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Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds i
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU |
Date: |
Thu, 29 Sep 2016 08:41:54 -0700 |
On 28 September 2016 at 21:17, David Gibson <address@hidden> 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
- Re: [Qemu-devel] How to add my implementation of the fmadds instruction to QEMU, (continued)
- Re: [Qemu-devel] How to add my implementation of the fmadds instruction to QEMU, Peter Maydell, 2016/09/27
- Re: [Qemu-devel] How to add my implementation of the fmadds instruction to QEMU, Eric Blake, 2016/09/27
- Re: [Qemu-devel] How to add my implementation of the fmadds instruction to QEMU, G 3, 2016/09/27
- Re: [Qemu-devel] How to add my implementation of the fmadds instruction to QEMU, Peter Maydell, 2016/09/27
- Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU, David Gibson, 2016/09/29
- Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU, Programmingkid, 2016/09/29
- Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU, Alex Bennée, 2016/09/29
- Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU, Programmingkid, 2016/09/29
- Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU, Alex Bennée, 2016/09/29
- Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU, Programmingkid, 2016/09/29
- Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU,
Peter Maydell <=
- Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU, Programmingkid, 2016/09/29
- Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU, David Gibson, 2016/09/29
- Re: [Qemu-devel] [Qemu-ppc] How to add my implementation of the fmadds instruction to QEMU, Programmingkid, 2016/09/29