Really enjoyed reading this. Thanks for writing it!

That's an incredible find and once I saw the assembly I was right along with them on the debug path. Interestingly it doesn't need to be assembly for this to work, it's just that that's where the split was. The IR could've done it, it just doesn't for very good reasons. So another win for being able to read arm assembly.

Unsure if this would be another way to do it but to save an instruction at the cost of a memory access you could push then pop the stack size maybe? Since presumably you're doing that pair of moves on function entry and exit. I'm not really sure what the garbage collector is looking for so maybe that doesn't work, but I'd be interested to hear some takes on it

Excellent article as always from the cloudflare blog - engineering without magic infrastructure and ml. One day I will apply !

Compiler bugs are actually quite common ( I used to find several a year in gcc ), but as the author says, some of them only appear when you work at a very large scale, and most people never dive that far.