AloveIs / COT_lab

Introduction

This is a compiler for the PL\0 language.

The EBNF grammar

program = block "." .

block = [ "const" ident "=" number {"," ident "=" number}* ";"]
        [ "var" ident {"," ident} ";"]
        { "procedure" ident ";" block ";" }* statement .

statement = [ ident ":=" expression 
			| "call" ident
            | "?" ident | "!" expression
            | "begin" statement {";" statement }* "end"
            | "if" condition "then" statement ["else" statement]
            | "while" condition "do" statement ].

condition = "odd" expression |
            expression ("="|"#"|"<"|"<="|">"|">=") expression .

expression = [ "+"|"-"] term { ("+"|"-") term}*.

term = factor {("*"|"/") factor}*.

factor = ident | number | "(" expression ")".

Tools

Useful information

Sites where to plot .dot file

• webraphviz
• GraphvizOnline

Problems to fix

• translate x := y
• constant folding
• calls cannot be the first instruciton in a BB
• problem with useless variables that might be assigned to the same register as one useful variable
• InputStat
• Test functions

Solved

• Functions can call only other functions that have been previously defined (FEATURE)
• at least one instruction after begin-end blocks
• In the construction of the CFG if we have 2 omonymous functions one will overwrite the CFG of the other one (only the graph because of the name)
• Test the for loop