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From: Olivier Matz <olivier.matz@6wind.com>
To: Georg Sauthoff <mail@gms.tf>
Cc: Thomas Monjalon <thomas@monjalon.net>,
	David Marchand <david.marchand@redhat.com>,
	dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 1/1] net: fix aliasing issue in checksum computation
Date: Fri, 15 Oct 2021 16:39:02 +0200	[thread overview]
Message-ID: <YWmShn+U/qdpN+Ch@platinum> (raw)
In-Reply-To: <20210918114930.245387-2-mail@gms.tf>

Hi Georg,

On Sat, Sep 18, 2021 at 01:49:30PM +0200, Georg Sauthoff wrote:
> That means a superfluous cast is removed and aliasing through a uint8_t
> pointer is eliminated. Note that uint8_t doesn't have the same
> strict-aliasing properties as unsigned char.

Interesting. Out of curiosity, do you have links that explains
this?

I found these, but these are just discussions:
  https://stackoverflow.com/questions/16138237/when-is-uint8-t-%E2%89%A0-unsigned-char
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66110

What about rewording the sentence "uint8_t doesn't have the same
strict-aliasing properties as unsigned char" to clarify that unsigned
char may alias, but uint8_t may not?

> Also simplified the loop since a modern C compiler can speed up (i.e.
> auto-vectorize) it in a similar way. For example, GCC auto-vectorizes it
> for Haswell using AVX registers while halving the number of instructions
> in the generated code.
> 
> Signed-off-by: Georg Sauthoff <mail@gms.tf>

The patch looks good to me, thanks!

Acked-by: Olivier Matz <olivier.matz@6wind.com>

  parent reply	other threads:[~2021-10-15 14:39 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-18 11:49 [dpdk-dev] [PATCH 0/1] net: fix aliasing issue in checksum computation Georg Sauthoff
2021-09-18 11:49 ` [dpdk-dev] [PATCH 1/1] " Georg Sauthoff
2021-10-14 17:20   ` Ferruh Yigit
2021-10-14 20:22     ` Morten Brørup
2021-10-16  8:21     ` Morten Brørup
2021-10-16 17:17       ` Georg Sauthoff
2021-10-16  8:24     ` Morten Brørup
2021-10-15 14:39   ` Olivier Matz [this message]
2021-10-16 17:02     ` Georg Sauthoff

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