323-

Lecture1IntroductionEliasAthanasopoulos

eliasathan@cs.ucy.ac.cy

Contract- Logistics

Officehours EveryTuesday,10:00 12:00,B105(01)

Credits:7.5ECTS LectureTimetableMonday,Thursday,12:00 13:30,006(01)Wednesday,9:00-10:00,110(01),onlywhenannounced!

Contract- Logistics

Labs(Dr.Petros Panayi) EveryWednesday,B103(01) Group1:15:00- 17:00 Group2:17:00- 19:00

Contract- Logistics

Score ProgrammingAssignments(Quizzes),15% Project(multiplesteps),15%Midterm,30% Final,40%

Requirements Averagegradeofwrittenexamsshouldbeatleast4.5

Finalgradeshouldbeatleast5

Contract- Logistics

Requiredcourses CS132(Cprogramming), CS211 (Complexity), CS231 (DataStructures)

Studentswithconflictsshouldletmeknow

Contract- Logistics

Readingmaterial Dragonbook,Compilers Principles,Techniques,andTools(2ndEdition),A.V.Aho,M.S.Lam,R.Sethi andJ.D.Ullman,PrenticeHall,2006.

Communication

Labs Blackboard

Lectures http://www.cs.ucy.ac.cy/courses/EPL323

INTRODUCTION(Chapter1fromDragonBook)

Whythiscourseisimportant?

Manycoreconcepts ofCSinareal-lifesetting CS132:BehindthescenesofCprogramming CS211,CS231:DFAs,parsingalgorithms CS372,CS221:Assembly,ComputerArchitecture

Compilersareeverywhere Fromexoticdevices(IoT)towebbrowsers(JavaScriptengines,DOMparsers,etc.)

TweakingcompilersforSecurity

Compilerisatoughone

Significantefforttobuildacompilerfromscratch FirstFortrancompilertook18staff-years

Nowadays,manytoolsexisttohelp Ourunderstandingismuchbetter Bettertechniques,betterprogramminglanguages

Whatisacompiler?

Acompilerisaprogramthat readsaprogramwritteninonelanguage(source) andtranslatesittoanequivalentprograminanotherlanguage(target)

important:errorreportingduringtranslation

Compilersourceprogram targetprogram

errormessages

Examples

GCC(GnuCompilerCollection) gcc,g++,javac,etc.

LLVM(LowLevelVirtualMachine) clang,clang++

Compilersareeverywhere, Prettyprinters(i.e.,colorsyntaxineditors),staticcheckers,interpreters(i.e.,scriptinglanguages),etc.

Analysis-SynthesisModel

Therearetwopartsincompilation: Analysis Synthesis

Analysis Breaksupthesourceprogram tosubpartsandcreatesintermediaterepresentation(s)

Synthesis Constructsthetargetprogram fromintermediaterepresentation(s)

Example1(LaTeX)\begin{table}[tb]

\centering\caption{We name gadgets based on their type (prefix), payload (body),and exit instruction (suffix). In total, we name 2$\times$3$\times$3=18different gadget types.}\begin{tabular}{|c|c|c|}

\hline\textbf{Gadget type} & \textbf{Payload instructions} &

\textbf{Exit instruction} \\\hline{Prefix} & {Body} & {Suffix} \\\hline

\begin{tabular}{l}CS - Call site\\EP - Entry point\\\end{tabular} &...

$ pdflatex main.tex

Example2(Database)

class

student Seq. Scan

Hash Join

Aggregate

SELECT AVG(grade)FROM student, classWHEREclass.name = epl223 ANDclass.id = student.id;

Requirements

Compiler Reliability Fastexecution Lowmemoryoverhead Gooderrorreporting Errorrecovery Portability Maintainability

Targetprogram Fastexecution Lowmemoryoverhead

Sourcecode/program

Easytoread/writebyhuman

int expr(int n) {int d;

d = 4 * n * n * (n + 1) * (n + 1);

return d;}

AssemblyandMachineCode

Optimizedforexecutionbyamachine(CPU) Lessdescriptive Hardtobeprocessedbyahuman

lda $30,-32($30)stq $26,0($30)stq $15,8($30)bis $30,$30,$15bis $16,$16,$1stl $1,16($15)lds $f1,16($15)sts $f1,24($15)ldl $5,24($15)bis $5,$5,$2s4addq $2,0,$3ldl $4,16($15)mull $4,$3,$2ldl $3,16($15)

Optimizations

Compilershaveseverallayersofoptimizationsint expr(int n){

int d;d = 4 * n * n * (n + 1) * (n + 1);

return d;}

.expr:stw 31,-4(1) lwz 11,64(31)stwu 1,-40(1) addi 9,11,1mr 31,1 mullw 0,0,9stw 3,64(31) stw 0,24(31)lwz 0,64(31) lwz 0,24(31)mr 9,0 mr 3,0slwi 0,9,2 b L..2lwz 9,64(31) L..2:mullw 0,0,9 lwz 1,0(1)lwz 11,64(31) lwz 31,-4(1)addi 9,11,1 blrmullw 0,0,9

.expr:addi 9,3,1slwi 0,3,2mullw 3,3,0mullw 3,3,9mullw 3,3,9blr

Nooptimizations$ gcc O0

Optimizations$ gcc O3

Cross-compiler

Compilerscangeneratecodefordifferentmachines(targets) int expr(int n){

int d;d = 4 * n * n * (n + 1) * (n + 1);

return d;}

expr:pushl %ebpmovl %esp, %ebpmovl 8(%ebp), %eaxleal 1(%eax), %edximull %eax, %eaximull %edx, %eaximull %edx, %eaxsall $2, %eaxpopl %ebpret

.expr:addi 9,3,1slwi 0,3,2mullw 3,3,0mullw 3,3,9mullw 3,3,9blr

Forx86$ gcc O3 b i586

ForPowerPC$ gcc O3 b powerpc

Compilationlifecycle

Phases Sourcecodeistransformedtointermediaterepresentations

Eachintermediaterepresentationissuitableforaparticularprocessing(lexical,syntax,optimization,etc.)

