From: Georg Sauthoff <mail@georg.so>
To: musl@lists.openwall.com
Subject: Re: memchr() performance
Date: Tue, 20 Sep 2016 19:57:32 +0200 [thread overview]
Message-ID: <20160920175732.GB7983@dell12.lru.li> (raw)
In-Reply-To: <20160919175847.GA1280@port70.net>
On Mon, Sep 19, 2016 at 07:58:48PM +0200, Szabolcs Nagy wrote:
> * Georg Sauthoff <mail@georg.so> [2016-09-19 15:29:53 +0200]:
> > Yes. Sure, ub means that anything can happen, but this case should be ok
> > with GCC - if the function is compiled in isolation in its own
> > translation unit.
> unless you use lto
> (which musl does not support now, but ppl are doing this)
Yes, with lto there is no isolation.
For lto you can do one of the following:
- write a version in pure assembler, doesn't have to be harder to read
than a C version
- use the may_alias attribute (supported at least by GCC/Clang)
- apply the memcpy() trick:
https://github.com/gsauthof/find-memchr/blob/master/find_avx2_memcpy_impl.cc
Best regards
Georg
prev parent reply other threads:[~2016-09-20 17:57 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-18 18:54 Georg Sauthoff
2016-09-18 20:40 ` Rich Felker
2016-09-18 20:40 ` Szabolcs Nagy
2016-09-19 13:29 ` Georg Sauthoff
2016-09-19 13:37 ` Rich Felker
2016-09-19 17:58 ` Szabolcs Nagy
2016-09-20 17:57 ` Georg Sauthoff [this message]
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