Here are some things to think about when implementing goto statements

Here are some things to think about when implementing goto statements.

You will add the following productions to your grammar:

stmt: ID ‘:’ stmt

| goto ID

1. Note that you are going to expect ID to have UNDEF stored in its type field. If you find S_INT or S_FLOAT, you should emit an error such as “Invalid Label Type”.

2. You need to consider the following two cases:

a. If ID ‘:’ stmt comes before goto ID in your program

The semantic action for ID ‘:’ stmt should store progp in a new field you add to ID ($1->br_addr=progp)

The semantic action for goto ID should emit code2(branch, (Inst)$2->br_addr);

b. If goto ID comes before ID ‘:’ stmt in your program

The semantic action for goto ID should emit code2(branch, STOP); and save address of STOP in a new field in you add to ID ($2->fixup_addr=progp-1

The semantic action for ID ‘:’ stmt should fix-up the branch emitted at the goto. For example: ($1->fixup_addr)[0]=$1->br_addr;

c. You are just inhumanly cool if you can figure out how to implement:

goto a;

…

goto a;

…

goto a;

…