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) {
305 /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
306 /// maintains information about queries across the clients' queries.
307 class LazyValueInfoCache {
309 /// ValueCacheEntryTy - This is all of the cached block information for
310 /// exactly one Value*. The entries are sorted by the BasicBlock* of the
311 /// entries, allowing us to do a lookup with a binary search.
312 typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
315 friend struct LVIValueHandle;
317 /// OverDefinedCacheUpdater - A helper object that ensures that the
318 /// OverDefinedCache is updated whenever solveBlockValue returns.
319 struct OverDefinedCacheUpdater {
320 LazyValueInfoCache *Parent;
325 OverDefinedCacheUpdater(Value *V, BasicBlock *B, LVILatticeVal &LV,
326 LazyValueInfoCache *P)
327 : Parent(P), Val(V), BB(B), BBLV(LV) { }
329 bool markResult(bool changed) {
330 if (changed && BBLV.isOverdefined())
331 Parent->OverDefinedCache.insert(std::make_pair(BB, Val));
336 /// ValueCache - This is all of the cached information for all values,
337 /// mapped from Value* to key information.
338 DenseMap<LVIValueHandle, ValueCacheEntryTy> ValueCache;
340 /// OverDefinedCache - This tracks, on a per-block basis, the set of
341 /// values that are over-defined at the end of that block. This is required
342 /// for cache updating.
343 std::set<std::pair<AssertingVH<BasicBlock>, Value*> > OverDefinedCache;
345 LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
346 bool getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T,
347 LVILatticeVal &Result);
348 bool hasBlockValue(Value *Val, BasicBlock *BB);
350 // These methods process one work item and may add more. A false value
351 // returned means that the work item was not completely processed and must
352 // be revisited after going through the new items.
353 bool solveBlockValue(Value *Val, BasicBlock *BB);
354 bool solveBlockValueNonLocal(LVILatticeVal &BBLV,
355 Value *Val, BasicBlock *BB);
356 bool solveBlockValuePHINode(LVILatticeVal &BBLV,
357 PHINode *PN, BasicBlock *BB);
358 bool solveBlockValueConstantRange(LVILatticeVal &BBLV,
359 Instruction *BBI, BasicBlock *BB);
363 ValueCacheEntryTy &lookup(Value *V) {
364 return ValueCache[LVIValueHandle(V, this)];
367 std::stack<std::pair<BasicBlock*, Value*> > block_value_stack;
370 /// getValueInBlock - This is the query interface to determine the lattice
371 /// value for the specified Value* at the end of the specified block.
372 LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB);
374 /// getValueOnEdge - This is the query interface to determine the lattice
375 /// value for the specified Value* that is true on the specified edge.
376 LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB);
378 /// threadEdge - This is the update interface to inform the cache that an
379 /// edge from PredBB to OldSucc has been threaded to be from PredBB to
381 void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
383 /// eraseBlock - This is part of the update interface to inform the cache
384 /// that a block has been deleted.
385 void eraseBlock(BasicBlock *BB);
387 /// clear - Empty the cache.
390 OverDefinedCache.clear();
393 } // end anonymous namespace
397 struct DenseMapInfo<LVIValueHandle> {
398 typedef DenseMapInfo<Value*> PointerInfo;
399 static inline LVIValueHandle getEmptyKey() {
400 return LVIValueHandle(PointerInfo::getEmptyKey(),
401 static_cast<LazyValueInfoCache*>(0));
403 static inline LVIValueHandle getTombstoneKey() {
404 return LVIValueHandle(PointerInfo::getTombstoneKey(),
405 static_cast<LazyValueInfoCache*>(0));
407 static unsigned getHashValue(const LVIValueHandle &Val) {
408 return PointerInfo::getHashValue(Val);
410 static bool isEqual(const LVIValueHandle &LHS, const LVIValueHandle &RHS) {
416 void LVIValueHandle::deleted() {
417 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
418 I = Parent->OverDefinedCache.begin(),
419 E = Parent->OverDefinedCache.end();
421 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator tmp = I;
423 if (tmp->second == getValPtr())
424 Parent->OverDefinedCache.erase(tmp);
427 // This erasure deallocates *this, so it MUST happen after we're done
428 // using any and all members of *this.
