//
//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "lazy-value-info"
#include "llvm/Analysis/LazyValueInfo.h"
+#include "llvm/Constants.h"
+#include "llvm/Instructions.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/STLExtras.h"
using namespace llvm;
char LazyValueInfo::ID = 0;
FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
}
-LazyValueInfo::LazyValueInfo() : FunctionPass(&ID) {
+
+//===----------------------------------------------------------------------===//
+// 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 LLVM Value has no known value yet.
+ undefined,
+ /// constant - This LLVM Value has a specific constant value.
+ constant,
+
+ /// notconstant - This LLVM value is known to not have the specified value.
+ notconstant,
+
+ /// overdefined - This instruction is not known to be constant, and we know
+ /// 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.
+ PointerIntPair<Constant *, 2, LatticeValueTy> Val;
+
+public:
+ LVILatticeVal() : Val(0, undefined) {}
+
+ static LVILatticeVal get(Constant *C) {
+ LVILatticeVal Res;
+ Res.markConstant(C);
+ return Res;
+ }
+ static LVILatticeVal getNot(Constant *C) {
+ LVILatticeVal Res;
+ Res.markNotConstant(C);
+ return Res;
+ }
+
+ bool isUndefined() const { return Val.getInt() == undefined; }
+ bool isConstant() const { return Val.getInt() == constant; }
+ bool isNotConstant() const { return Val.getInt() == notconstant; }
+ bool isOverdefined() const { return Val.getInt() == overdefined; }
+
+ Constant *getConstant() const {
+ assert(isConstant() && "Cannot get the constant of a non-constant!");
+ return Val.getPointer();
+ }
+
+ Constant *getNotConstant() const {
+ assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
+ return Val.getPointer();
+ }
+
+ /// markOverdefined - Return true if this is a change in status.
+ bool markOverdefined() {
+ if (isOverdefined())
+ return false;
+ Val.setInt(overdefined);
+ return true;
+ }
+
+ /// markConstant - Return true if this is a change in status.
+ bool markConstant(Constant *V) {
+ if (isConstant()) {
+ assert(getConstant() == V && "Marking constant with different value");
+ return false;
+ }
+
+ assert(isUndefined());
+ Val.setInt(constant);
+ assert(V && "Marking constant with NULL");
+ Val.setPointer(V);
+ return true;
+ }
+
+ /// markNotConstant - Return true if this is a change in status.
+ bool markNotConstant(Constant *V) {
+ if (isNotConstant()) {
+ assert(getNotConstant() == V && "Marking !constant with different value");
+ return false;
+ }
+
+ if (isConstant())
+ assert(getConstant() != V && "Marking not constant with different value");
+ else
+ assert(isUndefined());
+
+ Val.setInt(notconstant);
+ assert(V && "Marking constant with NULL");
+ Val.setPointer(V);
+ 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 (RHS.isNotConstant()) {
+ if (isNotConstant()) {
+ if (getNotConstant() != RHS.getNotConstant() ||
+ isa<ConstantExpr>(getNotConstant()) ||
+ isa<ConstantExpr>(RHS.getNotConstant()))
+ return markOverdefined();
+ return false;
+ }
+ if (isConstant()) {
+ if (getConstant() == RHS.getNotConstant() ||
+ isa<ConstantExpr>(RHS.getNotConstant()) ||
+ isa<ConstantExpr>(getConstant()))
+ return markOverdefined();
+ return markNotConstant(RHS.getNotConstant());
+ }
+
+ assert(isUndefined() && "Unexpected lattice");
+ return markNotConstant(RHS.getNotConstant());
+ }
+
+ // RHS must be a constant, we must be undef, constant, or notconstant.
+ if (isUndefined())
+ return markConstant(RHS.getConstant());
+
+ if (isConstant()) {
+ if (getConstant() != RHS.getConstant())
+ return markOverdefined();
+ return false;
+ }
+
+ // If we are known "!=4" and RHS is "==5", stay at "!=4".
+ if (getNotConstant() == RHS.getConstant() ||
+ isa<ConstantExpr>(getNotConstant()) ||
+ isa<ConstantExpr>(RHS.getConstant()))
+ return markOverdefined();
+ return false;
+ }
+
+};
+
+} // end anonymous namespace.
+
+namespace llvm {
+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() << '>';
+ return OS << "constant<" << *Val.getConstant() << '>';
+}
+}
+
+//===----------------------------------------------------------------------===//
+// LazyValueInfoCache Decl
+//===----------------------------------------------------------------------===//
+
+namespace {
+ /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
+ /// maintains information about queries across the clients' queries.
+ class LazyValueInfoCache {
+ public:
+ /// BlockCacheEntryTy - This is a computed lattice value at the end of the
+ /// specified basic block for a Value* that depends on context.
