Re: [ptxdist] OSELAS Toolchain for ARM Cortex A5

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Thu, Jul 16, 2015 at 03:14:30PM +0200, Jean-Claude Monnin wrote:
> > Can you provide some additional detail on why this had to be disabled?
> > The arm-v7a-linux-gnueabihf toolchain also has "cortex-strings" in
> > PTXCONF_GLIBC_EXTRA_ADDONS and so far it seems to work fine (although
> > I have only been able to do limited testing)
> 
> With the "cortex-strings" enabled, it crashed somewhere in the boot process.
> I assumed this option provided some optimised functions using NEON
> instructions. However I never verified exactly what that option does. Maybe
> someone else can clarify?
> What hardware do you use? SAMA5D3 lacks NEON instructions, but SAMA5D4 does
> support it.
> 'cortex-strings' seems to be enabled in the 'arm-v7a-linux-gnueabihf' of
> 'OSELAS toolchain 2013.12.2', but disabled in more recent versions of the
> toolchain.

In the cortex-a8 toolchains we have 'cortex-strings'. These are string
funtions that use NEON instructions unconditionally and are (in the version
we use here) optimized for cortex-a8.

A newer version of these functions reached mainline in gcc-4.9. There are
optimized for cortex-a9. Also, NEON support is detected at runtime and
approriate versions of the functions are selected. This is what we use in
the arm-v7a-linux-gnueabihf toolchain since OSELAS.Toolchain-2014.12.0.

Michael

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