[olliej]

Ok, I said this elsewhere: FJCVTZS is not special, and while JS may have been a motivating factor, the actual behavior is "emulate the x86 double->int conversion"

There is nothing magic about it.

A more correct name for FJCVTZS would be FXCVTZS. What FJCVTZS does is override the default FPU rounding and signaling results for double to integer conversion to match the x86 behaviour. There is no special logic needed in the FPU, all that happens is instead of the instruction passing the current thread FPU rounding and clamping flags, it passes the flags that exactly match x86 behaviour.

That's it.

Because the JS label is inaccurate everyone believes it to be useless outside of js, when in reality it's useful to anything that needs x86 behavior for double->int conversion, so any x86 emulators on arm (Qemu, presumably the translation runtimes, etc).

God I hate that they named it that.