Compilers

Intended Learning Outcomes

1. Describe the process how high and level programming software translate to the hardware via low level language(s).​

2. Recall the steps of the compile

Types of Programming Languages

• High Level / low level – C#, Java, Python, Ruby, C, C++, assembly ​

• Declarative / imperative/procedural – SQL, Curl, Prolog​

• General-purpose/domain specific – HTML, Markdown/up, MATLAB​

• Object-orientated/concurrent – C#, Java, Python,​

• Command/complied/script language – batch, bash, Javascript​

• Answer set - Prolog

Some Examples of Non-English Programming Languages

Linotte​
It has been a developer for using French keywords, and its “Hello world” program looks like this:​

BonjourLeMonde:​
  début​
    affiche "Bonjour le monde!"​

------------------------

HelloWorld:​
  beginning
    poster "Hello world!

Has a web engine for HTML and PHP and JSP.

SAKO​
System Automatycznego Kodowania Operacji (Automatic Operation Encoding System) programming language, which uses polish as for its keywords:​

LINIA​
  TEKST:​
  HELLO WORLD​
KONIEC​

---------------------------------

LINE
  TEXT:
  HELLO WORLD
END

Really only used in the late 1950s and early 1960s for the XYZ computers.

Rapira​

Rapira is another awesome example of non-english programming languages. It uses Russian keywords:​

ПРОЦ СТАРТ()​

    ВЫВОД: 'Привет, мир!'​

КОН ПРОЦ​

-------------------

proc start()
     output: 'Hello, world!!!';
end proc

EPL​

易语言 (Easy Programming Language, as known as EPL):​

公开 类 启动类​
{​
  公开 静态 启动()​
  {​
    控制台.输出("你好，世界！");​
  }​
}
​
-----------------------------------------

public class startup class​
{
  public static start()
  {
    console.output("Hello, World!");
  }
}

Compiler

A compiler is a program that processes source code written in a programming language.

• Program Processing: A compiler serves as a crucial tool in handling programs written in various programming languages.

• Program Generation: It functions as a program generator, capable of producing executable programs in a specified language.

• Language Translation: The compiler translates programs written in one language into equivalent programs in another language.

A tool to enable you to program at a higher level , by mapping high level concepts to low level implementation

• Increased Productivity: Allows for faster and more efficient development by focusing on the logic and design rather than intricate details.

• Enhanced Readability: Code becomes more readable and understandable, facilitating collaboration and maintenance.

• Code Portability: Encourages code portability by minimizing dependencies on specific hardware or architecture

• Translates from one language into another

• Output a low level program which behaves as specified by
  the input, higher level program.

• Mediate between higher level human concepts, and the
  word by word data manipulation which the machine performs.

Compliler and Interpreter

**Command: gcc -S -O test.c **

(the flag S tells the compiler to produce assembly code, O turns optimisation on).

Assembly code

Assembly code is a low-level programming language that serves as an interface between high-level programming languages and the computer's hardware.

• Human-Readable Machine Code: Assembly code is a human-readable representation of machine code, making it more understandable than binary machine code.

• Close to Hardware: Unlike high-level languages, assembly code provides a direct correspondence to the architecture and operations of the underlying hardware.

• Symbolic Representation: Uses mnemonics and symbols to represent machine instructions, making it more comprehensible than raw machine code.

Example:

• The .data section declares a null-terminated string "Hello, Assembly!".
• The .text section contains the program logic.
• The _start label marks the entry point of the program.

Compiler Stages

Lexical Analysis

• The compiler begins converting the series of characters into tokens​

High Level Code​

int n = 11;​
float q = 1.618;​
if (n < 12)
{​ 
  return q;​
}​
else​
{
  return n;
​}​

Syntax Analysis

Syntax analysis is based on the rules based on the specific programming language by constructing the parse tree with the help of tokens. ​

Semantic Analyser

Semantic Analyser will check for Type mismatches, incompatible operands, a function called with improper arguments, an undeclared variable, etc.​

int n = 11;​
float q = 1.618*n;​

In the above code, the semantic analyser will typecast the int n 11 to float 11.0 before multiplication​.

Intermediate Code Generation

Removes unnecessary code lines​.

Arranges the sequence of statements to speed up the execution of the program without wasting resources. ​

Consider the following code, how can we remove unnecessary code? ​

a = int_to_float(10)​
b = c * a​
d = e + b​
f = d​

b = c * 10.0​
f = e+b​

Code Generation

The objective of this phase is to allocate memory locations, storage and generate relocatable machine code or machine instructions.​​

The code generated by this phase is executed to take inputs and generate expected outputs, therefore, checks for unreachable statements.​
Consider the following code, what error would be generated at this stage?​

while (p == 10)​
{ ​
  break;​
  int q = (0.5*8)*p;​
}​

Code Generation

Now we are going to see how we go from C to Assembly to machine code…​

int square(int num) {​
    return num * num;​
}

square:​
  pushq  %rbp​
  movq   %rsp, %rbp​
  movl   %edi, -4(%rbp)​
  movl   -4(%rbp), %eax​
  imull  %eax, %eax​
  popq   %rbp​
  ret​

int square(int num) {​
    return num * num;​
}

square:​
  pushq  %rbp​
  movq   %rsp, %rbp​
  movl   %edi, -4(%rbp)​
  movl   -4(%rbp), %eax​
  imull  %eax, %eax​
  popq   %rbp​
  ret​

HEX
55           01010101​
48 89 e5​     01001000 10001001 11100101 ​
89 7d fc     10001001 01111101 11111100​
0f af c0​     00001111 10011111 11000000​
54           01010100 ​
C3           11000011​

Error Handling Routine

During compilation process error(s) may occur in all the below-given phases:​

​

• Lexical analyser: Wrongly spelled tokens​
• Syntax analyser: Missing parenthesis​
• Semantic analyser: Mismatched data types, missing arguments​
• Intermediate code generator: Mismatched operands for an operator​
• Code Optimizer: When the statement is not reachable​
• Code Generator: Unreachable statements​
• Symbol tables: Error of multiple declared identifiers​

Menti (What have you leant today?)

• Scan this
• Or go to Menti.com and using this code (1613 4215)

Labs

• Start your lab from here where you are going experience compilation of languages C and Python [Optional], and see how the code compiles and the subsequent outputs!​

• We will be using Godbolt/Compliler Explorer Simulator