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/Constants.h"
18 #include "llvm/Instructions.h"
19 #include "llvm/Analysis/ConstantFolding.h"
20 #include "llvm/Target/TargetData.h"
21 #include "llvm/Support/CFG.h"
22 #include "llvm/Support/ConstantRange.h"
23 #include "llvm/Support/Debug.h"
24 #include "llvm/Support/raw_ostream.h"
25 #include "llvm/Support/ValueHandle.h"
26 #include "llvm/ADT/DenseMap.h"
27 #include "llvm/ADT/DenseSet.h"
28 #include "llvm/ADT/STLExtras.h"
31 char LazyValueInfo::ID = 0;
32 INITIALIZE_PASS(LazyValueInfo, "lazy-value-info",
33 "Lazy Value Information Analysis", false, true);
36 FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
40 //===----------------------------------------------------------------------===//
42 //===----------------------------------------------------------------------===//
44 /// LVILatticeVal - This is the information tracked by LazyValueInfo for each
47 /// FIXME: This is basically just for bringup, this can be made a lot more rich
53 /// undefined - This LLVM Value has no known value yet.
56 /// constant - This LLVM Value has a specific constant value.
58 /// notconstant - This LLVM value is known to not have the specified value.
64 /// overdefined - This instruction is not known to be constant, and we know
69 /// Val: This stores the current lattice value along with the Constant* for
70 /// the constant if this is a 'constant' or 'notconstant' value.
76 LVILatticeVal() : Tag(undefined), Val(0), Range(1, true) {}
78 static LVILatticeVal get(Constant *C) {
80 if (ConstantInt *CI = dyn_cast<ConstantInt>(C))
81 Res.markConstantRange(ConstantRange(CI->getValue(), CI->getValue()+1));
82 else if (!isa<UndefValue>(C))
86 static LVILatticeVal getNot(Constant *C) {
88 if (ConstantInt *CI = dyn_cast<ConstantInt>(C))
89 Res.markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue()));
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) {
133 assert(getConstant() == V && "Marking constant with different value");
137 assert(isUndefined());
139 assert(V && "Marking constant with NULL");
144 /// markNotConstant - Return true if this is a change in status.
145 bool markNotConstant(Constant *V) {
146 if (isNotConstant()) {
147 assert(getNotConstant() == V && "Marking !constant with different value");
152 assert(getConstant() != V && "Marking not constant with different value");
154 assert(isUndefined());
157 assert(V && "Marking constant with NULL");
162 /// markConstantRange - Return true if this is a change in status.
163 bool markConstantRange(const ConstantRange NewR) {
164 if (isConstantRange()) {
165 if (NewR.isEmptySet())
166 return markOverdefined();
168 bool changed = Range == NewR;
173 assert(isUndefined());
174 if (NewR.isEmptySet())
175 return markOverdefined();
176 else if (NewR.isFullSet()) {
186 /// mergeIn - Merge the specified lattice value into this one, updating this
187 /// one and returning true if anything changed.
188 bool mergeIn(const LVILatticeVal &RHS) {
189 if (RHS.isUndefined() || isOverdefined()) return false;
190 if (RHS.isOverdefined()) return markOverdefined();
192 if (RHS.isNotConstant()) {
193 if (isNotConstant()) {
194 if (getNotConstant() != RHS.getNotConstant() ||
195 isa<ConstantExpr>(getNotConstant()) ||
196 isa<ConstantExpr>(RHS.getNotConstant()))
197 return markOverdefined();
201 if (getConstant() == RHS.getNotConstant() ||
202 isa<ConstantExpr>(RHS.getNotConstant()) ||
203 isa<ConstantExpr>(getConstant()))
204 return markOverdefined();
205 return markNotConstant(RHS.getNotConstant());
208 assert(isUndefined() && "Unexpected lattice");
209 return markNotConstant(RHS.getNotConstant());
212 if (RHS.isConstantRange()) {
213 if (isConstantRange()) {
214 ConstantRange NewR = Range.unionWith(RHS.getConstantRange());
215 if (NewR.isFullSet())
216 return markOverdefined();
218 return markConstantRange(NewR);
221 assert(isUndefined() && "Unexpected lattice");
222 return markConstantRange(RHS.getConstantRange());
225 // RHS must be a constant, we must be undef, constant, or notconstant.
