This document discusses macro processors and macro expansion. It defines macro expansion as replacing a macro call with the sequence of assembly statements defined by the macro. It describes the tasks of identifying macro calls, formal parameters, maintaining expansion variables, and organizing control flow. It also discusses nested macro calls, recursive macros, and the design of macro assemblers as having three passes - definition processing, expansion, and target code generation.

1. MacroMacro
&&
Macro ProcessorsMacro Processors

2. INDEXINDEX
1.1. Macro expansionMacro expansion
2.2. Handling Nested Macro CallsHandling Nested Macro Calls
3.3. Design of Macro AssemblerDesign of Macro Assembler

3. Macro ExpansioNMacro ExpansioN

4. Macro ExpansioNMacro ExpansioN
Macro call leads to Macro Expansion.Macro call leads to Macro Expansion.
In Macro Expansion , Macro CallIn Macro Expansion , Macro Call
statement is replaced by astatement is replaced by a Sequence ofSequence of
Assembly statementsAssembly statements..
2 key notations used,,2 key notations used,,
Expansion time control flowExpansion time control flow
Lexical SubstitutionLexical Substitution

5. • AlgorithmAlgorithm::
– Initialize theInitialize the MEC (Macro Expansion counter)MEC (Macro Expansion counter)..
– Check the statement which is pointed by MEC isCheck the statement which is pointed by MEC is
notnot MENDMEND..
– If the statement is model statement.If the statement is model statement.
– Exit.Exit.
If( Statement = model Statement) thenIf( Statement = model Statement) then
Expand the statementExpand the statement
Increment MECIncrement MEC
ElseElse
MEC:=new value specified in statementMEC:=new value specified in statement
If( Statement = model Statement) thenIf( Statement = model Statement) then
Expand the statementExpand the statement
Increment MECIncrement MEC
ElseElse
MEC:=new value specified in statementMEC:=new value specified in statement
Macro ExpansioNMacro ExpansioN

6. • Tasks involvedTasks involved,,,,
– IdentifyIdentify Macro CallMacro Call
– Identify the Value OfIdentify the Value Of Formal ParameterFormal Parameter..
– MaintainMaintain Expansion time variablesExpansion time variables..
– OrganizeOrganize Expansion time control flowExpansion time control flow..
– Determining the values ofDetermining the values of sequencingsequencing
SymbolsSymbols..
– Expansion ofExpansion of model statementmodel statement..
Macro ExpansioNMacro ExpansioN

7. MACROMACRO
CLRMEMCLRMEM &P,&Q,&R1=AREG&P,&Q,&R1=AREG
LCCLCC &A&A
&A&A SETSET 00
MOVERMOVER &R1,=‘0’&R1,=‘0’
.MORE.MORE MOVEMMOVEM &R1,&P+&A&R1,&P+&A
&A&A SETSET &A+1&A+1
AIFAIF (&A NE Q).MORE(&A NE Q).MORE
MENDMEND
MACROMACRO
CLRMEMCLRMEM &P,&Q,&R1=AREG&P,&Q,&R1=AREG
LCCLCC &A&A
&A&A SETSET 00
MOVERMOVER &R1,=‘0’&R1,=‘0’
.MORE.MORE MOVEMMOVEM &R1,&P+&A&R1,&P+&A
&A&A SETSET &A+1&A+1
AIFAIF (&A NE Q).MORE(&A NE Q).MORE
MENDMEND
11 CLRMEMCLRMEM A,BA,BCLRMEMCLRMEM A,BA,B
22
33
44
55
66
Macro ExpansioNMacro ExpansioN

8. • Macro DefinitionMacro Definition  ParameterParameter
• Macro InvocationMacro Invocation  ArgumentArgument
• Body of Macro is Defined betweenBody of Macro is Defined between
MACROMACRO && MENDMEND directive statements.directive statements.
• After macro processing , the expandedAfter macro processing , the expanded
file can be used as I/P to thefile can be used as I/P to the
assembler.assembler.
Macro ExpansioNMacro ExpansioN

9. Lexical SubstitutioNLexical SubstitutioN
ConsistConsist 3 types3 types of string,,of string,,
11.Ordinary string..Ordinary string.
22.Name of Formal parameter preceded by.Name of Formal parameter preceded by
““&&”.”.
33.Name of Preprocessor Variables..Name of Preprocessor Variables.
Take stringTake string
as it is asas it is as
I/P.I/P.
Take stringTake string
as it is asas it is as
I/P.I/P.
TakeTake
ActualActual
parameterparameter
as I/P.as I/P.
TakeTake
ActualActual
parameterparameter
as I/P.as I/P.
TakeTake
ActualActual
parameterparameter
as I/P.as I/P.
TakeTake
ActualActual
parameterparameter
as I/P.as I/P.

