It’s simply matching the c86 float to int conversion, because JS specifies that behavior in the spec - all this instruction does is even the playing field it is

It’s simply matching the c86 float to int conversion, because JS specifies that behavior in the spec - all this instruction does is even the playing field it isn’t some magic instruction that does more than x86 does. At a logic level there are no changes to the expensive part of rounding, only changes to the overflow values in the result.