429 Parent->ValueCache.erase(*this);
432 void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
433 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
434 I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ) {
435 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator tmp = I;
437 if (tmp->first == BB)
438 OverDefinedCache.erase(tmp);
441 for (DenseMap<LVIValueHandle, ValueCacheEntryTy>::iterator
442 I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
446 void LazyValueInfoCache::solve() {
447 while (!block_value_stack.empty()) {
448 std::pair<BasicBlock*, Value*> &e = block_value_stack.top();
449 if (solveBlockValue(e.second, e.first))
450 block_value_stack.pop();
454 bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
455 // If already a constant, there is nothing to compute.
456 if (isa<Constant>(Val))
459 return lookup(Val).count(BB);
462 LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
463 // If already a constant, there is nothing to compute.
464 if (Constant *VC = dyn_cast<Constant>(Val))
465 return LVILatticeVal::get(VC);
467 return lookup(Val)[BB];
470 bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
471 if (isa<Constant>(Val))
474 ValueCacheEntryTy &Cache = lookup(Val);
475 LVILatticeVal &BBLV = Cache[BB];
477 // OverDefinedCacheUpdater is a helper object that will update
478 // the OverDefinedCache for us when this method exits. Make sure to
479 // call markResult on it as we exist, passing a bool to indicate if the
480 // cache needs updating, i.e. if we have solve a new value or not.
481 OverDefinedCacheUpdater ODCacheUpdater(Val, BB, BBLV, this);
483 // If we've already computed this block's value, return it.
484 if (!BBLV.isUndefined()) {
485 DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
487 // Since we're reusing a cached value here, we don't need to update the
488 // OverDefinedCahce. The cache will have been properly updated
489 // whenever the cached value was inserted.
490 ODCacheUpdater.markResult(false);
494 // Otherwise, this is the first time we're seeing this block. Reset the
495 // lattice value to overdefined, so that cycles will terminate and be
496 // conservatively correct.
497 BBLV.markOverdefined();
499 Instruction *BBI = dyn_cast<Instruction>(Val);
500 if (BBI == 0 || BBI->getParent() != BB) {
501 return ODCacheUpdater.markResult(solveBlockValueNonLocal(BBLV, Val, BB));
504 if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
505 return ODCacheUpdater.markResult(solveBlockValuePHINode(BBLV, PN, BB));
508 // We can only analyze the definitions of certain classes of instructions
509 // (integral binops and casts at the moment), so bail if this isn't one.
510 LVILatticeVal Result;
511 if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
512 !BBI->getType()->isIntegerTy()) {
513 DEBUG(dbgs() << " compute BB '" << BB->getName()
514 << "' - overdefined because inst def found.\n");
515 BBLV.markOverdefined();
516 return ODCacheUpdater.markResult(true);
519 // FIXME: We're currently limited to binops with a constant RHS. This should
521 BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
522 if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
523 DEBUG(dbgs() << " compute BB '" << BB->getName()
524 << "' - overdefined because inst def found.\n");
526 BBLV.markOverdefined();
527 return ODCacheUpdater.markResult(true);
530 return ODCacheUpdater.markResult(solveBlockValueConstantRange(BBLV, BBI, BB));
533 static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
534 if (LoadInst *L = dyn_cast<LoadInst>(I)) {
535 return L->getPointerAddressSpace() == 0 &&
536 GetUnderlyingObject(L->getPointerOperand()) ==
537 GetUnderlyingObject(Ptr);
539 if (StoreInst *S = dyn_cast<StoreInst>(I)) {
540 return S->getPointerAddressSpace() == 0 &&
541 GetUnderlyingObject(S->getPointerOperand()) ==
542 GetUnderlyingObject(Ptr);
544 // FIXME: llvm.memset, etc.
548 bool LazyValueInfoCache::solveBlockValueNonLocal(LVILatticeVal &BBLV,
549 Value *Val, BasicBlock *BB) {
550 LVILatticeVal Result; // Start Undefined.
552 // If this is a pointer, and there's a load from that pointer in this BB,
553 // then we know that the pointer can't be NULL.
554 bool NotNull = false;
555 if (Val->getType()->isPointerTy()) {
556 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){
557 if (InstructionDereferencesPointer(BI, Val)) {
564 // If this is the entry block, we must be asking about an argument. The
565 // value is overdefined.
