[clang] [Serialization] Fix lazy template loading (PR #133057)

[Alexander Kornienko via cfe-commits]

alexfh wrote:

> > The reduction has been crawling for 5 days now. The input is down to 275MB, but the progress has slowed down a lot.
> 
> Ouch... I don't know if it would already be possible to share it (offline with me only if needed) or does it still contain Google-internal code? Then I could at least have a look with a debugger and see if I can "guess" what is happening

It's all internal code, so sharing it in any way wouldn't be possible. But if you have any ideas of how to stuff Clang with debug logs and/or assertions to make the issue easier to diagnose, I could run Clang and send you logs.

Meanwhile, CVise made some progress (but not much). The input is down to 250MB and ~12.5K files.

https://github.com/llvm/llvm-project/pull/133057