Surround rtx with debugging assembly

[William Tambe]

how to prepend and suffixed an rtx with assembly lines, in a similar
manner that it is possible to use fprintf (asm_out_file, "xxxx") to
output assembly. ie:

The below generate an rtx that access memory using the argument
pointer register; and wherever that rtx is generated, I would like to
have it surrounded by assembly lines for debugging purposes:

rtx addr, mem;
addr = plus_constant (Pmode, arg_pointer_rtx, 2 * UNITS_PER_WORD);
mem = gen_rtx_MEM (Pmode, addr);

Your response would be much appreciated.