On Mon, Sep 27, 1999 at 04:22:53AM -0700, Paul Leyland wrote:
>Actually, we at Microsoft Research in Cambridge have seen similar effects
>when compiling and running FFTW code. Our discovery is that the alignment
>of FP data values is critical.
It is generally for _all_ FP code. Unfortunately, the ABI for x86 `gets it
wrong', and uses too little alignment.
For gcc/egcs, try -malign-double if you don't need ABI compatibility (ie.
you compile all libraries containing structures with floats with -malign-
double). pgcc (a gcc/egcs derivative) has a way of aligning the stack,
so that the floats will be aligned by 8 most of the time, without breaking
the ABI. Check http://www.goof.com/pcg/
Note that Prime95 already has correct alignment; would you expect anything
else from George? ;-)
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