226 assert(!isConstantRange() &&
227 "Constant and ConstantRange cannot be merged.");
230 return markConstant(RHS.getConstant());
233 if (getConstant() != RHS.getConstant())
234 return markOverdefined();
238 // If we are known "!=4" and RHS is "==5", stay at "!=4".
239 if (getNotConstant() == RHS.getConstant() ||
240 isa<ConstantExpr>(getNotConstant()) ||
241 isa<ConstantExpr>(RHS.getConstant()))
242 return markOverdefined();
248 } // end anonymous namespace.
251 raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
252 if (Val.isUndefined())
253 return OS << "undefined";
254 if (Val.isOverdefined())
255 return OS << "overdefined";
257 if (Val.isNotConstant())
258 return OS << "notconstant<" << *Val.getNotConstant() << '>';
259 else if (Val.isConstantRange())
260 return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
261 << Val.getConstantRange().getUpper() << '>';
262 return OS << "constant<" << *Val.getConstant() << '>';
266 //===----------------------------------------------------------------------===//
267 // LazyValueInfoCache Decl
268 //===----------------------------------------------------------------------===//
271 /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
272 /// maintains information about queries across the clients' queries.
273 class LazyValueInfoCache {
275 /// BlockCacheEntryTy - This is a computed lattice value at the end of the
276 /// specified basic block for a Value* that depends on context.
277 typedef std::pair<AssertingVH<BasicBlock>, LVILatticeVal> BlockCacheEntryTy;
279 /// ValueCacheEntryTy - This is all of the cached block information for
280 /// exactly one Value*. The entries are sorted by the BasicBlock* of the
281 /// entries, allowing us to do a lookup with a binary search.
282 typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
285 /// LVIValueHandle - A callback value handle update the cache when
286 /// values are erased.
287 struct LVIValueHandle : public CallbackVH {
288 LazyValueInfoCache *Parent;
290 LVIValueHandle(Value *V, LazyValueInfoCache *P)
291 : CallbackVH(V), Parent(P) { }
294 void allUsesReplacedWith(Value* V) {
298 LVIValueHandle &operator=(Value *V) {
299 return *this = LVIValueHandle(V, Parent);
303 /// ValueCache - This is all of the cached information for all values,
304 /// mapped from Value* to key information.
305 std::map<LVIValueHandle, ValueCacheEntryTy> ValueCache;
307 /// OverDefinedCache - This tracks, on a per-block basis, the set of
308 /// values that are over-defined at the end of that block. This is required
309 /// for cache updating.
310 std::set<std::pair<AssertingVH<BasicBlock>, Value*> > OverDefinedCache;
314 /// getValueInBlock - This is the query interface to determine the lattice
315 /// value for the specified Value* at the end of the specified block.
316 LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB);
318 /// getValueOnEdge - This is the query interface to determine the lattice
319 /// value for the specified Value* that is true on the specified edge.
320 LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB);
322 /// threadEdge - This is the update interface to inform the cache that an
323 /// edge from PredBB to OldSucc has been threaded to be from PredBB to
325 void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
327 /// eraseBlock - This is part of the update interface to inform the cache
328 /// that a block has been deleted.
329 void eraseBlock(BasicBlock *BB);
331 /// clear - Empty the cache.
334 OverDefinedCache.clear();
337 } // end anonymous namespace
339 //===----------------------------------------------------------------------===//
341 //===----------------------------------------------------------------------===//
344 /// LVIQuery - This is a transient object that exists while a query is
347 /// TODO: Reuse LVIQuery instead of recreating it for every query, this avoids
348 /// reallocation of the densemap on every query.
350 typedef LazyValueInfoCache::BlockCacheEntryTy BlockCacheEntryTy;
351 typedef LazyValueInfoCache::ValueCacheEntryTy ValueCacheEntryTy;
353 /// This is the current value being queried for.
356 /// This is a pointer to the owning cache, for recursive queries.
357 LazyValueInfoCache &Parent;
359 /// This is all of the cached information about this value.
360 ValueCacheEntryTy &Cache;
362 /// This tracks, for each block, what values are overdefined.
