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"
33 char LazyValueInfo::ID = 0;
34 INITIALIZE_PASS(LazyValueInfo, "lazy-value-info",
35 "Lazy Value Information Analysis", false, true);
38 FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
42 //===----------------------------------------------------------------------===//
44 //===----------------------------------------------------------------------===//
46 /// LVILatticeVal - This is the information tracked by LazyValueInfo for each
49 /// FIXME: This is basically just for bringup, this can be made a lot more rich
55 /// undefined - This LLVM Value has no known value yet.
58 /// constant - This LLVM Value has a specific constant value.
60 /// notconstant - This LLVM value is known to not have the specified value.
66 /// overdefined - This instruction is not known to be constant, and we know
71 /// Val: This stores the current lattice value along with the Constant* for
72 /// the constant if this is a 'constant' or 'notconstant' value.
78 LVILatticeVal() : Tag(undefined), Val(0), Range(1, true) {}
80 static LVILatticeVal get(Constant *C) {
82 if (ConstantInt *CI = dyn_cast<ConstantInt>(C))
83 Res.markConstantRange(ConstantRange(CI->getValue(), CI->getValue()+1));
84 else if (!isa<UndefValue>(C))
88 static LVILatticeVal getNot(Constant *C) {
90 if (ConstantInt *CI = dyn_cast<ConstantInt>(C))
91 Res.markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue()));
93 Res.markNotConstant(C);
96 static LVILatticeVal getRange(ConstantRange CR) {
98 Res.markConstantRange(CR);
102 bool isUndefined() const { return Tag == undefined; }
103 bool isConstant() const { return Tag == constant; }
104 bool isNotConstant() const { return Tag == notconstant; }
105 bool isConstantRange() const { return Tag == constantrange; }
106 bool isOverdefined() const { return Tag == overdefined; }
108 Constant *getConstant() const {
109 assert(isConstant() && "Cannot get the constant of a non-constant!");
113 Constant *getNotConstant() const {
114 assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
118 ConstantRange getConstantRange() const {
119 assert(isConstantRange() &&
120 "Cannot get the constant-range of a non-constant-range!");
124 /// markOverdefined - Return true if this is a change in status.
125 bool markOverdefined() {
132 /// markConstant - Return true if this is a change in status.
133 bool markConstant(Constant *V) {
135 assert(getConstant() == V && "Marking constant with different value");
139 assert(isUndefined());
141 assert(V && "Marking constant with NULL");
146 /// markNotConstant - Return true if this is a change in status.
147 bool markNotConstant(Constant *V) {
148 if (isNotConstant()) {
149 assert(getNotConstant() == V && "Marking !constant with different value");
154 assert(getConstant() != V && "Marking not constant with different value");
156 assert(isUndefined());
159 assert(V && "Marking constant with NULL");
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();
190 if (RHS.isNotConstant()) {
191 if (isNotConstant()) {
192 if (getNotConstant() != RHS.getNotConstant() ||
193 isa<ConstantExpr>(getNotConstant()) ||
194 isa<ConstantExpr>(RHS.getNotConstant()))
195 return markOverdefined();
197 } else if (isConstant()) {
198 if (getConstant() == RHS.getNotConstant() ||
199 isa<ConstantExpr>(RHS.getNotConstant()) ||
200 isa<ConstantExpr>(getConstant()))
201 return markOverdefined();
202 return markNotConstant(RHS.getNotConstant());
203 } else if (isConstantRange()) {
204 // FIXME: This could be made more precise.
205 return markOverdefined();
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);
219 } else if (!isUndefined()) {
220 return markOverdefined();
223 assert(isUndefined() && "Unexpected lattice");
224 return markConstantRange(RHS.getConstantRange());
227 // RHS must be a constant, we must be constantrange,
228 // undef, constant, or notconstant.
229 if (isConstantRange()) {
230 // FIXME: This could be made more precise.
231 return markOverdefined();
235 return markConstant(RHS.getConstant());
238 if (getConstant() != RHS.getConstant())
239 return markOverdefined();
243 // If we are known "!=4" and RHS is "==5", stay at "!=4".
244 if (getNotConstant() == RHS.getConstant() ||
245 isa<ConstantExpr>(getNotConstant()) ||
246 isa<ConstantExpr>(RHS.getConstant()))
247 return markOverdefined();
253 } // end anonymous namespace.
