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+//===- LazyValueInfo.cpp - Value constraint analysis ----------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the interface for lazy computation of value constraint
+// information.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "lazy-value-info"
+#include "llvm/Analysis/LazyValueInfo.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/Constants.h"
+#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/ConstantRange.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/ValueHandle.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/STLExtras.h"
+#include <map>
+#include <stack>
+using namespace llvm;
+
+char LazyValueInfo::ID = 0;
+INITIALIZE_PASS(LazyValueInfo, "lazy-value-info",
+ "Lazy Value Information Analysis", false, true)
+
+namespace llvm {
+ FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
+}
+
+
+//===----------------------------------------------------------------------===//
+// LVILatticeVal
+//===----------------------------------------------------------------------===//
+
+/// LVILatticeVal - This is the information tracked by LazyValueInfo for each
+/// value.
+///
+/// FIXME: This is basically just for bringup, this can be made a lot more rich
+/// in the future.
+///
+namespace {
+class LVILatticeVal {
+ enum LatticeValueTy {
+ /// undefined - This Value has no known value yet.
+ undefined,
+
+ /// constant - This Value has a specific constant value.
+ constant,
+ /// notconstant - This Value is known to not have the specified value.
+ notconstant,
+
+ /// constantrange - The Value falls within this range.
+ constantrange,
+
+ /// overdefined - This value is not known to be constant, and we know that
+ /// it has a value.
+ overdefined
+ };
+
+ /// Val: This stores the current lattice value along with the Constant* for
+ /// the constant if this is a 'constant' or 'notconstant' value.
+ LatticeValueTy Tag;
+ Constant *Val;
+ ConstantRange Range;
+
+public:
+ LVILatticeVal() : Tag(undefined), Val(0), Range(1, true) {}
+
+ static LVILatticeVal get(Constant *C) {
+ LVILatticeVal Res;
+ if (!isa<UndefValue>(C))
+ Res.markConstant(C);
+ return Res;
+ }
+ static LVILatticeVal getNot(Constant *C) {
+ LVILatticeVal Res;
+ if (!isa<UndefValue>(C))
+ Res.markNotConstant(C);
+ return Res;
+ }
+ static LVILatticeVal getRange(ConstantRange CR) {
+ LVILatticeVal Res;
+ Res.markConstantRange(CR);
+ return Res;
+ }
+
+ bool isUndefined() const { return Tag == undefined; }
+ bool isConstant() const { return Tag == constant; }
+ bool isNotConstant() const { return Tag == notconstant; }
+ bool isConstantRange() const { return Tag == constantrange; }
+ bool isOverdefined() const { return Tag == overdefined; }
+
+ Constant *getConstant() const {
+ assert(isConstant() && "Cannot get the constant of a non-constant!");
+ return Val;
+ }
+
+ Constant *getNotConstant() const {
+ assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
+ return Val;
+ }
+
+ ConstantRange getConstantRange() const {
+ assert(isConstantRange() &&
+ "Cannot get the constant-range of a non-constant-range!");
+ return Range;
+ }
+
+ /// markOverdefined - Return true if this is a change in status.
+ bool markOverdefined() {
+ if (isOverdefined())
+ return false;
+ Tag = overdefined;
+ return true;
+ }
+
+ /// markConstant - Return true if this is a change in status.
+ bool markConstant(Constant *V) {
+ assert(V && "Marking constant with NULL");
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
+ return markConstantRange(ConstantRange(CI->getValue()));
+ if (isa<UndefValue>(V))
+ return false;
+
+ assert((!isConstant() || getConstant() == V) &&
+ "Marking constant with different value");
+ assert(isUndefined());
+ Tag = constant;
+ Val = V;
+ return true;
+ }
+
+ /// markNotConstant - Return true if this is a change in status.
+ bool markNotConstant(Constant *V) {
+ assert(V && "Marking constant with NULL");
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
+ return markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue()));
+ if (isa<UndefValue>(V))
+ return false;
+
+ assert((!isConstant() || getConstant() != V) &&
+ "Marking constant !constant with same value");
+ assert((!isNotConstant() || getNotConstant() == V) &&
+ "Marking !constant with different value");
+ assert(isUndefined() || isConstant());
+ Tag = notconstant;
+ Val = V;
+ return true;
+ }
+
+ /// markConstantRange - Return true if this is a change in status.
+ bool markConstantRange(const ConstantRange NewR) {
+ if (isConstantRange()) {
+ if (NewR.isEmptySet())
+ return markOverdefined();
+
+ bool changed = Range == NewR;
+ Range = NewR;
+ return changed;
+ }
+
+ assert(isUndefined());
+ if (NewR.isEmptySet())
+ return markOverdefined();
+
+ Tag = constantrange;
+ Range = NewR;
+ return true;
+ }
+
+ /// mergeIn - Merge the specified lattice value into this one, updating this
+ /// one and returning true if anything changed.
