[deadsy]

The Tensilica guys took this thing an extra step. ie- profile real code to find out what constants are most typically used, enumerate the top n constants, encode the constant with 0..n-1 in the immediate instruction - the immediate value is a hardware based lookup. You can still do arbitrary immediates with longer instructions but you can apparently get some nice code size reductions using this technique.

[fidotron]

The flipside of that is that the scheme described here will take less silicon, fewer transistors and thus . . . use less power, if you happen to optimise the code appropriately.

Code size reductions are good, but for power purposes it is a case of balancing them against decoding complexity.