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Re: [Qemu-devel] [patch] make qemu work with GCC 4
From: |
Michael Matz |
Subject: |
Re: [Qemu-devel] [patch] make qemu work with GCC 4 |
Date: |
Thu, 30 Aug 2007 18:52:19 +0200 (CEST) |
Hi,
On Wed, 29 Aug 2007, Michael Matz wrote:
> > > I solved that by placing one of the T[012] operands into memory
> > > for HOST_I386, thereby freeing one reg. Here's some justification
> > > of why that doesn't really cost performance: with three free regs
> > > GCC is already spilling like mad in the snippets, we just trade one
> > > of those memory accesses (to stack) with one other mem access to
> > > the cpu_state structure, which will be in cache.
> >
> > Do you have any evidence to support this claim?
>
> Not really, only an apple and orange comparison. A 10000 iteration
> tests/sha1 run in the same Linux image, with -no-kqemu, on host and target
> i386: time ./sha1
>
> with qemu-0.8.2 (compiled by gcc 3.3-hammer): 7.92 seconds
> with qemu-0.9.0-cvs (gcc4.1 compiled, with the patch): 8.15 seconds
>
> I'll try to get a better comparison.
So, I've now compared our 0.9.0 package, once without patch compiled by
3.3-hammer, and once with patch and compiled by gcc 4.2:
gcc33 compiled: 7.81 seconds (i.e. a bit faster than 0.8.2 was)
gcc42 compiled: 8.07 seconds
I.e. 3% slower.
Ciao,
Michael.
Re: [Qemu-devel] [patch] make qemu work with GCC 4, Johannes Schindelin, 2007/08/29
Re: [Qemu-devel] [patch] make qemu work with GCC 4, Paul Brook, 2007/08/29
Re: [Qemu-devel] [patch] make qemu work with GCC 4, Anthony Liguori, 2007/08/29
Re: [Qemu-devel] [patch] make qemu work with GCC 4, Thiemo Seufer, 2007/08/30