Mooly Sagiv and Greta Yorsh School of Computer Science Tel-Aviv University [email_address] http://www.cs.tau.ac.il/~gretay Modern Compiler Design T1 - Overview

Who Greta Yorsh Schrieber Open-space Tel: 640-5358 [email_address] Wednesday 16:00-17:00 http://www.cs.tau.ac.il/~gretay

Greta Yorsh

Schrieber Open-space

Tel: 640-5358

[email_address]

Wednesday 16:00-17:00

http://www.cs.tau.ac.il/~gretay

What Semantic Representation Backend (synthesis) Compiler Frontend (analysis) Executable code exe Source text txt

Say What? Semantic Representation Backend (synthesis) Compiler Frontend (analysis) Lexical Analysis Syntax Analysis Parsing AST Symbol Table etc. Inter. Rep. (IR) Code Gen. Executable code exe Source text txt Cool Language txt Executable code exe

How Lexical Analysis Syntax Analysis Parsing AST Symbol Table etc. Inter. Rep. (IR) Code Gen. flex bison C++ Cool GC MIPS assembly SPIM Cool Language txt Executable code exe

Project - a complete compiler Cool to MIPS assembly language Implemented in C++ Split into assignments

Cool to MIPS assembly language

Implemented in C++

Split into assignments

Grading 50% exam 10% theoretical assignment 40% project 5 assignments – different weights code checked both automatically and manually today exam teams PA1 PA2 TA1 PA3 PA4 PA5

50% exam

10% theoretical assignment

40% project

5 assignments – different weights

code checked both automatically and manually

Project Guidelines Teams of 3 students email me before next practice team account In case of doubt – ask questions in the Forum There is adequate time to complete assignments Start early and please follow directions Submit assignments on schedule

Teams of 3 students

email me before next practice

team account

In case of doubt – ask questions in the Forum

There is adequate time to complete assignments

Start early and please follow directions

Submit assignments on schedule

Goals: Understand the scope of the project How to write a Cool program Today Lexical Analysis Syntax Analysis Parsing AST Symbol Table etc. Inter. Rep. (IR) Code Gen. Cool Language txt Executable code exe

Goals:

Understand the scope of the project

How to write a Cool program

Cool Overview Classroom Object Oriented Language Implementation of modern abstraction static typing reuse (inheritance) memory management and more…

Classroom Object Oriented Language

Implementation of modern

abstraction

static typing

reuse (inheritance)

memory management

and more…

Good News No arrays No floating point operations No “static” modifier No interfaces No method overloading (but still allow overriding) No exceptions No packages

No arrays

No floating point operations

No “static” modifier

No interfaces

No method overloading (but still allow overriding)

No exceptions

No packages

Better News Cool language is still rich enough for doing interesting things

Cool language is still rich enough for doing interesting things

A Simple Example class Point { x : Int  0; y : Int  0; }; Cool programs are sets of class definitions class = a collection of attributes and methods A special class Main with a special method main No separate notion of subroutine Instance of a class are objects

class Point {

x : Int  0;

y : Int  0;

};

Cool programs are sets of class definitions

class = a collection of attributes and methods

A special class Main with a special method main

No separate notion of subroutine

Instance of a class are objects

Cool Objects class Point { x : Int  0; y : Int ; (* use default value *) }; The expression “new Point” creates a new object of class Point An object can be thought of as a struct (record) with a slot for each attribute 0 0 x y

class Point {

x : Int  0;

y : Int ; (* use default value *)

};

The expression “new Point” creates a new object of class Point

An object can be thought of as a struct (record) with a slot for each attribute

Methods class Point { x : Int  0; y : Int  0; movePoint (newx : Int, newy : Int) : Point { { x  newx; y  newy; self; } – close block expression }; -- close method }; -- close class A class can also define methods for manipulating the attributes Methods can refer to the current object using self

class Point {

x : Int  0;

y : Int  0;

movePoint (newx : Int, newy : Int) : Point {

{ x  newx;

y  newy;

self;

