Do we really need SNE & FSNE?

[mbitsnbites]

Problem

We already have SEQ, and we can branch on BNS, for instance. Thus SNE appears to be superfluous (eating up encoding space).

Investigate if any code sequences would be worse if we didn't have SNE.

Also investigate FSNE.

Code sequences

With SNE	Without SNE	Good/Bad	Comment
sne r1, r1, r5 bs r1, #foo	seq r1, r1, r5 bns r1, #foo	Good	Branch if not equal
sne r1, r1, r5 bns r1, #foo	seq r1, r1, r5 bs r1, #foo	Good	Branch if equal
sne r1, r1, #123 sub r1, z, r1	seq r1, r1, #123 add r1, r1, #1	Good	a != b -> 0 / 1 (C/C++ arithmetic) (Tricky to get working in GCC?)
sne r4, r1, #0 sel r4, r2, r3	seq r4, r1, #0 sel.132 r4, r2, r3	Good	Conditional select with registers
sne r3, r1, #0 sel r3, r2, #123	seq r3, r1, #0 xor r3, r3, #-1 sel r3, r2, #123	BAD	Conditional select with immediates