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From: Joseph Myers <joseph@codesourcery.com>
To: "Ondřej Bílka" <neleai@seznam.cz>
Cc: <libc-alpha@sourceware.org>
Subject: Re: [PATCH 2/3] Optimize strchrnul with unrolling, better header and  unaligned loads
Date: Thu, 28 May 2015 17:45:00 -0000	[thread overview]
Message-ID: <alpine.DEB.2.10.1505281659460.16930@digraph.polyomino.org.uk> (raw)
In-Reply-To: <20150526180007.GB26817@domone>

[-- Attachment #1: Type: text/plain, Size: 687 bytes --]

On Tue, 26 May 2015, Ondøej Bílka wrote:

> +static always_inline
> +int
> +found_in_long_bytes(char *s, unsigned long int cmask, char **result)
> +{
> +  const unsigned long int *lptr = (const unsigned long int *) s;
> +  unsigned long int mask = contains_zero (*lptr) | contains_zero (*lptr ^ cmask);
> +  if (mask)
> +    {
> +      *result = s + ffsl (mask) / 8 - 1;

If this gets used in strchr, note ffsl is in the user's namespace.  Are 
you sure this will always be inlined by all supported GCC versions on all 
supported architectures (or converted to a call to a libgcc __clz* 
function, which is just as good in namespace terms)?

-- 
Joseph S. Myers
joseph@codesourcery.com

  reply	other threads:[~2015-05-28 17:02 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-26 18:48 [PATCH 1/3] Use generic strchrnul for strchr Ondřej Bílka
2015-05-26 18:51 ` [PATCH 2/3] Optimize strchrnul with unrolling, better header and unaligned loads Ondřej Bílka
2015-05-28 17:45   ` Joseph Myers [this message]
2015-05-28 17:48     ` Ondřej Bílka
2015-05-26 18:55 ` [RFC PATCH 3/3] Exploit that strchr needle is mostly ascii Ondřej Bílka
2015-05-26 20:34   ` [RFC PATCH 4/3] Fix previous patch and add header Ondřej Bílka
2015-05-26 20:38     ` Ondřej Bílka
2015-05-28 17:49     ` Joseph Myers
2015-05-28 17:59       ` Ondřej Bílka

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