Interesting... I hadn't heard about that bug. Here's my current theory about what was happening. Back then, I was using an Intel Atom notebook, and some resea

Interesting... I hadn't heard about that bug. Here's my current theory about what was happening. Back then, I was using an Intel Atom notebook, and some research tells me that the early Atom processors don't have the popcount instruction. This would make GCC fall back to its implementation. I looked at GCC's current implementation, and it's using a 256-entry lookup table. My implementation was faster... so either (1) I was using a larger lookup table than I remembered, maybe 65536-entry, or (2) GCC was doing something different back then.