C# Compiler

A compiler for compiling code from C# to MIPS, implemented in Python.

Usage

python codegen.py <filename>

This outputs the MIPS code on standard output along with compilation status (errors if any and success if none). The mips code is also saved in a file.

Example : On running

python codegen.py test/prog1.cs

mips code is saved in test/prog1.asm. It can be run using

spim -file test/prog1.asm

Tests

The compiler is tested using test programs numbered from prog1 to prog10 present in test folder. Some of these programs perform useful things like bubble sort, merge sort, tower of hanoi, power, gcd, factorial, segment tree, prime sieve etc.

Language Specifications

Language Features

Data Types - int, bool, char, string(of size <= 200), arrays, objects
Operators
- int
  - Unary -> !,-,~,+
  - Relational -> <, >, <=, >=, ==, !=
  - Arithmetic -> +,-,/,%
  - Bitwise -> <<,>>,&,|,^
  - Logical ops -> &&,||
  - Assignment -> =,+=,-=,*=,/=,%=,^=,&=,|= (only work for identifiers,not member/element access)
- bool
  - Unary-> !
  - Logical -> &&,||
  - Assignment -> =
- Objects
  - Assignment -> = (make reference to object, assign something to object data member)
- String
  - Initialization and Assignment -> = (assign string constants to string variables)
- Arrays
  - Unary -> !,-,~,+
  - Relational -> <, >, <=, >=, ==, !=
  - Arithmetic -> +,-,/,%
  - Bitwise -> <<,>>,&,|,^
  - Logical ops -> &&,||
  - Assignment -> =
- Char
  - Only read,assign,write operations on non-escape characters
Loops -> for, while, do-while
Selection Statements -> if-else, switch, conditional (c = expression ? a : b)
Jump Statements -> return, continue, break
Arrays -> 1-D arrays of types - {int,bool}
Classes
- Inheritance (from a chain of parents as well)
- Structural Checl : Exactly one class must have a function Main(), this class does not have variables as class members(only methods allowed although method may have any variables/arrays/objects). Execution begins from Main()
- scope modifiers- {public,private} for data members of class only(not functions)
- Data members can only be of simple or array of simple types.
Functions
- Allowed return types -> int, bool, void, char
- Allowed argument types -> int, bool, objects, char (no arrays or strings)
- Function width is decided optimally in case of nested scopes.
Scoping
- Lexical scoping has been implemented which allows us to support nested scopes. The width for a block with nested blocks is determined optimally.
- In our scoping, we don't allow redeclaration of variables sharing name with container function arguments or container class data members.
Short-circuiting of boolean expressions
Return statements supported within blocks as well; garbage/void value returned if no return statement according to return type
Read and Write
- Our write statement can take expression with different type in the same statement(int,char,bool and string)
- Read statement takes one variable in which you want to read(int,char,bool,string)
Multiple Declarations and Sequential Assignments
- Multiple Declarations -> int a,b,c=3;
- Sequential Assignments -> a=b=c=3;
Type Checking
- Language is strictly typed and type checking is done for validating every expression and to check that the operator is operating on valid types.
- In if-else, while, do-while etc., it is checked that the expression has bool type
- Type checking has also been implemented at other places as required
Dynamic Memory Allocation
- Objects are allocated dynamically from heap

NOTE: Braces required in blocks (even if single statement) for if, else, while, for etc.

Features not supported