Re: [Qemu-devel] 64-on-32 TCG broken

[Aurelien Jarno <aurelien@aurel32.net>]

On Tue, Oct 30, 2012 at 11:24:34PM +0100, Stefan Weil wrote:
> Am 30.10.2012 09:15, schrieb Paolo Bonzini:
> >Il 29/10/2012 19:29, Aurelien Jarno ha scritto:
> >>On Mon, Oct 29, 2012 at 06:53:14PM +0100, Paolo Bonzini wrote:
> >>>>Known-good commit: 8473f377393219390ea6f2d8d450a2b054bb823e
> >>>>Known-bad commit: d262cb02861dd33375c08fc798930653b14769e9
> >>>>
> >>>>i386-softmmu seems to work.  I may try to bisect it tomorrow, but I'd be
> >>>>glad if somebody else beats me.  It can be reproduced with Wine and
> >>>>"x86_64-softmmu/qemu-system-x86_64.exe -L ../pc-bios"; it hangs at iPXE.
> >>Oops, sorry about that. Is it win32 or win64? I'll try to fix it asap,
> >>but right now I don't have a good network connection enough to either
> >>setup a mingw build environment or to connect to a remote machine with
> >>such an environment.
> >
> >It's win32, and the first bad commit is 9c43b68 (tcg: rework liveness
> >analysis, 2012-10-09).  But it looks like 64-on-32 emulation is more
> >generally broken.  I now tried x86_64-linux-user compiled for 32-bit,
> >and it segfaults on startup.  Even the previous commit cannot run
> >qemu-x86_64 /bin/ls correctly:
> >
> 
> I just tested with latest qemu-system-x86_64 on 32 bit Linux.
> 
> It also hangs during boot (BIOS), so it looks like this
> is not a MinGW only problem.
> 
> Your test with x86_64-linux-user indicates that, too.
> 
> I also get the problem with TCI. Therefore I expect that any
> 32 bit TCG target will show it.
> 

The problem is related to the recent cases for add2/sub2/mulu2 addition
which do not play well with the optimizations. I am still trying to
understand why.

-- 
Aurelien Jarno	                        GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net