363 std::set<std::pair<AssertingVH<BasicBlock>, Value*> > &OverDefinedCache;
365 /// NewBlocks - This is a mapping of the new BasicBlocks which have been
366 /// added to cache but that are not in sorted order.
367 DenseSet<BasicBlock*> NewBlockInfo;
370 LVIQuery(Value *V, LazyValueInfoCache &P,
371 ValueCacheEntryTy &VC,
372 std::set<std::pair<AssertingVH<BasicBlock>, Value*> > &ODC)
373 : Val(V), Parent(P), Cache(VC), OverDefinedCache(ODC) {
377 // When the query is done, insert the newly discovered facts into the
378 // cache in sorted order.
379 if (NewBlockInfo.empty()) return;
381 for (DenseSet<BasicBlock*>::iterator I = NewBlockInfo.begin(),
382 E = NewBlockInfo.end(); I != E; ++I) {
383 if (Cache[*I].isOverdefined())
384 OverDefinedCache.insert(std::make_pair(*I, Val));
388 LVILatticeVal getBlockValue(BasicBlock *BB);
389 LVILatticeVal getEdgeValue(BasicBlock *FromBB, BasicBlock *ToBB);
392 LVILatticeVal getCachedEntryForBlock(BasicBlock *BB);
394 } // end anonymous namespace
396 void LazyValueInfoCache::LVIValueHandle::deleted() {
397 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
398 I = Parent->OverDefinedCache.begin(),
399 E = Parent->OverDefinedCache.end();
401 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator tmp = I;
403 if (tmp->second == getValPtr())
404 Parent->OverDefinedCache.erase(tmp);
407 // This erasure deallocates *this, so it MUST happen after we're done
408 // using any and all members of *this.
409 Parent->ValueCache.erase(*this);
412 void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
413 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
414 I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ) {
415 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator tmp = I;
417 if (tmp->first == BB)
418 OverDefinedCache.erase(tmp);
421 for (std::map<LVIValueHandle, ValueCacheEntryTy>::iterator
422 I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
426 /// getCachedEntryForBlock - See if we already have a value for this block. If
427 /// so, return it, otherwise create a new entry in the Cache map to use.
428 LVILatticeVal LVIQuery::getCachedEntryForBlock(BasicBlock *BB) {
429 NewBlockInfo.insert(BB);
433 LVILatticeVal LVIQuery::getBlockValue(BasicBlock *BB) {
434 // See if we already have a value for this block.
435 LVILatticeVal BBLV = getCachedEntryForBlock(BB);
437 // If we've already computed this block's value, return it.
438 if (!BBLV.isUndefined()) {
439 DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
443 // Otherwise, this is the first time we're seeing this block. Reset the
444 // lattice value to overdefined, so that cycles will terminate and be
445 // conservatively correct.
446 BBLV.markOverdefined();
449 // If V is live into BB, see if our predecessors know anything about it.
450 Instruction *BBI = dyn_cast<Instruction>(Val);
451 if (BBI == 0 || BBI->getParent() != BB) {
452 LVILatticeVal Result; // Start Undefined.
453 unsigned NumPreds = 0;
455 // Loop over all of our predecessors, merging what we know from them into
457 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
458 Result.mergeIn(getEdgeValue(*PI, BB));
460 // If we hit overdefined, exit early. The BlockVals entry is already set
462 if (Result.isOverdefined()) {
463 DEBUG(dbgs() << " compute BB '" << BB->getName()
464 << "' - overdefined because of pred.\n");
470 // If this is the entry block, we must be asking about an argument. The
471 // value is overdefined.
472 if (NumPreds == 0 && BB == &BB->getParent()->front()) {
473 assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
474 Result.markOverdefined();
478 // Return the merged value, which is more precise than 'overdefined'.
479 assert(!Result.isOverdefined());
480 return Cache[BB] = Result;
483 // If this value is defined by an instruction in this block, we have to
484 // process it here somehow or return overdefined.
