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Re: [Qemu-devel] [patch] gcc4 host support

From: John Hogerhuis
Subject: Re: [Qemu-devel] [patch] gcc4 host support
Date: Thu, 19 May 2005 15:25:57 -0700

On 5/19/05, Thomas Steffen <address@hidden> wrote:

> It as also because C avoids the n by m problem.

My point is that you can have your cake and eat it too.

For any given architecture gcc can generate the first approximation by
way of dyngen or dyngen + gcc enhancements.

But once you are past that point gcc for a given arch, gcc isn't
really going to help you any more. So bring on the hand
coding/optimizations. There's no doubt the hand coded stuff would be
at least as good as gcc output. And that's because you can always make
use of what gcc did if you can't think of anything better.

There's really nothing magic going on we're in any danger of losing.
QEMU generates a dynamic code generator dynamically. Clever but lucky
hack, in that it really has no business working (yet it does, but the
lucky part is why it is going to continue to break).

Short of collusion from the gcc folks, I'm saying that it is no less
than the Halting Problem that is staring us in the face here. But no
more than that either. Practically speaking, we can probably go on
like this indefinitely, it just seems unnecessary to me.

The thing that separates QEMU from other projects like Bochs in my
mind is that it dynamically generates code and it has other clever
bits like samba and slirp integration. A high level view is that QEMU
puts a high priority on usability compared to these other projects.

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