+ bool mergeIn(const LVILatticeVal &RHS) {
+ if (RHS.isUndefined() || isOverdefined()) return false;
+ if (RHS.isOverdefined()) return markOverdefined();
+
+ if (isUndefined()) {
+ Tag = RHS.Tag;
+ Val = RHS.Val;
+ Range = RHS.Range;
+ return true;
+ }
+
+ if (isConstant()) {
+ if (RHS.isConstant()) {
+ if (Val == RHS.Val)
+ return false;
+ return markOverdefined();
+ }
+
+ if (RHS.isNotConstant()) {
+ if (Val == RHS.Val)
+ return markOverdefined();
+
+ // Unless we can prove that the two Constants are different, we must
+ // move to overdefined.
+ // FIXME: use TargetData for smarter constant folding.
+ if (ConstantInt *Res = dyn_cast<ConstantInt>(
+ ConstantFoldCompareInstOperands(CmpInst::ICMP_NE,
+ getConstant(),
+ RHS.getNotConstant())))
+ if (Res->isOne())
+ return markNotConstant(RHS.getNotConstant());
+
+ return markOverdefined();
+ }
+
+ // RHS is a ConstantRange, LHS is a non-integer Constant.
+
+ // FIXME: consider the case where RHS is a range [1, 0) and LHS is
+ // a function. The correct result is to pick up RHS.
+
+ return markOverdefined();
+ }
+
+ if (isNotConstant()) {
+ if (RHS.isConstant()) {
+ if (Val == RHS.Val)
+ return markOverdefined();
+
+ // Unless we can prove that the two Constants are different, we must
+ // move to overdefined.
+ // FIXME: use TargetData for smarter constant folding.
+ if (ConstantInt *Res = dyn_cast<ConstantInt>(
+ ConstantFoldCompareInstOperands(CmpInst::ICMP_NE,
+ getNotConstant(),
+ RHS.getConstant())))
+ if (Res->isOne())
+ return false;
+
+ return markOverdefined();
+ }
+
+ if (RHS.isNotConstant()) {
+ if (Val == RHS.Val)
+ return false;
+ return markOverdefined();
+ }
+
+ return markOverdefined();
+ }
+
+ assert(isConstantRange() && "New LVILattice type?");
+ if (!RHS.isConstantRange())
+ return markOverdefined();
+
+ ConstantRange NewR = Range.unionWith(RHS.getConstantRange());
+ if (NewR.isFullSet())
+ return markOverdefined();
+ return markConstantRange(NewR);
+ }
+};
+
+} // end anonymous namespace.
+
+namespace llvm {
+raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val)
+ LLVM_ATTRIBUTE_USED;
+raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
+ if (Val.isUndefined())
+ return OS << "undefined";
+ if (Val.isOverdefined())
+ return OS << "overdefined";
+
+ if (Val.isNotConstant())
+ return OS << "notconstant<" << *Val.getNotConstant() << '>';
+ else if (Val.isConstantRange())
+ return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
+ << Val.getConstantRange().getUpper() << '>';
+ return OS << "constant<" << *Val.getConstant() << '>';
+}
+}
+
+//===----------------------------------------------------------------------===//
+// LazyValueInfoCache Decl
+//===----------------------------------------------------------------------===//
+
+namespace {
+ /// LVIValueHandle - A callback value handle update the cache when
+ /// values are erased.