256 raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
257 if (Val.isUndefined())
258 return OS << "undefined";
259 if (Val.isOverdefined())
260 return OS << "overdefined";
262 if (Val.isNotConstant())
263 return OS << "notconstant<" << *Val.getNotConstant() << '>';
264 else if (Val.isConstantRange())
265 return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
266 << Val.getConstantRange().getUpper() << '>';
267 return OS << "constant<" << *Val.getConstant() << '>';
271 //===----------------------------------------------------------------------===//
272 // LazyValueInfoCache Decl
273 //===----------------------------------------------------------------------===//
276 /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
277 /// maintains information about queries across the clients' queries.
278 class LazyValueInfoCache {
280 /// BlockCacheEntryTy - This is a computed lattice value at the end of the
281 /// specified basic block for a Value* that depends on context.
282 typedef std::pair<AssertingVH<BasicBlock>, LVILatticeVal> BlockCacheEntryTy;
284 /// ValueCacheEntryTy - This is all of the cached block information for
285 /// exactly one Value*. The entries are sorted by the BasicBlock* of the
286 /// entries, allowing us to do a lookup with a binary search.
287 typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
290 /// LVIValueHandle - A callback value handle update the cache when
291 /// values are erased.
292 struct LVIValueHandle : public CallbackVH {
293 LazyValueInfoCache *Parent;
295 LVIValueHandle(Value *V, LazyValueInfoCache *P)
296 : CallbackVH(V), Parent(P) { }
299 void allUsesReplacedWith(Value* V) {
304 /// ValueCache - This is all of the cached information for all values,
305 /// mapped from Value* to key information.
306 std::map<LVIValueHandle, ValueCacheEntryTy> ValueCache;
308 /// OverDefinedCache - This tracks, on a per-block basis, the set of
309 /// values that are over-defined at the end of that block. This is required
310 /// for cache updating.
311 std::set<std::pair<AssertingVH<BasicBlock>, Value*> > OverDefinedCache;
315 /// getValueInBlock - This is the query interface to determine the lattice
316 /// value for the specified Value* at the end of the specified block.
317 LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB);
319 /// getValueOnEdge - This is the query interface to determine the lattice
320 /// value for the specified Value* that is true on the specified edge.
321 LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB);
323 /// threadEdge - This is the update interface to inform the cache that an
324 /// edge from PredBB to OldSucc has been threaded to be from PredBB to
326 void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
328 /// eraseBlock - This is part of the update interface to inform the cache
329 /// that a block has been deleted.
330 void eraseBlock(BasicBlock *BB);
332 /// clear - Empty the cache.
335 OverDefinedCache.clear();
338 } // end anonymous namespace
340 //===----------------------------------------------------------------------===//
342 //===----------------------------------------------------------------------===//
345 /// LVIQuery - This is a transient object that exists while a query is
348 /// TODO: Reuse LVIQuery instead of recreating it for every query, this avoids
349 /// reallocation of the densemap on every query.
351 typedef LazyValueInfoCache::BlockCacheEntryTy BlockCacheEntryTy;
352 typedef LazyValueInfoCache::ValueCacheEntryTy ValueCacheEntryTy;
354 /// This is the current value being queried for.
357 /// This is a pointer to the owning cache, for recursive queries.
358 LazyValueInfoCache &Parent;
360 /// This is all of the cached information about this value.
361 ValueCacheEntryTy &Cache;
363 /// This tracks, for each block, what values are overdefined.
364 std::set<std::pair<AssertingVH<BasicBlock>, Value*> > &OverDefinedCache;
366 /// NewBlocks - This is a mapping of the new BasicBlocks which have been
367 /// added to cache but that are not in sorted order.
368 DenseSet<BasicBlock*> NewBlockInfo;
372 LVIQuery(Value *V, LazyValueInfoCache &P,
373 ValueCacheEntryTy &VC,
374 std::set<std::pair<AssertingVH<BasicBlock>, Value*> > &ODC)
375 : Val(V), Parent(P), Cache(VC), OverDefinedCache(ODC) {
379 // When the query is done, insert the newly discovered facts into the
380 // cache in sorted order.