+ typedef std::pair<BasicBlock*, LVILatticeVal> BlockCacheEntryTy;
+
+ /// 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::vector<BlockCacheEntryTy> ValueCacheEntryTy;
+
+ private:
+ /// ValueCache - This is all of the cached information for all values,
+ /// mapped from Value* to key information.
+ DenseMap<Value*, ValueCacheEntryTy> ValueCache;
+ 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);
+ };
+} // end anonymous namespace
+
+namespace {
+ struct BlockCacheEntryComparator {
+ static int Compare(const void *LHSv, const void *RHSv) {
+ const LazyValueInfoCache::BlockCacheEntryTy *LHS =
+ static_cast<const LazyValueInfoCache::BlockCacheEntryTy *>(LHSv);
+ const LazyValueInfoCache::BlockCacheEntryTy *RHS =
+ static_cast<const LazyValueInfoCache::BlockCacheEntryTy *>(RHSv);
+ if (LHS->first < RHS->first)
+ return -1;
+ if (LHS->first > RHS->first)
+ return 1;
+ return 0;
+ }
+
+ bool operator()(const LazyValueInfoCache::BlockCacheEntryTy &LHS,
+ const LazyValueInfoCache::BlockCacheEntryTy &RHS) const {
+ return LHS.first < RHS.first;
+ }
+ };
+}
+
+//===----------------------------------------------------------------------===//
+// LVIQuery Impl
+//===----------------------------------------------------------------------===//
+
+namespace {
+ /// LVIQuery - This is a transient object that exists while a query is
+ /// being performed.
+ ///
+ /// TODO: Reuse LVIQuery instead of recreating it for every query, this avoids
+ /// reallocation of the densemap on every query.
+ class LVIQuery {
+ typedef LazyValueInfoCache::BlockCacheEntryTy BlockCacheEntryTy;
+ typedef LazyValueInfoCache::ValueCacheEntryTy ValueCacheEntryTy;
+
+ /// This is the current value being queried for.
+ Value *Val;
+
+ /// This is all of the cached information about this value.
+ ValueCacheEntryTy &Cache;
+
+ /// NewBlocks - This is a mapping of the new BasicBlocks which have been
+ /// added to cache but that are not in sorted order.
+ DenseMap<BasicBlock*, LVILatticeVal> NewBlockInfo;
+ public:
+
+ LVIQuery(Value *V, ValueCacheEntryTy &VC) : Val(V), Cache(VC) {
+ }
+
+ ~LVIQuery() {
+ // When the query is done, insert the newly discovered facts into the
+ // cache in sorted order.
+ if (NewBlockInfo.empty()) return;
+
+ // Grow the cache to exactly fit the new data.
+ Cache.reserve(Cache.size() + NewBlockInfo.size());
+
+ // If we only have one new entry, insert it instead of doing a full-on
+ // sort.
+ if (NewBlockInfo.size() == 1) {
+ BlockCacheEntryTy Entry = *NewBlockInfo.begin();
+ ValueCacheEntryTy::iterator I =
+ std::lower_bound(Cache.begin(), Cache.end(), Entry,
+ BlockCacheEntryComparator());
+ assert((I == Cache.end() || I->first != Entry.first) &&
+ "Entry already in map!");
+
+ Cache.insert(I, Entry);
+ return;
+ }
+
+ // TODO: If we only have two new elements, INSERT them both.
+
+ Cache.insert(Cache.end(), NewBlockInfo.begin(), NewBlockInfo.end());
+ array_pod_sort(Cache.begin(), Cache.end(),
+ BlockCacheEntryComparator::Compare);
+
+ }
+
+ LVILatticeVal getBlockValue(BasicBlock *BB);
+ LVILatticeVal getEdgeValue(BasicBlock *FromBB, BasicBlock *ToBB);
+
+ private:
+ LVILatticeVal &getCachedEntryForBlock(BasicBlock *BB);
+ };
+} // end anonymous namespace
+
+/// getCachedEntryForBlock - See if we already have a value for this block. If
+/// so, return it, otherwise create a new entry in the NewBlockInfo map to use.
+LVILatticeVal &LVIQuery::getCachedEntryForBlock(BasicBlock *BB) {
+
+ // Do a binary search to see if we already have an entry for this block in
+ // the cache set. If so, find it.
+ if (!Cache.empty()) {
+ ValueCacheEntryTy::iterator Entry =
+ std::lower_bound(Cache.begin(), Cache.end(),
+ BlockCacheEntryTy(BB, LVILatticeVal()),
+ BlockCacheEntryComparator());
+ if (Entry != Cache.end() && Entry->first == BB)
+ return Entry->second;
+ }
+
+ // Otherwise, check to see if it's in NewBlockInfo or create a new entry if
+ // not.