566 if (BB == &BB->getParent()->getEntryBlock()) {
567 assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
569 const PointerType *PTy = cast<PointerType>(Val->getType());
570 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
572 Result.markOverdefined();
578 // Loop over all of our predecessors, merging what we know from them into
580 bool EdgesMissing = false;
581 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
582 LVILatticeVal EdgeResult;
583 EdgesMissing |= !getEdgeValue(Val, *PI, BB, EdgeResult);
587 Result.mergeIn(EdgeResult);
589 // If we hit overdefined, exit early. The BlockVals entry is already set
591 if (Result.isOverdefined()) {
592 DEBUG(dbgs() << " compute BB '" << BB->getName()
593 << "' - overdefined because of pred.\n");
594 // If we previously determined that this is a pointer that can't be null
595 // then return that rather than giving up entirely.
597 const PointerType *PTy = cast<PointerType>(Val->getType());
598 Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
608 // Return the merged value, which is more precise than 'overdefined'.
609 assert(!Result.isOverdefined());
614 bool LazyValueInfoCache::solveBlockValuePHINode(LVILatticeVal &BBLV,
615 PHINode *PN, BasicBlock *BB) {
616 LVILatticeVal Result; // Start Undefined.
618 // Loop over all of our predecessors, merging what we know from them into
620 bool EdgesMissing = false;
621 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
622 BasicBlock *PhiBB = PN->getIncomingBlock(i);
623 Value *PhiVal = PN->getIncomingValue(i);
624 LVILatticeVal EdgeResult;
625 EdgesMissing |= !getEdgeValue(PhiVal, PhiBB, BB, EdgeResult);
629 Result.mergeIn(EdgeResult);
631 // If we hit overdefined, exit early. The BlockVals entry is already set
633 if (Result.isOverdefined()) {
634 DEBUG(dbgs() << " compute BB '" << BB->getName()
635 << "' - overdefined because of pred.\n");
644 // Return the merged value, which is more precise than 'overdefined'.
645 assert(!Result.isOverdefined() && "Possible PHI in entry block?");
650 bool LazyValueInfoCache::solveBlockValueConstantRange(LVILatticeVal &BBLV,
653 // Figure out the range of the LHS. If that fails, bail.
654 if (!hasBlockValue(BBI->getOperand(0), BB)) {
655 block_value_stack.push(std::make_pair(BB, BBI->getOperand(0)));
659 LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
660 if (!LHSVal.isConstantRange()) {
661 BBLV.markOverdefined();
665 ConstantRange LHSRange = LHSVal.getConstantRange();
666 ConstantRange RHSRange(1);
667 const IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
668 if (isa<BinaryOperator>(BBI)) {
669 if (ConstantInt *RHS = dyn_cast<ConstantInt>(BBI->getOperand(1))) {
670 RHSRange = ConstantRange(RHS->getValue());
672 BBLV.markOverdefined();
677 // NOTE: We're currently limited by the set of operations that ConstantRange
678 // can evaluate symbolically. Enhancing that set will allows us to analyze
680 LVILatticeVal Result;
681 switch (BBI->getOpcode()) {
682 case Instruction::Add:
683 Result.markConstantRange(LHSRange.add(RHSRange));
685 case Instruction::Sub:
686 Result.markConstantRange(LHSRange.sub(RHSRange));
688 case Instruction::Mul:
689 Result.markConstantRange(LHSRange.multiply(RHSRange));
691 case Instruction::UDiv:
692 Result.markConstantRange(LHSRange.udiv(RHSRange));
694 case Instruction::Shl:
695 Result.markConstantRange(LHSRange.shl(RHSRange));
697 case Instruction::LShr:
698 Result.markConstantRange(LHSRange.lshr(RHSRange));
700 case Instruction::Trunc:
701 Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
703 case Instruction::SExt:
704 Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
706 case Instruction::ZExt:
707 Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
709 case Instruction::BitCast:
710 Result.markConstantRange(LHSRange);
712 case Instruction::And:
713 Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
715 case Instruction::Or:
716 Result.markConstantRange(LHSRange.binaryOr(RHSRange));
719 // Unhandled instructions are overdefined.
721 DEBUG(dbgs() << " compute BB '" << BB->getName()
722 << "' - overdefined because inst def found.\n");
723 Result.markOverdefined();
731 /// getEdgeValue - This method attempts to infer more complex
732 bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom,
733 BasicBlock *BBTo, LVILatticeVal &Result) {
734 // If already a constant, there is nothing to compute.
735 if (Constant *VC = dyn_cast<Constant>(Val)) {
736 Result = LVILatticeVal::get(VC);
740 // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
742 if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
743 // If this is a conditional branch and only one successor goes to BBTo, then
744 // we maybe able to infer something from the condition.
