Re: Alternatives to Syntax Trees

On Sun, 15 Jan 2017 16:52:15 -0500 (EST), Seima Rao
<seimarao@gmail.com> wrote:


> Are there alternatives to syntax trees(i.e. the tree data structure)
> when compiling via yacc or yacc like tools ?


Parser tools don't limit the structure of the intermediate
representation.


>[There's quadruples, doubly linked lists of data structures. They
>make it easier to rearrange code, but harder to do just about anything
>else. There's also DAGs, which are trees that can have shared subtrees,
>useful when you're doing common subexpressions or tail merging. -John]


To add a bit to John's excellent response:


You can use a combined representation: e.g., a graph to represent
control - function defintions, loops, conditionals, etc. - and within
the graph use 3-address form to represent basic blocks (straight line
code).


Some analyses, e.g., determining dominance for EBB def/kill chains,
require both the basic blocks and the graph of their connectivity.




Also, "quadruples" are one form of 3-address representation. There
are other forms of 3-address and you can implement them using either
lists or arrays. Quadruples are the most commonly used because - as
John mentioned - they are the easiest to rearrange.


George

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