On 28 September 2016 at 21:17, David Gibson <da...@gibson.dropbear.id.au> wrote: > I think there is a way you could get both speed and accuracy, but it's > a huge project: > > You'd need to add full float awareness to TCG - so floating point TCG > values and floating point operations as tcp micro-ops, defined > according to IEEE semantics. Then you'd need to rewrite the TCG > frontends in terms of those new ops, at least for target CPUs close > enough to IEEE semantics for that to work. And you'd need to rewrite > the TCG backends to implement those fp ops in terms of host cpu fp > instructions .. at least when the host has fp behaviour close enough > to IEEE to make that work, with a fallback to soft float when that's > not the case.
Also even if you have float support in both frontend and backend you still need to fall back to fully-emulated for the runtime corner cases (like where tininess before/after rounding makes a difference or where you need to care about minutiae of the floating point exception flags, etc). It's not impossible but it is a very large amount of technically complicated work. thanks -- PMM
