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();
182 /// mergeIn - Merge the specified lattice value into this one, updating this
183 /// one and returning true if anything changed.
184 bool mergeIn(const LVILatticeVal &RHS) {
185 if (RHS.isUndefined() || isOverdefined()) return false;
186 if (RHS.isOverdefined()) return markOverdefined();
188 if (RHS.isNotConstant()) {
189 if (isNotConstant()) {
190 if (getNotConstant() != RHS.getNotConstant() ||
191 isa<ConstantExpr>(getNotConstant()) ||
192 isa<ConstantExpr>(RHS.getNotConstant()))
193 return markOverdefined();
195 } else if (isConstant()) {
196 if (getConstant() == RHS.getNotConstant() ||
197 isa<ConstantExpr>(RHS.getNotConstant()) ||
198 isa<ConstantExpr>(getConstant()))
199 return markOverdefined();
200 return markNotConstant(RHS.getNotConstant());
201 } else if (isConstantRange()) {
202 return markOverdefined();
205 assert(isUndefined() && "Unexpected lattice");
206 return markNotConstant(RHS.getNotConstant());
209 if (RHS.isConstantRange()) {
210 if (isConstantRange()) {
211 ConstantRange NewR = Range.unionWith(RHS.getConstantRange());
212 if (NewR.isFullSet())
213 return markOverdefined();
215 return markConstantRange(NewR);
216 } else if (!isUndefined()) {
217 return markOverdefined();
220 assert(isUndefined() && "Unexpected lattice");
221 return markConstantRange(RHS.getConstantRange());
224 // RHS must be a constant, we must be undef, constant, or notconstant.
225 assert(!isConstantRange() &&
226 "Constant and ConstantRange cannot be merged.");
229 return markConstant(RHS.getConstant());
232 if (getConstant() != RHS.getConstant())
233 return markOverdefined();
237 // If we are known "!=4" and RHS is "==5", stay at "!=4".
238 if (getNotConstant() == RHS.getConstant() ||
239 isa<ConstantExpr>(getNotConstant()) ||
240 isa<ConstantExpr>(RHS.getConstant()))
241 return markOverdefined();
247 } // end anonymous namespace.
250 raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
251 if (Val.isUndefined())
252 return OS << "undefined";
253 if (Val.isOverdefined())
254 return OS << "overdefined";
256 if (Val.isNotConstant())
257 return OS << "notconstant<" << *Val.getNotConstant() << '>';
258 else if (Val.isConstantRange())
259 return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
260 << Val.getConstantRange().getUpper() << '>';
261 return OS << "constant<" << *Val.getConstant() << '>';
265 //===----------------------------------------------------------------------===//
266 // LazyValueInfoCache Decl
267 //===----------------------------------------------------------------------===//
270 /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
271 /// maintains information about queries across the clients' queries.
272 class LazyValueInfoCache {
274 /// BlockCacheEntryTy - This is a computed lattice value at the end of the
275 /// specified basic block for a Value* that depends on context.
276 typedef std::pair<AssertingVH<BasicBlock>, LVILatticeVal> BlockCacheEntryTy;
278 /// ValueCacheEntryTy - This is all of the cached block information for
279 /// exactly one Value*. The entries are sorted by the BasicBlock* of the
280 /// entries, allowing us to do a lookup with a binary search.
281 typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
284 /// LVIValueHandle - A callback value handle update the cache when
285 /// values are erased.
286 struct LVIValueHandle : public CallbackVH {
287 LazyValueInfoCache *Parent;
289 LVIValueHandle(Value *V, LazyValueInfoCache *P)
290 : CallbackVH(V), Parent(P) { }
293 void allUsesReplacedWith(Value* V) {
298 /// ValueCache - This is all of the cached information for all values,
299 /// mapped from Value* to key information.
