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Re: [Qemu-devel] [PATCH 00/18] target-arm cleanup
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH 00/18] target-arm cleanup |
Date: |
Tue, 10 Nov 2009 23:38:49 +0000 |
User-agent: |
KMail/1.12.2 (Linux/2.6.30-2-amd64; KDE/4.3.2; x86_64; ; ) |
> > Some of the generated tcg code is not very optimal, for example a
> > single vld4.8 instruction can generate over 250 tcg ops. I did some
> > optimizations and got it under 200 but do you think it could be an
> > issue that a single instruction can expand to so many tcg ops? I mean
> > besides the fact that it causes TBs for only one or two guest
> > instructions to be generated.
>
> Fabrice wrote this (tcg/README):
>
> Don't hesitate to use helpers for complicated or seldom used target
> intructions. There is little performance advantage in using TCG to
> implement target instructions taking more than about twenty TCG
> instructions.
>
> How applicable is it, I can't say. It'd probably be a good thing
> to benchmark the two versions, TCG vs helper.
The problem is that you can not do memory accesses from within a helper
function.
Paul
- Re: [Qemu-devel] [PATCH 00/18] target-arm cleanup,
Paul Brook <=