10. Positional ParameterSPositional ParameterS
• Parameters & arguments associatedParameters & arguments associated
with each other according to theirwith each other according to their
PositioNPositioN in macro call & macroin macro call & macro
definition.definition.
• Syntax ,,Syntax ,,
• Ex,,Ex,, &&ROLLNOROLLNO
& < parameter name >& < parameter name >

11. MACROMACRO
INCRINCR &MEM_VAL,&INCR_VAL,&REG&MEM_VAL,&INCR_VAL,&REG
MOVERMOVER &REG,&MEM_VAL&REG,&MEM_VAL
ADDADD &REG,&INCR_VAL&REG,&INCR_VAL
MOVEMMOVEM &REG,&MEM_VAL&REG,&MEM_VAL
MENDMEND
MACROMACRO
INCRINCR &MEM_VAL,&INCR_VAL,&REG&MEM_VAL,&INCR_VAL,&REG
MOVERMOVER &REG,&MEM_VAL&REG,&MEM_VAL
ADDADD &REG,&INCR_VAL&REG,&INCR_VAL
MOVEMMOVEM &REG,&MEM_VAL&REG,&MEM_VAL
MENDMEND
INCR A,B,AREGINCR A,B,AREGINCR A,B,AREGINCR A,B,AREG
Formal ParameterFormal Parameter ValueValue
MEM_VALMEM_VAL AA
INCR_VALINCR_VAL BB
REGREG AREGAREG
Positional ParameterSPositional ParameterS

12. Keyword ParameterSKeyword ParameterS
• For keyword parameters,,For keyword parameters,,
<Parameter name><Parameter name> Ordinary stringOrdinary string
<Parameter kind><Parameter kind>  String “String “==””
<formal Parameter name><formal Parameter name>< Ordinary< Ordinary
string >string >
exex,,,, XYZ = ABCXYZ = ABC
SUMUPSUMUP X,Y,A=10,B=nX,Y,A=10,B=n Positional parameters:Positional parameters: X , YX , Y
Keyword parameters:Keyword parameters: A , BA , B
Positional parameters:Positional parameters: X , YX , Y
Keyword parameters:Keyword parameters: A , BA , B

13. Handling Nested MacroHandling Nested Macro
CallSCallS

14. Nested Macro CallSNested Macro CallS
• Nested macroNested macro  Macro may callMacro may call
another macro.another macro.
• Called macroCalled macro Inner macro.Inner macro.
MOVERMOVER BREG,TMPBREG,TMP
MOVERMOVER BREG,PBREG,P
ADDADD BREG,QBREG,Q
MOVEMMOVEM BREG,PBREG,P
MOVERMOVER BREG,TMPBREG,TMP
MOVERMOVER BREG,TMPBREG,TMP
MOVERMOVER BREG,PBREG,P
ADDADD BREG,QBREG,Q
MOVEMMOVEM BREG,PBREG,P
MOVERMOVER BREG,TMPBREG,TMP
MACROMACRO
COMPUTECOMPUTE &F,&S&F,&S
MOVERMOVER BREG,TMPBREG,TMP
INCR_DINCR_D &F,&S,REG=BREG&F,&S,REG=BREG
MOVERMOVER BREG,TMPBREG,TMP
MENDMEND
MACROMACRO
COMPUTECOMPUTE &F,&S&F,&S
MOVERMOVER BREG,TMPBREG,TMP
INCR_DINCR_D &F,&S,REG=BREG&F,&S,REG=BREG
MOVERMOVER BREG,TMPBREG,TMP
MENDMEND

