80x86 Instruction Set Reference.docx

80x86 Instruction Set Reference.docx

《80x86 Instruction Set Reference.docx》由会员分享，可在线阅读，更多相关《80x86 Instruction Set Reference.docx（22页珍藏版）》请在冰豆网上搜索。

80x86InstructionSetReference

80x86InstructionSetReference

1.3.3.InstructionOperands

Wheninstructionsarerepresentedsymbolically,asubsetoftheIA-32assemblylanguageisused.Inthissubset,aninstructionhasthefollowingformat:

label:

mnemonicargument1,argument2,argument3

where:

•Alabelisanidentifierwhichisfollowedbyacolon.

•Amnemonicisareservednameforaclassofinstructionopcodeswhichhavethesamefunction.opcode:

operatingcode的缩写。

•Theoperandsargument1,argument2,andargument3areoptional.Theremaybefromzerotothreeoperands,dependingontheopcode.Whenpresent,theytaketheformofeitherliteralsoridentifiersfordataitems.Operandidentifiersareeitherreservednamesofregistersorareassumedtobeassignedtodataitemsdeclaredinanotherpartoftheprogram（whichmaynotbeshownintheexample）.Whentwooperandsarepresentinanarithmeticorlogicalinstruction,therightoperandisthesourceandtheleftoperandisthedestination.

Forexample:

LOADREG:

MOVEAX,SUBTOTAL

Inthisexample,LOADREGisalabel,MOVisthemnemonicidentifierofanopcode,EAXisthedestinationoperand,andSUBTOTAListhesourceoperand.Someassemblylanguagesputthesourceanddestinationinreverseorder.

1.3.4.HexadecimalandBinaryNumbers

Base16（hexadecimal）numbersarerepresentedbyastringofhexadecimaldigitsfollowedbythecharacterH（forexample,F82EH）.Ahexadecimaldigitisacharacterfromthefollowingset:

0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,andF.

Base2（binary）numbersarerepresentedbyastringof1sand0s,sometimesfollowedbythecharacterB（forexample,1010B）.The“B”designationisonlyusedinsituationswhereconfusionastothetypeofnumbermightarise.

1.3.5.SegmentedAddressing

Theprocessorusesbyteaddressing.Thismeansmemoryisorganizedandaccessedasasequenceofbytes.Whetheroneormorebytesarebeingaccessed,abyteaddressisusedtolocatethebyteorbytesinmemory.Therangeofmemorythatcanbeaddressediscalledanaddressspace.

Theprocessoralsosupportssegmentedaddressing.Thisisaformofaddressingwhereaprogrammayhavemanyindependentaddressspaces,calledsegments.Forexample,aprogramcankeepitscode（instructions）andstackinseparatesegments.Codeaddresseswouldalwaysrefertothecodespace,andstackaddresseswouldalwaysrefertothestackspace.Thefollowingnotationisusedtospecifyabyteaddresswithinasegment:

Segment-register:

Byte-address

Forexample,thefollowingsegmentaddressidentifiesthebyteataddressFF79HinthesegmentpointedbytheDSregister:

DS:

FF79H

Thefollowingsegmentaddressidentifiesaninstructionaddressinthecodesegment.TheCSregisterpointstothecodesegmentandtheEIPregistercontainstheaddressoftheinstruction.

CS:

EIP

InstructionFormat

2.1.GENERALINSTRUCTIONFORMAT

AllIA-32instructionencodingsaresubsetsoftheformatshowninFigure2-1.Instructionsconsistofoptionalinstructionprefixes（inanyorder）,primaryopcodebytesofuptothreeopcodebytes,anaddressing-formspecifier（ifrequired）consistingoftheModR/MbyteandsometimestheSIB（Scale-Index-Base）byte,adisplacement（ifrequired）,andanimmediatedatafield（ifrequired）.

2.3.OPCODES

Aprimaryopcodecanbe1,2,or3bytesinlength.Anadditional3-bitopcodefieldissometimesencodedintheModR/Mbyte.Smallerfieldscanbedefinedwithintheprimaryopcode.Suchfieldsdefinethedirectionofoperation,sizeofdisplacements,registerencoding,conditioncodes,orsignextension.Theencodingfieldsusedbyanopcodevarydependingontheclassofoperation.

Two-byteopcodeformatsforgeneral-purposeandSIMDinstructionsconsistof:

•Anescapeopcodebyte0FHastheprimaryopcodeandasecondopcodebyte

•Amandatoryprefix（66FH,F2H,F3H）,anescapeopcodebyte,andasecondopcodebyte

TheModR/Mbyteconsistsofthreebitfields（seeSection2.4.）.Inadditiontotheregfieldbeingtreatedasanextendedopcodefieldforsomeinstructions,somepatternsoftheothertwobitfieldsintheModR/Mbytemayalsobeusedtoexpressopcodeinformation.Usingundefinedexpressionoftheprimaryopcodebytes,and/orundefinedexpressionintheopcodeextensionfieldintheModR/Mbyte,and/orundefinedexpressioninotherbitfieldsoftheModR/Mbyteisreserved.ValidopcodeexpressionsaredefinedinAppendixAandAppendixB.Useofanyofreservedopcodeexpressioncancauseunpredictablebehavior.

2.4.MODR/MANDSIBBYTES

Manyinstructionsthatrefertoanoperandinmemoryhaveanaddressing-formspecifierbyte（calledtheModR/Mbyte）followingtheprimaryopcode.TheModR/Mbytecontainsthreefieldsofinformation:

•Themodfieldcombineswithther/mfieldtoform32possiblevalues:

eightregistersand24addressingmodes.