} – close block expression

}; -- close method

}; -- close class

A class can also define methods for manipulating the attributes

Methods can refer to the current object using self

Information Hiding in Cool Methods are global (public) Attributes are local to a class (private) they can only be accessed by the class’s methods Example class Point { … getx () : Int { x }; setx (newx : Int) : Int { x  newx }; };

Methods are global (public)

Attributes are local to a class (private)

they can only be accessed by the class’s methods

Example

class Point {

…

getx () : Int { x };

setx (newx : Int) : Int { x  newx };

};

Methods Each object knows how to access the code of a method As if the object contains a slot pointing to the node In reality implementations save space by sharing these pointers among instances of the same class 0 0 x y * movePoint methods 0 0 x y * movePoint

Each object knows how to access the code of a method

As if the object contains a slot pointing to the node

In reality implementations save space by sharing these pointers among instances of the same class

Inheritance We can extend points to colored points using subclass (class hierarchy) class ColorPoint inherits Points { color : Int  0; movePoint(newx : Int, newy : Int) : Point { { color  0; x  newx; y  newy; self; } }; }; 0 0 y color * movePoint 0 x

We can extend points to colored points using subclass (class hierarchy)

class ColorPoint inherits Points {

color : Int  0;

movePoint(newx : Int, newy : Int) : Point {

{ color  0;

x  newx; y  newy;

self;

}

};

};

Cool Types Every class is a type Base classes: Int Bool (true, false) String Object (root of the class hierarchy) All variables must be declared compiler infers types for expressions

Every class is a type

Base classes:

Int

Bool (true, false)

String

Object (root of the class hierarchy)

All variables must be declared

compiler infers types for expressions

Cool Type Checking x : A; x  new B; Is well typed if A is an ancestor of B in the class hierarchy anywhere an A is expected a B can be used Type safety A well-typed program cannot result in runtype type errors

x : A;

x  new B;

Is well typed if A is an ancestor of B in the class hierarchy

anywhere an A is expected a B can be used

Type safety

A well-typed program cannot result in runtype type errors

Method Invocation and Ingeritance Methods are invoked by dispatch Understanding dispatch in the presence of inheritance is a subtle aspect of OO languages p : Point ; p  new ColorPoint; p.movePoint(1,2); p has static type Point p has dynamic type ColorPoint p.movePoint must invoke the ColorPoint version

Methods are invoked by dispatch

Understanding dispatch in the presence of inheritance is a subtle aspect of OO languages

p : Point ;

p  new ColorPoint;

p.movePoint(1,2);

p has static type Point

p has dynamic type ColorPoint

p.movePoint must invoke the ColorPoint version

Method Invokation Example: invoke one-argument method m e.m(e’) Eval e Find class of e Find code of m Eval argument Bind self and x Run method

Example: invoke one-argument method m

e.m(e’)

Eval e

Find class of e

Find code of m

Eval argument

Bind self and x

Run method

Other Expressions Expression language every expression has a type and a value Loops: while E loop E pool Conditionals: if E then E else E fi Case statement: case E of x: Type  E; esac Arithmetic operations Logical operations Assignment x  E

Expression language

every expression has a type and a value

Loops: while E loop E pool

Conditionals: if E then E else E fi

Case statement: case E of x: Type  E; esac

Arithmetic operations

Logical operations

Assignment x  E

Cool Memory Management Memory is allocated every time new is invoked Memory is deallocated automatically when an object is not reachable anymore done by the garbage collector (GC) There is a Cool GC

Memory is allocated every time new is invoked

Memory is deallocated automatically when an object is not reachable anymore

done by the garbage collector (GC)

There is a Cool GC

Cool Language - Main features Object oriented Objects, virtual method calls, but no overloading Strongly typed Primitives for int, boolean, string Reference types Dynamic allocation and Garbage Collection Heap allocation, automatic deallocation Many things are left out short time implementation Adapted with permission from Prof. Alex Aiken (Berkeley,Standford)

Object oriented

Objects, virtual method calls, but no overloading

Strongly typed

Primitives for int, boolean, string

Reference types

Dynamic allocation and Garbage Collection

Heap allocation, automatic deallocation

Many things are left out

short time implementation

Adapted with permission from Prof. Alex Aiken (Berkeley,Standford)