MACROS

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MACRO

Macro instructions are single-line abbreviations for group of instructions.

Macro is an abbreviation for a sequence of operations . Syntax/structure

start of definition MACROmacro name {Sequence to be abbreviated }End of definition MEND

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MACRO Example

::

A 1, DATAA 2, DATA

:A 1, DATAA 2, DATA

:DATA DC F’5’ 05/03/23jaya

3

MACRO Example(Macro definition)Syntax exampleMACRO MACROMACRO NAME INCRINSTRUCTION 1 A 1, DATAINSTRUCTION 2 A 2, DATA...MEND MEND

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MACRO Example(Macro call)Macro call(SYNTAX) macro call(example)MACRO MACROMACRO NAME INCRINSTRUCTION 1 A 1, DATAINSTRUCTION 2 A 2, DATA::MEND MEND:INSTRUCTION A 3, DATA:MACRO NAME INCR: DATA DC F’5

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MACRO Example(Macro definition)Syntax exampleMACRO MACROMACRO NAME INCRINSTRUCTION 1 A 1, DATAINSTRUCTION 2 A 2, DATA...

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CONDITIONAL MACRO EXPANSION

Two pseudo-ops are used

AIF:- It is conditional branch pseudo-op that performs an arithmetic test and branches to specified macro-label only if test is true.

AGO:- It is unconditional branch pseudo-op. It is equivalent to go-to statement.

.FINI:- Labels starting with a period(.), such as .FINI, are macro label do not appear in the output of the macro processor.

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MACRO

: macro definition :LOOP1 A 1,DATA1 MACRO

A 2,DATA2 ARG0 VARY &COUNT,&ARG1,&ARG2,&ARG3A 3,DATA3 &ARG0 A 1,&ARG1: AIF (&COUNT EQ 1).FINI

LOOP2 A 1,DATA3 A 2,&ARG2A 2,DATA2 AIF (&COUNT EQ 2).FINI: A 3,&ARG3

LOOP3 A 1,DATA1 .FINI MEND: macro call :

DATA1 DC F’5’ LOOP1 VARY 3,DATA1,DATA2,DATA3DATA2 DC F’10’ :DATA3 DC F’15’ LOOP2 VARY 2,DATA3,DATA2

: :LOOP3 VARY 1,DATA1:DATA1 DC F’5’DATA2 DC F’10’DATA3 DC F’15’

Pgm with macro definition (macro call)

example

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MACRO

: :

MACRO MACRO&ARG0 VARY &COUNT,&ARG1,&ARG2,&ARG3 &ARGO VARY &COUNT,&ARG1,&ARG2,&ARG3&ARG0 A 1,&ARG1 &ARG0 A 1,&ARG1

AIF (&COUNT EQ 1).FINI AIF (&COUNT EQ 1).FINIA 2,&ARG2 A 2,&ARG2AIF (&COUNT EQ 2).FINI AIF (&COUNT EQ 2).FINIA 3,&ARG3 A 3.&ARG3

.FINI MEND .FINI MEND 3,&ARG3: :

LOOP1 VARY 3,DATA1,DATA2,DATA3 LOOP1 A 1,DATA1: A 2,DATA2

LOOP2 VARY 2,DATA3,DATA2 A 3,DATA3: :

LOOP3 VARY 1,DATA1 LOOP2 A 1,DATA3: A 2,DATA2

DATA1 DC F’5’ :DATA2 DC F’10’ LOOP3 A 1,DATA1DATA3 DC F’15’ :

Macro callMacro expansion

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MACRO CALLS WITHIN MACROS:L 1,DATA1A 1,=F’1’ST 1,DATA1L 1,DATA2A 1,=F’1’ST 1,DATA2L 1,DATA3A 1,=F’1’ST 1,DATA3::

DATA1 DC F’5’DATA2 DC F’10’DATA3 DC F’15’

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MACRO CALLS WITHIN MACROSMACROADD1 &ARGL 1,&ARGA 1,=F’1’ST 1,&ARGMEND

MACROADDS &ARG1,&ARG2,&ARG3ADD1 &ARG1ADD1 &ARG2ADD1 &ARG3MEND

Macro call

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MACRO EXPANSIONSOURCE

: MACRO

ADD1 &ARGL 1,&ARGA 1,=F’1’ST 1,&ARGMENDMACROADDS &ARG1,&ARG2,

&ARG3ADD1 &ARG1 : :ADD1 &ARG2ADD1 &ARG3 L 1,DATA1

: ADD1 DATA1 A 1,=F’1’

: ST 1,DATA1: L 1,DATA2: ADD1 DATA2 A

1,=F’1’ADDS DATA1,DATA2, ST

1,DATA2DATA3 ADD1 DATA3 L

1,DATA3 A 1,=F’1’

