编译原理2E全套配套课件龙书 Chapter_eight(1).ppt

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1、COMPILERCONSTRUCTIONPrinciplesandPracticeKennethC.Louden8.CodeGenerationPARTONEGenerateexecutablecodeforatargetmachinethatisafaithfulrepresentationofthesemanticsofthesourcecodeDependsnotonlyonthecharacteristicsofthesourcelanguagebutalsoondetailedinformationaboutthetargetarchitecture,thestructureo

2、ftheruntimeenvironment,andtheoperatingsystemrunningonthetargetmachineContentsPartOne8.1IntermediateCodeandDataStructureforcodeGeneration8.2BasicCodeGenerationTechniquesOtherParts8.3CodeGenerationofDataStructureReference8.4CodeGenerationofControlStatementsandLogicalExpression8.5CodeGenerationofPro

3、cedureandFunctioncalls8.6CodeGenerationonCommercialCompilers:TwoCaseStudies8.7TM:ASimpleTargetMachine8.8ACodeGeneratorfortheTINYLanguage8.9ASurveyofCodeOptimizationTechniques8.10SimpleOptimizationsforTINYCodeGenerator8.1IntermediateCodeandDataStructuresforCodeGeneration8.1.1Three-AddressCodeAdata

4、structurethatrepresentsthesourceprogramduringtranslationiscalledanintermediaterepresentation,orIR,forshortSuchanintermediaterepresentationthatresemblestargetcodeiscalledintermediatecodeIntermediatecodeisparticularlyusefulwhenthegoalofthecompileristoproduceextremelyefficientcode;Intermediatecodeca

5、nalsobeusefulinmakingacompilermoreeasilyretarget-able.Studytwopopularformsofintermediatecode:Three-AddresscodeandP-codeThemostbasicinstructionofthree-addresscodeisdesignedtorepresenttheevaluationofarithmeticexpressionsandhasthefollowinggeneralform:X=yopzFigure8.1SampleTINYprogram:{sampleprogramin

6、TINYlanguage--computesfactorial}readx;{inputaninteger}if0>xthen{don’tcomputeifx<=0}fact:=1;repeatfact:=fact*x;x:=x-1untilx=0;writefact{outputfactorialofx}endsTheThree-addresscodesforaboveTINYprogramreadxt1=x>0if_falset1gotoL1fact=1labelL2t2=fact*xfact=t2t3=x-1x=t3t4=x==0if_falset4gotoL2writefact

7、labelL1halt8.1.2DataStructuresfortheImplementationofThree-AddressCodeThemostcommonimplementationistoimplementthree-addresscodeasquadruple,whichmeansthatfourfieldsarenecessary:OnefortheoperationandthreefortheaddressesAd