300 std::map<LVIValueHandle, ValueCacheEntryTy> ValueCache;
302 /// OverDefinedCache - This tracks, on a per-block basis, the set of
303 /// values that are over-defined at the end of that block. This is required
304 /// for cache updating.
305 std::set<std::pair<AssertingVH<BasicBlock>, Value*> > OverDefinedCache;
309 /// getValueInBlock - This is the query interface to determine the lattice
310 /// value for the specified Value* at the end of the specified block.
311 LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB);
313 /// getValueOnEdge - This is the query interface to determine the lattice
314 /// value for the specified Value* that is true on the specified edge.
315 LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB);
317 /// threadEdge - This is the update interface to inform the cache that an
318 /// edge from PredBB to OldSucc has been threaded to be from PredBB to
320 void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
322 /// eraseBlock - This is part of the update interface to inform the cache
323 /// that a block has been deleted.
324 void eraseBlock(BasicBlock *BB);
326 /// clear - Empty the cache.
329 OverDefinedCache.clear();
332 } // end anonymous namespace
334 //===----------------------------------------------------------------------===//
336 //===----------------------------------------------------------------------===//
339 /// LVIQuery - This is a transient object that exists while a query is
342 /// TODO: Reuse LVIQuery instead of recreating it for every query, this avoids
343 /// reallocation of the densemap on every query.
345 typedef LazyValueInfoCache::BlockCacheEntryTy BlockCacheEntryTy;
346 typedef LazyValueInfoCache::ValueCacheEntryTy ValueCacheEntryTy;
348 /// This is the current value being queried for.
351 /// This is a pointer to the owning cache, for recursive queries.
352 LazyValueInfoCache &Parent;
354 /// This is all of the cached information about this value.
355 ValueCacheEntryTy &Cache;
357 /// This tracks, for each block, what values are overdefined.
358 std::set<std::pair<AssertingVH<BasicBlock>, Value*> > &OverDefinedCache;
360 /// NewBlocks - This is a mapping of the new BasicBlocks which have been
361 /// added to cache but that are not in sorted order.
362 DenseSet<BasicBlock*> NewBlockInfo;
366 LVIQuery(Value *V, LazyValueInfoCache &P,
367 ValueCacheEntryTy &VC,
368 std::set<std::pair<AssertingVH<BasicBlock>, Value*> > &ODC)
369 : Val(V), Parent(P), Cache(VC), OverDefinedCache(ODC) {
373 // When the query is done, insert the newly discovered facts into the
374 // cache in sorted order.
375 if (NewBlockInfo.empty()) return;
377 for (DenseSet<BasicBlock*>::iterator I = NewBlockInfo.begin(),
378 E = NewBlockInfo.end(); I != E; ++I) {
379 if (Cache[*I].isOverdefined())
380 OverDefinedCache.insert(std::make_pair(*I, Val));
384 LVILatticeVal getBlockValue(BasicBlock *BB);
385 LVILatticeVal getEdgeValue(BasicBlock *FromBB, BasicBlock *ToBB);
388 LVILatticeVal getCachedEntryForBlock(BasicBlock *BB);
390 } // end anonymous namespace
392 void LazyValueInfoCache::LVIValueHandle::deleted() {
393 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
394 I = Parent->OverDefinedCache.begin(),
395 E = Parent->OverDefinedCache.end();
397 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator tmp = I;
399 if (tmp->second == getValPtr())
400 Parent->OverDefinedCache.erase(tmp);
403 // This erasure deallocates *this, so it MUST happen after we're done
404 // using any and all members of *this.
405 Parent->ValueCache.erase(*this);
408 void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
409 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
410 I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ) {
411 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator tmp = I;
413 if (tmp->first == BB)
414 OverDefinedCache.erase(tmp);
417 for (std::map<LVIValueHandle, ValueCacheEntryTy>::iterator
418 I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
422 /// getCachedEntryForBlock - See if we already have a value for this block. If
423 /// so, return it, otherwise create a new entry in the Cache map to use.
