#include "llvm/Support/CFG.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/PointerIntPair.h"
#include "llvm/ADT/STLExtras.h"
using namespace llvm;
char LazyValueInfo::ID = 0;
-static RegisterPass<LazyValueInfo>
-X("lazy-value-info", "Lazy Value Information Analysis", false, true);
+INITIALIZE_PASS(LazyValueInfo, "lazy-value-info",
+ "Lazy Value Information Analysis", false, true);
namespace llvm {
FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
/// 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;
+ typedef std::map<BasicBlock*, LVILatticeVal> ValueCacheEntryTy;
private:
+ /// LVIValueHandle - A callback value handle update the cache when
+ /// values are erased.
+ struct LVIValueHandle : public CallbackVH {
+ LazyValueInfoCache *Parent;
+
+ LVIValueHandle(Value *V, LazyValueInfoCache *P)
+ : CallbackVH(V), Parent(P) { }
+
+ void deleted();
+ void allUsesReplacedWith(Value* V) {
+ deleted();
+ }
+
+ LVIValueHandle &operator=(Value *V) {
+ return *this = LVIValueHandle(V, Parent);
+ }
+ };
+
/// ValueCache - This is all of the cached information for all values,
/// mapped from Value* to key information.
- DenseMap<Value*, ValueCacheEntryTy> ValueCache;
+ std::map<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.
+ std::set<std::pair<BasicBlock*, Value*> > OverDefinedCache;
+
public:
/// getValueInBlock - This is the query interface to determine the lattice
/// 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;
- }
+ /// 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);
};
-}
+} // end anonymous namespace
//===----------------------------------------------------------------------===//
// LVIQuery Impl
/// This is the current value being queried for.
Value *Val;
+ /// This is a pointer to the owning cache, for recursive queries.
+ LazyValueInfoCache &Parent;
+
/// This is all of the cached information about this value.
ValueCacheEntryTy &Cache;
- /// NewBlocks - This is a mpping of the new BasicBlocks which have been
+ /// This tracks, for each block, what values are overdefined.
+ std::set<std::pair<BasicBlock*, Value*> > &OverDefinedCache;
+
+ /// 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;
+ DenseSet<BasicBlock*> NewBlockInfo;
public:
- LVIQuery(Value *V, ValueCacheEntryTy &VC) : Val(V), Cache(VC) {
+ LVIQuery(Value *V, LazyValueInfoCache &P,
+ ValueCacheEntryTy &VC,
+ std::set<std::pair<BasicBlock*, Value*> > &ODC)
+ : Val(V), Parent(P), Cache(VC), OverDefinedCache(ODC) {
}
~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;
+ for (DenseSet<BasicBlock*>::iterator I = NewBlockInfo.begin(),
+ E = NewBlockInfo.end(); I != E; ++I) {
+ if (Cache[*I].isOverdefined())
+ OverDefinedCache.insert(std::make_pair(*I, Val));
}
-
- // 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);
};
} // end anonymous namespace
+void LazyValueInfoCache::LVIValueHandle::deleted() {
+ Parent->ValueCache.erase(*this);
+ for (std::set<std::pair<BasicBlock*, Value*> >::iterator
+ I = Parent->OverDefinedCache.begin(),
+ E = Parent->OverDefinedCache.end();
+ I != E; ) {
+ std::set<std::pair<BasicBlock*, Value*> >::iterator tmp = I;
+ ++I;
+ if (tmp->second == getValPtr())
+ Parent->OverDefinedCache.erase(tmp);
+ }
+}
+
+
/// 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.
+/// so, return it, otherwise create a new entry in the Cache 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];
+ NewBlockInfo.insert(BB);
+ return Cache[BB];
}
LVILatticeVal LVIQuery::getBlockValue(BasicBlock *BB) {
// If we've already computed this block's value, return it.
if (!BBLV.isUndefined()) {
- DEBUG(errs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
+ DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
return BBLV;
}
// If we hit overdefined, exit early. The BlockVals entry is already set
// to overdefined.
if (Result.isOverdefined()) {
- DEBUG(errs() << " compute BB '" << BB->getName()
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because of pred.\n");
return 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.
+ LVILatticeVal Result; // Start Undefined.
+
+ // 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) {
+ Value* PhiVal = PN->getIncomingValueForBlock(*PI);
+ Result.mergeIn(Parent.getValueOnEdge(PhiVal, *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;
+ }
+ }
+
+ // Return the merged value, which is more precise than 'overdefined'.
+ assert(!Result.isOverdefined());
+ return getCachedEntryForBlock(BB) = Result;
+
} else {
}
- DEBUG(errs() << " compute BB '" << BB->getName()
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because inst def found.\n");
LVILatticeVal Result;
}
-/// getEdgeValue - This method
+/// 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.
}
}
}
-
- // TODO: Info from switch.
-
- // TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
- // know that v != 0.
+
+ // 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);
if (Constant *VC = dyn_cast<Constant>(V))
return LVILatticeVal::get(VC);
- DEBUG(errs() << "LVI Getting block end value " << *V << " at '"
+ DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
<< BB->getName() << "'\n");
- LVILatticeVal Result = LVIQuery(V, ValueCache[V]).getBlockValue(BB);
+ LVILatticeVal Result = LVIQuery(V, *this,
+ ValueCache[LVIValueHandle(V, this)],
+ OverDefinedCache).getBlockValue(BB);
- DEBUG(errs() << " Result = " << Result << "\n");
+ DEBUG(dbgs() << " Result = " << Result << "\n");
return Result;
}
if (Constant *VC = dyn_cast<Constant>(V))
return LVILatticeVal::get(VC);
- DEBUG(errs() << "LVI Getting edge value " << *V << " from '"
+ DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
<< FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
+
LVILatticeVal Result =
- LVIQuery(V, ValueCache[V]).getEdgeValue(FromBB, ToBB);
+ LVIQuery(V, *this, ValueCache[LVIValueHandle(V, this)],
+ OverDefinedCache).getEdgeValue(FromBB, ToBB);
- DEBUG(errs() << " Result = " << Result << "\n");
+ 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 (std::set<std::pair<BasicBlock*, Value*> >::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...
+ std::set<std::pair<BasicBlock*, Value*> >::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
//===----------------------------------------------------------------------===//
return False;
} else if (Pred == ICmpInst::ICMP_NE) {
// !C1 != C -> true iff C1 == C.
- Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_EQ,
+ Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
Result.getNotConstant(), C, TD);
if (Res->isNullValue())
return True;
return Unknown;
}
-
+void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
+ BasicBlock* NewSucc) {
+ getCache(PImpl).threadEdge(PredBB, OldSucc, NewSucc);
+}
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