!InBlock.isConstantRange()) {
822 Result = LVILatticeVal::getRange(TrueValues);
826 // Find all potential values that satisfy both the input and output
828 ConstantRange PossibleValues =
829 TrueValues.intersectWith(InBlock.getConstantRange());
831 Result = LVILatticeVal::getRange(PossibleValues);
838 // If the edge was formed by a switch on the value, then we may know exactly
840 if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
841 if (SI->getCondition() == Val) {
842 // We don't know anything in the default case.
843 if (SI->getDefaultDest() == BBTo) {
844 Result.markOverdefined();
848 // We only know something if there is exactly one value that goes from
850 unsigned NumEdges = 0;
851 ConstantInt *EdgeVal = 0;
852 for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
853 if (SI->getSuccessor(i) != BBTo) continue;
854 if (NumEdges++) break;
855 EdgeVal = SI->getCaseValue(i);
857 assert(EdgeVal && "Missing successor?");
859 Result = LVILatticeVal::get(EdgeVal);
865 // Otherwise see if the value is known in the block.
866 if (hasBlockValue(Val, BBFrom)) {
867 Result = getBlockValue(Val, BBFrom);
870 block_value_stack.push(std::make_pair(BBFrom, Val));
874 LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) {
875 DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
876 << BB->getName() << "'\n");
878 block_value_stack.push(std::make_pair(BB, V));
880 LVILatticeVal Result = getBlockValue(V, BB);
882 DEBUG(dbgs() << " Result = " << Result << "\n");
886 LVILatticeVal LazyValueInfoCache::
887 getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) {
888 DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
889 << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
891 LVILatticeVal Result;
892 if (!getEdgeValue(V, FromBB, ToBB, Result)) {
894 bool WasFastQuery = getEdgeValue(V, FromBB, ToBB, Result);
896 assert(WasFastQuery && "More work to do after problem solved?");
899 DEBUG(dbgs() << " Result = " << Result << "\n");
903 void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
904 BasicBlock *NewSucc) {
905 // When an edge in the graph has been threaded, values that we could not
906 // determine a value for before (i.e. were marked overdefined) may be possible
907 // to solve now. We do NOT try to proactively update these values. Instead,
908 // we clear their entries from the cache, and allow lazy updating to recompute
911 // The updating process is fairly simple: we need to dropped cached info
912 // for all values that were marked overdefined in OldSucc, and for those same
913 // values in any successor of OldSucc (except NewSucc) in which they were
914 // also marked overdefined.
915 std::vector<BasicBlock*> worklist;
916 worklist.push_back(OldSucc);
918 DenseSet<Value*> ClearSet;
919 for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
920 E = OverDefinedCache.end(); I != E; ++I) {
921 if (I->first == OldSucc)
922 ClearSet.insert(I->second);
925 // Use a worklist to perform a depth-first search of OldSucc's successors.
926 // NOTE: We do not need a visited list since any blocks we have already
927 // visited will have had their overdefined markers cleared already, and we
928 // thus won't loop to their successors.
929 while (!worklist.empty()) {
930 BasicBlock *ToUpdate = worklist.back();
933 // Skip blocks only accessible through NewSucc.
934 if (ToUpdate == NewSucc) continue;
936 bool changed = false;
937 for (DenseSet<Value*>::iterator I = ClearSet.begin(), E = ClearSet.end();
939 // If a value was marked overdefined in OldSucc, and is here too...
940 DenseSet<OverDefinedPairTy>::iterator OI =
941 OverDefinedCache.find(std::make_pair(ToUpdate, *I));
942 if (OI == OverDefinedCache.end()) continue;
944 // Remove it from the caches.
945 ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
946 ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
948 assert(CI != Entry.end() && "Couldn't find entry to update?");
950 OverDefinedCache.erase(OI);
952 // If we removed anything, then we potentially need to update
953 // blocks successors too.
