Python parser (Parser/tokenizer.c) has a translate_into_utf8() function to decode a string from the input encoding and encode it to UTF-8.

This function is unnecessary if the input string is already encoded to UTF-8, which is something common nowadays. Linux, Mac OS X and many other operating systems are now using UTF-8 as the default locale encoding, UTF-8 is the default encoding for Python scripts, etc. compile(), eval() and exec() functions pass UTF-8 encoded strings to the parser.

Attached patch adds an input_is_utf8 flag to the tokenizer to skip translate_into_utf8() if the input string is already encoded to UTF-8.