Strict std. IEEE 754 compliance mode bit on x86

[Tom Lynch]

In relation to the conversation on "strict" x86 IEEE compatibility, I
was wonder if someone would be willing to try and quantify the
performance effect of a "strict IEEE compatibility mode" on C
compilers - both in generally, and perhaps specifically with an
example.

Such a mode would cause the precision control register to be a
"format" control register.  Setting it to double would result in
double precision calculation with double precision dynamic range.
This would eliminate double rounding problems (which I don't think a
compiler can prevent), and eliminate divergence for small and large
values.

I could do this at AMD, and Norbert Juffa suggested that he could
look into doing it at NexGen.  It would be nice to have some
data to support its usefulness.

-tom