AND指令可用于復(fù)位某些位(同0相與)

Chapter8BitManipulationContents:LogicalOperationsShiftandRotateInstructions8.1LogicalOperationsANDdestination,sourceTESTdestination,sourceThesameasANDinstructionbutnotchangedestinationNOTdestinationORdestination,sourceinclusiveXORdestination,sourceexclusiveTruetableABT000010100111ANDsrcregmemimmreg√√√mem√√destABT000011101110ABT000011101111AT0110flagsLogicaloperationexceptforNOTwillaffectflagregister.CF=0OF=0AF:undefinedPF,SF,ZF:setbythevalueofresult.Clearselectedbits(marking)ClearallbutthelastfourbitsinEAXANDeax,0000000fhSetselectedbitsSetallbutthelastfourbitsinEAXOReax,fffffff0hnegateselectedbitsnegateallbutthelastfourbitsinEAXXOReax,fffffff0hXoreax,eax；AND指令可用于復(fù)位某些位（同0相與），不影響其他位：將BL中D3和D0位清0，其他位不變and

bl,11110110B；OR指令可用于置位某些位（同1相或），不影響其他位：將BL中D3和D0位置1，其他位不變or

bl,00001001B；XOR指令可用于求反某些位（同1相異或），不影響其他位：將BL中D3和D0位求反，其他不變xor

bl,00001001BPerformcertainarithmeticoperationmovedx,0movebx,32divebxmovedx,eaxandedx,0000001fhManipulateASCIIcodesConvertASCIIcodetointegerSubeax,00000030hAndeax,0000000fhConvertintegertoASCIIOrbl,30hChangethecaseofASCIIcodeXorcl,00100000bApplicationofTESTExamineaparticularbitis“1”or“0”Testdx,2023hGetinformationaboutavalueTestcx,cxThefollowinginstructionusuallyis“jcc”testal,01h

；測試AL旳最低位D0jnzthere ；標(biāo)志ZF=0，即D0=1 ；則程序轉(zhuǎn)移到there... ；不然ZF=1，即D0=0，順序執(zhí)行there:...

TEST指令一般用于檢測某些條件是否滿足，但又不希望變化原操作數(shù)旳情況TESTShiftandRotateShiftandrotateinstructionsmanipulatebinarynumbersatthebinarybitlevel,asdidtheAND,OR,Exclusive-OR,andNOTinstructions.Shiftsandrotatesfindtheirmostcommonapplicationsinlow-levelsoftwareusedtocontrolI/Odevices.Themicroprocessorcontainsacompletesetofshiftandrotateinstructionsthatareusedtoshiftorrotateanymemorydataorregister.ShiftinstructionsShiftinstructionspositionormovenumberstotheleftorrightwithinaregisterormemorylocation.LogicalshiftArithmeticshiftLogicalshifts

multiplyordivide

unsigneddata,andarithmeticshiftsmultiplyordividesigneddata.Ashiftleftmultipliesby2foreachbitpositionshiftedashiftrightdividesby2foreachbitpositionshiftedShiftinstructions

SHLdest,count SHRdest,count SALdest,count SARdest,count ;destisthetargetoperandbeingshiftedusingregisterormemoryaddressingmode ;countisthenumberoftimes(orbits)thattheoperandisshifted,itcanbespecifieddirectlyusinganimmediateshiftcount,orthroughtheCLregister.SHL/SALinstructionSHRinstructionSARinstructionflagsShiftinstructionswillchangeflags:CF:changebyshiftedbitOF:Multiple-bitshift:undefinedSingle-bitshift0:ifthesignbitoftheresultisthesameasthesignbitoftheoriginaloperandvalue.1:theyaredifferentZF,PF:assignedaccordingtoresultAF:undesignedExamplessalcx,1;beforecx=a9d7shrax,1;beforeax=a9d7sarbx,1;beforebx=a9d7salace,4;beforeace=a9d7shrdx,4;beforedx=a9d7sarax,cl;beforeax=a9d7,cl=04；將DX.AX中32位數(shù)值左移一位shlax,1rcldx,1DXAXCF0；把AL最低位送BL最低位，保持AL不變rorbl,1roral,1rclbl,1rolal,1AL、BLCFBLCFALCFAL之D0Figure8.7…leaebx,hexOut+7movecx,8forCount:movedx,eaxandedx,0000000fhcmpedx,9jnleelseLetteroredx,30h

