Just some self made notes from disassembling that could be handy.

Notes

• bts reg, val -> Translates to intrinsic _interlockedbittestandset. Observed interacting with a union field where 0x1D is passed over a union type. This atomic operations first divides by the width (8 bytes) to give the union section, and then does val mod width, aka 1dh % 8 to get the bit index to set to 1. Calling the intrinsic gives a return value of the original value of the specified bit. So example: bts [rax], 1dh = ²⁹⁄₈ = bit is in the 3rd quadrant, 29 mod 8 = 5, thus the 5th bit.