15. Nested Macro CallSNested Macro CallS
MOVER BREG,TMPMOVER BREG,TMP
MOVERMOVER BREG,PBREG,P
COMPUTE P,QCOMPUTE P,Q INCR P,QINCR P,Q ADDADD BREG,QBREG,Q
MOVEMMOVEM BREG,PBREG,P
MOVERMOVER BREG,TMPBREG,TMP
MOVER BREG,TMPMOVER BREG,TMP
MOVERMOVER BREG,PBREG,P
COMPUTE P,QCOMPUTE P,Q INCR P,QINCR P,Q ADDADD BREG,QBREG,Q
MOVEMMOVEM BREG,PBREG,P
MOVERMOVER BREG,TMPBREG,TMP

16. Recursive MacroSRecursive MacroS
• Special caseSpecial case nested macros.nested macros.
• Recursive macroRecursive macro  MacroMacro expandsexpands
itself.itself.
• Not good but very useful.Not good but very useful.
• ProblemProblem: recursively expands so quickly: recursively expands so quickly
overflow theoverflow the MESMES..
• SolutionSolution: mechanism required to stop: mechanism required to stop
recursion.recursion. (conditional assembly(conditional assembly))

17. • Recursively generate INST1.Recursively generate INST1.
• No stop point.No stop point.
NOGOODNOGOOD MACROMACRO
INST1INST1
NOGOODNOGOOD
INST2INST2
ENDMENDM
Recursive MacroSRecursive MacroS

18. Design of Macro AssembleRDesign of Macro AssembleR

19. Design of Macro AssembleRDesign of Macro AssembleR
• 3 passes in macro Assembler.3 passes in macro Assembler.
Pass 1:Pass 1:
– Macro definition processing.Macro definition processing.
– SYMTAB construction.SYMTAB construction.
Pass 2Pass 2::
– Macro expansion.Macro expansion.
– Memory allocation & LC processing.Memory allocation & LC processing.
– Processing of Literals.Processing of Literals.
– Intermediate Code Generation.Intermediate Code Generation.

20. pass 3:pass 3:
– Target code Generation.Target code Generation.
– Macro processorMacro processor can be added as acan be added as a
processor to an assembler.processor to an assembler.
– It is implemented inIt is implemented in pass 1pass 1 of theof the
assembler.assembler.
Design of Macro AssembleRDesign of Macro AssembleR

21. Advantages:Advantages:
– Many functions don’t have to beMany functions don’t have to be
implemented twice.implemented twice.
– Less overheadLess overhead during processing. (byduring processing. (by
removing intermediate code)removing intermediate code)
– More flexibilityMore flexibility is available to theis available to the
programmer.programmer.
Design of Macro AssembleRDesign of Macro AssembleR

22. Disadvantages:Disadvantages:
• Combined pass 1 of the assembler &Combined pass 1 of the assembler &
macro processor may be toomacro processor may be too large for alarge for a
programprogram to fit into core of someto fit into core of some
machine.machine.
• ComplexityComplexity of such program may beof such program may be
overwhelming.overwhelming.
Design of Macro AssembleRDesign of Macro AssembleR

23. PASS 1PASS 1PASS 1PASS 1
RRRR
SearchSearch
pseudo-op Tablepseudo-op Table
SearchSearch
pseudo-op Tablepseudo-op Table
SearchSearch
Macro name TableMacro name Table
SearchSearch
Macro name TableMacro name Table
SearchSearch
machine-op Tablemachine-op Table
SearchSearch
machine-op Tablemachine-op Table
Go toGo to
PASS 2PASS 2
Go toGo to
PASS 2PASS 2Type?Type?Type?Type?
ProcessProcess
Macro definitionMacro definition
ProcessProcess
Macro definitionMacro definition
ProcessProcess
Pseudo-opsPseudo-ops
ProcessProcess
Pseudo-opsPseudo-ops
ProcessProcess
Machine instructionMachine instruction
ProcessProcess
Machine instructionMachine instruction
Setup macroSetup macro
stack frame ,etc.stack frame ,etc.
Setup macroSetup macro
stack frame ,etc.stack frame ,etc.
READREADREADREAD
RRRR
RRRR
RRRR
RRRR
Found, macroFound, macro
callscalls
FoundFound
NotNot
NotNot
EndEnd
pseudo-oppseudo-op
OthersOthers
MacroMacro
pseudo-oppseudo-op

24. @@
ThankThank
U!U!