编译原理2E全套配套课件龙书 Chapter_six(1).ppt

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1、COMPILERCONSTRUCTIONPrinciplesandPracticeKennethC.Louden6.SemanticAnalysisPARTONESemanticAnalysisPhasePurpose:computeadditionalinformationneededforcompilationthatisbeyondthecapabilitiesofContext-FreeGrammarsandStandardParsingAlgorithmsStaticsemanticanalysis:Takeplacepriortoexecution(Su

2、chasbuildingasymboltable、performingtypeinferenceandtypechecking)ClassificationAnalysisofaprogramrequiredbytherulesoftheprogramminglanguagetoestablishitscorrectnessandtoguaranteeproperexecutionAnalysisperformedbyacompilertoenhancetheefficiencyofexecutionofthetranslatedprogramDescription

3、ofthestaticsemanticanalysisAttributegrammaridentifyattributesoflanguageentitiesthatmustbecomputedandtowriteattributeequationsorsemanticrulesthatexpresshowthecomputationofsuchattributesisrelatedtothegrammarrulesofthelanguageWhichismostusefulforlanguagesthatobeytheprincipleofSyntax-Direc

4、tedSemanticsAbstractsyntaxasrepresentedbyanabstractsyntaxtreeImplementationofthestaticsemanticanalysis:NotasclearlyexpressibleasparsingalgorithmsbecauseoftheadditionproblemcausedbythetimingoftheanalysisduringthecompilationprocessMulti-pass(morecommon)orsinglepassleadtototallydifferentp

5、rocessEmphasis:AttributesandattributegrammarsAlgorithmsforattributecomputationThesymboltableDatatypesandtypecheckingAsemanticanalyzerfortheTINYlanguageContentsPartOne6.1AttributesandAttributeGrammars6.2AlgorithmsforAttributeComputationPartTwo6.3TheSymbolTable6.4DataTypesandTypeChecking

6、6.5ASemanticAnalyzerfortheTINYLanguage6.1AttributesandAttributeGrammarsAttributesAnypropertyofaprogramminglanguageconstructsuchasThedatatypeofavariableThevalueofanexpressionThelocationofavariableinmemoryTheobjectcodeofaprocedureThenumberofsignificantdigitsinanumberBindingoftheattribute

7、TheprocessofcomputinganattributeandassociatingitscomputedvaluewiththelanguageconstructinquestionBindingtimeThetimeduringthecompilation/executionprocesswhenthebindingofanattributeoccursBasedonthedifferenceofthebindingtime,attributesisdividedintoStaticattributes(beboundpriortoexecution