计算机组织与结构：版7-13-RISC

WilliamStallings

ComputerOrganization

andArchitecture

7thEditionChapter13ReducedInstructionSetComputers1Chapter13

ReducedInstructionSetComputersKeytermsCISCcomplexinstructionsetcomputerRISCreducedinstructionsetcomputerDelayedbranchDelayedloadHLLhigh-levellanguageRegisterfileRegisterwindowSPARC2MajorAdvancesinComputers(1)ThefamilyconceptIBMSystem/3601964DECPDP-8SeparatesarchitecturefromimplementationMicroporgrammedcontrolunitIdeabyWilkes1951ProducedbyIBMS/3601964CachememoryIBMS/360model8519693MajorAdvancesinComputers(2)SolidStateRAM(Seememorynotes)MicroprocessorsIntel40041971PipeliningIntroducesparallelismintofetchexecutecycleMultipleprocessors4TheNextStep-RISCReducedInstructionSetComputerKeyfeaturesLargenumberofgeneralpurposeregistersoruseofcompilertechnologytooptimizeregisteruseLimitedandsimpleinstructionsetEmphasisonoptimisingtheinstructionpipeline5Comparisonofprocessors6DrivingforceforCISCSoftwarecostsfarexceedhardwarecostsIncreasinglycomplexhighlevellanguagesSemanticgapLeadsto:LargeinstructionsetsMoreaddressingmodesHardwareimplementationsofHLLstatementse.g.CASE(switch)onVAXSemantic:语义的;语义学的

Gap英音：[gæp]豁口,裂口

7IntentionofCISCEasecompilerwritingImproveexecutionefficiencyComplexoperationsinmicrocodeSupportmorecomplexHLLsease减轻

HLL

缩写词abbr.

high-levellanguage【电脑】高级语言8ExecutionCharacteristicsOperationsperformedOperandsusedExecutionsequencingStudieshavebeendonebasedonprogramswritteninHLLsDynamicstudiesaremeasuredduringtheexecutionoftheprogram9OperationsAssignmentsMovementofdataConditionalstatements(IF,LOOP)SequencecontrolProcedurecall-returnisverytimeconsumingSomeHLLinstructionleadtomanymachinecodeoperationsAssignment

分配;指派,选派10WeightedRelativeDynamicFrequencyofHLLOperations[PATT82a]

DynamicOccurrenceMachine-InstructionWeightedMemory-ReferenceWeighted

PascalCPascalCPascalCASSIGN45%38%13%13%14%15%LOOP5%3%42%32%33%26%CALL15%12%31%33%44%45%IF29%43%11%21%7%13%GOTO—3%————OTHER6%1%3%1%2%1%11OperandsMainlylocalscalarvariablesOptimisationshouldconcentrateonaccessinglocalvariables

PascalCAverageIntegerConstant16%23%20%ScalarVariable58%53%55%Array/Structure26%24%25%12ProcedureCallsVerytimeconsumingDependsonnumberofparameterspassedDependsonlevelofnestingMostprogramsdonotdoalotofcallsfollowedbylotsofreturnsMostvariablesarelocal(c.f.localityofreference)13ImplicationsBestsupportisgivenbyoptimisingmostusedandmosttimeconsumingfeaturesLargenumberofregistersOperandreferencingCarefuldesignofpipelinesBranchpredictionetc.Simplified(reduced)instructionset14LargeRegisterFileSoftwaresolutionRequirecompilertoallocateregistersAllocatebasedonmostusedvariablesinagiventimeRequiressophisticatedprogramanalysisHardwaresolutionHavemoreregistersThusmorevariableswillbeinregisters15RegistersforLocalVariablesStorelocalscalarvariablesinregistersReducesmemoryaccessEveryprocedure(function)callchangeslocalityParametersmustbepassedResultsmustbereturnedVariablesfromcallingprogramsmustberestored16RegisterWindowsOnlyfewparametersLimitedrangeofdepthofcallUsemultiplesmallsetsofregistersCallsswitchtoadifferentsetofregistersReturnsswitchbacktoapreviouslyusedsetofregisters17RegisterWindowscont.ThreeareaswithinaregistersetParameterregistersLocalregistersTemporaryregistersTemporaryregistersfromonesetoverlapparameterregistersfromthenextThisallowsparameterpassingwithoutmovingdatacont.