381 if (NewBlockInfo.empty()) return;
383 for (DenseSet<BasicBlock*>::iterator I = NewBlockInfo.begin(),
384 E = NewBlockInfo.end(); I != E; ++I) {
385 if (Cache[*I].isOverdefined())
386 OverDefinedCache.insert(std::make_pair(*I, Val));
390 LVILatticeVal getBlockValue(BasicBlock *BB);
391 LVILatticeVal getEdgeValue(BasicBlock *FromBB, BasicBlock *ToBB);
394 LVILatticeVal getCachedEntryForBlock(BasicBlock *BB);
396 } // end anonymous namespace
398 void LazyValueInfoCache::LVIValueHandle::deleted() {
399 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
400 I = Parent->OverDefinedCache.begin(),
401 E = Parent->OverDefinedCache.end();
403 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator tmp = I;
405 if (tmp->second == getValPtr())
406 Parent->OverDefinedCache.erase(tmp);
409 // This erasure deallocates *this, so it MUST happen after we're done
410 // using any and all members of *this.
411 Parent->ValueCache.erase(*this);
414 void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
415 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
416 I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ) {
417 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator tmp = I;
419 if (tmp->first == BB)
420 OverDefinedCache.erase(tmp);
423 for (std::map<LVIValueHandle, ValueCacheEntryTy>::iterator
424 I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
428 /// getCachedEntryForBlock - See if we already have a value for this block. If
429 /// so, return it, otherwise create a new entry in the Cache map to use.
430 LVILatticeVal LVIQuery::getCachedEntryForBlock(BasicBlock *BB) {
431 NewBlockInfo.insert(BB);
435 LVILatticeVal LVIQuery::getBlockValue(BasicBlock *BB) {
436 // See if we already have a value for this block.
437 LVILatticeVal BBLV = getCachedEntryForBlock(BB);
439 // If we've already computed this block's value, return it.
440 if (!BBLV.isUndefined()) {
441 DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
445 // Otherwise, this is the first time we're seeing this block. Reset the
446 // lattice value to overdefined, so that cycles will terminate and be
447 // conservatively correct.
448 BBLV.markOverdefined();
451 Instruction *BBI = dyn_cast<Instruction>(Val);
452 if (BBI == 0 || BBI->getParent() != BB) {
453 LVILatticeVal Result; // Start Undefined.
455 // If this is a pointer, and there's a load from that pointer in this BB,
456 // then we know that the pointer can't be NULL.
457 bool NotNull = false;
458 if (Val->getType()->isPointerTy()) {
459 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){
460 LoadInst *L = dyn_cast<LoadInst>(BI);
461 if (L && L->getPointerAddressSpace() == 0 &&
462 L->getPointerOperand()->getUnderlyingObject() ==
463 Val->getUnderlyingObject()) {
470 unsigned NumPreds = 0;
471 // Loop over all of our predecessors, merging what we know from them into
473 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
474 Result.mergeIn(getEdgeValue(*PI, BB));
476 // If we hit overdefined, exit early. The BlockVals entry is already set
478 if (Result.isOverdefined()) {
479 DEBUG(dbgs() << " compute BB '" << BB->getName()
480 << "' - overdefined because of pred.\n");
481 // If we previously determined that this is a pointer that can't be null
482 // then return that rather than giving up entirely.
484 const PointerType *PTy = cast<PointerType>(Val->getType());
485 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
494 // If this is the entry block, we must be asking about an argument. The
495 // value is overdefined.
496 if (NumPreds == 0 && BB == &BB->getParent()->front()) {
497 assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
498 Result.markOverdefined();
502 // Return the merged value, which is more precise than 'overdefined'.
503 assert(!Result.isOverdefined());
504 return Cache[BB] = Result;
507 // If this value is defined by an instruction in this block, we have to
508 // process it here somehow or return overdefined.
509 if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
510 LVILatticeVal Result; // Start Undefined.
512 // Loop over all of our predecessors, merging what we know from them into
514 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
515 Value* PhiVal = PN->getIncomingValueForBlock(*PI);
516 Result.mergeIn(Parent.getValueOnEdge(PhiVal, *PI, BB));
518 // If we hit overdefined, exit early. The BlockVals entry is already set
520 if (Result.isOverdefined()) {
521 DEBUG(dbgs() << " compute BB '" << BB->getName()
522 << "' - overdefined because of pred.\n");
527 // Return the merged value, which is more precise than 'overdefined'.
