Linaro GCC 4.4 and 4.5 2010.09 released

Guillaume Letellier Guillaume.Letellier at arm.com
Tue Sep 14 18:19:10 BST 2010


Hi,

> Also available is an early release of optimised string routines for
> the Cortex-A series, including a mix of NEON and Thumb-2 versions of
> memcpy(), memset(), strcpy(), strcmp(), and strlen().  For more
> information see:
>  https://launchpad.net/cortex-strings

My understanding is that the NEON optimisation will give some performance gain *ONLY* on Cortex-A8 but it will also burn more energy. On other CPU, e.g. Cortex-A9, there is no performance gain but still it will cost more energy.
Linaro toolchain doesn't target a specific platform but is generic for armv7 platforms. Are you expecting to see those optimisations turned on in Linaro toolchain?

The NEON-optimised version is also beneficial for large copies, but it is not on short copies when the NEON unit has to be powered up (Linux kernel will get an exception to turn it on). I guess your benchmark didn't take that into account. Can the NEON-optimised version be changed so that it is not used for small copies?

Guillaume

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