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From: Pekka Paalanen <ppaalanen@gmail.com>
To: Paul Gofman <pgofman@codeweavers.com>
Cc: dri-devel@lists.freedesktop.org
Subject: Re: [PATCH libdrm 2/2] include: Avoid potentially infinite loop in log2_int().
Date: Fri, 30 Oct 2020 13:07:39 +0200	[thread overview]
Message-ID: <20201030130739.0e6770c6@eldfell> (raw)
In-Reply-To: <20201028100602.168752-2-pgofman@codeweavers.com>


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On Wed, 28 Oct 2020 13:06:02 +0300
Paul Gofman <pgofman@codeweavers.com> wrote:

> Signed-off-by: Paul Gofman <pgofman@codeweavers.com>
> ---
>  util_math.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/util_math.h b/util_math.h
> index e2fa95f5..f6bbe192 100644
> --- a/util_math.h
> +++ b/util_math.h
> @@ -38,6 +38,9 @@ static inline unsigned log2_int(unsigned x)
>      if (x < 2) {
>          return 0;
>      }
> +    if (x & 0x80000000) {
> +        return 31;
> +    }
>      for (l = 2; ; l++) {
>          if ((unsigned)(1 << l) > x) {
>              return l - 1;

Hi,

I guess that does it, but it seems quite a lot of code that could be
a two-liner:
http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogObvious


Thanks,
pq

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  reply	other threads:[~2020-10-30 11:08 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-28 10:06 [PATCH libdrm 1/2] include: Factor out log2_int() function Paul Gofman
2020-10-28 10:06 ` [PATCH libdrm 2/2] include: Avoid potentially infinite loop in log2_int() Paul Gofman
2020-10-30 11:07   ` Pekka Paalanen [this message]
2020-10-30 13:07     ` Paul Gofman

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