Stefan Monnier <monnier@iro.umontreal.ca> writes:

> BTW, when debugging such performance problem, I often resort to
> a few `DEFVAR_INT` defining ad-hoc counter variables, then sprinkle
> corresponding increments of those variables from various places
> (typically function entry point, loops, ...).

Well. I just tried, but my Emacs-C foo is not good enough.
The attached patch fails to compile.