[Python-Dev] memcmp performance (original) (raw)

Scott Dial scott+python-dev at scottdial.com
Thu Oct 20 23:38:16 CEST 2011

On 10/20/2011 5:08 PM, Antoine Pitrou wrote:

Have you reported gcc's "outdated optimization" issue to them? Or is it already solved in newer gcc versions?

I checked this on gcc 4.6, and it still optimizes memcmp/strcmp into a "repz cmpsb" instruction on x86. This has been known to be a problem since at least 2002[1][2]. There are also some alternative implementations available on their mailing list. It seems the main objection to removing the optimization was that gcc isn't always compiling against an optimized libc, so they didn't want to drop the optimization. Beyond that, I think nobody was willing to put in the effort to change the optimization itself.

[1] http://gcc.gnu.org/ml/gcc/2002-10/msg01616.html [2] http://gcc.gnu.org/ml/gcc/2003-04/msg00166.html

-- Scott Dial scott at scottdial.com

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