528 assert(!Result.isOverdefined());
529 return Cache[BB] = Result;
532 assert(Cache[BB].isOverdefined() && "Recursive query changed our cache?");
534 // We can only analyze the definitions of certain classes of instructions
535 // (integral binops and casts at the moment), so bail if this isn't one.
536 LVILatticeVal Result;
537 if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
538 !BBI->getType()->isIntegerTy()) {
539 DEBUG(dbgs() << " compute BB '" << BB->getName()
540 << "' - overdefined because inst def found.\n");
541 Result.markOverdefined();
545 // FIXME: We're currently limited to binops with a constant RHS. This should
547 BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
548 if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
549 DEBUG(dbgs() << " compute BB '" << BB->getName()
550 << "' - overdefined because inst def found.\n");
552 Result.markOverdefined();
556 // Figure out the range of the LHS. If that fails, bail.
557 LVILatticeVal LHSVal = Parent.getValueInBlock(BBI->getOperand(0), BB);
558 if (!LHSVal.isConstantRange()) {
559 Result.markOverdefined();
563 ConstantInt *RHS = 0;
564 ConstantRange LHSRange = LHSVal.getConstantRange();
565 ConstantRange RHSRange(1);
566 const IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
567 if (isa<BinaryOperator>(BBI)) {
568 RHS = dyn_cast<ConstantInt>(BBI->getOperand(1));
570 Result.markOverdefined();
574 RHSRange = ConstantRange(RHS->getValue(), RHS->getValue()+1);
577 // NOTE: We're currently limited by the set of operations that ConstantRange
578 // can evaluate symbolically. Enhancing that set will allows us to analyze
580 switch (BBI->getOpcode()) {
581 case Instruction::Add:
582 Result.markConstantRange(LHSRange.add(RHSRange));
584 case Instruction::Sub:
585 Result.markConstantRange(LHSRange.sub(RHSRange));
587 case Instruction::Mul:
588 Result.markConstantRange(LHSRange.multiply(RHSRange));
590 case Instruction::UDiv:
591 Result.markConstantRange(LHSRange.udiv(RHSRange));
593 case Instruction::Shl:
594 Result.markConstantRange(LHSRange.shl(RHSRange));
596 case Instruction::LShr:
597 Result.markConstantRange(LHSRange.lshr(RHSRange));
599 case Instruction::Trunc:
600 Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
602 case Instruction::SExt:
603 Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
605 case Instruction::ZExt:
606 Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
608 case Instruction::BitCast:
609 Result.markConstantRange(LHSRange);
611 case Instruction::And:
612 Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
614 case Instruction::Or:
615 Result.markConstantRange(LHSRange.binaryOr(RHSRange));
618 // Unhandled instructions are overdefined.
620 DEBUG(dbgs() << " compute BB '" << BB->getName()
621 << "' - overdefined because inst def found.\n");
622 Result.markOverdefined();
626 return Cache[BB] = Result;
630 /// getEdgeValue - This method attempts to infer more complex
631 LVILatticeVal LVIQuery::getEdgeValue(BasicBlock *BBFrom, BasicBlock *BBTo) {
632 // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
634 if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
635 // If this is a conditional branch and only one successor goes to BBTo, then
636 // we maybe able to infer something from the condition.
637 if (BI->isConditional() &&
638 BI->getSuccessor(0) != BI->getSuccessor(1)) {
639 bool isTrueDest = BI->getSuccessor(0) == BBTo;
640 assert(BI->getSuccessor(!isTrueDest) == BBTo &&
641 "BBTo isn't a successor of BBFrom");
643 // If V is the condition of the branch itself, then we know exactly what
645 if (BI->getCondition() == Val)
646 return LVILatticeVal::get(ConstantInt::get(
647 Type::getInt1Ty(Val->getContext()), isTrueDest));
649 // If the condition of the branch is an equality comparison, we may be
650 // able to infer the value.
651 ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
652 if (ICI && ICI->getOperand(0) == Val &&
653 isa<Constant>(ICI->getOperand(1))) {
654 if (ICI->isEquality()) {
655 // We know that V has the RHS constant if this is a true SETEQ or
657 if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
658 return LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
659 return LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
662 if (ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
663 // Calculate the range of values that would satisfy the comparison.
