Re: [Qemu-devel] Re: QEMU regression problems - Update FPU

[Peter Maydell]

On 18 February 2011 07:12, Gerhard Wiesinger <address@hidden> wrote:
> Issue 1.) with FPU still present
> I tracked down the problematic code and it is a rounding error from double
> precision to 64bit floats: Any ideas how to fix such an issue in general?
>
> QEMU result in ST0: 0.42925860786976457 (wrong emulated)
> KVM result in ST0:  0.42925860786975449 (correct)

This is an error when running QEMU in TCG mode, right?
At the moment x86 is the odd-one-out in that it doesn't
use CONFIG_SOFTFLOAT for its FPU emulation, so somebody
has made an explicit choice of preferring speed over
accuracy, and I am unsurprised that there are rounding
errors as a result.

-- PMM