#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;
};
} // 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.
+ /// This is the current value being queried for.
Value *Val;
/// This is all of the cached information about this value.
ValueCacheEntryTy &Cache;
- /// BlockVals Temporary Cache used while processing a query.
- DenseMap<BasicBlock*, LVILatticeVal> BlockVals;
-
+ /// 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 = BlockVals[BB];
+ LVILatticeVal &BBLV = getCachedEntryForBlock(BB);
// If we've already computed this block's value, return it.
- if (!BBLV.isUndefined())
+ 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.
// If we hit overdefined, exit early. The BlockVals entry is already set
// to overdefined.
- if (Result.isOverdefined())
+ if (Result.isOverdefined()) {
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because of pred.\n");
return Result;
+ }
++NumPreds;
}
// Return the merged value, which is more precise than 'overdefined'.
assert(!Result.isOverdefined());
- return BlockVals[BB] = Result;
+ return getCachedEntryForBlock(BB) = Result;
}
// If this value is defined by an instruction in this block, we have to
}
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because inst def found.\n");
+
LVILatticeVal Result;
Result.markOverdefined();
- return BlockVals[BB] = Result;
+ return getCachedEntryForBlock(BB) = 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() << "Getting value " << *V << " at end of block '"
+ DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
<< BB->getName() << "'\n");
LVILatticeVal Result = LVIQuery(V, ValueCache[V]).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() << "Getting value " << *V << " on edge from '"
+ DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
<< FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
LVILatticeVal Result =
LVIQuery(V, ValueCache[V]).getEdgeValue(FromBB, ToBB);
- DEBUG(errs() << " Result = " << Result << "\n");
+ DEBUG(dbgs() << " Result = " << Result << "\n");
return Result;
}
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;
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