-fvia-C seems to break things!
   The problem is that the prototypes of the imported functions don't get
   propagated properly, leading to warnings like this:

   /tmp/ghc7602_0/ghc7602_0.hc:718:0:
        warning: implicit declaration of function 'mix_bits'

   This is actually an error on 32 bit machines - the default return type
   int is not large enough to hold the 64 bit result.

   This is fixed in ghc 6.9; the compiler emits its own prototypes.
Check sequences are repeatable
Investigate slow conversion to Double (x86 at least)
   looking at the core, the conversion goes through toInteger and encodeFloat.
   That's a pity, because the FPU has an instruction for this purpose.
profile/benchmark
tests driver