The document discusses compilers as translators that convert high-level programming languages into machine code, detailing their functionalities, structure, and historical development. It explains the front-end and back-end processes involved in compiling, along with optimization and instruction selection, and touches on various types of compilers such as source-to-source and just-in-time compilers. Additionally, it highlights advantages and limitations of compiled programs, emphasizing the need for efficient hardware optimization while considering security and platform dependency.

1. Compilers
Group #4
Independent studies and
seminar
CST 477-1
Computer Science and
Technology
Uva Wellassa University

2. Introduction
What is translator
A Translator is a computer program that translates one
programming language instruction(s) into another
programming language instruction(s) without the loss
of original meaning.

3. What is a compiler?
If the translator translates a high level language into an
assembly or machine language it is called a compiler.
Functionalities of a Compiler
• recognize legal (and illegal) programs
• generate correct code
• manage storage of all variables and code
• agree on format for object (or assembly) code
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4. History
1952: First compiler (linker/loader) written by Grace Hopper
for A-0 programming language
1957: First complete compiler for FORTRAN by John Backus
and team
1960: COBOL compilers for multiple architectures
1962: First self-hosting compiler for LISP

5. Some examples for compilers
Compiler Author Windows Unix-like Other OSs IDE
GNU Java GNU Project No Yes No No
Sun
Microsystem
Javac Yes Yes Yes No
s (Owned by
Oracle)
C++ Builder Embarcadero Yes No OS X Yes
Yes IBM
mainframe,
GCC C GNU Project Yes Yes AmigaOS, No
VAX/VMS,
RTEMS
Visual Basic Microsoft Yes No DOS Yes

6. Structure of a compiler
• intermediate representation (IR)
• front end maps legal code into IR
• back end maps IR onto target machine
• simplify retargeting
• allows multiple front ends
• multiple passes better code

7. Intermediate representation
Suppose we wish to build compilers for n source
languages and m target machines.
Case 1: no IR
Need separate compiler for each source language/target
machine combination.
A total of n ∗ m compilers necessary.
Front-end becomes cluttered with machine specific
details, back-end becomes cluttered with source
language specific details.
Case 2: IR present
Need just n front-ends, m back ends.

8. Front end
•Line reconstruction.
•Lexical analysis
•Preprocessing
•Syntax analysis
•Semantic analysis

9. Scanner
• Lexical analysis breaks the source code text into small pieces called
tokens.
• Each token is a single atomic unit of the language, for instance a
keyword, identifier or symbol name
• This phase is also called lexing or scanning

10. Parser
• recognize context-free syntax
• guide context-sensitive analysis
• produce meaningful error messages
• attempt error correction

11. Back end
 Analysis
This is the gathering of program information from the intermediate
representation derived from the input.
 Optimization
the intermediate language representation is transformed into functionally
equivalent but faster (or smaller) forms.
 Code generation
the transformed intermediate language is translated into the output
language, usually the native machine language of the system.

12. Instruction selection
• produce compact, fast code
• use available addressing modes
• pattern matching problem
— ad hoc techniques
— tree pattern matching
— string pattern matching
— dynamic programming

13. Register allocation
• have value in a register when used
• limited resources
• changes instruction choices
• can move loads and stores
• optimal allocation is difficult

14. Other types of compilers
source-to-source compiler
a type of compiler that takes a high level language as its
input and outputs a high level language.
Stage compiler
compiles to assembly language of a theoretical
machine, like some Prolog implementations
This Prolog machine is also known as the Warren Abstract
Machine (or WAM).
Bytecode compilers for Java, Python, and many more are also a
subtype of this.
Just-in-time compiler
Applications are delivered in bytecode, which is compiled to
native machine code just prior to execution.

15. Issues Driving Compiler Design
Advantage:
Self-Contained and Efficient
Hardware Optimization
Disadvantage:
Compiled programs are targeted towards a particular
platform and hence are platform dependent.
Compile Times
They are slower in execution than assembly programs.
Compiled programs do not allow security to be implemented
with in the code - e.g. a compiled program can access any area of the
memory, and can do whatever it wants with your PC (most of the viruses are made
in compiled languages).
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16. Reference
http://lambda.uta.edu/cse5317/notes/node5.html
http://dragonbook.stanford.edu/lecture-
notes/Stanford-CS143/16-Intermediate-Rep.pdf
http://en.wikipedia.org/wiki/Compiler
http://www.personal.kent.edu/~rmuhamma/Compiler
s/MyCompiler/phase.htm

17. Group members
UWU/CST/08/0019 LANKATHILAKA B.A.R.
UWU/CST/08/0020 LIYANAGE C.J.V.
UWU/CST/08/0021 MAHANAMA A.C.
UWU/CST/08/0023 MUTUNAYAKE M.N.A.
UWU/CST/08/0024 NASHAN M.H.M.
UWU/CST/08/0025 NAYANATHARA J.A.J.U.

18. Thank You