424 LVILatticeVal LVIQuery::getCachedEntryForBlock(BasicBlock *BB) {
425 NewBlockInfo.insert(BB);
429 LVILatticeVal LVIQuery::getBlockValue(BasicBlock *BB) {
430 // See if we already have a value for this block.
431 LVILatticeVal BBLV = getCachedEntryForBlock(BB);
433 // If we've already computed this block's value, return it.
434 if (!BBLV.isUndefined()) {
435 DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
439 // Otherwise, this is the first time we're seeing this block. Reset the
440 // lattice value to overdefined, so that cycles will terminate and be
441 // conservatively correct.
442 BBLV.markOverdefined();
445 Instruction *BBI = dyn_cast<Instruction>(Val);
446 if (BBI == 0 || BBI->getParent() != BB) {
447 LVILatticeVal Result; // Start Undefined.
449 // If this is a pointer, and there's a load from that pointer in this BB,
450 // then we know that the pointer can't be NULL.
451 bool NotNull = false;
452 if (Val->getType()->isPointerTy()) {
453 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){
454 LoadInst *L = dyn_cast<LoadInst>(BI);
455 if (L && L->getPointerAddressSpace() == 0 &&
456 L->getPointerOperand()->getUnderlyingObject() ==
457 Val->getUnderlyingObject()) {
464 unsigned NumPreds = 0;
465 // Loop over all of our predecessors, merging what we know from them into
467 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
468 Result.mergeIn(getEdgeValue(*PI, BB));
470 // If we hit overdefined, exit early. The BlockVals entry is already set
472 if (Result.isOverdefined()) {
473 DEBUG(dbgs() << " compute BB '" << BB->getName()
474 << "' - overdefined because of pred.\n");
475 // If we previously determined that this is a pointer that can't be null
476 // then return that rather than giving up entirely.
478 const PointerType *PTy = cast<PointerType>(Val->getType());
479 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
488 // If this is the entry block, we must be asking about an argument. The
489 // value is overdefined.
490 if (NumPreds == 0 && BB == &BB->getParent()->front()) {
491 assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
492 Result.markOverdefined();
496 // Return the merged value, which is more precise than 'overdefined'.
497 assert(!Result.isOverdefined());
498 return Cache[BB] = Result;
501 // If this value is defined by an instruction in this block, we have to
502 // process it here somehow or return overdefined.
503 if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
504 LVILatticeVal Result; // Start Undefined.
506 // Loop over all of our predecessors, merging what we know from them into
508 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
509 Value* PhiVal = PN->getIncomingValueForBlock(*PI);
510 Result.mergeIn(Parent.getValueOnEdge(PhiVal, *PI, BB));
512 // If we hit overdefined, exit early. The BlockVals entry is already set
514 if (Result.isOverdefined()) {
515 DEBUG(dbgs() << " compute BB '" << BB->getName()
516 << "' - overdefined because of pred.\n");
521 // Return the merged value, which is more precise than 'overdefined'.
522 assert(!Result.isOverdefined());
523 return Cache[BB] = Result;
526 assert(Cache[BB].isOverdefined() && "Recursive query changed our cache?");
528 // We can only analyze the definitions of certain classes of instructions
529 // (integral binops and casts at the moment), so bail if this isn't one.
530 LVILatticeVal Result;
531 if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
532 !BBI->getType()->isIntegerTy()) {
533 DEBUG(dbgs() << " compute BB '" << BB->getName()
534 << "' - overdefined because inst def found.\n");
535 Result.markOverdefined();
539 // FIXME: We're currently limited to binops with a constant RHS. This should
541 BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
542 if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
543 DEBUG(dbgs() << " compute BB '" << BB->getName()
544 << "' - overdefined because inst def found.\n");
546 Result.markOverdefined();
550 // Figure out the range of the LHS. If that fails, bail.