664 ConstantRange CmpRange(CI->getValue(), CI->getValue()+1);
665 ConstantRange TrueValues =
666 ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
668 // If we're interested in the false dest, invert the condition.
669 if (!isTrueDest) TrueValues = TrueValues.inverse();
671 // Figure out the possible values of the query BEFORE this branch.
672 LVILatticeVal InBlock = getBlockValue(BBFrom);
673 if (!InBlock.isConstantRange())
674 return LVILatticeVal::getRange(TrueValues);
676 // Find all potential values that satisfy both the input and output
678 ConstantRange PossibleValues =
679 TrueValues.intersectWith(InBlock.getConstantRange());
681 return LVILatticeVal::getRange(PossibleValues);
687 // If the edge was formed by a switch on the value, then we may know exactly
689 if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
690 if (SI->getCondition() == Val) {
691 // We don't know anything in the default case.
692 if (SI->getDefaultDest() == BBTo) {
693 LVILatticeVal Result;
694 Result.markOverdefined();
698 // We only know something if there is exactly one value that goes from
700 unsigned NumEdges = 0;
701 ConstantInt *EdgeVal = 0;
702 for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
703 if (SI->getSuccessor(i) != BBTo) continue;
704 if (NumEdges++) break;
705 EdgeVal = SI->getCaseValue(i);
707 assert(EdgeVal && "Missing successor?");
709 return LVILatticeVal::get(EdgeVal);
713 // Otherwise see if the value is known in the block.
714 return getBlockValue(BBFrom);
718 //===----------------------------------------------------------------------===//
719 // LazyValueInfoCache Impl
720 //===----------------------------------------------------------------------===//
722 LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) {
723 // If already a constant, there is nothing to compute.
724 if (Constant *VC = dyn_cast<Constant>(V))
725 return LVILatticeVal::get(VC);
727 DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
728 << BB->getName() << "'\n");
730 LVILatticeVal Result = LVIQuery(V, *this,
731 ValueCache[LVIValueHandle(V, this)],
732 OverDefinedCache).getBlockValue(BB);
734 DEBUG(dbgs() << " Result = " << Result << "\n");
738 LVILatticeVal LazyValueInfoCache::
739 getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) {
740 // If already a constant, there is nothing to compute.
741 if (Constant *VC = dyn_cast<Constant>(V))
742 return LVILatticeVal::get(VC);
744 DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
745 << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
747 LVILatticeVal Result =
748 LVIQuery(V, *this, ValueCache[LVIValueHandle(V, this)],
749 OverDefinedCache).getEdgeValue(FromBB, ToBB);
751 DEBUG(dbgs() << " Result = " << Result << "\n");
756 void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
757 BasicBlock *NewSucc) {
758 // When an edge in the graph has been threaded, values that we could not
759 // determine a value for before (i.e. were marked overdefined) may be possible
760 // to solve now. We do NOT try to proactively update these values. Instead,
761 // we clear their entries from the cache, and allow lazy updating to recompute
764 // The updating process is fairly simple: we need to dropped cached info
765 // for all values that were marked overdefined in OldSucc, and for those same
766 // values in any successor of OldSucc (except NewSucc) in which they were
767 // also marked overdefined.
768 std::vector<BasicBlock*> worklist;
769 worklist.push_back(OldSucc);
771 DenseSet<Value*> ClearSet;
772 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
773 I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ++I) {
774 if (I->first == OldSucc)
775 ClearSet.insert(I->second);
778 // Use a worklist to perform a depth-first search of OldSucc's successors.
779 // NOTE: We do not need a visited list since any blocks we have already
780 // visited will have had their overdefined markers cleared already, and we
781 // thus won't loop to their successors.
782 while (!worklist.empty()) {
783 BasicBlock *ToUpdate = worklist.back();
786 // Skip blocks only accessible through NewSucc.
787 if (ToUpdate == NewSucc) continue;
789 bool changed = false;
790 for (DenseSet<Value*>::iterator I = ClearSet.begin(),E = ClearSet.end();
792 // If a value was marked overdefined in OldSucc, and is here too...
