STATISTIC(NumCacheCompleteNonLocalPtr,
"Number of block queries that were completely cached");
+// Limit for the number of instructions to scan in a block.
+// FIXME: Figure out what a sane value is for this.
+// (500 is relatively insane.)
+static const int BlockScanLimit = 500;
+
char MemoryDependenceAnalysis::ID = 0;
// Register this pass...
MemDepResult MemoryDependenceAnalysis::
getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
BasicBlock::iterator ScanIt, BasicBlock *BB) {
+ unsigned Limit = BlockScanLimit;
+
// Walk backwards through the block, looking for dependencies
while (ScanIt != BB->begin()) {
+ // Limit the amount of scanning we do so we don't end up with quadratic
+ // running time on extreme testcases.
+ --Limit;
+ if (!Limit)
+ return MemDepResult::getUnknown();
+
Instruction *Inst = --ScanIt;
// If this inst is a memory op, get the pointer it accessed
}
}
- // No dependence found. If this is the entry block of the function, it is a
- // clobber, otherwise it is non-local.
+ // No dependence found. If this is the entry block of the function, it is
+ // unknown, otherwise it is non-local.
if (BB != &BB->getParent()->getEntryBlock())
return MemDepResult::getNonLocal();
- return MemDepResult::getClobber(ScanIt);
+ return MemDepResult::getUnknown();
}
/// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that
const Value *MemLocBase = 0;
int64_t MemLocOffset = 0;
-
+
+ unsigned Limit = BlockScanLimit;
+
// Walk backwards through the basic block, looking for dependencies.
while (ScanIt != BB->begin()) {
+ // Limit the amount of scanning we do so we don't end up with quadratic
+ // running time on extreme testcases.
+ --Limit;
+ if (!Limit)
+ return MemDepResult::getUnknown();
+
Instruction *Inst = --ScanIt;
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
// location is 1 byte at P+1). If so, return it as a load/load
// clobber result, allowing the client to decide to widen the load if
// it wants to.
- if (const IntegerType *ITy = dyn_cast<IntegerType>(LI->getType()))
+ if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType()))
if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() &&
isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase,
MemLocOffset, LI, TD))
if (R == AliasAnalysis::MustAlias)
return MemDepResult::getDef(Inst);
+#if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads
+ // in terms of clobbering loads, but since it does this by looking
+ // at the clobbering load directly, it doesn't know about any
+ // phi translation that may have happened along the way.
+
// If we have a partial alias, then return this as a clobber for the
// client to handle.
if (R == AliasAnalysis::PartialAlias)
return MemDepResult::getClobber(Inst);
+#endif
// Random may-alias loads don't depend on each other without a
// dependence.
}
}
- // No dependence found. If this is the entry block of the function, it is a
- // clobber, otherwise it is non-local.
+ // No dependence found. If this is the entry block of the function, it is
+ // unknown, otherwise it is non-local.
if (BB != &BB->getParent()->getEntryBlock())
return MemDepResult::getNonLocal();
- return MemDepResult::getClobber(ScanIt);
+ return MemDepResult::getUnknown();
}
/// getDependency - Return the instruction on which a memory operation
// Do the scan.
if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) {
- // No dependence found. If this is the entry block of the function, it is a
- // clobber, otherwise it is non-local.
+ // No dependence found. If this is the entry block of the function, it is
+ // unknown, otherwise it is non-local.
if (QueryParent != &QueryParent->getParent()->getEntryBlock())
LocalCache = MemDepResult::getNonLocal();
else
- LocalCache = MemDepResult::getClobber(QueryInst);
+ LocalCache = MemDepResult::getUnknown();
} else {
AliasAnalysis::Location MemLoc;
AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA);
QueryParent);
} else
// Non-memory instruction.
- LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos));
+ LocalCache = MemDepResult::getUnknown();
}
// Remember the result!
Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB);
} else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) {
// No dependence found. If this is the entry block of the function, it is
- // a clobber, otherwise it is non-local.
+ // a clobber, otherwise it is unknown.
Dep = MemDepResult::getNonLocal();
} else {
- Dep = MemDepResult::getClobber(ScanPos);
+ Dep = MemDepResult::getUnknown();
}
// If we had a dirty entry for the block, update it. Otherwise, just add
return;
Result.clear();
Result.push_back(NonLocalDepResult(FromBB,
- MemDepResult::getClobber(FromBB->begin()),
+ MemDepResult::getUnknown(),
const_cast<Value *>(Loc.Ptr)));
}
// If the block has a dependency (i.e. it isn't completely transparent to
// the value), remember the reverse association because we just added it
// to Cache!
- if (Dep.isNonLocal())
+ if (Dep.isNonLocal() || Dep.isUnknown())
return Dep;
// Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
// If getNonLocalPointerDepFromBB fails here, that means the cached
// result conflicted with the Visited list; we have to conservatively
- // assume a clobber, but this also does not block PRE of the load.
+ // assume it is unknown, but this also does not block PRE of the load.
if (!CanTranslate ||
getNonLocalPointerDepFromBB(PredPointer,
Loc.getWithNewPtr(PredPtrVal),
isLoad, Pred,
Result, Visited)) {
// Add the entry to the Result list.
- NonLocalDepResult Entry(Pred,
- MemDepResult::getClobber(Pred->getTerminator()),
- PredPtrVal);
+ NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal);
Result.push_back(Entry);
// Since we had a phi translation failure, the cache for CacheKey won't
// results from the set". Clear out the indicator for this.
CacheInfo->Pair = BBSkipFirstBlockPair();
- // If *nothing* works, mark the pointer as being clobbered by the first
- // instruction in this block.
+ // If *nothing* works, mark the pointer as unknown.
//
// If this is the magic first block, return this as a clobber of the whole
// incoming value. Since we can't phi translate to one of the predecessors,
assert(I->getResult().isNonLocal() &&
"Should only be here with transparent block");
- I->setResult(MemDepResult::getClobber(BB->begin()));
- ReverseNonLocalPtrDeps[BB->begin()].insert(CacheKey);
+ I->setResult(MemDepResult::getUnknown());
Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(),
Pointer.getAddr()));
break;
projects / oota-llvm.git / blobdiff