01_12-01-_Introduction_to_Code_Generation_7m57s_0_Slides_Original_PDF

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1、CompilersIntroductiontoCodeGenerationAlexAikenCodeGeneration•Wefocusongeneratingcodeforastackmachinewithaccumulator•Wewanttoruntheresultingcodeonarealmachine–e.g.,theMIPSprocessor(orsimulator)•WesimulatestackmachineinstructionsusingMIPSinstructionsandregister

2、sAlexAikenCodeGeneration•TheaccumulatoriskeptinMIPSregister$a0•Thestackiskeptinmemory–Thestackgrowstowardsloweraddresses–StandardconventiononMIPS•TheaddressofthenextlocationonthestackiskeptinMIPSregister$sp–Thetopofthestackisataddress$sp+4AlexAikenCodeGenerat

3、ionMIPSarchitecture–PrototypicalReducedInstructionSetComputer(RISC)–Mostoperationsuseregistersforoperands&results–Useload&storeinstructionstousevaluesinmemory–32generalpurposeregisters(32bitseach)•Weuse$sp,$a0and$t1(atemporaryregister)•ReadtheSPIMdocumentatio

4、nfordetailsAlexAikenCodeGeneration–lwregoffset(reg)12•Load32-bitwordfromaddressreg+offsetintoreg21–addregregreg123•regreg+reg123–swreg1offset(reg2)•Store32-bitwordinregataddressreg+offset12–addiuregregimm12•regreg+imm12•“u”meansoverflowisnotchecked–liregimm

5、•regimmAlexAikenCodeGenerationThestack-machinecodefor7+5inMIPS:acc7li$a07pushaccsw$a00($sp)addiu$sp$sp-4acc5li$a05accacc+top_of_stacklw$t14($sp)add$a0$a0$t1popaddiu$sp$sp4AlexAiken