I remember reading a short CS paper concerning continuation
equivalence in C; the authors (apparently students) had been given an
assignment wherein they would write a single program that would be
linked either with a test harness (which would verify its correctness)
or a profiler (which just measured its speed). I assume the various
entries were going to be be assigned points according to speed.

The authors solved the problem by examining the call stack to see
whether the calling program would ever use the return value, and if
not, avoid calculating it. Most of the paper was, iirc, spent showing
that this optimization was legal and semantics-preserving.

The title was along the lines of "the =) operator for intentional
continuation equivalence".