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

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

Thanks Thiemo.
I'll look at TCG, some more doc reading ahead apparently.

Bye
Chris

On Feb 18, 2008 9:49 PM, Thiemo Seufer <ths@networkno.de> wrote:
> Alexander Graf 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,
>
> The migration to tcg can be done gradually, fixing the immediate problem
> shouldn't get too involved.
>
> > 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 added those as workarounds, they should rather go away than expand to
> cover even more flags.
>
>
> Thiemo
>
>
>