: ST 1,DATA3::: :: :

DATA1 DC F’5’ DATA1 DC F’5’DATA2 DC F’10’ DATA2 DC F’10’

DATA3 DC F’15’ DATA3 DC F’15’

Expanded source of ADDS

Expanded source of ADD1

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MACRO DEFINITION WITHIN MACRO DEFINITION

MACRODEFINE &SUB

MACRO&SUB &YCNOP 0,4BAL 1,*+8DC A(&Y)L 15,=V(&SUB)BALR 14,15MEND

MEND

Definition of macro &sub

DEFINITION OF

MaCRO dEFINe

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MACRO DEFINITION WITHIN MACRO DEFINITION

Inner macro will not be defined until outer macro is called. Macro call sequence

DEFINE COS The statement expands into a new macro definition

COS AR The macro processor will generate the calling sequence:

BAL 1,*+8DC A(AR)L 15,=V(COS)BALR 14,15

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IMPLEMENTATION

STATEMENT OF PROBLEM

SPECIFICATION OF DATA BASES

SPECIFICATION OF DATA BASE FORMAT

ALGORITHM05/03/23jaya15

STATEMENT OF PROBLEM

Macro processor is a system program which accepts an assembly language program with macro definition and macro calls and produce an equivalent assembly language program in which all macro calls are expanded.

Four basic tasks of macro instruction processor Recognize macro definitions Save the definition Recognize calls Expand calls and substitute arguments

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STATEMENT OF PROBLEM

Macro processor performs expansion using 2 passes

Pass I It examines every operation code Save all macro definitions in a macro definition

table and macro name table Save a copy of the input text , minus macro

definition Pass II

Identify macro calls Replace each macro name with the appropriate

text from macro definition(expand macro call)

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SPECIFICATION OF DATA BASE

PASS I The input macro source deck Output macro source deck copy for use by pass2 Macro Definition Table(MDT) Macro Name Table(MNT) Macro Definition Table Counter(MDNTC) Macro Name Table Counter(MNTC) Argument List Array(ALA)

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SPECIFICATION OF DATA BASE

PASS II The copy input macro source deck Output expanded source deck copy for use by

assembler Macro Definition Table(MDT) created by pass1 Macro Name Table(MNT) created by pass1 Macro Definition Table Pointer(MDNTP) Argument List Array(ALA)

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PASS 1- PROCESSING MACRO DEFINITIONS

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EXAMPLE

MACRO

&LAB INCR &ARG1,&ARG2,&ARG3

&LAB A 1,&ARG1

A 2,&ARG2

A 3,&ARG3

MEND

|

|

INCR

Index Contents(80 bytes per entry)

5 &LAB INCR &ARG1,&ARG2,&ARG3

6 #0 A 2,#1

7 A 3,#2

8 A 2,#3

9 MEND

10

INDEX NAME(8 bytes)

0 #0(&LAB)

1 #1(&ARG1)

2 #2(&ARG2)

3 #3(&ARG3)

INDEX NAME( 8 bytes

MDT POSITION( 4 bytes)

1 INCR 5

2

3

Macro Definition TableArgument List Array

Macro Name Table

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PASS 2 – PROCESSING MACRO CALLS AND EXPANSION

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EXAMPLE

MACRO

&LAB INCR &ARG1,&ARG2,&ARG3

&LAB A 1,&ARG1

A 2,&ARG2

A 3,&ARG3

MEND

|

|

LOOP1 INCR DATA1,DATA2,DATA3

Index Contents ( 80 bytes per entry)

5 &LAB INCR &ARG1,&ARG2,&ARG3

6 #0 A 2,#1

7 A 3,#2

8 A 2,#3

9 MEND

10

INDEX NAME ( 8 bytes)

0 “LOOP1bbb”

1 “DATA1bbb”

2 “DATA2bbb”

3 “DATA3bbb”

INDEX NAME ( 8 bytes)

MDT POSITION ( 4 byte)

1 “INCRbbb” 5

2

3

Macro Definition TableArgument List Array

Macro Name Table

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MACRO&LAB INCR &ARG1,&ARG2,&ARG3&LAB A 1,&ARG1

A 2,&ARG2A 3,&ARG3MEND||

LOOP1 INCR DATA1,DATA2,DATA3

LOOP1 A 1,DATA1

A 2, DATA2A 3,DATA3

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IMPLEMENTATION OF MACRO CALL WITHIN MACRO

Basic problem in implementing macro calls within macros is “recursion”

Need to expand both macro Each call might be expanded by another macro More macros vs single macro

