Several comment strings are appended to compiler-generated assembly instructions by the code generator. These comments are typically used by the assembler optimizer.
The comment string ;volatile is used to indicate that the
memory location being accessed in the instruction is associated with a variable that was
declared as volatile in the C source code. Accesses to this location which
appear to be redundant will not be removed by the assembler optimizer if this string is
present.
This comment string can also be used in hand-written assembly source to achieve the same effect for locations defined and accessed in assembly code.
The comment string ;wreg free is placed on some
call instructions. The string indicates that the W register was not
loaded with a function parameter; i.e., it is not in use. If this string is present,
optimizations can be made to assembler instructions before the function call, which loads
the W register redundantly.