+ return NewBlockInfo[BB];
+}
+
+LVILatticeVal LVIQuery::getBlockValue(BasicBlock *BB) {
+ // See if we already have a value for this block.
+ LVILatticeVal &BBLV = getCachedEntryForBlock(BB);
+
+ // If we've already computed this block's value, return it.
+ if (!BBLV.isUndefined()) {
+ DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
+ return BBLV;
+ }
+
+ // 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();
+
+ // If V is live into BB, see if our predecessors know anything about it.
+ Instruction *BBI = dyn_cast<Instruction>(Val);
+ if (BBI == 0 || BBI->getParent() != BB) {
+ LVILatticeVal Result; // Start Undefined.
+ unsigned NumPreds = 0;
+
+ // Loop over all of our predecessors, merging what we know from them into
+ // result.
+ for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
+ Result.mergeIn(getEdgeValue(*PI, BB));
+
+ // 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");
+ return Result;
+ }
+ ++NumPreds;
+ }
+
+ // If this is the entry block, we must be asking about an argument. The
+ // value is overdefined.
+ if (NumPreds == 0 && BB == &BB->getParent()->front()) {
+ assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
+ Result.markOverdefined();
+ return Result;
+ }
+
+ // Return the merged value, which is more precise than 'overdefined'.
+ assert(!Result.isOverdefined());
+ return getCachedEntryForBlock(BB) = Result;
+ }
+
+ // If this value is defined by an instruction in this block, we have to
+ // process it here somehow or return overdefined.
+ if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
+ (void)PN;
+ // TODO: PHI Translation in preds.
+ } else {
+
+ }
+
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because inst def found.\n");
+
+ LVILatticeVal Result;
+ Result.markOverdefined();
+ return getCachedEntryForBlock(BB) = Result;
+}
+
+
+/// getEdgeValue - This method attempts to infer more complex
+LVILatticeVal LVIQuery::getEdgeValue(BasicBlock *BBFrom, BasicBlock *BBTo) {
+ // 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)
+ return LVILatticeVal::get(ConstantInt::get(
+ Type::getInt1Ty(Val->getContext()), isTrueDest));
+
+ // If the condition of the branch is an equality comparison, we may be
+ // able to infer the value.
+ if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition()))
+ if (ICI->isEquality() && ICI->getOperand(0) == Val &&
+ isa<Constant>(ICI->getOperand(1))) {
+ // We know that V has the RHS constant if this is a true SETEQ or
+ // false SETNE.
+ if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
+ return LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
+ return LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
+ }
+ }
+ }
+
+ // 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 BBTo is the default destination of the switch, we don't know anything.
+ // Given a more powerful range analysis we could know stuff.
+ if (SI->getCondition() == Val && SI->getDefaultDest() != BBTo) {
+ // 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)
+ return LVILatticeVal::get(EdgeVal);
+ }
+ }
+
+ // Otherwise see if the value is known in the block.
+ return getBlockValue(BBFrom);
+}
+
+
+//===----------------------------------------------------------------------===//
+// LazyValueInfoCache Impl
+//===----------------------------------------------------------------------===//
+
+LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) {
+ // If already a constant, there is nothing to compute.
+ if (Constant *VC = dyn_cast<Constant>(V))
+ return LVILatticeVal::get(VC);
+
+ DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
+ << BB->getName() << "'\n");
+
+ LVILatticeVal Result = LVIQuery(V, ValueCache[V]).getBlockValue(BB);
+
+ DEBUG(dbgs() << " Result = " << Result << "\n");
+ return Result;
+}
+
+LVILatticeVal LazyValueInfoCache::
+getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) {
+ // If already a constant, there is nothing to compute.
+ if (Constant *VC = dyn_cast<Constant>(V))
+ return LVILatticeVal::get(VC);
+
+ DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
+ << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
+ LVILatticeVal Result =
+ LVIQuery(V, ValueCache[V]).getEdgeValue(FromBB, ToBB);
+
+ DEBUG(dbgs() << " Result = " << Result << "\n");
+
+ return Result;
+}
+
+//===----------------------------------------------------------------------===//
+// LazyValueInfo Impl
+//===----------------------------------------------------------------------===//
+
+bool LazyValueInfo::runOnFunction(Function &F) {
+ TD = getAnalysisIfAvailable<TargetData>();
+ // Fully lazy.
+ return false;
+}
+
+/// getCache - This lazily constructs the LazyValueInfoCache.
+static LazyValueInfoCache &getCache(void *&PImpl) {
+ if (!PImpl)
+ PImpl = new LazyValueInfoCache();
+ return *static_cast<LazyValueInfoCache*>(PImpl);
}
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();
+ 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();
+ 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_or_null<ConstantInt>(Res))
+ return ResCI->isZero() ? False : True;
+ 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;
+}
+
+
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