Optimizations for the compiler performances

LOOKING UP SYMBOLS. One should avoid intensive searching for symbols in the symbol table during type checking and translation.

• The syntax-directed definitions shown earlier for simple code generation use names as the attributes $\bf id$.place.
• In fact, names should be represented by pointers to symbol-table entries (rather than strings).
• These pointers can be set up during the lexical analysis.
• Hence the value associated with a token TOK_ID (for identifiers) returned by LEX should better be a pointer to an entry of the symbol table rather than a string.

EMISSION RATHER THAN CONCATENATION. Instead of attaching a string S.string to each instance of the grammar symbol S encountered during the translation, one should try

• either to write 3-address statements directly into output.
• or to append linked lists of strings (where previously we were concatenating strings).

In the next syntax-directed definitions, the procedure emit writes 3-address statements directly into output.