+ class LazyValueInfoCache;
+ struct LVIValueHandle : public CallbackVH {
+ LazyValueInfoCache *Parent;
+
+ LVIValueHandle(Value *V, LazyValueInfoCache *P)
+ : CallbackVH(V), Parent(P) { }
+
+ void deleted();
+ void allUsesReplacedWith(Value *V) {
+ deleted();
+ }
+ };
+}
+
+namespace llvm {
+ template<>
+ struct DenseMapInfo<LVIValueHandle> {
+ typedef DenseMapInfo<Value*> PointerInfo;
+ static inline LVIValueHandle getEmptyKey() {
+ return LVIValueHandle(PointerInfo::getEmptyKey(),
+ static_cast<LazyValueInfoCache*>(0));
+ }
+ static inline LVIValueHandle getTombstoneKey() {
+ return LVIValueHandle(PointerInfo::getTombstoneKey(),
+ static_cast<LazyValueInfoCache*>(0));
+ }
+ static unsigned getHashValue(const LVIValueHandle &Val) {
+ return PointerInfo::getHashValue(Val);
+ }
+ static bool isEqual(const LVIValueHandle &LHS, const LVIValueHandle &RHS) {
+ return LHS == RHS;
+ }
+ };
+
+ template<>
+ struct DenseMapInfo<std::pair<AssertingVH<BasicBlock>, Value*> > {
+ typedef std::pair<AssertingVH<BasicBlock>, Value*> PairTy;
+ typedef DenseMapInfo<AssertingVH<BasicBlock> > APointerInfo;
+ typedef DenseMapInfo<Value*> BPointerInfo;
+ static inline PairTy getEmptyKey() {
+ return std::make_pair(APointerInfo::getEmptyKey(),
+ BPointerInfo::getEmptyKey());
+ }
+ static inline PairTy getTombstoneKey() {
+ return std::make_pair(APointerInfo::getTombstoneKey(),
+ BPointerInfo::getTombstoneKey());
+ }
+ static unsigned getHashValue( const PairTy &Val) {
+ return APointerInfo::getHashValue(Val.first) ^
+ BPointerInfo::getHashValue(Val.second);
+ }
+ static bool isEqual(const PairTy &LHS, const PairTy &RHS) {
+ return APointerInfo::isEqual(LHS.first, RHS.first) &&
+ BPointerInfo::isEqual(LHS.second, RHS.second);
+ }
+ };
+}
+
+namespace {
+ /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
+ /// maintains information about queries across the clients' queries.
+ class LazyValueInfoCache {
+ /// ValueCacheEntryTy - This is all of the cached block information for
+ /// exactly one Value*. The entries are sorted by the BasicBlock* of the
+ /// entries, allowing us to do a lookup with a binary search.
+ typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
+
+ /// ValueCache - This is all of the cached information for all values,
+ /// mapped from Value* to key information.
+ DenseMap<LVIValueHandle, ValueCacheEntryTy> ValueCache;
+
+ /// OverDefinedCache - This tracks, on a per-block basis, the set of
+ /// values that are over-defined at the end of that block. This is required
+ /// for cache updating.
+ typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
+ DenseSet<OverDefinedPairTy> OverDefinedCache;
+
+ /// BlockValueStack - This stack holds the state of the value solver
+ /// during a query. It basically emulates the callstack of the naive
+ /// recursive value lookup process.
+ std::stack<std::pair<BasicBlock*, Value*> > BlockValueStack;
+
+ friend struct LVIValueHandle;
+
+ /// OverDefinedCacheUpdater - A helper object that ensures that the
+ /// OverDefinedCache is updated whenever solveBlockValue returns.
+ struct OverDefinedCacheUpdater {
+ LazyValueInfoCache *Parent;
+ Value *Val;
+ BasicBlock *BB;
+ LVILatticeVal &BBLV;
+
+ OverDefinedCacheUpdater(Value *V, BasicBlock *B, LVILatticeVal &LV,
+ LazyValueInfoCache *P)
+ : Parent(P), Val(V), BB(B), BBLV(LV) { }
+
+ bool markResult(bool changed) {
+ if (changed && BBLV.isOverdefined())
+ Parent->OverDefinedCache.insert(std::make_pair(BB, Val));
+ return changed;
+ }
+ };
+
+
+
+ LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
+ bool getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T,
+ LVILatticeVal &Result);
+ bool hasBlockValue(Value *Val, BasicBlock *BB);
+
+ // These methods process one work item and may add more. A false value
+ // returned means that the work item was not completely processed and must
+ // be revisited after going through the new items.
+ bool solveBlockValue(Value *Val, BasicBlock *BB);
+ bool solveBlockValueNonLocal(LVILatticeVal &BBLV,
+ Value *Val, BasicBlock *BB);
+ bool solveBlockValuePHINode(LVILatticeVal &BBLV,
+ PHINode *PN, BasicBlock *BB);
+ bool solveBlockValueConstantRange(LVILatticeVal &BBLV,
+ Instruction *BBI, BasicBlock *BB);
+
+ void solve();
+
+ ValueCacheEntryTy &lookup(Value *V) {
+ return ValueCache[LVIValueHandle(V, this)];
+ }
+
+ public:
+ /// getValueInBlock - This is the query interface to determine the lattice
+ /// value for the specified Value* at the end of the specified block.
+ LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB);
+
+ /// getValueOnEdge - This is the query interface to determine the lattice
+ /// value for the specified Value* that is true on the specified edge.
+ LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB);
+
+ /// threadEdge - This is the update interface to inform the cache that an
+ /// edge from PredBB to OldSucc has been threaded to be from PredBB to
+ /// NewSucc.
+ void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
+
+ /// eraseBlock - This is part of the update interface to inform the cache
+ /// that a block has been deleted.