793 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator OI =
794 OverDefinedCache.find(std::make_pair(ToUpdate, *I));
795 if (OI == OverDefinedCache.end()) continue;
797 // Remove it from the caches.
798 ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
799 ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
801 assert(CI != Entry.end() && "Couldn't find entry to update?");
803 OverDefinedCache.erase(OI);
805 // If we removed anything, then we potentially need to update
806 // blocks successors too.
810 if (!changed) continue;
812 worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
816 //===----------------------------------------------------------------------===//
817 // LazyValueInfo Impl
818 //===----------------------------------------------------------------------===//
820 /// getCache - This lazily constructs the LazyValueInfoCache.
821 static LazyValueInfoCache &getCache(void *&PImpl) {
823 PImpl = new LazyValueInfoCache();
824 return *static_cast<LazyValueInfoCache*>(PImpl);
827 bool LazyValueInfo::runOnFunction(Function &F) {
829 getCache(PImpl).clear();
831 TD = getAnalysisIfAvailable<TargetData>();
836 void LazyValueInfo::releaseMemory() {
837 // If the cache was allocated, free it.
839 delete &getCache(PImpl);
844 Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) {
845 LVILatticeVal Result = getCache(PImpl).getValueInBlock(V, BB);
847 if (Result.isConstant())
848 return Result.getConstant();
849 else if (Result.isConstantRange()) {
850 ConstantRange CR = Result.getConstantRange();
851 if (const APInt *SingleVal = CR.getSingleElement())
852 return ConstantInt::get(V->getContext(), *SingleVal);
857 /// getConstantOnEdge - Determine whether the specified value is known to be a
858 /// constant on the specified edge. Return null if not.
859 Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
861 LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
863 if (Result.isConstant())
864 return Result.getConstant();
865 else if (Result.isConstantRange()) {
866 ConstantRange CR = Result.getConstantRange();
867 if (const APInt *SingleVal = CR.getSingleElement())
868 return ConstantInt::get(V->getContext(), *SingleVal);
873 /// getPredicateOnEdge - Determine whether the specified value comparison
874 /// with a constant is known to be true or false on the specified CFG edge.
875 /// Pred is a CmpInst predicate.
876 LazyValueInfo::Tristate
877 LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
878 BasicBlock *FromBB, BasicBlock *ToBB) {
879 LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
881 // If we know the value is a constant, evaluate the conditional.
883 if (Result.isConstant()) {
884 Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, TD);
885 if (ConstantInt *ResCI = dyn_cast_or_null<ConstantInt>(Res))
886 return ResCI->isZero() ? False : True;
890 if (Result.isConstantRange()) {
891 ConstantInt *CI = dyn_cast<ConstantInt>(C);
892 if (!CI) return Unknown;
894 ConstantRange CR = Result.getConstantRange();
895 if (Pred == ICmpInst::ICMP_EQ) {
896 if (!CR.contains(CI->getValue()))
899 if (CR.isSingleElement() && CR.contains(CI->getValue()))
901 } else if (Pred == ICmpInst::ICMP_NE) {
902 if (!CR.contains(CI->getValue()))
905 if (CR.isSingleElement() && CR.contains(CI->getValue()))
909 // Handle more complex predicates.
910 ConstantRange RHS(CI->getValue(), CI->getValue()+1);
911 ConstantRange TrueValues = ConstantRange::makeICmpRegion(Pred, RHS);
912 if (CR.intersectWith(TrueValues).isEmptySet())
914 else if (TrueValues.contains(CR))
920 if (Result.isNotConstant()) {
921 // If this is an equality comparison, we can try to fold it knowing that
923 if (Pred == ICmpInst::ICMP_EQ) {
924 // !C1 == C -> false iff C1 == C.
925 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
926 Result.getNotConstant(), C, TD);
927 if (Res->isNullValue())
929 } else if (Pred == ICmpInst::ICMP_NE) {
930 // !C1 != C -> true iff C1 == C.
931 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
932 Result.getNotConstant(), C, TD);
933 if (Res->isNullValue())
942 void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
943 BasicBlock* NewSucc) {
944 if (PImpl) getCache(PImpl).threadEdge(PredBB, OldSucc, NewSucc);
947 void LazyValueInfo::eraseBlock(BasicBlock *BB) {
948 if (PImpl) getCache(PImpl).eraseBlock(BB);