On Sep 29, 2016, at 2:19 PM, Alex Bennée wrote: > > Programmingkid <programmingk...@gmail.com> writes: > >> On Sep 29, 2016, at 12:17 AM, David Gibson wrote: >> >>> On Tue, Sep 27, 2016 at 09:58:02AM -0700, Peter Maydell wrote: >>>> On 27 September 2016 at 09:51, G 3 <programmingk...@gmail.com> wrote: >>>>> The problem with your reasoning is you assume this instruction has to be >>>>> 100% correctly implemented. That every single "corner-case" has to be >>>>> accounted for. >>>> >>>> For upstream QEMU we've already made this design decision -- >>>> emulation accuracy comes first, and speed is secondary. >>>> That's why we implement this the way we do. >>> >>> 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. >> >> Interesting idea. Do you think we would see a large enough increase in speed >> to justify this project? > > It really depends on workload. If you want to run lots of encoding/audio > workloads in TCG guests it is certainly something that could be > improved. > > As others have pointed out however it is a fairly big project. > > -- > Alex Bennée
Alex Bennée? I was just watching your KVM video about MTTCG! Small world. I so want audio to play correctly in a PowerPC Mac OS guest. So this project might be necessary. If it is a fairly big project, then I will need to map it out some more. I've made a mind map of what I know so far. It is attached to this email. Let me know if you can think of anything to add. http://i.imgur.com/MYkiKGx.png
