If we add this canonicalization to use 'select', existing transforms should find the simplification:

%gt = icmp sgt i32 %x, %y
%zgt = zext i1 %gt to i32
%lt = icmp slt i32 %x, %y
%zlt = zext i1 %lt to i32
%d = sub nsw i32 %zgt, %zlt
=>
%d = select i1 %lt, i32 -1, i32 %zgt

https://rise4fun.com/Alive/pQN

Note that that canonicalization would undo what I was trying in the first place, which is this difference https://godbolt.org/z/to7D8q

example::spaceship1:
        cmp     edi, esi
        seta    al
        sbb     al, 0
        ret

example::spaceship2:
        xor     ecx, ecx
        cmp     edi, esi
        seta    cl
        mov     eax, 255
        cmovae  eax, ecx
        ret

It's not obvious to me which of those is better in general (is byte sbb or cmov worse?), but llvm-mca does say the former is better on the (old) core2 CPU I'm currently running.