Please consider this piece of code:

void testif(unsigned int a) {
   data unsigned int b = 0;

   if (10 > (a - b)) {
      _nop_(); // correct
   } else {
      _nop_(); // wrong result !!!!
   }   
}

void main() {
   testif(5);
}

If I initialize b with 1 everything is ok, and the compiled code became very different

void testif(unsigned int a) {
   data unsigned int b = 1;  // ***** with this value the test is working ******

   if (10 > (a - b)) {
      _nop_(); // correct
   } else {
      _nop_(); // wrong result !!!!
   }   
}

void main() {
   testif(5);
}

            ; FUNCTION _testif (BEGIN)
              ; Register R6R7 is assigned to parameter a
                                           ; SOURCE LINE # 1083 
0000 EE             MOV    A,R6
0001 9400           SUBB   A,#000H    ; here the carry is setted, and so the accumulator became 0xFF, probably the CLR C istruction is missing
0003 B40003         CJNE   A,#000H,?LAB283     
0006 BF0A00         CJNE   R7,#00AH,?LAB283
0009         ?LAB283:
0009 5002           JNC    ?ELSE109
                                           ; SOURCE LINE # 1084 
000B 00             NOP    
000C 22             RET    
000D         ?ELSE109:
                                           ; SOURCE LINE # 1086 
000D 00             NOP    
                                           ; SOURCE LINE # 1088 
000E 22             RET    

            ; FUNCTION _testif (END)

Thank you