Digital Architecture Design Question: Fast way to perform a floating point exponential operation

Floating-point operations are available, see this document. Try the Xilinx forums for support.

That document, in the FPU section on page 78, says that the processor supports:

The FPU implements the following floating point operations:
• addition, fadd
• subtraction, fsub
• multiplication, fmul
• division, fdiv
• square root, fsqrt (available if C_USE_FPU = 2)
Comparison
• compare less-than, fcmp.lt
• compare equal, fcmp.eq
• compare less-or-equal, fcmp.le
• compare greater-than, fcmp.gt
• compare not-equal, fcmp.ne
• compare greater-or-equal, fcmp.ge
• compare unordered, fcmp.un (used for NaN)
Conversion
The FPU implements the following conversions (available if C_USE_FPU = 2):
• convert from signed integer to floating point, flt
• convert from floating point to signed integer, fint

Unfortunately, I do not think that the Picoblaze has hardware support for floating-point. If it does, you can do it in hardware. Otherwise, you will need to do it in software emulation mode.

Since I noticed that you asked the same question for both the Picoblaze and the Microblaze, maybe you need to ask yourself why you need to do floating-point operations.

In many cases, there are alternatives to floating-point operations. Fixed-point operations are a common alternative to floating point. You will need to study your algorithms to determine if it is possible to represent the values in a fixed-point math alternative to floating-point math.

For example, if you use an 4-bit fixed-point width, you can represent values in quantums of 0.125 between -1.0 to 0.875 with fixed-point representation. Larger values can be scalar multiples of these values.

Edit: Article explaining float-to-fixed-point conversion.