// Instrumenting some of the accesses may be proven redundant.
// Currently handled:
// - read-before-write (within same BB, no calls between)
//
// We do not handle some of the patterns that should not survive
// after the classic compiler optimizations.
// E.g. two reads from the same temp should be eliminated by CSE,
// two writes should be eliminated by DSE, etc.
//
// 'Local' is a vector of insns within the same BB (no calls between).
// 'All' is a vector of insns that will be instrumented.
void ThreadSanitizer::chooseInstructionsToInstrument(
SmallVectorImpl<Instruction*> &Local,
SmallVectorImpl<Instruction*> &All) {
SmallSet<Value*, 8> WriteTargets;
// Iterate from the end.
for (SmallVectorImpl<Instruction*>::reverse_iterator It = Local.rbegin(),
E = Local.rend(); It != E; ++It) {
Instruction *I = *It;
if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
WriteTargets.insert(Store->getPointerOperand());
} else {
LoadInst *Load = cast<LoadInst>(I);
Value *Addr = Load->getPointerOperand();
if (WriteTargets.count(Addr)) {
// We will write to this temp, so no reason to analyze the read.
NumOmittedReadsBeforeWrite++;
continue;
}
if (addrPointsToConstantData(Addr)) {
// Addr points to some constant data -- it can not race with any writes.
continue;
}
}
All.push_back(I);
}
Local.clear();
}
// Instrumenting some of the accesses may be proven redundant.
// Currently handled:
// - read-before-write (within same BB, no calls between)
// - not captured variables
//
// We do not handle some of the patterns that should not survive
// after the classic compiler optimizations.
// E.g. two reads from the same temp should be eliminated by CSE,
// two writes should be eliminated by DSE, etc.
//
// 'Local' is a vector of insns within the same BB (no calls between).
// 'All' is a vector of insns that will be instrumented.
void ThreadSanitizer::chooseInstructionsToInstrument(
SmallVectorImpl<Instruction *> &Local, SmallVectorImpl<Instruction *> &All,
const DataLayout &DL) {
SmallSet<Value*, 8> WriteTargets;
// Iterate from the end.
for (SmallVectorImpl<Instruction*>::reverse_iterator It = Local.rbegin(),
E = Local.rend(); It != E; ++It) {
Instruction *I = *It;
if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
Value *Addr = Store->getPointerOperand();
if (!shouldInstrumentReadWriteFromAddress(Addr))
continue;
WriteTargets.insert(Addr);
} else {
LoadInst *Load = cast<LoadInst>(I);
Value *Addr = Load->getPointerOperand();
if (!shouldInstrumentReadWriteFromAddress(Addr))
continue;
if (WriteTargets.count(Addr)) {
// We will write to this temp, so no reason to analyze the read.
NumOmittedReadsBeforeWrite++;
continue;
}
if (addrPointsToConstantData(Addr)) {
// Addr points to some constant data -- it can not race with any writes.
continue;
}
}
Value *Addr = isa<StoreInst>(*I)
? cast<StoreInst>(I)->getPointerOperand()
: cast<LoadInst>(I)->getPointerOperand();
if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
!PointerMayBeCaptured(Addr, true, true)) {
// The variable is addressable but not captured, so it cannot be
// referenced from a different thread and participate in a data race
// (see llvm/Analysis/CaptureTracking.h for details).
NumOmittedNonCaptured++;
continue;
}
All.push_back(I);
}
Local.clear();
}
static void filterForDiscriminator(SmallVectorImpl<Result> &results,
DebuggerClient *debugClient) {
Identifier discriminator = debugClient->getPreferredPrivateDiscriminator();
if (discriminator.empty())
return;
auto doesNotMatch = [discriminator](Result next) -> bool {
return !matchesDiscriminator(discriminator, next);
};
auto lastMatchIter = std::find_if_not(results.rbegin(), results.rend(),
doesNotMatch);
if (lastMatchIter == results.rend())
return;
Result lastMatch = *lastMatchIter;
auto newEnd = std::remove_if(results.begin(), lastMatchIter.base()-1,
doesNotMatch);
results.erase(newEnd, results.end());
results.push_back(lastMatch);
}
/// iterate - Repeatedly update the Hopfield nodes until stability or the
/// maximum number of iterations is reached.
/// @param Linked - Numbers of linked nodes that need updating.
void SpillPlacement::iterate(const SmallVectorImpl<unsigned> &Linked) {
DEBUG(dbgs() << "Iterating over " << Linked.size() << " linked nodes:\n");
if (Linked.empty())
return;
// Run up to 10 iterations. The edge bundle numbering is closely related to
// basic block numbering, so there is a strong tendency towards chains of
// linked nodes with sequential numbers. By scanning the linked nodes
// backwards and forwards, we make it very likely that a single node can
// affect the entire network in a single iteration. That means very fast
// convergence, usually in a single iteration.
for (unsigned iteration = 0; iteration != 10; ++iteration) {
// Scan backwards, skipping the last node which was just updated.
bool Changed = false;
for (SmallVectorImpl<unsigned>::const_reverse_iterator I =
llvm::next(Linked.rbegin()), E = Linked.rend(); I != E; ++I) {
unsigned n = *I;
bool C = nodes[n].update(nodes);
Changed |= C;
DEBUG(dbgs() << " \\EB#" << n << format(" = %+2.0f", nodes[n].Value)
<< (C ? " *\n" : "\n"));
}
if (!Changed)
return;
// Scan forwards, skipping the first node which was just updated.
Changed = false;
for (SmallVectorImpl<unsigned>::const_iterator I =
llvm::next(Linked.begin()), E = Linked.end(); I != E; ++I) {
unsigned n = *I;
bool C = nodes[n].update(nodes);
Changed |= C;
DEBUG(dbgs() << " /EB#" << n << format(" = %+2.0f", nodes[n].Value)
<< (C ? " *\n" : "\n"));
}
if (!Changed)
return;
}
}
