MVME5500 broken with gcc-4.0.2

Peter Dufault dufault at
Mon Oct 31 23:36:19 UTC 2005

On Oct 31, 2005, at 6:05 PM, Till Straumann wrote:

> rtems/gcc (implicitely) uses -maltivec on all 74xx CPUS and
> the MVME5500 calls for -mcpu=7450.
> Unfortunately, with -maltivec, gcc uses vector registers for
> some optimizations.
> --> until proper altivec support is implemented in RTEMS random
>     *data corruption* must be expected.
> Workaround:
> make/custom/mvme5500: use -mcpu=750
> -- Till

I've been using the mvme5500 24/7 using an earlier rev of gcc 4.0 in  
a heavily floating point control application, with optimization on,  
with a similar gcc configuration.  I don't explicitly use the  
altivec.  I assume you're saying that gcc is using the vector  
registers for data movement but RTEMS isn't saving / restoring them  
and that's where the problem should come in, but I'm not noticing any  
problems.  I've got lots of multi-axis floating point control going  
on and a heavy network load.  Did anything change in newer 4.0.x  
releases?  I've built everything with 4.0.2 but haven't run things yet.


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