Re: FWD: FLOATING-POINT CONSISTENCY, -FFLOAT-STORE, AND X86

[hjstein at bfr dot co dot il (Harvey J. Stein)]

Toon Moene <toon@moene.indiv.nluug.nl> writes:

 > I must say that I am *not* amused.  This discussion goes into a
 > direction that will leave us with a compiler that, although
 > numerical-politically correct, will be generating such slow code as
 > to be totally unuseable.

Do you really think it'll make it that much slower?  If you're doing
computations, how much time is spent dumping & restoring FP registers?
Is dumping 10 bytes instead of 8 bytes (current practice) going to
have a substantial impact in total run time?  You've mentioned in
other posts a factor of 2, as if because it's 16 byte aligned it has
to move 16 bytes of data.  But even if it's 16 byte aligned, it's
still only 10 bytes of data, so why should it take 2x as long?

(This discussion has gotten heated enough that I'd better include the
disclaimer that I'm not advocating 80 bit spills.  I just hate seeing
things accepted or rejected for incorrect reasons.)

-- 
Harvey J. Stein
BFM Financial Research
hjstein@bfr.co.il