+ void eraseBlock(BasicBlock *BB);
+
+ /// clear - Empty the cache.
+ void clear() {
+ ValueCache.clear();
+ OverDefinedCache.clear();
+ }
+ };
+} // end anonymous namespace
+
+void LVIValueHandle::deleted() {
+ typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
+
+ SmallVector<OverDefinedPairTy, 4> ToErase;
+ for (DenseSet<OverDefinedPairTy>::iterator
+ I = Parent->OverDefinedCache.begin(),
+ E = Parent->OverDefinedCache.end();
+ I != E; ++I) {
+ if (I->second == getValPtr())
+ ToErase.push_back(*I);
+ }
+
+ for (SmallVector<OverDefinedPairTy, 4>::iterator I = ToErase.begin(),
+ E = ToErase.end(); I != E; ++I)
+ Parent->OverDefinedCache.erase(*I);
+
+ // This erasure deallocates *this, so it MUST happen after we're done
+ // using any and all members of *this.
+ Parent->ValueCache.erase(*this);
+}
+
+void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
+ SmallVector<OverDefinedPairTy, 4> ToErase;
+ for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
+ E = OverDefinedCache.end(); I != E; ++I) {
+ if (I->first == BB)
+ ToErase.push_back(*I);
+ }
+
+ for (SmallVector<OverDefinedPairTy, 4>::iterator I = ToErase.begin(),
+ E = ToErase.end(); I != E; ++I)
+ OverDefinedCache.erase(*I);
+
+ for (DenseMap<LVIValueHandle, ValueCacheEntryTy>::iterator
+ I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
+ I->second.erase(BB);
+}
+
+void LazyValueInfoCache::solve() {
+ while (!BlockValueStack.empty()) {
+ std::pair<BasicBlock*, Value*> &e = BlockValueStack.top();
+ if (solveBlockValue(e.second, e.first))
+ BlockValueStack.pop();
+ }
+}
+
+bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
+ // If already a constant, there is nothing to compute.
+ if (isa<Constant>(Val))
+ return true;
+
+ LVIValueHandle ValHandle(Val, this);
+ if (!ValueCache.count(ValHandle)) return false;
+ return ValueCache[ValHandle].count(BB);
+}
+
+LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
+ // If already a constant, there is nothing to compute.
+ if (Constant *VC = dyn_cast<Constant>(Val))
+ return LVILatticeVal::get(VC);
+
+ return lookup(Val)[BB];
+}
+
+bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
+ if (isa<Constant>(Val))
+ return true;
+
+ ValueCacheEntryTy &Cache = lookup(Val);
+ LVILatticeVal &BBLV = Cache[BB];
+
+ // OverDefinedCacheUpdater is a helper object that will update
+ // the OverDefinedCache for us when this method exits. Make sure to
+ // call markResult on it as we exist, passing a bool to indicate if the
+ // cache needs updating, i.e. if we have solve a new value or not.
+ OverDefinedCacheUpdater ODCacheUpdater(Val, BB, BBLV, this);
+
+ // If we've already computed this block's value, return it.
+ if (!BBLV.isUndefined()) {
+ DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
+
+ // Since we're reusing a cached value here, we don't need to update the
+ // OverDefinedCahce. The cache will have been properly updated
+ // whenever the cached value was inserted.
+ ODCacheUpdater.markResult(false);
+ return true;
+ }
+
+ // Otherwise, this is the first time we're seeing this block. Reset the
+ // lattice value to overdefined, so that cycles will terminate and be
+ // conservatively correct.
+ BBLV.markOverdefined();
+
+ Instruction *BBI = dyn_cast<Instruction>(Val);
+ if (BBI == 0 || BBI->getParent() != BB) {
+ return ODCacheUpdater.markResult(solveBlockValueNonLocal(BBLV, Val, BB));
+ }
+
+ if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
+ return ODCacheUpdater.markResult(solveBlockValuePHINode(BBLV, PN, BB));
+ }
+
+ if (AllocaInst *AI = dyn_cast<AllocaInst>(BBI)) {
+ BBLV = LVILatticeVal::getNot(ConstantPointerNull::get(AI->getType()));
+ return ODCacheUpdater.markResult(true);
+ }
+
+ // We can only analyze the definitions of certain classes of instructions
+ // (integral binops and casts at the moment), so bail if this isn't one.
+ LVILatticeVal Result;
+ if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
+ !BBI->getType()->isIntegerTy()) {
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because inst def found.\n");
+ BBLV.markOverdefined();
+ return ODCacheUpdater.markResult(true);
+ }
+
+ // FIXME: We're currently limited to binops with a constant RHS. This should
+ // be improved.
+ BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
+ if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because inst def found.\n");
+
+ BBLV.markOverdefined();
+ return ODCacheUpdater.markResult(true);
+ }
+
+ return ODCacheUpdater.markResult(solveBlockValueConstantRange(BBLV, BBI, BB));
+}
+
+static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
+ if (LoadInst *L = dyn_cast<LoadInst>(I)) {
+ return L->getPointerAddressSpace() == 0 &&
+ GetUnderlyingObject(L->getPointerOperand()) ==
+ GetUnderlyingObject(Ptr);
+ }
+ if (StoreInst *S = dyn_cast<StoreInst>(I)) {
+ return S->getPointerAddressSpace() == 0 &&
+ GetUnderlyingObject(S->getPointerOperand()) ==
+ GetUnderlyingObject(Ptr);
+ }
+ if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
+ if (MI->isVolatile()) return false;
+
+ // FIXME: check whether it has a valuerange that excludes zero?
+ ConstantInt *Len = dyn_cast<ConstantInt>(MI->getLength());
+ if (!Len || Len->isZero()) return false;
+
+ if (MI->getDestAddressSpace() == 0)
+ if (MI->getRawDest() == Ptr || MI->getDest() == Ptr)
+ return true;
+ if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
+ if (MTI->getSourceAddressSpace() == 0)
+ if (MTI->getRawSource() == Ptr || MTI->getSource() == Ptr)
+ return true;
+ }
+ return false;
+}
+
+bool LazyValueInfoCache::solveBlockValueNonLocal(LVILatticeVal &BBLV,
+ Value *Val, BasicBlock *BB) {
+ LVILatticeVal Result; // Start Undefined.
+
+ // If this is a pointer, and there's a load from that pointer in this BB,
+ // then we know that the pointer can't be NULL.
+ bool NotNull = false;
+ if (Val->getType()->isPointerTy()) {
+ if (isa<AllocaInst>(Val)) {
+ NotNull = true;
+ } else {
+ for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){
+ if (InstructionDereferencesPointer(BI, Val)) {
+ NotNull = true;
+ break;
+ }
+ }
+ }
+ }
+
+ // If this is the entry block, we must be asking about an argument. The
+ // value is overdefined.
+ if (BB == &BB->getParent()->getEntryBlock()) {
+ assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
+ if (NotNull) {
+ PointerType *PTy = cast<PointerType>(Val->getType());
+ Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
+ } else {
+ Result.markOverdefined();
+ }
+ BBLV = Result;
+ return true;
+ }
+
+ // Loop over all of our predecessors, merging what we know from them into
+ // result.
+ bool EdgesMissing = false;
+ for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
+ LVILatticeVal EdgeResult;
+ EdgesMissing |= !getEdgeValue(Val, *PI, BB, EdgeResult);
+ if (EdgesMissing)
+ continue;
+
+ Result.mergeIn(EdgeResult);
+
+ // If we hit overdefined, exit early. The BlockVals entry is already set
+ // to overdefined.
+ if (Result.isOverdefined()) {
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because of pred.\n");
+ // If we previously determined that this is a pointer that can't be null
+ // then return that rather than giving up entirely.
+ if (NotNull) {
+ PointerType *PTy = cast<PointerType>(Val->getType());
+ Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
+ }
+
+ BBLV = Result;
+ return true;
+ }
+ }
+ if (EdgesMissing)
+ return false;
+
+ // Return the merged value, which is more precise than 'overdefined'.
+ assert(!Result.isOverdefined());
+ BBLV = Result;
+ return true;
+}
+
+bool LazyValueInfoCache::solveBlockValuePHINode(LVILatticeVal &BBLV,
+ PHINode *PN, BasicBlock *BB) {
+ LVILatticeVal Result; // Start Undefined.
+
+ // Loop over all of our predecessors, merging what we know from them into
+ // result.
+ bool EdgesMissing = false;
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ BasicBlock *PhiBB = PN->getIncomingBlock(i);
+ Value *PhiVal = PN->getIncomingValue(i);
+ LVILatticeVal EdgeResult;
+ EdgesMissing |= !getEdgeValue(PhiVal, PhiBB, BB, EdgeResult);
+ if (EdgesMissing)
+ continue;
+
+ Result.mergeIn(EdgeResult);
+
+ // If we hit overdefined, exit early. The BlockVals entry is already set
+ // to overdefined.
+ if (Result.isOverdefined()) {
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because of pred.\n");
+
+ BBLV = Result;
+ return true;
+ }
+ }
+ if (EdgesMissing)
+ return false;
+
+ // Return the merged value, which is more precise than 'overdefined'.
