On Tue, Sep 25, 2012 at 1:44 PM, George Spelvin wrote:
> Thanks to Denys Vlasenko for sending me his benchmarking code.
>
> I went and hacked on it to ransomize the numbers being converted more,
> since repeatedly converting the same number underestimates the number
> of branch mispredictions.
>
>
Thanks to Denys Vlasenko for sending me his benchmarking code.
I went and hacked on it to ransomize the numbers being converted more,
since repeatedly converting the same number underestimates the number
of branch mispredictions.
Then I tried computing the number of digits beforehand, as mentione
On Mon, Sep 24 2012, George Spelvin wrote:
> Michal Nazarewicz wrote:
>> static noinline_for_stack
>> char *put_dec_trunc8(char *buf, unsigned r) {
>> unsigned q;
>>
>> if (r > 1) {
>> do {
>> q = r + '0';
>> r = (r * (uint64_t)
On Mon, Sep 24 2012, Michal Nazarewicz wrote:
> Ah, right. I also thought about that first but than started worrying
> that it could produce unnecessary zeros if the loop iterates at least
> once and exits with r being zero, but now I see that this cannot happen
> since if the loop condition was t
On Mon, Sep 24 2012, George Spelvin wrote:
> The fix is straightforward:
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index e755083..9872855 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -180,8 +180,6 @@ char *put_dec_trunc8(char *buf, unsigned r)
> *buf++ = q - 10*r
Rabin Vincent wrote:
> This patch breaks IP address printing with "%pI4" (and by extension,
> nfsroot). Example:
>
> - Before: 10.0.0.1
> - After: 10...1
Mea culpa, and thank you for catching it! As I said in my earlier
comment, I tested this most extensively wrapped by some sprintf code
that
Michal Nazarewicz wrote:
> The original has it a bit awkwardly because it just copies code from
> put_dec_full9() with the first iteration skipped.
Yeah, it also makes the comments pretty confusing.
> I guess the following should work, even though it's not so pretty:
>
> static noinline_for_sta
>>> @@ -174,20 +174,12 @@ char *put_dec_trunc8(char *buf, unsigned r)
>>> unsigned q;
>>> /* Copy of previous function's body with added early returns */
>>> - q = (r * (uint64_t)0x199a) >> 32;
>>> - *buf++ = (r - 10 * q) + '0'; /* 2 */
>>> - if (q == 0)
>>> - retur
>> lib/vsprintf.c | 20 ++--
>> 1 file changed, 6 insertions(+), 14 deletions(-)
>>
>> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
>> index a8e7392..3ca77b8 100644
>> --- a/lib/vsprintf.c
>> +++ b/lib/vsprintf.c
>> @@ -174,20 +174,12 @@ char *put_dec_trunc8(char *buf, unsigned r
Oh, joy, a new week and a nice dose of public humiliation to start it off.
(Remind me never to go AFK for a weekend again.)
Seriously, Rabin, thank you very much for the bug report and my
apologies for inflicting the bug on you in the first place.
Denys, good to hear from you. I had hoped this w
On Fri, Aug 03 2012, George Spelvin wrote:
> If you're going to have a conditional branch after
> each 32x32->64-bit multiply, might as well shrink the code
> and make it a loop.
>
> This also avoids using the long multiply for small integers.
>
> (This leaves the comments in a confusing state, but
2012/8/3 George Spelvin :
> If you're going to have a conditional branch after
> each 32x32->64-bit multiply, might as well shrink the code
> and make it a loop.
>
> This also avoids using the long multiply for small integers.
>
> (This leaves the comments in a confusing state, but that's a separat
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