551 LVILatticeVal LHSVal = Parent.getValueInBlock(BBI->getOperand(0), BB);
552 if (!LHSVal.isConstantRange()) {
553 Result.markOverdefined();
557 ConstantInt *RHS = 0;
558 ConstantRange LHSRange = LHSVal.getConstantRange();
559 ConstantRange RHSRange(1);
560 const IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
561 if (isa<BinaryOperator>(BBI)) {
562 RHS = dyn_cast<ConstantInt>(BBI->getOperand(1));
564 Result.markOverdefined();
568 RHSRange = ConstantRange(RHS->getValue(), RHS->getValue()+1);
571 // NOTE: We're currently limited by the set of operations that ConstantRange
572 // can evaluate symbolically. Enhancing that set will allows us to analyze
574 switch (BBI->getOpcode()) {
575 case Instruction::Add:
576 Result.markConstantRange(LHSRange.add(RHSRange));
578 case Instruction::Sub:
579 Result.markConstantRange(LHSRange.sub(RHSRange));
581 case Instruction::Mul:
582 Result.markConstantRange(LHSRange.multiply(RHSRange));
584 case Instruction::UDiv:
585 Result.markConstantRange(LHSRange.udiv(RHSRange));
587 case Instruction::Shl:
588 Result.markConstantRange(LHSRange.shl(RHSRange));
590 case Instruction::LShr:
591 Result.markConstantRange(LHSRange.lshr(RHSRange));
593 case Instruction::Trunc:
594 Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
596 case Instruction::SExt:
597 Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
599 case Instruction::ZExt:
600 Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
602 case Instruction::BitCast:
603 Result.markConstantRange(LHSRange);
605 case Instruction::And:
606 Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
608 case Instruction::Or:
609 Result.markConstantRange(LHSRange.binaryOr(RHSRange));
612 // Unhandled instructions are overdefined.
614 DEBUG(dbgs() << " compute BB '" << BB->getName()
615 << "' - overdefined because inst def found.\n");
616 Result.markOverdefined();
620 return Cache[BB] = Result;
624 /// getEdgeValue - This method attempts to infer more complex
625 LVILatticeVal LVIQuery::getEdgeValue(BasicBlock *BBFrom, BasicBlock *BBTo) {
626 // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
628 if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
629 // If this is a conditional branch and only one successor goes to BBTo, then
630 // we maybe able to infer something from the condition.
631 if (BI->isConditional() &&
632 BI->getSuccessor(0) != BI->getSuccessor(1)) {
633 bool isTrueDest = BI->getSuccessor(0) == BBTo;
634 assert(BI->getSuccessor(!isTrueDest) == BBTo &&
635 "BBTo isn't a successor of BBFrom");
637 // If V is the condition of the branch itself, then we know exactly what
639 if (BI->getCondition() == Val)
640 return LVILatticeVal::get(ConstantInt::get(
641 Type::getInt1Ty(Val->getContext()), isTrueDest));
643 // If the condition of the branch is an equality comparison, we may be
644 // able to infer the value.
645 ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
646 if (ICI && ICI->getOperand(0) == Val &&
647 isa<Constant>(ICI->getOperand(1))) {
648 if (ICI->isEquality()) {
649 // We know that V has the RHS constant if this is a true SETEQ or
651 if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
652 return LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
653 return LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
656 if (ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
657 // Calculate the range of values that would satisfy the comparison.
658 ConstantRange CmpRange(CI->getValue(), CI->getValue()+1);
659 ConstantRange TrueValues =
660 ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
662 // If we're interested in the false dest, invert the condition.
663 if (!isTrueDest) TrueValues = TrueValues.inverse();
665 // Figure out the possible values of the query BEFORE this branch.
666 LVILatticeVal InBlock = getBlockValue(BBFrom);
667 if (!InBlock.isConstantRange())
668 return LVILatticeVal::getRange(TrueValues);
670 // Find all potential values that satisfy both the input and output
672 ConstantRange PossibleValues =
673 TrueValues.intersectWith(InBlock.getConstantRange());
675 return LVILatticeVal::getRange(PossibleValues);
681 // If the edge was formed by a switch on the value, then we may know exactly
683 if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
684 if (SI->getCondition() == Val) {
685 // We don't know anything in the default case.
