estimating CPU load /MFLOPS for software emulation of floating point

estimating CPU load /MFLOPS for software emulation of floating point

Post by Terje Mathise » Tue, 23 Dec 2003 04:47:07






>>>And speaking of emulating IEEE 754 float operations, speed and
>>>code size go south in a big hurry if infinities, denormalized
>>>numbers, NaNs, and rounding are handled properly.

>>Those are rare cases -- affect code size, yes, but only a small
>>effect on speed.

> But every operation pays the price of checking for the rare
> values whether they are present/occur or not.

Not really:

All the special values (NaN, Inf, Zero and Denorm) can be handled (at
least approximately) with a simple test of the exponent field, before
falling through with the normal case.

Since the Denorms all would be included in the normal
'Special_exponent()' test, the overhead is only in the fixup part.

Terje

--

"almost all programming can be viewed as an exercise in caching"