1 October 1, 2015 1 October 1, 2015October 1, 2015October 1, 2015 Azusa, CA Sheldon X. Liang Ph. D....

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April 19, 2023April 19, 2023 Azusa, CAAzusa, CA

Sheldon X. Liang Ph. D.

Computer Science at Computer Science at Azusa Pacific UniversityAzusa Pacific University

Azusa Pacific University, Azusa, CA 91702, Tel: (800) 825-5278 Department of Computer Science, http://www.apu.edu/clas/computerscience/

CS400 Compiler ConstructionCS400 Compiler Construction

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• Building a compiler involves:– Defining the syntax of a programming language

– Develop a source code parser: for our compiler we will use predictive parsing (greedy eater)

– Implementing syntax directed translation to generate intermediate code: our target is the JVM abstract stack machine

– Generating Java bytecode for the JVM

– Optimize the Java bytecode (optional)

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CS@APU: CS400 Compiler ConstructionCS@APU: CS400 Compiler Construction

Building a Simple CompilerBuilding a Simple Compiler

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• Intermediate Representation (IR) is the product of front end compilation:– The front end of a compiler constructs IR– From which the back end generates the target– Machine-independent optimization– There are two kinds of IRs

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Intermediate RepresentationIntermediate Representation

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Keep in mind following questionsKeep in mind following questions

• Intermediate Representation– Machine-independent– Front end of compilation– Source of target code (back end)

• Why we need IRs– To delay machine-dependent code– To check semantics– To optimize performance

• What further use of IRs– Executable IRs– Machine-independent optimization– Target code generation from IRs

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The Structure of the CompilerThe Structure of the Compiler

http://www.apu.edu/clas/computerscience/

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Graphical• Graphical representations (e.g. AST-->abstract syntax tree)

Linear• Postfix notation: operations on values stored on operand

stack (similar to JVM bytecode)• Three-address code: (e.g. triples and quads)

x := y op z • Two-address code:

x := op ywhich is the same as x := x op y

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Intermediate RepresentationsIntermediate Representations


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Intermediate Representations (AST)Intermediate Representations (AST)E.nptr

*E.nptr

E.nptra

b

+E.nptr

*

a +

b c

E.nptr

c

E.nptr

( )

a * (b + c)

Pro: easy restructuring of codeand/or expressions forintermediate code optimization

Cons: memory intensive


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• Abstract stack machine architecture– Emulated in software with JVM interpreter

– Just-In-Time (JIT) compilers

– Hardware implementations available

• Java bytecode– Platform independent

– Small

– Safe

• The JavaTM Virtual Machine Specification, 2nd ed.http://java.sun.com/docs/books/vmspec

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The JVMThe JVM


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pc

method code

operand stack

heapconstant pool frame

local vars &method args

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Runtime Data Areas (§3.5)Runtime Data Areas (§3.5)


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byte a 8-bit signed two’s complement integer short a 16-bit signed two’s complement integer int a 32-bit signed two’s complement integer long a 64-bit signed two’s complement integer char a 16-bit Unicode characterfloat a 32-bit IEEE 754 single-precision float valuedouble a 64-bit IEEE 754 double-precision float valueboolean a virtual type only, int is used to represent true (1) false (0)returnAddress the location of the pc after method invocationreference a 32-bit address reference to an object of class type, array type, or interface type (value can be NULL)

Operand stack has 32-bit slots, thus long and double occupy two slots

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Data Types (§3.2, §3.3, §3.4)Data Types (§3.2, §3.3, §3.4)


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Flow of Control: loopFlow of Control: loop

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import java.lang.*;public class Hello{ public static void main(String[] arg) { System.out.println("Hello World!"); }}

Compilerjavac Hello.java

Hello.java

Disassemblerjavap -c Hello

JVMjava Hello

Hello.class

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javac, javap, javajavac, javap, java#javac – The compiler, which converts source code into Java bytecode #java –Interpreter, which interprets the class files generated by the javac compiler. #javap – The class file disassembler, disassembles compiled Java files and prints out a representation of the Java program.


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stmt id := expr { emit2(istore, id.index) }

stmt if expr { emit(iconst_0); loc := pc; emit3(if_icmpeq, 0) } then stmt { backpatch(loc, pc-loc) }

code for expr

if_icmpeq off1 off2

code for stmt

code for expr

istore id.index

iconst_0

pc:backpatch() sets the offsets of the relative branchwhen the target pc value is known

loc:

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Generating Code for the JVMGenerating Code for the JVM


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Got it with following questionsGot it with following questions

• Intermediate Representation– Machine-independent– Front end of compilation– Source of target code (back end)

• Why we need IRs– To delay machine-dependent code– To check semantics– To optimize performance

• What further use of IRs– Executable IRs– Machine-independent optimization– Target code generation from IRs

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Thank you very much!

Questions?

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A Simple Syntax-Directed TranslatorA Simple Syntax-Directed Translator


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