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Example with 2 macros ADDS and ADD1MACROADD1 &ARGL 1,&ARGA 1,=F’1’ST 1,&ARGMENDMACROADDS &ARG1,&ARG2,&ARG3ADD1 &ARG1ADD2 &ARG2ADD3 &ARG3MEND

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MDT(Macro Definition Table)

Index Contents

1 ADD1 &ARG

2 L 1,#1

3 A 1,=F’1’

4 ST 1,#1

5 MEND

6 ADDS &ARG1,&ARG2,&ARG3

7 ADD1 #1

8 ADD2 #2

9 ADD3 #3

10 MEND05/03/23jaya27

IMPLEMENTATION WITHIN AN ASSEMBLER

Macro processor can be added as a pre-processor to an assembler

Combining similar functions Ex- MNT+MOT/POT

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MACRO PROCESSOR COMBINED WITH ASSEMBLER PASS 1

PASS 1!

Search Pseudo-Op Table (POT)!

Search Macro Name Table (MNT)!!

GO TO PASS2!

Search Machine -Op Table (MOT)!

Process machine instruction

Type?

Process macro definition

Set up macro stack frame , etc.

Process pseudo-ops

READ *R

RR

R R

END pseudo-op

Found others

Not macro call

Not pseudo op

Found macro call

Macro pseudo op

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ADVANTAGES & DISADVANTAGES OF INCORPORATING MACRO INTO PASS1

Advantages functions do not have to implemented twice Less overhead during processing More flexible for programmer

Disadvantages Large program More complex

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SINGLE PASS ALGORITHM Problem of macro definition with macros Combine pass1 and pass2 Two additional variables MDI(Macro Definition Input) indicator MDLC(Macro Definition Level Counter)

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One-pass macro processor

MDTC 1MNTC 1

MDI “OFF”MDLC 0

Search MNT for match with operation code

MDTP MDT index from MNT entry

READ

Macro name found

MDI “ON”

Set up macro call argument list array

Macro

pseudo-op ?

READ*

Enter macro name & current value of MDTC in MNT entry number MNTC

MNTC MNTC+1

Prepare macro definition argument list array

Enter macro name card into MDT

MDTC MDTC+1

MDLC MDLC+1

READ*

MDTC MDTC+1

Substitute index notation for argument in definition

Enter line into MDT

Macro pseudo-

op ?

MEND pseudo-

op ?

MDLC MDLC+1

MDLC MDLC-1

MDLC 0 ?

MNTC MNTC+1

END Pseudo-

op?

Supply expanded source file to processing

a

a

a

no

Yes macro call

no

no

yes

yes

noyes

no

yes

no

Yes macro definition

READ *subroutine

MDI = “OFF”

?

Read next source card from input file

Return to main processing

Increment MDT pointer to next entry MDTP

MDTP + 1

MDI “OFF”

Get next card from MDT

Substitute arguments from macro call

Process AIF or AGO set new value to MDTP

MDLC = 0 ?

MEND pseudo-

op ?

AIF or

AGO ?

yes

yes

yes

yes

No within macro call

no

no

no

Detail of read function used for macro expansion

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One-pass macro processor

MDTC 1MNTC 1

MDI “OFF”MDLC 0

Search MNT for match with operation code

SP SP+N+2

READ

Macro name found

S(SP+N+2) SP

Set up macro call argument list array in S(SP+2)---- S(SP+N+1) where N = total

number of arguments

Macro

pseudo-op ?

READ*

Enter macro name & current value of MDTC in MNT entry number MNTC

Prepare macro definition argument list array

Enter macro name card into MDT

MDLC MDLC+1

READ*

Substitute index notation for argument in definition

Enter line into MDT

Macro pseudo-

op ?

MEND pseudo-op ?

MDLC MDLC+1

MDLC MDLC-1

MDLC 0 ?

MNTC MNTC+1

END Pseudo-

op?

Supply expanded source file to processing

a

a

a

no

Yes macro call

no

no

yes

yes

noyes

no

yes

no

Yes macro definition

S(SP+1) MDT index from MNT entry

b

b

b

One pass macro processor capable of handling macro calls within macro definitions

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READ *subroutine

SP = -1

Read next source card from input file

Return to main processing

Increment MDT pointer to next entry S(SP+1)+1

Get next card from MDT ; pointer is S(SP+1)

Substitute arguments from macro call S(SP+2)…S(SP+N+1)

N SP – S(SP)-2

AIF or AGO ? MEND

pseudo-op ?

MDLC = 0 ?

yes

yes

yes

No within macro call

no

no

yes

Process AIF or AGO set new value to MDTP

SP S(SP)

yes

no

b

b

Detail of read function for recursive macro expansion

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