jmpendifDigitelseLetter:addedx,‘A’-10EndifDigit:movBYTEPTR[ebx],dlDecebxshreax,4LoopforCount…Doubleshiftinstructionssh-ddest,src,count-:l(leftshift),r(rightshift)dest:wordordoublewordinaregisterormemorysrc:wordordoublewordinaregistercount:immediateorCLflagsCF:lastbitshiftedoutgoestoCFSF,ZF,PF:assignedcorrespondingtotheresultOF:undefinedExamples:shldecx,eax,12;beforeECX=12345678,EAX=90ABCDEFshrdecx,eax,CL;beforeECX=12345678,EAX=90ABCDEF,CL=08Figure8.7…

leaebx,hexOut

;leaebx,hexOut+7movecx,8forCount:shldedx,eax,4

;movedx,eaxandedx,0000000fhcmpedx,9jnleelseLetteroredx,30hjmpendifDigitelseLetter:addedx,‘A’-10EndifDigit:movBYTEPTR[ebx],dl

incebx

;decebx

shleax,4

;shreax,4loopforCount…Rotateinstructions

rotatedest,count ;rotateisRCL(rotateleftwithcarry),RCR(rotaterightwithcarry),ROL(rotateleft),andROR(rotateright) ;destisthetargetoperandbeingrotatedusingregisterormemoryaddressingmode ;countisthenumberoftimes(orbits)thattheoperandisrotated,itcanbespecifieddirectlyusinganimmediateshiftcount,orthroughtheCLregister.RotateoperationRotateinstructionspositionbinarydatabyrotatingtheinformationinaregisterormemorylocation,eitherfromoneendtoanotherorthroughthecarryflag.Rotateinstructionsareoftenusedtowidenumberstotheleftorright.ROLinstructionRORinstructionRCLinstructionRCRinstruction；將DX.AX中32位數(shù)值左移一位shlax,1rcldx,1DXAXCF0；把AL最低位送BL最低位，保持AL不變rorbl,1roral,1rclbl,1rolal,1AL、BLCFBLCFALCFAL之D0Figure8.7…

leaebx,hexOut+7

;leaebx,hexOutmovecx,8forCount:roleax,4

movedx,eaxandedx,0000000fhcmpedx,9jnleelseLetteroredx,30hjmpendifDigitelseLetter:addedx,‘A’-10EndifDigit:movBYTEPTR[ebx],dl

incebx

;decebx

;shreax,4loopforCount…ASCIItodoubleintegerconversionAtodprocedureatodprocPROCNEAR32pushebp;savebasepointermovebp,esp;establishstackframesubesp,4;localspaceforsignpushebx;Saveregisterspushecxpushedxpushf;saveflagsmovesi,[ebp+8];getparameter(sourceaddr)WhileBlankD:cmpBYTEPTR[esi],'';space?jneEndWhileBlankD;exitifnotincesi;incrementcharacterpointerjmpWhileBlankD;andtryagainEndWhileBlankD:moveax,1;defaultsignmultiplierIfPlusD:cmpBYTEPTR[esi],'+';leading+?jeSkipSignD;ifso,skipoverIfMinusD:cmpBYTEPTR[esi],'-';leading-?jneEndIfSignD;ifnot,savedefault+moveax,-1;-1forminussignSkipSignD:incesi;movepastsignEndIfSignD:mov[ebp-4],eax;savesignmultipliermoveax,0;numberbeingaccumulatedmovcx,0;countofdigitssofarWhileDigitD:cmpBYTEPTR[esi],'0';comparenextcharacterto'0'jlEndWhileDigitD;notadigitifsmallerthan'0'cmpBYTEPTR[esi],'9';compareto'9'jgEndWhileDigitD;notadigitifbiggerthan'9'imuleax,10;multiplyoldnumberby10jooverflowD;exitifproducttoolargemovbl,[esi];ASCIIcharactertoBLandebx,0000000Fh;converttosingle-digitintegeraddeax,ebx;addtosumjcoverflowD;exitifsumtoolargeinccx;incrementdigitcountincesi;incrementcharacterpointerjmpWhileDigitD;gotrynextcharacterEndWhileDigitD:cmpcx,0;nodigits?jzoverflowD;ifso,setoverflowerrorflag;ifvalueis80000000handsignis'-',;wanttoreturn80000000h(-2^32)cmpeax,80000000h;80000000h?jneTooBigD?cmpDWORDPTR[ebp-4],-1;multiplier-1?jeok1D;ifso,return8000hTooBigD?:testeax,eax;checksignflag