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Date: Sat, 1 Nov 2008 01:54:35 +0100
From: Aurelien Jarno <aurelien@aurel32.net>
Subject: Re: [Qemu-devel] [5506] target-ppc: convert logical instructions
	to TCG
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To: qemu-devel@nongnu.org

On Thu, Oct 30, 2008 at 04:10:55AM +0100, andrzej zaborowski wrote:
> Hi,
> 
> 2008/10/21 Aurelien Jarno <aurelien@aurel32.net>:
> > -void do_popcntb (void)
> > +target_ulong helper_popcntb (target_ulong val)
> >  {
> >     uint32_t ret;
> >     int i;
> >
> >     ret = 0;
> >     for (i = 0; i < 32; i += 8)
> > -        ret |= ctpop8((T0 >> i) & 0xFF) << i;
> > -    T0 = ret;
> > +        ret |= ctpop8((val >> i) & 0xFF) << i;
> > +    return ret;
> >  }
> >
> >  #if defined(TARGET_PPC64)
> > -void do_popcntb_64 (void)
> > +target_ulong helper_popcntb_64 (target_ulong val)
> >  {
> >     uint64_t ret;
> >     int i;
> >
> >     ret = 0;
> >     for (i = 0; i < 64; i += 8)
> > -        ret |= ctpop8((T0 >> i) & 0xFF) << i;
> > -    T0 = ret;
> > +        ret |= ctpop8((val >> i) & 0xFF) << i;
> > +    return ret;
> 
> Just noting, before I forget how ctpopXX() works, that the 8
> iterations here can be replaced with one ctpop64 if you take only the
> first 3 lines of it, i.e.
> 
>     val = (val & 0x5555555555555555ULL) + ((val >>  1) & 0x5555555555555555ULL);
>     val = (val & 0x3333333333333333ULL) + ((val >>  2) & 0x3333333333333333ULL);
>     val = (val & 0x0f0f0f0f0f0f0f0fULL) + ((val >>  4) & 0x0f0f0f0f0f0f0f0fULL);
> 
> stores the ctpop8() value for each byte in the same byte.  Similarly
> the 4 iterations above and ctpop32().
> 

Thanks, I applied you suggestion.

-- 
  .''`.  Aurelien Jarno	            | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
 `. `'   aurel32@debian.org         | aurelien@aurel32.net
   `-    people.debian.org/~aurel32 | www.aurel32.net