686 if (SI->getDefaultDest() == BBTo) {
687 LVILatticeVal Result;
688 Result.markOverdefined();
692 // We only know something if there is exactly one value that goes from
694 unsigned NumEdges = 0;
695 ConstantInt *EdgeVal = 0;
696 for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
697 if (SI->getSuccessor(i) != BBTo) continue;
698 if (NumEdges++) break;
699 EdgeVal = SI->getCaseValue(i);
701 assert(EdgeVal && "Missing successor?");
703 return LVILatticeVal::get(EdgeVal);
707 // Otherwise see if the value is known in the block.
708 return getBlockValue(BBFrom);
712 //===----------------------------------------------------------------------===//
713 // LazyValueInfoCache Impl
714 //===----------------------------------------------------------------------===//
716 LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) {
717 // If already a constant, there is nothing to compute.
718 if (Constant *VC = dyn_cast<Constant>(V))
719 return LVILatticeVal::get(VC);
721 DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
722 << BB->getName() << "'\n");
724 LVILatticeVal Result = LVIQuery(V, *this,
725 ValueCache[LVIValueHandle(V, this)],
726 OverDefinedCache).getBlockValue(BB);
728 DEBUG(dbgs() << " Result = " << Result << "\n");
732 LVILatticeVal LazyValueInfoCache::
733 getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) {
734 // If already a constant, there is nothing to compute.
735 if (Constant *VC = dyn_cast<Constant>(V))
736 return LVILatticeVal::get(VC);
738 DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
739 << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
741 LVILatticeVal Result =
742 LVIQuery(V, *this, ValueCache[LVIValueHandle(V, this)],
743 OverDefinedCache).getEdgeValue(FromBB, ToBB);
745 DEBUG(dbgs() << " Result = " << Result << "\n");
750 void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
751 BasicBlock *NewSucc) {
752 // When an edge in the graph has been threaded, values that we could not
753 // determine a value for before (i.e. were marked overdefined) may be possible
754 // to solve now. We do NOT try to proactively update these values. Instead,
755 // we clear their entries from the cache, and allow lazy updating to recompute
758 // The updating process is fairly simple: we need to dropped cached info
759 // for all values that were marked overdefined in OldSucc, and for those same
760 // values in any successor of OldSucc (except NewSucc) in which they were
761 // also marked overdefined.
762 std::vector<BasicBlock*> worklist;
763 worklist.push_back(OldSucc);
765 DenseSet<Value*> ClearSet;
766 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
767 I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ++I) {
768 if (I->first == OldSucc)
769 ClearSet.insert(I->second);
772 // Use a worklist to perform a depth-first search of OldSucc's successors.
773 // NOTE: We do not need a visited list since any blocks we have already
774 // visited will have had their overdefined markers cleared already, and we
775 // thus won't loop to their successors.
776 while (!worklist.empty()) {
777 BasicBlock *ToUpdate = worklist.back();
780 // Skip blocks only accessible through NewSucc.
781 if (ToUpdate == NewSucc) continue;
783 bool changed = false;
784 for (DenseSet<Value*>::iterator I = ClearSet.begin(),E = ClearSet.end();
786 // If a value was marked overdefined in OldSucc, and is here too...
787 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator OI =
788 OverDefinedCache.find(std::make_pair(ToUpdate, *I));
789 if (OI == OverDefinedCache.end()) continue;
791 // Remove it from the caches.
792 ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
793 ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
795 assert(CI != Entry.end() && "Couldn't find entry to update?");
797 OverDefinedCache.erase(OI);
799 // If we removed anything, then we potentially need to update
800 // blocks successors too.
