Reading for this homework includes chp the dragon book

Reading for this homework includes Chp 5 of the Dragon book. We will be using the LLVM Compiler Infrastructure for code generation and code optimization: http://llvm.org. 

1. Global variables
Add support for global variables. The following rules in Decaf are the ones that involve the use of global variables.

2. Control-flow and loops
The following fragment of Decaf syntax adds control flow (if statements) and loops (while and for statements) to Decaf.
Your program must implement short-circuit evaluation for boolean expressions.

3. Semantic checks
Perform at least the following semantic checks for any syntactically valid input Decaf program:

(a)  A method called main has to exist in the Decaf program.