+ assert(!Result.isOverdefined() && "Possible PHI in entry block?");
+ BBLV = Result;
+ return true;
+}
+
+bool LazyValueInfoCache::solveBlockValueConstantRange(LVILatticeVal &BBLV,
+ Instruction *BBI,
+ BasicBlock *BB) {
+ // Figure out the range of the LHS. If that fails, bail.
+ if (!hasBlockValue(BBI->getOperand(0), BB)) {
+ BlockValueStack.push(std::make_pair(BB, BBI->getOperand(0)));
+ return false;
+ }
+
+ LVILatticeVal LHSVal = getBlockValue(BBI->getOperand(0), BB);
+ if (!LHSVal.isConstantRange()) {
+ BBLV.markOverdefined();
+ return true;
+ }
+
+ ConstantRange LHSRange = LHSVal.getConstantRange();
+ ConstantRange RHSRange(1);
+ IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
+ if (isa<BinaryOperator>(BBI)) {
+ if (ConstantInt *RHS = dyn_cast<ConstantInt>(BBI->getOperand(1))) {
+ RHSRange = ConstantRange(RHS->getValue());
+ } else {
+ BBLV.markOverdefined();
+ return true;
+ }
+ }
+
+ // NOTE: We're currently limited by the set of operations that ConstantRange
+ // can evaluate symbolically. Enhancing that set will allows us to analyze
+ // more definitions.
+ LVILatticeVal Result;
+ switch (BBI->getOpcode()) {
+ case Instruction::Add:
+ Result.markConstantRange(LHSRange.add(RHSRange));
+ break;
+ case Instruction::Sub:
+ Result.markConstantRange(LHSRange.sub(RHSRange));
+ break;
+ case Instruction::Mul:
+ Result.markConstantRange(LHSRange.multiply(RHSRange));
+ break;
+ case Instruction::UDiv:
+ Result.markConstantRange(LHSRange.udiv(RHSRange));
+ break;
+ case Instruction::Shl:
+ Result.markConstantRange(LHSRange.shl(RHSRange));
+ break;
+ case Instruction::LShr:
+ Result.markConstantRange(LHSRange.lshr(RHSRange));
+ break;
+ case Instruction::Trunc:
+ Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
+ break;
+ case Instruction::SExt:
+ Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
+ break;
+ case Instruction::ZExt:
+ Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
+ break;
+ case Instruction::BitCast:
+ Result.markConstantRange(LHSRange);
+ break;
+ case Instruction::And:
+ Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
+ break;
+ case Instruction::Or:
+ Result.markConstantRange(LHSRange.binaryOr(RHSRange));
+ break;
+
+ // Unhandled instructions are overdefined.
+ default:
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because inst def found.\n");
+ Result.markOverdefined();
+ break;
+ }
+
+ BBLV = Result;
+ return true;
+}
+
+/// getEdgeValue - This method attempts to infer more complex
+bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom,
+ BasicBlock *BBTo, LVILatticeVal &Result) {
+ // If already a constant, there is nothing to compute.
+ if (Constant *VC = dyn_cast<Constant>(Val)) {
+ Result = LVILatticeVal::get(VC);
+ return true;
+ }
+
+ // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
+ // know that v != 0.
+ if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
+ // If this is a conditional branch and only one successor goes to BBTo, then
+ // we maybe able to infer something from the condition.
+ if (BI->isConditional() &&
+ BI->getSuccessor(0) != BI->getSuccessor(1)) {
+ bool isTrueDest = BI->getSuccessor(0) == BBTo;
+ assert(BI->getSuccessor(!isTrueDest) == BBTo &&
+ "BBTo isn't a successor of BBFrom");
+
+ // If V is the condition of the branch itself, then we know exactly what
+ // it is.
+ if (BI->getCondition() == Val) {
+ Result = LVILatticeVal::get(ConstantInt::get(
+ Type::getInt1Ty(Val->getContext()), isTrueDest));
+ return true;
+ }
+
+ // If the condition of the branch is an equality comparison, we may be
+ // able to infer the value.
+ ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
+ if (ICI && ICI->getOperand(0) == Val &&
+ isa<Constant>(ICI->getOperand(1))) {
+ if (ICI->isEquality()) {
+ // We know that V has the RHS constant if this is a true SETEQ or
+ // false SETNE.
+ if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
+ Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
+ else
+ Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
+ return true;
+ }
+
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
+ // Calculate the range of values that would satisfy the comparison.
+ ConstantRange CmpRange(CI->getValue(), CI->getValue()+1);
+ ConstantRange TrueValues =
+ ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
+
+ // If we're interested in the false dest, invert the condition.
+ if (!isTrueDest) TrueValues = TrueValues.inverse();
+
+ // Figure out the possible values of the query BEFORE this branch.