804 if (!changed) continue;
806 worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
810 //===----------------------------------------------------------------------===//
811 // LazyValueInfo Impl
812 //===----------------------------------------------------------------------===//
814 /// getCache - This lazily constructs the LazyValueInfoCache.
815 static LazyValueInfoCache &getCache(void *&PImpl) {
817 PImpl = new LazyValueInfoCache();
818 return *static_cast<LazyValueInfoCache*>(PImpl);
821 bool LazyValueInfo::runOnFunction(Function &F) {
823 getCache(PImpl).clear();
825 TD = getAnalysisIfAvailable<TargetData>();
830 void LazyValueInfo::releaseMemory() {
831 // If the cache was allocated, free it.
833 delete &getCache(PImpl);
838 Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) {
839 LVILatticeVal Result = getCache(PImpl).getValueInBlock(V, BB);
841 if (Result.isConstant())
842 return Result.getConstant();
843 else if (Result.isConstantRange()) {
844 ConstantRange CR = Result.getConstantRange();
845 if (const APInt *SingleVal = CR.getSingleElement())
846 return ConstantInt::get(V->getContext(), *SingleVal);
851 /// getConstantOnEdge - Determine whether the specified value is known to be a
852 /// constant on the specified edge. Return null if not.
853 Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
855 LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
857 if (Result.isConstant())
858 return Result.getConstant();
859 else if (Result.isConstantRange()) {
860 ConstantRange CR = Result.getConstantRange();
861 if (const APInt *SingleVal = CR.getSingleElement())
862 return ConstantInt::get(V->getContext(), *SingleVal);
867 /// getPredicateOnEdge - Determine whether the specified value comparison
868 /// with a constant is known to be true or false on the specified CFG edge.
869 /// Pred is a CmpInst predicate.
870 LazyValueInfo::Tristate
871 LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
872 BasicBlock *FromBB, BasicBlock *ToBB) {
873 LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
875 // If we know the value is a constant, evaluate the conditional.
877 if (Result.isConstant()) {
878 Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, TD);
879 if (ConstantInt *ResCI = dyn_cast_or_null<ConstantInt>(Res))
880 return ResCI->isZero() ? False : True;
884 if (Result.isConstantRange()) {
885 ConstantInt *CI = dyn_cast<ConstantInt>(C);
886 if (!CI) return Unknown;
888 ConstantRange CR = Result.getConstantRange();
889 if (Pred == ICmpInst::ICMP_EQ) {
890 if (!CR.contains(CI->getValue()))
893 if (CR.isSingleElement() && CR.contains(CI->getValue()))
895 } else if (Pred == ICmpInst::ICMP_NE) {
896 if (!CR.contains(CI->getValue()))
899 if (CR.isSingleElement() && CR.contains(CI->getValue()))
903 // Handle more complex predicates.
904 ConstantRange RHS(CI->getValue(), CI->getValue()+1);
905 ConstantRange TrueValues = ConstantRange::makeICmpRegion(Pred, RHS);
906 if (CR.intersectWith(TrueValues).isEmptySet())
908 else if (TrueValues.contains(CR))
914 if (Result.isNotConstant()) {
915 // If this is an equality comparison, we can try to fold it knowing that
917 if (Pred == ICmpInst::ICMP_EQ) {
918 // !C1 == C -> false iff C1 == C.
919 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
920 Result.getNotConstant(), C, TD);
921 if (Res->isNullValue())
923 } else if (Pred == ICmpInst::ICMP_NE) {
924 // !C1 != C -> true iff C1 == C.
925 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
926 Result.getNotConstant(), C, TD);
927 if (Res->isNullValue())
936 void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
937 BasicBlock* NewSucc) {
938 if (PImpl) getCache(PImpl).threadEdge(PredBB, OldSucc, NewSucc);
941 void LazyValueInfo::eraseBlock(BasicBlock *BB) {
942 if (PImpl) getCache(PImpl).eraseBlock(BB);