It was almost certainly "Superoptimizer -- A Look at the Smallest Program" [1], authored by the ingenious Dr. Massalin.

Dr. Massalin is also responsible for "The Synthesis Kernel" [2], a kernel written around the idea of wringing out performance.

Definitely worth a look for speed demon-type programmers like compiler engineers.

[1] http://www.stanford.edu/class/cs343/resources/superoptimizer... [2] https://www.usenix.org/legacy/publications/compsystems/1988/...