Ineachphasetheprogramistranslatedtoaformclosertothemachinerepresentationandlesssimilartothe(human-oriented)sourcerepresentation

CompilerPhases

Lexical Analyzer

Source Program

Target Program

Syntax Analyzer

Semantic Analyzer

Intermediate codegenerator

Code optimizer

Code generator

Error HandlerSymbol Table Manager

1

2

2

3

3

Optional

1:Tokens()2:Syntaxtree()3:Intermediatecode()

Analysisofthesourceprogram

Linearanalysis Sourceistreatedasastreamofcharacters(left-to-right)andisgroupedintotokens

Hierarchicalanalysis Tokensarefurthergroupedinlargergrammaticalstructures(e.g.,nestedparenthesesandblocks)

Semanticanalysis Certainchecksareperformedtoensurethevalidityoftheidentifiedgrammaticalstructures

LexicalAnalysis

Linearscanning Considertheexpression

position := initial + rate *60

Lexicalanalysisproducesid(1) op(:=) id(2) op(+) id(3) op(*) cons(60)id: identifier, op: operator, cons: constant

SymbolTable 1 position 2 initial 3 rate 4

SyntaxAnalysis

Hierarchical Involvesgroupingthetokensintogrammaticalphases

Constructsthestructurewiththetokenrelationship

op(:=)

id(3) cons(60)

id(2) op(*)

id(1) op(+)

position := initial + rate * 60

SimpleGrammar

Thehierarchicalstructureoftheprogramisusuallyexpressedbyrecursiverules

1. Anyidentifier isanexpression2. Anynumber isanexpression3. Ifexpression1 andexpression2 areexpressions,

thensoare:expression1 +expression2expression1 *expression2(expression1 )

Applyingthegrammar

op(:=)

id(3) cons(60)

id(2) op(*)

id(1) op(+)

(1)Anyidentifier isanexpression(2)Anynumber isanexpression(3)Ifexpression1 andexpression2 areexpressions,thensoare:

expression1 +expression2expression1 *expression2(expression1 )

SemanticAnalysis

Checkstheprogramforsemanticerrors Gatherstypeinformation Operandsandoperators Type-checking

op(:=)

id(3) int_2_real

id(2) op(*)

id(1) op(+)

cons(60)

FLOAT

INTposition := initial + rate * 60

int_2_real() isanextranodeforconverting60 toarealnumber.Remember:themachinerepresentationofintegersandrealnumbersisdifferent!

Errordetectionandreporting

Allphasescanissueerrors Acompilerthatstopsatthefirsterrorisnothelpful Mostoftheerrorsarehandledinthesyntax/semanticanalysisphases Lexicalanalysisdetectserrorswhereastreamofcharactersdoesnotformavalidtoken

Syntaxanalysisdetectserrorswherethestreamofvalidtokensviolatethestructurerules(syntax)

Semanticanalysisdetectserrorswherethesyntaxisvalidbytheoperationnot(addinganarraywitharealnumber)

IntermediateCodeandOptimization

Eachphaseproducesintermediatecode

Optimization

temp1 := int_2_real(60)temp2 := id(3) * temp1temp3 := id(2) + temp2id(1) := temp3

temp1 := id(3) * 60.0id(1) := id(2) + temp1

three-addresscode:asimpleassembly-likelanguage,whichconsistsofinstructions,eachofwhichhasatmostthreeoperands

Operator:Operand:

CodeGeneration

Thelastphaseofthecompileristhegenerationofthetargetcode

Registerallocation Eachexpressionshoulduseregistersthatareavailable

Relocationinformation Variablesarestoredinrelocatable addresses

MOVF id3, R2MULF #60.0, R2MOVF id2, R1ADDF R2, R1MOVF R1, id1

GenericPictureCompilerandFriends

Sourcecode

Compiler

Assemblycode

Assembler

Machinecode

Executable

Linker

SLoader

FrontandBackends

Separationofcommontasks Makesdesignand

implementationeasier KcompilersforNmachines Nbackends,Kfrontends InsteadofK*Ncompilers

Frontend(machine-

independent)

Backend

Lexical Analyzer

Source Program

Target Program

Syntax Analyzer

Semantic Analyzer

Intermediate codegenerator

Code optimizer

Code generator

Passes

Apass iswhenthecompilerreadsthesourcecode(orintermediatefiles)

Thenumberofpassesdependsonthesourceandtargetlanguageandtherunningenvironment

Differentphasesthatcooperatecanbegroupedtoasinglepass(notalwayspossible)

Whengroupingisnotpossible Backpatching:leaveemptyinformationthatisgoingtobefilledbyalaterphase/pass

Compiler-constructionTools

Parsergenerators Scannergenerators Syntax-directedtranslationengines Automaticcodegenerators Data-flowengines