Short: Finds optimal asm instruction sequences. V2.5
Author: tege@gnu.ai.mit.edu (Torbjorn Granlund)
Type: dev/ade
Version: 2.5
Architecture: m68k-amigaos
Origin: Amiga Development Environment, ftp.ninemoons.com:pub/ade
The superoptimizer is a function sequence generator that uses an
exhaustive generate-and-test approach to finding the shortest
instruction sequence for a given function. You have to tell the
superoptimizer which function and which CPU you want to generate code
for, and how many instructions you can accept.
The superoptimizer can't generate very long sequences, unless you have
a very fast computer or very much spare time. The time complexity of
the used algorithm is approximately O(m n*2n) where m is the number of
available instructions on the architecture and n is the shortest
sequence for the goal function. The practical sequence length limit
depends on the target architecture and goal function arity; In most
cases it is about 5, but for a rich instruction set as the HPPA it is
just 4. The longest sequence ever generated was for the MC68020 and 7
instructions long. It took several weeks to generate it...
The superoptimizer can't guarantee that it finds the best possible
instruction sequences for all possible goal functions. For example,
it doesn't even try to include immediate constants (other that -1, 0,
+1, and the smallest negative and biggest positive numbers) in the
sequences.
Other reasons why not optimal sequences might be found is that not all
instructions are included, not even in their register-only form.
Also, some instructions included might not be correctly simulated. If
you encounter any of these problems, please report them to the address
below.