MetadataResponse
LocalTypeDataCache::tryGet(IRGenFunction &IGF, LocalTypeDataKey key,
bool allowAbstract, DynamicMetadataRequest request) {
// Use the caching key.
key = key.getCachingKey();
auto it = Map.find(key);
if (it == Map.end()) return MetadataResponse();
auto &chain = it->second;
CacheEntry *best = nullptr;
Optional<OperationCost> bestCost;
CacheEntry *next = chain.Root;
while (next) {
CacheEntry *cur = next;
next = cur->getNext();
// Ignore abstract entries if so requested.
if (!allowAbstract && !isa<ConcreteCacheEntry>(cur))
continue;
// Ignore unacceptable entries.
if (!IGF.isActiveDominancePointDominatedBy(cur->DefinitionPoint))
continue;
// If there's a collision, compare by cost, ignoring higher-cost entries.
if (best) {
// Compute the cost of the best entry if we haven't done so already.
// If that's zero, go ahead and short-circuit out.
if (!bestCost) {
bestCost = best->costForRequest(key, request);
if (*bestCost == OperationCost::Free) break;
}
auto curCost = cur->costForRequest(key, request);
if (curCost >= *bestCost) continue;
// Replace the best cost and fall through.
bestCost = curCost;
}
best = cur;
}
// If we didn't find anything, we're done.
if (!best) return MetadataResponse();
// Okay, we've found the best entry available.
switch (best->getKind()) {
// For concrete caches, this is easy.
case CacheEntry::Kind::Concrete: {
auto entry = cast<ConcreteCacheEntry>(best);
if (entry->immediatelySatisfies(key, request))
return entry->Value;
assert(key.Kind.isAnyTypeMetadata());
// Emit a dynamic check that the type metadata matches the request.
// TODO: we could potentially end up calling this redundantly with a
// dynamic request. Fortunately, those are used only in very narrow
// circumstances.
auto response = emitCheckTypeMetadataState(IGF, request, entry->Value);
// Add a concrete entry for the checked result.
IGF.setScopedLocalTypeData(key, response);
return response;
}
// For abstract caches, we need to follow a path.
case CacheEntry::Kind::Abstract: {
auto entry = cast<AbstractCacheEntry>(best);
// Follow the path.
auto &source = AbstractSources[entry->SourceIndex];
auto response = entry->follow(IGF, source, request);
// Following the path automatically caches at every point along it,
// including the end.
assert(chain.Root->DefinitionPoint == IGF.getActiveDominancePoint());
assert(isa<ConcreteCacheEntry>(chain.Root));
return response;
}
}
llvm_unreachable("bad cache entry kind");
}
