[Bug 1740] Change PowerPC multi-libs for e200 and e500 cores

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https://www.rtems.org/bugzilla/show_bug.cgi?id=1740

--- Comment #23 from dufault at hda.com 2011-02-28 04:26:19 CST ---
(In reply to comment #22)
> (In reply to comment #20)
> > (In reply to comment #16)
> > 
> > > From my point of view -mspe and -mabi=spe is mandatory, if you want to use any
> > > SPE instructions.
> > The later half of your sentence is the key question to me.
> > Why would you want to use "any spe instruction" and what would doing so buy to
> > you?
> 
> The SPE and embedded floating point unit is a key feature of this processor. 
> Doing floating point calculations with this unit is considerable faster than
> software floating point calculations.  Competing operation systems like Linux,
> QNX, and VxWorks provide support for it.
> 
> One application we want to support uses the embedded floating point unit for
> pattern recognition and has to cope with 500MByte/s of video data (we use more
> than one e500v2 core of course).

And I've been using the e200v6 on the Phytec Phycore mpc5554 to implement a
six-axis servo controller using -mspe -mfloat-gprs=single in an application
released last June on a patched 4.9.  It has 40.4KHz current feedback loops
using the ETPU and 4KHz position feedback loops using -mfloat-gprs=single. 
Without the floating point I'd need to switch to integer math with the
associated hand-scaling that would complicate the code and make it harder to
reuse in other applications.

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