Oh I have no idea when qemu wouldn't be doing those, but I wasn't very clear about precision. The x87 unit has control bits that you control (shocking!) behavi

Oh I have no idea when qemu wouldn't be doing those, but I wasn't very clear about precision. The x87 unit has control bits that you control (shocking!) behaviour of the unit, one of the things you can control is the precision it will operate at operate. People think that if the x87 unit is in the lower precision modes it's possible to simply use the common 32 or 64 bit FPUs, but the x87's 32/64 bit modes only impact the mantissa, not the the exponent so they reduced precision modes are still not interchangeable with fp32 or fp64.