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4. Macro Processors1

Chapter IV: Macro Processors

Overview: To study the designand implementationof macro

processors.

A macrorepresents a commonly used group ofstatements in the source programming language.

The macro processor replaces each macro instruction

with the corresponding group of source language

statements. (expanding)

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Macro definition

Invocation

Expansion (with substitution of parameters)

Basic macro processor functions

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Macro definition

Invocation

Expansion (with substitution of parameters)

Basic macro processor functions

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4. Macro Processors4

Macro definition

Invocation

Expansion (with substitution of parameters)

Basic macro processor functions

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Use of macros in a SIC/XE program

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Use of macros in a SIC/XE program (cont.)

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Program from above with macros expanded

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Program from above with macros expanded(cont.)

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Discussions

Why does macro statement use JLT *-14?

Allow label?

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Macro processor algorithm and data structures

For one-pass macro processor, the definition of a

macro must appear in the source program before

any statements that invoke that macro.

Three important tables are used for the macro

processor: NAMTABDEFTABand

ARGTAB.

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Macro processor algorithm and data structures(cont.)

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Macro processor algorithmand data structures

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Macro processor algorithmand data structures (cont.)

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Macro processor algorithmand data structures (cont.)

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Machine-Independent Macro Processor Features

---- Concatenation of Macro Parameters

This feature enable a program to generate a seriesof variables named by XA1, XA2, XA3, , etc.and XB1, XB2, XB3, , etc. as well.

The body of the macro definition might contain astatement like

LDA X&ID1

It has some problems!!(solution: concatenation operator)

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Machine-Independent Macro Processor Features

---- Concatenation of Macro Parameters (cont.)

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Machine-Independent Macro Processor Features

---- Generation of unique labels

In general, the body of a macro instruction thatcontains labels is not possible.

It will cause duplicate definition.

Solution: use relative addressing (e.g., JEQ *03)

Drawback: For short jump, it is acceptable.For longer jump, it is not convenient, error-

prone, and difficult to read .

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Machine-Independent Macro Processor Features

---- Generation of unique labels (cont.)

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Machine-Independent Macro Processor Features

---- Conditional Macro Expansion

For previous examples of macro instructions, thesestatements could be varied by the substitution of

parameters, but the form of the statement, and theorder in which they appeared, were unchanged.

Conditional macro expansion adds greatly to thepower and flexibility of a macro language.

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Machine-Independent Macro Processor Features

---- Conditional Macro Expansion (cont.)

Ps. &EORCK is a macro-time variable.

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Machine-Independent Macro Processor Features

---- Conditional Macro Expansion (cont.)

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Machine-Independent Macro Processor Features

---- Conditional Macro Expansion (cont.)

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Machine-Independent Macro Processor Features

---- Macro-time looping statements

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Machine-Independent Macro Processor Features

---- Macro-time looping statements (cont.)

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Machine-Independent Macro Processor Features

---- Keyword Macro Parameters

Positional parametervs. Keyword parameter

GENER , , DIRECT, , , , , , 3.

GENER TYPE=DIRECT, CHANNEL=3.

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Machine-Independent Macro Processor Features

---- Keyword Macro Parameters (cont.)

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Machine-Independent Macro Processor Features

---- Keyword Macro Parameters (cont.)

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Macro Processor Design Options

---- Recursive Macro Expansion

The invocation of one macro, which is defined byanother macro instruction.

Using a programming language that allows recursivecallsto write the macro processor.

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