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Re: [Qemu-devel] [RFC PATCH] s390x-linux-user
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [RFC PATCH] s390x-linux-user |
Date: |
Fri, 26 Jun 2009 19:39:21 +0100 |
User-agent: |
KMail/1.11.4 (Linux/2.6.29-2-amd64; KDE/4.2.4; x86_64; ; ) |
> > OTOH, tweaking the TCG interface so that it works as an interpreter
> > shouldn't be all that hard. It's something I've been considering to do
> > for a while, and would mean that you can build both interpreter and
> > translator from the same source.
>
> Like by adding an interpreter TCG target? If it were in C only, it
> could also serve as a portable (low performance) translator runtime.
There are a couple of different options.
You could spit out bytecode (or even some simplified form of an existing ISA)
then run that though an interpreter. This is gets you a portable target, and
behaves much like a native TCG target.
The alternative is to replace TCG altogether, and have tcg_gen_* perform the
operation immediately as the code is translated. You need a couple of tricks
to cope with conditional banches, but as long as you don't allow loops this
isn't too hairy. This is more invasive, gives you a pure interpreter, so may
be the fastest option for heavily self-modifying guest code.
Paul
Re: [Qemu-devel] [RFC PATCH] s390x-linux-user, Stuart Brady, 2009/06/26