957 if (!changed) continue;
959 worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
963 //===----------------------------------------------------------------------===//
964 // LazyValueInfo Impl
965 //===----------------------------------------------------------------------===//
967 /// getCache - This lazily constructs the LazyValueInfoCache.
968 static LazyValueInfoCache &getCache(void *&PImpl) {
970 PImpl = new LazyValueInfoCache();
971 return *static_cast<LazyValueInfoCache*>(PImpl);
974 bool LazyValueInfo::runOnFunction(Function &F) {
976 getCache(PImpl).clear();
978 TD = getAnalysisIfAvailable<TargetData>();
983 void LazyValueInfo::releaseMemory() {
984 // If the cache was allocated, free it.
986 delete &getCache(PImpl);
991 Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) {
992 LVILatticeVal Result = getCache(PImpl).getValueInBlock(V, BB);
994 if (Result.isConstant())
995 return Result.getConstant();
996 if (Result.isConstantRange()) {
997 ConstantRange CR = Result.getConstantRange();
998 if (const APInt *SingleVal = CR.getSingleElement())
999 return ConstantInt::get(V->getContext(), *SingleVal);
1004 /// getConstantOnEdge - Determine whether the specified value is known to be a
1005 /// constant on the specified edge. Return null if not.
1006 Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
1008 LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
1010 if (Result.isConstant())
1011 return Result.getConstant();
1012 if (Result.isConstantRange()) {
1013 ConstantRange CR = Result.getConstantRange();
1014 if (const APInt *SingleVal = CR.getSingleElement())
1015 return ConstantInt::get(V->getContext(), *SingleVal);
1020 /// getPredicateOnEdge - Determine whether the specified value comparison
1021 /// with a constant is known to be true or false on the specified CFG edge.
1022 /// Pred is a CmpInst predicate.
1023 LazyValueInfo::Tristate
1024 LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
1025 BasicBlock *FromBB, BasicBlock *ToBB) {
1026 LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
1028 // If we know the value is a constant, evaluate the conditional.
1030 if (Result.isConstant()) {
1031 Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, TD);
1032 if (ConstantInt *ResCI = dyn_cast<ConstantInt>(Res))
1033 return ResCI->isZero() ? False : True;
1037 if (Result.isConstantRange()) {
1038 ConstantInt *CI = dyn_cast<ConstantInt>(C);
1039 if (!CI) return Unknown;
1041 ConstantRange CR = Result.getConstantRange();
1042 if (Pred == ICmpInst::ICMP_EQ) {
1043 if (!CR.contains(CI->getValue()))
1046 if (CR.isSingleElement() && CR.contains(CI->getValue()))
1048 } else if (Pred == ICmpInst::ICMP_NE) {
1049 if (!CR.contains(CI->getValue()))
1052 if (CR.isSingleElement() && CR.contains(CI->getValue()))
1056 // Handle more complex predicates.
1057 ConstantRange TrueValues =
1058 ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
1059 if (TrueValues.contains(CR))
1061 if (TrueValues.inverse().contains(CR))
1066 if (Result.isNotConstant()) {
1067 // If this is an equality comparison, we can try to fold it knowing that
1069 if (Pred == ICmpInst::ICMP_EQ) {
1070 // !C1 == C -> false iff C1 == C.
1071 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
1072 Result.getNotConstant(), C, TD);
1073 if (Res->isNullValue())
1075 } else if (Pred == ICmpInst::ICMP_NE) {
1076 // !C1 != C -> true iff C1 == C.
1077 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
1078 Result.getNotConstant(), C, TD);
1079 if (Res->isNullValue())
1088 void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
1089 BasicBlock *NewSucc) {
1090 if (PImpl) getCache(PImpl).threadEdge(PredBB, OldSucc, NewSucc);
1093 void LazyValueInfo::eraseBlock(BasicBlock *BB) {
1094 if (PImpl) getCache(PImpl).eraseBlock(BB);