Re: [Qemu-devel] Patch for compiling with GCC 4

["Christian Roue" <croue7@gmail.com>]

Alex,
thanks for the hint.
I'll have a look at TCG.

Bye
Chris.


On Feb 18, 2008 1:07 PM, Alexander Graf <alex@csgraf.de> wrote:
>
> On Feb 17, 2008, at 9:22 PM, Christian Roue wrote:
>
> > Well, I somehow felt like it was a bit brutal and probably fixing the
> > symptoms which is apparently the case.
> > Looking more carefully, compile fails in :
> > sh4-linux-user for function op_cmp_str_T0_T1
> > gcc optimization leads to a ret followed by a last assignement with
> > a jump back.
> > I guess dyngen hopes to find function epilogue as the last bytes.
> > It's apparently the only function where it happens.
> >
> > I found that adding gcc option "-fno-tree-dominator-opts" for sh4
> > target avoids this (I suppose) unwanted optimization.
> > It may be a bit brutal again ( disabling too many optims or wrong
> > ones).
> > May be the op_cmp_str_T0_T1 function can be rewritten to something
> > that avoids this optimization.
> > Am I on a better track ?
>
> This looks like the right approach to the symptoms. The "real fix"
> would be to move the sh4 target to TCG, but for the meantime I believe
> this is the way to go. You can already find a lot of these
> unoptimization flags autodetected in the configure script, so I guess
> that'd be the right place for a patch.
>
> I am not sure if anybody with commit right listens, though.
>
> Regards,
>
> Alex
>
>
> >
> >
> > Bye
> > Chris.
> >
> >
> > On Feb 16, 2008 9:01 PM, Paul Brook <paul@codesourcery.com> wrote:
> >> On Saturday 16 February 2008, Christian Roue wrote:
> >>> Hi all,
> >>> I tried to compile qemu cvs head on my x86_64 linux with gcc 4.1.2
> >>> using
> >>> --disable-gcc-check, I found compile fails as stated in configure
> >>> before i
> >>> disabled gcc check..
> >>> Error message, points to a problem of dyngen not correctly detecting
> >>> function ends on i386 when last instruction is a jump. I applied
> >>> following
> >>> change and successfully compiled/run qemu i386.  This extra test
> >>> check for
> >>> a relative backward jump  to function exit ret,
> >>> gcc 4 apparently generates a few of these.
> >>
> >> You patch is wrong. The dyngen error is correct.
> >>
> >> Paul
> >>
> >
> >
>
>
>
>