Re: [PATCH 1/1] vsprintf: optimize decimal conversion (again)

[Michal Nazarewicz]

On Mon, 26 Mar 2012 22:20:52 +0200, H. Peter Anvin <hpa@xxxxxxxxx> wrote:

> On 03/26/2012 01:13 PM, Andrew Morton wrote:
> > On Mon, 26 Mar 2012 21:56:38 +0200
> > Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx> wrote:
> >
> > > > > +#if BITS_PER_LONG != 32 || (~(0ULL)>>1) != ((1ULL<<63)-1)
> > > >
> > > > What's this for?
> > >
> > > The second check should be just BITS_PER_LONG_LONG != 64,
> > > but we don't have BITS_PER_LONG_LONG.
> >
> > So let's add BITS_PER_LONG_LONG rather than hacking around its absence!
>
> First of all, the #if is wrong: the preprocessor doesn't support data
> types and does all arithmetic at (u)intmax_t precision.

Maybe a regular âifâ instead of macro would suffice here?  Compiler should
be smart enough to optimise out the dead path.

> As far as BITS_PER_LONG_LONG, there are tons of places in the kernel
> which already require that long long is exactly 64 bits.  That may or
> may not be a good thing, but for right now one could simply:
>
> #define BITS_PER_LONG_LONG 64

--
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.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  MichaÅ âmina86â Nazarewicz    (o o)
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