From: tkoenig@netcologne.de
Stephen Fuld schrieb:
> Some time ago, we discussed using the 5 bit immediates in floating point
> instructions as an index to an internal ROM with frequently used
> constants. The idea is that it would save some space in the instruction
> stream. Are you implementing that, and if not, why not?
I did some statistics on which floating point constants occurred how
often, looking at three different packages (Perl, gnuplot and GSL).
GSL implements a lot of special founctions, so it has a lot of
constants you are not likely to find often in a random sample of
other packages :-) Perl has very little floating point. gnuplot
is also special in its own way, of course.
A few constants occur quite often, but there are a lot of
differences between the floating point constants for different
programs, to nobody's surprise (presumably).
Here is the head of an output of a little script I wrote to count
all floating-point constants from My66000 assembler. Note that
the compiler is for the version that does not yet do 0.5 etc as
floating point. The first number is the number of occurrences,
the second one is the constant itself.
5-bit constants: 886
32-bit constants: 566
64-bit constants:597
303 0
290 1
96 0.5
81 6
58 -1
58 1e-14
49 2
46 -2
45 -8.98846567431158e+307
44 10
44 255
37 8.98846567431158e+307
29 -0.5
28 3
27 90
27 360
26 -1e-05
21 0.0174532925199433
20 0.9
18 -3
17 180
17 0.1
17 0.01
[...]
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