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Re: [PATCH] Use long for mantissa for generic mp code
On Wed, Feb 27, 2013 at 10:00:13AM +0530, Siddhesh Poyarekar wrote:
> On Tue, Feb 26, 2013 at 07:28:22PM -0800, Richard Henderson wrote:
> > On 2013-02-26 18:07, Siddhesh Poyarekar wrote:
> > >>>+/* Truncate IN to a multiple of F, where F is a power of two. */
> > >>>>>+#define TRUNCATE_TO_MUL(in, f) ((in) & ~(f))
> > >>>
> > >>>Err, ~f? Either this doesn't work at all, or the comment is wrong.
> > >Ugh, it should be ~(f - 1).
> > >
> >
> > Er... we are talking about in % f, when we can't necessarily
> > prove that F is a power of 2?
> >
> > Then no ~ at all, just (f-1).
>
> Not % f, it's 'align down to F'. This will only work for F as a power
> of two and not any other input. I didn't put any validation since
> that'll just slow things down.
>
Or even ((in) & -(f)).