Re: [Qemu-devel] qemu host-utils.c

[Jocelyn Mayer <l_indien@magic.fr>]

On Wed, 2007-10-24 at 18:37 +0100, Thiemo Seufer wrote:
> J. Mayer wrote:
> > 
> > On Wed, 2007-10-24 at 12:20 +0200, Fabrice Bellard wrote:
> > > I strongly suggest to reuse my code which was in target-i386/helper.c 
> > > revision 1.80 which was far easier to validate. Moreover, integer 
> > > divisions from target-i386/helper.c should be put in the same file.
> > 
> > I fully agree with this. I still use the same code in the PowerPC
> > op_helper.c file because I never conviced myself that the host_utils
> > version was bug-free. I would likely switch to the common version if I
> > could be sure it cannot lead to any regression.
> 
> Like this? Questions/Comments I have:
> - Is the BSD-style copyright still ok for this version?

This I cannot tell. Fabrice should say how he feels about it.
1 detail: I just copied Fabrice code from i386 target, then I don't own
any copyright on it...

> - The x86-64 assembler is untested for this version, could you check
>   it works for you?

I could check this, as I got an amd64 host. As the optimized version may
lead to emit only one or a few host instructions, it may be great to
have them be static inline to make gcc able to fully optimize the code.
One other point: you may prefer not to change the host-utils API to
avoid changes i386 and Mips. It may also be safer, to keep the x86_64
optimized code unchanged. I don't care about the argument order, I can
adapt and optimize the code in the PowerPC target for this later.

> - SPARC and Alpha look like they will break on 32bit hosts, they should
>   do multiplications the same way as the other 64bit targets.

I don't think Alpha would not work on 32 bits hosts but I fully agree it
should use the same helpers. Especially because it's obvious that umulh
is bugged !


-- 
Jocelyn Mayer <l_indien@magic.fr>