"My project is now counting clock..." <- For everyone who gave me suggestions for my unexpectedly slow execution times issue, I wanted to follow up with the solution. I turns out it was XIP--the Pico 2's flash is not able to keep up with the μC and running instructions directly from it introduces wait states (obvious in hindsight, but thank you James Munns, I'm not sure how long it would have taken me to suspect flash itself, but I *know* it would have been a while!! 😅) My `cycle_count()` routine is both marked to be placed in SRAM by the linker and with the `#[inline(always)]` hint. When it is being called from a function in flash, it will run from flash and will continue to be slow. So once I ensured the caller was also running from SRAM, clock cycles between consecutive calls fell from 237 & 115 to 33 & 8 (debug & release, respectively). Thanks to everyone for your help in figuring this out.