Table lookups aren't fast if the table isn't in cache. A modern processor can do a lot of instructions in the time it takes to do a cold memory access.

I'm picturing a naive lookup table solution for a 32-bit popcount, and wondering if there are any text editors that could handle the source gracefully.

You can format the source so any editor can handle it. But a 32-bit table is clearly going to be huge. Better to break it into two 16-bit or four 8-bit pieces and add the counts together.

Of course you can do the not-naive thing to make your editor happy. There's lots of reasons to do the not-naive thing, including but not limited to binary bloat and startup time. Doesn't really answer the question though, does it.

This was a Google phone screen question about 10 years ago. Using a lookup table for each byte was key.