745 if (BI->isConditional() &&
746 BI->getSuccessor(0) != BI->getSuccessor(1)) {
747 bool isTrueDest = BI->getSuccessor(0) == BBTo;
748 assert(BI->getSuccessor(!isTrueDest) == BBTo &&
749 "BBTo isn't a successor of BBFrom");
751 // If V is the condition of the branch itself, then we know exactly what
753 if (BI->getCondition() == Val) {
754 Result = LVILatticeVal::get(ConstantInt::get(
755 Type::getInt1Ty(Val->getContext()), isTrueDest));
759 // If the condition of the branch is an equality comparison, we may be
760 // able to infer the value.
761 ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
762 if (ICI && ICI->getOperand(0) == Val &&
763 isa<Constant>(ICI->getOperand(1))) {
764 if (ICI->isEquality()) {
765 // We know that V has the RHS constant if this is a true SETEQ or
767 if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
768 Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
770 Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
774 if (ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
775 // Calculate the range of values that would satisfy the comparison.
776 ConstantRange CmpRange(CI->getValue(), CI->getValue()+1);
777 ConstantRange TrueValues =
778 ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
780 // If we're interested in the false dest, invert the condition.
781 if (!isTrueDest) TrueValues = TrueValues.inverse();
783 // Figure out the possible values of the query BEFORE this branch.
784 LVILatticeVal InBlock = getBlockValue(Val, BBFrom);
785 if (!InBlock.isConstantRange()) {
786 Result = LVILatticeVal::getRange(TrueValues);
790 // Find all potential values that satisfy both the input and output
792 ConstantRange PossibleValues =
793 TrueValues.intersectWith(InBlock.getConstantRange());
795 Result = LVILatticeVal::getRange(PossibleValues);
802 // If the edge was formed by a switch on the value, then we may know exactly
804 if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
805 if (SI->getCondition() == Val) {
806 // We don't know anything in the default case.
807 if (SI->getDefaultDest() == BBTo) {
808 Result.markOverdefined();
812 // We only know something if there is exactly one value that goes from
814 unsigned NumEdges = 0;
815 ConstantInt *EdgeVal = 0;
816 for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
817 if (SI->getSuccessor(i) != BBTo) continue;
818 if (NumEdges++) break;
819 EdgeVal = SI->getCaseValue(i);
821 assert(EdgeVal && "Missing successor?");
823 Result = LVILatticeVal::get(EdgeVal);
829 // Otherwise see if the value is known in the block.
830 if (hasBlockValue(Val, BBFrom)) {
831 Result = getBlockValue(Val, BBFrom);
834 block_value_stack.push(std::make_pair(BBFrom, Val));
838 LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) {
839 DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
840 << BB->getName() << "'\n");
842 block_value_stack.push(std::make_pair(BB, V));
844 LVILatticeVal Result = getBlockValue(V, BB);
846 DEBUG(dbgs() << " Result = " << Result << "\n");
850 LVILatticeVal LazyValueInfoCache::
851 getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) {
852 DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
853 << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
855 LVILatticeVal Result;
856 if (!getEdgeValue(V, FromBB, ToBB, Result)) {
858 bool WasFastQuery = getEdgeValue(V, FromBB, ToBB, Result);
860 assert(WasFastQuery && "More work to do after problem solved?");
863 DEBUG(dbgs() << " Result = " << Result << "\n");
867 void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
868 BasicBlock *NewSucc) {
869 // When an edge in the graph has been threaded, values that we could not
870 // determine a value for before (i.e. were marked overdefined) may be possible
871 // to solve now. We do NOT try to proactively update these values. Instead,
872 // we clear their entries from the cache, and allow lazy updating to recompute
875 // The updating process is fairly simple: we need to dropped cached info
876 // for all values that were marked overdefined in OldSucc, and for those same
877 // values in any successor of OldSucc (except NewSucc) in which they were
878 // also marked overdefined.
879 std::vector<BasicBlock*> worklist;
880 worklist.push_back(OldSucc);
882 DenseSet<Value*> ClearSet;
883 for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
884 I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ++I) {
885 if (I->first == OldSucc)
886 ClearSet.insert(I->second);
889 // Use a worklist to perform a depth-first search of OldSucc's successors.
890 // NOTE: We do not need a visited list since any blocks we have already
891 // visited will have had their overdefined markers cleared already, and we
892 // thus won't loop to their successors.
893 while (!worklist.empty()) {
894 BasicBlock *ToUpdate = worklist.back();
897 // Skip blocks only accessible through NewSucc.
