This is a more basic pattern that we should handle before trying to solve:

https://llvm.org/PR48640

There might be a better way to think about this because the pre-condition that I came up with (number of sign bits in the compare constant) misses a potential transform for each of `ugt` and `ult` as commented on in the test file.

Tried to model this is in Alive:

https://rise4fun.com/Alive/juX1

...but I couldn't get the ComputeNumSignBits() pre-condition to work as expected, so replaced with leading 0/1 preconditions instead.

Name: ugt Pre: countLeadingZeros(C2) <= C1 && countLeadingOnes(C2) <= C1 %a = ashr %x, C1 %r = icmp ugt i8 %a, C2 => %r = icmp slt i8 %x, 0 Name: ult Pre: countLeadingZeros(C2) <= C1 && countLeadingOnes(C2) <= C1 %a = ashr %x, C1 %r = icmp ult i4 %a, C2 => %r = icmp sgt i4 %x, -1