Actually, it's the reverse. The JS spec accidentally baked in the x86 description of int/float conversion. This is done a LOT in JS because the JITs are actual

Actually, it's the reverse. The JS spec accidentally baked in the x86 description of int/float conversion. This is done a LOT in JS because the JITs are actually using integers instead of floats all over the place for improved performance. The ARM "JS" instruction just encodes the x86 semantics into hardware making the conversion several times faster than doing it in software.