I was going to write one of those “everything I did last year” posts, but now I don’t feel like it. Here’s a “one thing I did last year” post instead.
The most important patch I landed in 2010 was probably the one that added LIR type-checking to Nanojit (which was based on an earlier patch from Julian Seward). At the time of writing, it’s caught at least 14 type errors, most of which could have caused a crash or security problem.
Consistency checks within compilers are wonderful things.