485 if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
486 LVILatticeVal Result; // Start Undefined.
488 // Loop over all of our predecessors, merging what we know from them into
490 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
491 Value* PhiVal = PN->getIncomingValueForBlock(*PI);
492 Result.mergeIn(Parent.getValueOnEdge(PhiVal, *PI, BB));
494 // If we hit overdefined, exit early. The BlockVals entry is already set
496 if (Result.isOverdefined()) {
497 DEBUG(dbgs() << " compute BB '" << BB->getName()
498 << "' - overdefined because of pred.\n");
503 // Return the merged value, which is more precise than 'overdefined'.
504 assert(!Result.isOverdefined());
505 return Cache[BB] = Result;
508 assert(Cache[BB].isOverdefined() && "Recursive query changed our cache?");
510 // We can only analyze the definitions of certain classes of instructions
511 // (integral binops and casts at the moment), so bail if this isn't one.
512 LVILatticeVal Result;
513 if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
514 !BBI->getType()->isIntegerTy()) {
515 DEBUG(dbgs() << " compute BB '" << BB->getName()
516 << "' - overdefined because inst def found.\n");
517 Result.markOverdefined();
521 // FIXME: We're currently limited to binops with a constant RHS. This should
523 BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
524 if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
525 DEBUG(dbgs() << " compute BB '" << BB->getName()
526 << "' - overdefined because inst def found.\n");
528 Result.markOverdefined();
532 // Figure out the range of the LHS. If that fails, bail.
533 LVILatticeVal LHSVal = Parent.getValueInBlock(BBI->getOperand(0), BB);
534 if (!LHSVal.isConstantRange()) {
535 Result.markOverdefined();
539 ConstantInt *RHS = 0;
540 ConstantRange LHSRange = LHSVal.getConstantRange();
541 ConstantRange RHSRange(1);
542 const IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
543 if (isa<BinaryOperator>(BBI)) {
544 RHS = cast<ConstantInt>(BBI->getOperand(1));
545 RHSRange = ConstantRange(RHS->getValue(), RHS->getValue()+1);
548 // NOTE: We're currently limited by the set of operations that ConstantRange
549 // can evaluate symbolically. Enhancing that set will allows us to analyze
551 switch (BBI->getOpcode()) {
552 case Instruction::Add:
553 Result.markConstantRange(LHSRange.add(RHSRange));
555 case Instruction::Sub:
556 Result.markConstantRange(LHSRange.sub(RHSRange));
558 case Instruction::Mul:
559 Result.markConstantRange(LHSRange.multiply(RHSRange));
561 case Instruction::UDiv:
562 Result.markConstantRange(LHSRange.udiv(RHSRange));
564 case Instruction::Shl:
565 Result.markConstantRange(LHSRange.shl(RHSRange));
567 case Instruction::LShr:
568 Result.markConstantRange(LHSRange.lshr(RHSRange));
570 case Instruction::Trunc:
571 Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
573 case Instruction::SExt:
574 Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
576 case Instruction::ZExt:
577 Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
579 case Instruction::BitCast:
580 Result.markConstantRange(LHSRange);
583 // Unhandled instructions are overdefined.
585 DEBUG(dbgs() << " compute BB '" << BB->getName()
586 << "' - overdefined because inst def found.\n");
587 Result.markOverdefined();
591 return Cache[BB] = Result;
595 /// getEdgeValue - This method attempts to infer more complex
596 LVILatticeVal LVIQuery::getEdgeValue(BasicBlock *BBFrom, BasicBlock *BBTo) {
597 // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
599 if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
600 // If this is a conditional branch and only one successor goes to BBTo, then
601 // we maybe able to infer something from the condition.
602 if (BI->isConditional() &&
603 BI->getSuccessor(0) != BI->getSuccessor(1)) {
604 bool isTrueDest = BI->getSuccessor(0) == BBTo;
605 assert(BI->getSuccessor(!isTrueDest) == BBTo &&
606 "BBTo isn't a successor of BBFrom");
608 // If V is the condition of the branch itself, then we know exactly what
610 if (BI->getCondition() == Val)
611 return LVILatticeVal::get(ConstantInt::get(
612 Type::getInt1Ty(Val->getContext()), isTrueDest));
614 // If the condition of the branch is an equality comparison, we may be
615 // able to infer the value.
