MVME5500 broken with gcc-4.0.2

Joel Sherrill <> joel.sherrill at
Tue Nov 1 14:25:12 UTC 2005

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.

What are those optimizations?  Are they integer or floating point

The answer determines the proper thing for RTEMS to do.

> --> until proper altivec support is implemented in RTEMS random
>     *data corruption* must be expected.

I can't tell from the gcc code when Altivec registers might get used
so my first guess would be that we would need _CPU_Context_Switch to
switch the Altivec registers and the contexts to include Altivec registers.

> Workaround:
> make/custom/mvme5500: use -mcpu=750
> -- Till

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