•Thereg/opcodefieldspecifieseitheraregisternumberorthreemorebitsofopcodeinformation.Thepurposeofthereg/opcodefieldisspecifiedintheprimaryopcode.

•Ther/mfieldcanspecifyaregisterasanoperandoritcanbecombinedwiththemodfieldtoencodeanaddressingmode.Sometimes,certaincombinationsofthemodfieldandther/mfieldisusedtoexpressopcodeinformationforsomeinstructions.

CertainencodingsoftheModR/Mbyterequireasecondaddressingbyte（theSIBbyte）.Thebase-plus-indexandscale-plus-indexformsof32-bitaddressingrequiretheSIBbyte.TheSIBbyteincludesthefollowingfields:

•Thescalefieldspecifiesthescalefactor.

•Theindexfieldspecifiestheregisternumberoftheindexregister.

•Thebasefieldspecifiestheregisternumberofthebaseregister.

SeeSection2.6.,“Addressing-ModeEncodingofModR/MandSIBBytes”fortheencodingsoftheModR/MandSIBbytes.

2.5.DISPLACEMENTANDIMMEDIATEBYTES

SomeaddressingformsincludeadisplacementimmediatelyfollowingtheModR/Mbyte（ortheSIBbyteifoneispresent）.Ifadisplacementisrequired,itcanrequire1,2,or4bytes.

Iftheinstructionspecifiesanimmediateoperand,theoperandalwaysfollowsanydisplacementbytes.Animmediateoperandcanbe1,2or4bytes.

NOTES:

1.ThedefaultsegmentregisterisSSfortheeffectiveaddressescontainingaBPindex,DSforothereffectiveaddresses.

2.Thedisp16nomenclaturedenotesa16-bitdisplacementthatfollowstheModR/Mbyteandthatisaddedtotheindex.

3.Thedisp8nomenclaturedenotesan8-bitdisplacementthatfollowstheModR/Mbyteandthatissignextendedandaddedtotheindex.

•SRC—Representsthesourceoperand.

•DEST—Representsthedestinationoperand.

3.1.4.FlagsAffected

The“FlagsAffected”sectionliststheflagsintheEFLAGSregisterthatareaffectedbytheinstruction.Whenaflagiscleared,itisequalto0;whenitisset,itisequalto1.Thearithmeticandlogicalinstructionsusuallyassignvaluestothestatusflagsinauniformmanner（seeAppendixA,EFLAGSCross-Reference,intheIA-32IntelArchitectureSoftwareDeveloper’sManual,Volume1）.Non-conventionalassignmentsaredescribedinthe“Operation”section.Thevaluesofflagslistedasundefinedmaybechangedbytheinstructioninanindeterminatemanner.Flagsthatarenotlistedareunchangedbytheinstruction.

ADC—AddwithCarry

Description

Addsthedestinationoperand（firstoperand）,thesourceoperand（secondoperand）,andthecarry（CF）flagandstorestheresultinthedestinationoperand.Thedestinationoperandcanbearegisteroramemorylocation;thesourceoperandcanbeanimmediate,aregister,oramemorylocation.（However,twomemoryoperandscannotbeusedinoneinstruction.）ThestateoftheCFflagrepresentsacarryfromapreviousaddition.Whenanimmediatevalueisusedasanoperand,itissign-extendedtothelengthofthedestinationoperandformat.

TheADCinstructiondoesnotdistinguishbetweensignedorunsignedoperands.Instead,theprocessorevaluatestheresultforbothdatatypesandsetstheOFandCFflagstoindicateacarryinthesignedorunsignedresult,respectively.TheSFflagindicatesthesignofthesignedresult.TheADCinstructionisusuallyexecutedaspartofamultibyteormultiwordadditioninwhichanADDinstructionisfollowedbyanADCinstruction.

ThisinstructioncanbeusedwithaLOCKprefixtoallowtheinstructiontobeexecutedatomically.

Operation

DEST←DEST+SRC+CF;

FlagsAffected

TheOF,SF,ZF,AF,CF,andPFflagsaresetaccordingtotheresult.

ADD—Add

ADDAL,imm8Addimm8toAL

ADDAX,imm16Addimm16toAX

ADDEAX,imm32Addimm32toEAX

ADDr/m8,imm8Addimm8tor/m8

ADDr/m16,imm16Addimm16tor/m16

ADDr/m32,imm32Addimm32tor/m32

ADDr/m16,imm8Addsign-extendedimm8tor/m16

ADDr/m32,imm8Addsign-extendedimm8tor/m32

ADDr/m8,r8Addr8tor/m8

ADDr/m16,r16Addr16tor/m16

ADDr/m32,r32Addr32tor/m32

ADDr8,r/m8Addr/m8tor8

ADDr16,r/m16Addr/m16tor16

ADDr32,r/m32Addr/m32tor32

Description

Addsthefirstoperand（destinationoperand）andthesecondoperand（sourceoperand）andstorestheresultinthedestinationoperand.Thedestinationoperandcanbearegisteroramemorylocation;thesourceoperandcanbeanimmediate,aregister,oramemorylocation.（However,twomemoryoperandscannotbeusedinoneinstruction.）Whenanimmediatevalueisusedasanoperand,itissign-extendedtothelengthofthedestinationoperandformat.

TheADDinstructionperformsintegeraddition.ItevaluatestheresultforbothsignedandunsignedintegeroperandsandsetstheOFandCFflagstoindicateacarry（overflow）inthesignedorunsignedresult,respectively.TheSFflagindicatesthesignofthesignedresult.

ThisinstructioncanbeusedwithaLO