616 ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
617 if (ICI && ICI->getOperand(0) == Val &&
618 isa<Constant>(ICI->getOperand(1))) {
619 if (ICI->isEquality()) {
620 // We know that V has the RHS constant if this is a true SETEQ or
622 if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
623 return LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
624 return LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
627 if (ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
628 // Calculate the range of values that would satisfy the comparison.
629 ConstantRange CmpRange(CI->getValue(), CI->getValue()+1);
630 ConstantRange TrueValues =
631 ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
633 // If we're interested in the false dest, invert the condition.
634 if (!isTrueDest) TrueValues = TrueValues.inverse();
636 // Figure out the possible values of the query BEFORE this branch.
637 LVILatticeVal InBlock = getBlockValue(BBFrom);
638 if (!InBlock.isConstantRange()) return InBlock;
640 // Find all potential values that satisfy both the input and output
642 ConstantRange PossibleValues =
643 TrueValues.intersectWith(InBlock.getConstantRange());
645 return LVILatticeVal::getRange(PossibleValues);
651 // If the edge was formed by a switch on the value, then we may know exactly
653 if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
654 // If BBTo is the default destination of the switch, we don't know anything.
655 // Given a more powerful range analysis we could know stuff.
656 if (SI->getCondition() == Val && SI->getDefaultDest() != BBTo) {
657 // We only know something if there is exactly one value that goes from
659 unsigned NumEdges = 0;
660 ConstantInt *EdgeVal = 0;
661 for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
662 if (SI->getSuccessor(i) != BBTo) continue;
663 if (NumEdges++) break;
664 EdgeVal = SI->getCaseValue(i);
666 assert(EdgeVal && "Missing successor?");
668 return LVILatticeVal::get(EdgeVal);
672 // Otherwise see if the value is known in the block.
673 return getBlockValue(BBFrom);
677 //===----------------------------------------------------------------------===//
678 // LazyValueInfoCache Impl
679 //===----------------------------------------------------------------------===//
681 LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) {
682 // If already a constant, there is nothing to compute.
683 if (Constant *VC = dyn_cast<Constant>(V))
684 return LVILatticeVal::get(VC);
686 DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
687 << BB->getName() << "'\n");
689 LVILatticeVal Result = LVIQuery(V, *this,
690 ValueCache[LVIValueHandle(V, this)],
691 OverDefinedCache).getBlockValue(BB);
693 DEBUG(dbgs() << " Result = " << Result << "\n");
697 LVILatticeVal LazyValueInfoCache::
698 getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) {
699 // If already a constant, there is nothing to compute.
700 if (Constant *VC = dyn_cast<Constant>(V))
701 return LVILatticeVal::get(VC);
703 DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
704 << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
706 LVILatticeVal Result =
707 LVIQuery(V, *this, ValueCache[LVIValueHandle(V, this)],
708 OverDefinedCache).getEdgeValue(FromBB, ToBB);
710 DEBUG(dbgs() << " Result = " << Result << "\n");
715 void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
716 BasicBlock *NewSucc) {
717 // When an edge in the graph has been threaded, values that we could not
718 // determine a value for before (i.e. were marked overdefined) may be possible
719 // to solve now. We do NOT try to proactively update these values. Instead,
720 // we clear their entries from the cache, and allow lazy updating to recompute
723 // The updating process is fairly simple: we need to dropped cached info
724 // for all values that were marked overdefined in OldSucc, and for those same
725 // values in any successor of OldSucc (except NewSucc) in which they were
726 // also marked overdefined.
727 std::vector<BasicBlock*> worklist;
728 worklist.push_back(OldSucc);
730 DenseSet<Value*> ClearSet;
731 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
732 I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ++I) {
733 if (I->first == OldSucc)
734 ClearSet.insert(I->second);
737 // Use a worklist to perform a depth-first search of OldSucc's successors.
738 // NOTE: We do not need a visited list since any blocks we have already
739 // visited will have had their overdefined markers cleared already, and we
740 // thus won't loop to their successors.
741 while (!worklist.empty()) {
742 BasicBlock *ToUpdate = worklist.back();
745 // Skip blocks only accessible through NewSucc.
