The current version of the Byte Craft compiler (990) seems to implement the !=0 slightly more efficiently than ==1.
Try to use:
if (x!=0)
z = a + b;
rather than:
if (x==1)
z = a + b;
The ETEC compiler generally will generate code of the same effiiciency for both versions, but there may be some cases where the former code snippet allows slightly better opcode packing, so it is still recommended it be used if possible.