1.内容，所含之物(contents)2.继续的；不断的；连续的18OverlappingRegisterWindows……19CircularBufferdiagram主程序1子程序A2子程序B3子程序C4子程序D5子程序E6子程序F7子程序G20OperationofCircularBufferWhenacallismade,acurrentwindowpointerismovedtoshowthecurrentlyactiveregisterwindowIfallwindowsareinuse,aninterruptisgeneratedandtheoldestwindow(theonefurthestbackinthecallnesting)issavedtomemoryAsavedwindowpointerindicateswherethenextsavedwindowsshouldrestoreto21GlobalVariablesAllocatedbythecompilertomemoryInefficientforfrequentlyaccessedvariablesHaveasetofregistersforglobalvariables22RegistersvCacheLargeRegisterFileCacheAlllocalscalarsRecently-usedlocalscalarsIndividualvariablesBlocksofmemoryCompiler-assignedglobalvariablesRecently-usedglobalvariablesSave/RestorebasedonprocedurenestingdepthSave/RestorebasedoncachereplacementalgorithmRegisteraddressingMemoryaddressing23ReferencingaScalar-

WindowBasedRegisterFile24ReferencingaScalar-Cache25ReferencingaScalar-

WindowBasedRegisterFile26CompilerBasedRegisterOptimizationAssumesmallnumberofregisters(16-32)OptimizinguseisuptocompilerHLLprogramshavenoexplicitreferencestoregistersusually-thinkaboutC-registerintAssignsymbolicorvirtualregistertoeachcandidatevariableMap(unlimited)symbolicregisterstorealregistersSymbolicregistersthatdonotoverlapcansharerealregistersIfyourunoutofrealregisterssomevariablesusememory27GraphColoringGivenagraphofnodesandedgesAssignacolortoeachnodeAdjacentnodeshavedifferentcolorsUseminimumnumberofcolorsNodesaresymbolicregistersTworegistersthatareliveinthesameprogramfragmentarejoinedbyanedgeTrytocolorthegraphwithn

colors,wherenisthenumberofrealregistersNodesthatcannotbecoloredareplacedinmemory28GraphColoringApproach29GraphColoringApproach30WhyCISC(1)?Compilersimplification?

Disputed…ComplexmachineinstructionshardertoexploitOptimizationmoredifficult

(开发)Smallerprograms?Programtakesuplessmemorybut…MemoryisnowcheapMaynotoccupylessbits,justlookshorterinsymbolicformMoreinstructionsrequirelongerop-codesRegisterreferencesrequirefewerbits

dispute

英音：[di‘spju:t]争论;争执

simplification

1.单纯化2.简单化31WhyCISC(2)?Fasterprograms?BiastowardsuseofsimplerinstructionsMorecomplexcontrolunitMicroprogramcontrolstorelargerthussimpleinstructionstakelongertoexecuteItisfarfromclearthatCISCistheappropriatesolution

Bias倾向,趋势32RISCCharacteristicsOneinstructionpercycleRegistertoregisteroperationsFew,simpleaddressingmodesFew,simpleinstructionformatsHardwireddesign(nomicrocode)FixedinstructionformatMorecompiletime/effort33RISCvCISCNotclearcutManydesignsborrowfrombothphilosophiese.g.PowerPCandPentiumIIphilosophies

哲学；观点34RISCPipeliningMostinstructionsareregistertoregisterTwophasesofexecutionI:InstructionfetchE:ExecuteALUoperationwithregisterinputandoutputForloadandstoreI:InstructionfetchE:ExecuteCalculatememoryaddressD:MemoryRegistertomemoryormemorytoregisteroperation35Figure13.6cFigure13.6c,threeinstructionscanbeoverlapped,andtheimprovementisasmuchasafactorof3.I36Figure13.6dE1:RegisterfilereadE2:ALUoperationandregisterwriteI37EffectsofPipelining38OptimizationofPipeliningDelayedbranchDelayedLoadLoopUnrollingunroll

展开，打开（卷着的东西）39OptimizationofPipelining

（1）LoopUnrollingReplicatebodyofloopanumberoftimesIterateloopfewertimesReducesloopoverheadIncreasesinstructionparallelismImprovedregister,datacacheorTLBlocality

unroll

展开，打开（卷着的东西）

replicate

英音：[‘replikeit]折叠;复制

iterate

英音：['itəreit]反复,重复

overhead英音：[‘əuvə’hed]日常开支，额外开销40OptimizationofPipelining

（2）DelayedbranchDoesnottakeeffectuntilafterexecutionoffollowinginstructionThisfollowinginstructionisthedelayslot41NormalandDelayedBranchAddressNormalBranchDelayedBranchOptimizedDelayedBranch100LOAD X,rALOAD X,rALOADX,rA101ADD 1,rAADD 1,rAJUMP 105102JUMP 105JUMP 106ADD 1,rA103ADD rA,rBNOOP

ADD rA,rB104SUB rC,rBADD rA,rBSUB rC,rB105STORErA,Z

SUB rC,rBSTORErA,Z

106

STORErA,Z

42UseofDelayed

BranchAddressNormalBranchDelayedBranchOptimizedDelayedBranch100LOAD X,rALOADX,rALOADX,rA101ADD1,rAADD1,rAJUMP105102JUMP105JUMP106ADD1,rA103ADDrA,rBNOOP ADDrA,rB104SUBrC,rBADDrA,rBSUBrC,rB105STORErA,Z