On Fri, Aug 03 2012, George Spelvin <li...@horizon.com> wrote: > Shrink the reciprocal approximations used in put_dec_full4 > based on the comments in put_dec_full9. > > Signed-off-by: George Spelvin <li...@horizon.com> > Cc: Denys Vlasenko <vda.li...@googlemail.com> > Cc: Michal Nazarewicz <min...@mina86.com>
Have you verified that the comment is correct?
> ---
> lib/vsprintf.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> I was looking over the code and noticed that the constants could be smaller.
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index c3f36d41..2f32fe8 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -243,13 +243,14 @@ char *put_dec(char *buf, unsigned long long n)
>
> /* Second algorithm: valid only for 64-bit long longs */
>
> +/* See comment in put_dec_full9 for choice of constants */
> static noinline_for_stack
> char *put_dec_full4(char *buf, unsigned q)
> {
> unsigned r;
> - r = (q * 0xcccd) >> 19;
> + r = (q * 0xccd) >> 15;
> *buf++ = (q - 10 * r) + '0';
> - q = (r * 0x199a) >> 16;
> + q = (r * 0xcd) >> 11;
> *buf++ = (r - 10 * q) + '0';
> r = (q * 0xcd) >> 11;
If you are changing everything, this could also be changed to:
r = (q * 0x67) >> 10;
no?
> *buf++ = (q - 10 * r) + '0';
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +----<email/xmpp: m...@google.com>--------------ooO--(_)--Ooo--
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