898 if (ToUpdate == NewSucc) continue;
900 bool changed = false;
901 for (DenseSet<Value*>::iterator I = ClearSet.begin(), E = ClearSet.end();
903 // If a value was marked overdefined in OldSucc, and is here too...
904 std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator OI =
905 OverDefinedCache.find(std::make_pair(ToUpdate, *I));
906 if (OI == OverDefinedCache.end()) continue;
908 // Remove it from the caches.
909 ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
910 ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
912 assert(CI != Entry.end() && "Couldn't find entry to update?");
914 OverDefinedCache.erase(OI);
916 // If we removed anything, then we potentially need to update
917 // blocks successors too.
921 if (!changed) continue;
923 worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
927 //===----------------------------------------------------------------------===//
928 // LazyValueInfo Impl
929 //===----------------------------------------------------------------------===//
931 /// getCache - This lazily constructs the LazyValueInfoCache.
932 static LazyValueInfoCache &getCache(void *&PImpl) {
934 PImpl = new LazyValueInfoCache();
935 return *static_cast<LazyValueInfoCache*>(PImpl);
938 bool LazyValueInfo::runOnFunction(Function &F) {
940 getCache(PImpl).clear();
942 TD = getAnalysisIfAvailable<TargetData>();
947 void LazyValueInfo::releaseMemory() {
948 // If the cache was allocated, free it.
950 delete &getCache(PImpl);
955 Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) {
956 LVILatticeVal Result = getCache(PImpl).getValueInBlock(V, BB);
958 if (Result.isConstant())
959 return Result.getConstant();
960 if (Result.isConstantRange()) {
961 ConstantRange CR = Result.getConstantRange();
962 if (const APInt *SingleVal = CR.getSingleElement())
963 return ConstantInt::get(V->getContext(), *SingleVal);
968 /// getConstantOnEdge - Determine whether the specified value is known to be a
969 /// constant on the specified edge. Return null if not.
970 Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
972 LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
974 if (Result.isConstant())
975 return Result.getConstant();
976 if (Result.isConstantRange()) {
977 ConstantRange CR = Result.getConstantRange();
978 if (const APInt *SingleVal = CR.getSingleElement())
979 return ConstantInt::get(V->getContext(), *SingleVal);
984 /// getPredicateOnEdge - Determine whether the specified value comparison
985 /// with a constant is known to be true or false on the specified CFG edge.
986 /// Pred is a CmpInst predicate.
987 LazyValueInfo::Tristate
988 LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
989 BasicBlock *FromBB, BasicBlock *ToBB) {
990 LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
992 // If we know the value is a constant, evaluate the conditional.
994 if (Result.isConstant()) {
995 Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, TD);
996 if (ConstantInt *ResCI = dyn_cast<ConstantInt>(Res))
997 return ResCI->isZero() ? False : True;
1001 if (Result.isConstantRange()) {
1002 ConstantInt *CI = dyn_cast<ConstantInt>(C);
1003 if (!CI) return Unknown;
1005 ConstantRange CR = Result.getConstantRange();
1006 if (Pred == ICmpInst::ICMP_EQ) {
1007 if (!CR.contains(CI->getValue()))
1010 if (CR.isSingleElement() && CR.contains(CI->getValue()))
1012 } else if (Pred == ICmpInst::ICMP_NE) {
1013 if (!CR.contains(CI->getValue()))
1016 if (CR.isSingleElement() && CR.contains(CI->getValue()))
1020 // Handle more complex predicates.
1021 ConstantRange TrueValues =
1022 ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
1023 if (TrueValues.contains(CR))
1025 if (TrueValues.inverse().contains(CR))
1030 if (Result.isNotConstant()) {
1031 // If this is an equality comparison, we can try to fold it knowing that
1033 if (Pred == ICmpInst::ICMP_EQ) {
1034 // !C1 == C -> false iff C1 == C.
1035 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
1036 Result.getNotConstant(), C, TD);
1037 if (Res->isNullValue())
1039 } else if (Pred == ICmpInst::ICMP_NE) {
1040 // !C1 != C -> true iff C1 == C.
1041 Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
1042 Result.getNotConstant(), C, TD);
1043 if (Res->isNullValue())
1052 void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
1053 BasicBlock *NewSucc) {
1054 if (PImpl) getCache(PImpl).threadEdge(PredBB, OldSucc, NewSucc);
1057 void LazyValueInfo::eraseBlock(BasicBlock *BB) {
1058 if (PImpl) getCache(PImpl).eraseBlock(BB);