IR

The idea - make a smaller step from AST to IR and not directly 3-addr code because that would be somewhat chaotic, etc.

ast2IR function is the heart, walks tree, and for example:
      switch (type) ... 
           case INC_OP: /* ++ operator */
                if (left)
                     return genIRpostinc(left)
                else
                     return genIRpreinc(right)