746 if (ToUpdate == NewSucc) continue;
748 bool changed = false;
749 for (DenseSet<Value*>::iterator I = ClearSet.begin(),E = ClearSet.end();
751 // If a value was marked overdefined in OldSucc, and is here too...
752 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator OI =
753 OverDefinedCache.find(std::make_pair(ToUpdate, *I));
754 if (OI == OverDefinedCache.end()) continue;
756 // Remove it from the caches.
757 ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
758 ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
760 assert(CI != Entry.end() && "Couldn't find entry to update?");
762 OverDefinedCache.erase(OI);
764 // If we removed anything, then we potentially need to update
765 // blocks successors too.
769 if (!changed) continue;
771 worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
775 //===----------------------------------------------------------------------===//
776 // LazyValueInfo Impl
777 //===----------------------------------------------------------------------===//
779 /// getCache - This lazily constructs the LazyValueInfoCache.
780 static LazyValueInfoCache &getCache(void *&PImpl) {
782 PImpl = new LazyValueInfoCache();
783 return *static_cast<LazyValueInfoCache*>(PImpl);
786 bool LazyValueInfo::runOnFunction(Function &F) {
788 getCache(PImpl).clear();
790 TD = getAnalysisIfAvailable<TargetData>();
795 void LazyValueInfo::releaseMemory() {
796 // If the cache was allocated, free it.
798 delete &getCache(PImpl);
803 Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) {
804 LVILatticeVal Result = getCache(PImpl).getValueInBlock(V, BB);
806 if (Result.isConstant())
807 return Result.getConstant();
811 /// getConstantOnEdge - Determine whether the specified value is known to be a
812 /// constant on the specified edge. Return null if not.
813 Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
815 LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
817 if (Result.isConstant())
818 return Result.getConstant();
819 else if (Result.isConstantRange()) {
820 ConstantRange CR = Result.getConstantRange();
821 if (const APInt *SingleVal = CR.getSingleElement())
822 return ConstantInt::get(V->getContext(), *SingleVal);
827 /// getPredicateOnEdge - Determine whether the specified value comparison
828 /// with a constant is known to be true or false on the specified CFG edge.
829 /// Pred is a CmpInst predicate.
830 LazyValueInfo::Tristate
831 LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
832 BasicBlock *FromBB, BasicBlock *ToBB) {
833 LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
835 // If we know the value is a constant, evaluate the conditional.
837 if (Result.isConstant()) {
838 Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, TD);
839 if (ConstantInt *ResCI = dyn_cast_or_null<ConstantInt>(Res))
840 return ResCI->isZero() ? False : True;
844 if (Result.isConstantRange()) {
845 ConstantInt *CI = cast<ConstantInt>(C);
846 ConstantRange CR = Result.getConstantRange();
847 if (Pred == ICmpInst::ICMP_EQ) {
848 if (!CR.contains(CI->getValue()))
851 if (CR.isSingleElement() && CR.contains(CI->getValue()))
853 } else if (Pred == ICmpInst::ICMP_NE) {
854 if (!CR.contains(CI->getValue()))
857 if (CR.isSingleElement() && CR.contains(CI->getValue()))
861 // Handle more complex predicates.
862 ConstantRange RHS(CI->getValue(), CI->getValue()+1);
863 ConstantRange TrueValues = ConstantRange::makeICmpRegion(Pred, RHS);
864 if (CR.intersectWith(TrueValues).isEmptySet())
866 else if (TrueValues.contains(CR))
872 if (Result.isNotConstant()) {
873 // If this is an equality comparison, we can try to fold it knowing that
875 if (Pred == ICmpInst::ICMP_EQ) {
876 // !C1 == C -> false iff C1 == C.
877 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
878 Result.getNotConstant(), C, TD);
879 if (Res->isNullValue())
881 } else if (Pred == ICmpInst::ICMP_NE) {
882 // !C1 != C -> true iff C1 == C.
883 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
884 Result.getNotConstant(), C, TD);
885 if (Res->isNullValue())
894 void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
895 BasicBlock* NewSucc) {
896 if (PImpl) getCache(PImpl).threadEdge(PredBB, OldSucc, NewSucc);
899 void LazyValueInfo::eraseBlock(BasicBlock *BB) {
900 if (PImpl) getCache(PImpl).eraseBlock(BB);