Ok sure, I opened up a 1000 SLOC file and copied until it was a 20,000 SLOC file, and performance was still fine. So I made it a 60,000 SLOC file. This time there was a small drop in perf as the editor caught up then it was fine again (not sluggish at all when editing the file).

Are you taking this compiler log from a remote build server? AS in that case it's your network that is the bottleneck as the file is copied to your computer, which could be causing the lock up.

Note: I'm using a 4790k 4ghz with 8gb RAM.