+ if (!hasBlockValue(Val, BBFrom)) {
+ BlockValueStack.push(std::make_pair(BBFrom, Val));
+ return false;
+ }
+
+ LVILatticeVal InBlock = getBlockValue(Val, BBFrom);
+ if (!InBlock.isConstantRange()) {
+ Result = LVILatticeVal::getRange(TrueValues);
+ return true;
+ }
+
+ // Find all potential values that satisfy both the input and output
+ // conditions.
+ ConstantRange PossibleValues =
+ TrueValues.intersectWith(InBlock.getConstantRange());
+
+ Result = LVILatticeVal::getRange(PossibleValues);
+ return true;
+ }
+ }
+ }
+ }
+
+ // If the edge was formed by a switch on the value, then we may know exactly
+ // what it is.
+ if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
+ if (SI->getCondition() == Val) {
+ // We don't know anything in the default case.
+ if (SI->getDefaultDest() == BBTo) {
+ Result.markOverdefined();
+ return true;
+ }
+
+ // We only know something if there is exactly one value that goes from
+ // BBFrom to BBTo.
+ unsigned NumEdges = 0;
+ ConstantInt *EdgeVal = 0;
+ for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
+ if (SI->getSuccessor(i) != BBTo) continue;
+ if (NumEdges++) break;
+ EdgeVal = SI->getCaseValue(i);
+ }
+ assert(EdgeVal && "Missing successor?");
+ if (NumEdges == 1) {
+ Result = LVILatticeVal::get(EdgeVal);
+ return true;
+ }
+ }
+ }
+
+ // Otherwise see if the value is known in the block.
+ if (hasBlockValue(Val, BBFrom)) {
+ Result = getBlockValue(Val, BBFrom);
+ return true;
+ }
+ BlockValueStack.push(std::make_pair(BBFrom, Val));
+ return false;
+}
+
+LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) {
+ DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
+ << BB->getName() << "'\n");
+
+ BlockValueStack.push(std::make_pair(BB, V));
+ solve();
+ LVILatticeVal Result = getBlockValue(V, BB);
+
+ DEBUG(dbgs() << " Result = " << Result << "\n");
+ return Result;
+}
+
+LVILatticeVal LazyValueInfoCache::
+getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) {
+ DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
+ << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
+
+ LVILatticeVal Result;
+ if (!getEdgeValue(V, FromBB, ToBB, Result)) {
+ solve();
+ bool WasFastQuery = getEdgeValue(V, FromBB, ToBB, Result);
+ (void)WasFastQuery;
+ assert(WasFastQuery && "More work to do after problem solved?");
+ }
+
+ DEBUG(dbgs() << " Result = " << Result << "\n");
+ return Result;
+}
+
+void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
+ BasicBlock *NewSucc) {
+ // When an edge in the graph has been threaded, values that we could not
+ // determine a value for before (i.e. were marked overdefined) may be possible
+ // to solve now. We do NOT try to proactively update these values. Instead,
+ // we clear their entries from the cache, and allow lazy updating to recompute
+ // them when needed.
+
+ // The updating process is fairly simple: we need to dropped cached info
+ // for all values that were marked overdefined in OldSucc, and for those same
+ // values in any successor of OldSucc (except NewSucc) in which they were
+ // also marked overdefined.
+ std::vector<BasicBlock*> worklist;
+ worklist.push_back(OldSucc);
+
+ DenseSet<Value*> ClearSet;
+ for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
+ E = OverDefinedCache.end(); I != E; ++I) {
+ if (I->first == OldSucc)
+ ClearSet.insert(I->second);
+ }
+
+ // Use a worklist to perform a depth-first search of OldSucc's successors.
+ // NOTE: We do not need a visited list since any blocks we have already
+ // visited will have had their overdefined markers cleared already, and we
+ // thus won't loop to their successors.
+ while (!worklist.empty()) {
+ BasicBlock *ToUpdate = worklist.back();
+ worklist.pop_back();
+
+ // Skip blocks only accessible through NewSucc.
+ if (ToUpdate == NewSucc) continue;
+
+ bool changed = false;
+ for (DenseSet<Value*>::iterator I = ClearSet.begin(), E = ClearSet.end();
+ I != E; ++I) {
+ // If a value was marked overdefined in OldSucc, and is here too...
+ DenseSet<OverDefinedPairTy>::iterator OI =
+ OverDefinedCache.find(std::make_pair(ToUpdate, *I));
+ if (OI == OverDefinedCache.end()) continue;
+
+ // Remove it from the caches.
+ ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
+ ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
+
+ assert(CI != Entry.end() && "Couldn't find entry to update?");
+ Entry.erase(CI);
+ OverDefinedCache.erase(OI);
+
+ // If we removed anything, then we potentially need to update
+ // blocks successors too.
+ changed = true;
+ }
+
+ if (!changed) continue;
+
+ worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
+ }
+}
+
+//===----------------------------------------------------------------------===//
+// LazyValueInfo Impl
+//===----------------------------------------------------------------------===//
+
+/// getCache - This lazily constructs the LazyValueInfoCache.
+static LazyValueInfoCache &getCache(void *&PImpl) {
+ if (!PImpl)
+ PImpl = new LazyValueInfoCache();
+ return *static_cast<LazyValueInfoCache*>(PImpl);
+}
+
+bool LazyValueInfo::runOnFunction(Function &F) {
+ if (PImpl)
+ getCache(PImpl).clear();
+
+ TD = getAnalysisIfAvailable<TargetData>();
+ // Fully lazy.
+ return false;
+}
+
+void LazyValueInfo::releaseMemory() {
+ // If the cache was allocated, free it.
+ if (PImpl) {
+ delete &getCache(PImpl);
+ PImpl = 0;
+ }
+}
+
+Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) {
+ LVILatticeVal Result = getCache(PImpl).getValueInBlock(V, BB);
+
+ if (Result.isConstant())
+ return Result.getConstant();
+ if (Result.isConstantRange()) {
+ ConstantRange CR = Result.getConstantRange();
+ if (const APInt *SingleVal = CR.getSingleElement())
+ return ConstantInt::get(V->getContext(), *SingleVal);
+ }
+ return 0;
+}
+
+/// getConstantOnEdge - Determine whether the specified value is known to be a
+/// constant on the specified edge. Return null if not.
+Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
+ BasicBlock *ToBB) {
+ LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
+
+ if (Result.isConstant())
+ return Result.getConstant();
+ if (Result.isConstantRange()) {
+ ConstantRange CR = Result.getConstantRange();
+ if (const APInt *SingleVal = CR.getSingleElement())
+ return ConstantInt::get(V->getContext(), *SingleVal);
+ }
+ return 0;
+}
+
+/// getPredicateOnEdge - Determine whether the specified value comparison
+/// with a constant is known to be true or false on the specified CFG edge.
+/// Pred is a CmpInst predicate.
+LazyValueInfo::Tristate
+LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
+ BasicBlock *FromBB, BasicBlock *ToBB) {
+ LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
+
+ // If we know the value is a constant, evaluate the conditional.
+ Constant *Res = 0;
+ if (Result.isConstant()) {
+ Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, TD);
+ if (ConstantInt *ResCI = dyn_cast<ConstantInt>(Res))
+ return ResCI->isZero() ? False : True;
+ return Unknown;
+ }
+
+ if (Result.isConstantRange()) {
+ ConstantInt *CI = dyn_cast<ConstantInt>(C);
+ if (!CI) return Unknown;
+
+ ConstantRange CR = Result.getConstantRange();
+ if (Pred == ICmpInst::ICMP_EQ) {
+ if (!CR.contains(CI->getValue()))
+ return False;
+
+ if (CR.isSingleElement() && CR.contains(CI->getValue()))
+ return True;
+ } else if (Pred == ICmpInst::ICMP_NE) {
+ if (!CR.contains(CI->getValue()))
+ return True;
+
+ if (CR.isSingleElement() && CR.contains(CI->getValue()))
+ return False;
+ }
+
+ // Handle more complex predicates.
+ ConstantRange TrueValues =
+ ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
+ if (TrueValues.contains(CR))
+ return True;
+ if (TrueValues.inverse().contains(CR))
+ return False;
+ return Unknown;
+ }
+
+ if (Result.isNotConstant()) {
+ // If this is an equality comparison, we can try to fold it knowing that
+ // "V != C1".
+ if (Pred == ICmpInst::ICMP_EQ) {
+ // !C1 == C -> false iff C1 == C.
+ Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
+ Result.getNotConstant(), C, TD);
+ if (Res->isNullValue())
+ return False;
+ } else if (Pred == ICmpInst::ICMP_NE) {
+ // !C1 != C -> true iff C1 == C.
+ Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
+ Result.getNotConstant(), C, TD);
+ if (Res->isNullValue())
+ return True;
+ }
+ return Unknown;
+ }
+
+ return Unknown;
+}
+
+void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
+ BasicBlock *NewSucc) {
+ if (PImpl) getCache(PImpl).threadEdge(PredBB, OldSucc, NewSucc);
+}
+
+void LazyValueInfo::eraseBlock(BasicBlock *BB) {
+ if (PImpl) getCache(PImpl).eraseBlock(BB);
+}
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