rmaz added inline comments.
================
Comment at: clang/lib/Serialization/ASTReader.cpp:8188-8190
+ for (auto *L = &List; L; L = L->getNext()) {
+ seen.insert(L->getMethod());
+ }
----------------
dexonsmith wrote:
> I find quadratic algorithms a bit scary, even when current benchmarks don't
> expose problems. For example, it seems like this could blow up on the
> following workload:
> - one module adds many things to the global method list
> - there are many (fine-grained) modules that transitively load that module
>
> Or have I misunderstood the complexity here?
Yes, I take your point, if the method pool generation updates inbetween each of
the later modules then it is possible to hit this case.
================
Comment at: clang/lib/Serialization/ASTReader.cpp:8194
+ if (seen.insert(M).second) {
+ S.addMethodToGlobalList(&List, M);
+ }
----------------
dexonsmith wrote:
> rmaz wrote:
> > manmanren wrote:
> > > Does it make sense to check for duplication inside addMethodToGlobalList,
> > > as the function goes through the list as well? Maybe it is slower, as we
> > > will need to go through the list for each method, instead of a lookup.
> > Yes, you are right, it is slower as we need to do a list traverse per
> > insert rather than per selector lookup. I also profiled keeping some global
> > state along with the `MethodPool` so that the set didn't have to be rebuilt
> > each time, but the performance difference was negligible.
> Can you take another look at the approach you experimented with, putting the
> global state in the MethodPool? Besides the performance difference (you
> measured it as negligible but it'd avoid the concern I have about uncommon
> workloads hitting quadratic blowups), it'd also provide consistency in
> behaviour between callers of `addMethodToGlobalList`... and enable you to add
> a unit test for the API change to MethodPool.
I'll update with this approach, it should allow for moving the set insert logic
into `addMethodToGlobalList` in this case.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D109632/new/
https://reviews.llvm.org/D109632
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