23 Feb
2011
23 Feb
'11
12:16 a.m.
On 18 February 2011 07:12, Gerhard Wiesinger lists@wiesinger.com 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