Re: [Qemu-devel] Re: [PATCH 1/5] Fix i386 Host

[Michael Matz <matz@suse.de>]

Hi,

On Fri, 18 Jan 2008, Johannes Schindelin wrote:

> > But I'm not talking about the clobber list at all.  I reacted to the 
> > first mail forwarded to me, which was a question specifically about the 
> > hunk adding the "q" constraint, whose purpose I explained.  Are you now 
> > also asking about the changes regarding %ecx and the clobber list?
> 
> Okay, look, I do not have enough time to fix it myself.  But there _is_ a 
> breakage with gcc 3.4.2 on MinGW.  If that is not fixed, I will openly 
> oppose that patch going into CVS.

That's fine and is why I sent a test patch which might fix the 
breakage when applied on top of the constraint patch.

> All I tried was to get an understanding why the current patch "Fix i386" 
> (which is still misnamed) broke on MinGW.

Well, I can tell you why, but it doesn't help you: the 3.4.2 compiler has 
different deficiencies in reload than the 4.x line of compilers.  To make 
the whole thingy work on all compilers trying and testing is required to 
avoid all these different deficiencies.  My patch is partly real bug fixes 
(the "q" constraint part for instance) and partly changes helping to 
lessen the register pressure which reload needs to fix (the %ecx thingy 
for instance).  Both of these might expose the bugs in 3.4.2, in which 
case we need to hack around those as well.  That's what I tried to do with 
the patch from http://article.gmane.org/gmane.comp.emulators.qemu/22762 , 
but it needs of course testing by someone who actually uses 3.4.2.


Ciao,
Michael.