define i32 @t1_ult_slt_0(i32 %x, i32 %replacement_low, i32 %replacement_high) {
  %t0 = icmp slt i32 %x, 0
  %t1 = select i1 %t0, i32 %replacement_low, i32 %replacement_high
  %t2 = icmp ult i32 %x, 65536
  %1 = xor i1 %t2, true
  %r = select i1 %1, i32 %x, i32 %t1
  ret i32 %r
}

#include <stdio.h>

unsigned t1_ult_slt_0(unsigned a, unsigned b, unsigned c);

int main(void) {
  printf("%u\n", t1_ult_slt_0(2, 0, 1));
}

regehr@john-home:~/Downloads$ opt -instcombine foo.ll -S -o -
; ModuleID = 'foo.ll'
source_filename = "foo.ll"

define i32 @t1_ult_slt_0(i32 %x, i32 %replacement_low, i32 %replacement_high) {
  %1 = icmp slt i32 %x, 0
  %2 = icmp sgt i32 %x, 65535
  %3 = select i1 %1, i32 %replacement_low, i32 %x
  %4 = select i1 %2, i32 %replacement_high, i32 %3
  ret i32 %4
}
regehr@john-home:~/Downloads$