Illegal instruction in the GPSTracker firmware

[VoodooChild99]

While playing with the GPSTracker firmware, I noticed that it seems to contain an illegal instruction:

.text:00083F76                 STREX.W R3, R3, [R6]

The ISA documentation says that: "For STREX, Rd must not be the same register as Rt, Rt2, or Rn". However here we have Rd=3 and Rt=3, which is not allowed.

I also ran this firmware on QEMU, and when it reached this instruction, it triggered an Undefined Instruction exception as expected.

However, I don't have a SAM3 development board to verify this issue. Could you check if you can reproduce it?

Thanks!