[rllj]

Which extension is that?

[mjmas]

An extension he calls Xh3bextm. For extracting multiple bits from bitfields.

https://wren.wtf/hazard3/doc/#extension-xh3bextm-section

There are also four other custom extensions implemented.

[wren6991]

This extension wasn't strictly necessary but it makes decode of Arm instructions faster in the bootrom's Arm emulator.