4. Macro Processors1 Chapter IV: Macro Processors Overview: r To study the design and implementation of macro processors. r A macro represents a commonly.

4. Macro Processors1

Chapter IV: Macro Processors

Overview: To study the design and implementation of macro

processors. A macro represents a commonly used group of

statements in the source programming language. The macro processor replaces each macro instruction

with the corresponding group of source language statements. (expanding)

4. Macro Processors2

Macro definition Invocation Expansion (with substitution of parameters)

Basic macro processor functions

4. Macro Processors3

Macro definition

Invocation Expansion (with substitution of parameters)

Basic macro processor functions

4. Macro Processors4

Macro definition Invocation

Expansion (with substitution of parameters)

Basic macro processor functions

4. Macro Processors5

4. Macro Processors6

Use of macros in a SIC/XE program

4. Macro Processors7

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

4. Macro Processors8

Program from above with macros expanded

4. Macro Processors9

Program from above with macros expanded (cont.)

4. Macro Processors10

Discussions…

Why does macro statement use JLT *-14? Allow label?

4. Macro Processors11

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: NAMTAB 、 DEFTAB 、 and ARGTAB.

4. Macro Processors12

Macro processor algorithm and data structures (cont.)

4. Macro Processors13

Macro processor algorithm and data structures

4. Macro Processors14

Macro processor algorithm and data structures (cont.)

4. Macro Processors15

Macro processor algorithm and data structures (cont.)

4. Macro Processors16

Machine-Independent Macro Processor Features---- Concatenation of Macro Parameters

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

The body of the macro definition might contain a statement like

LDA X&ID1

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

4. Macro Processors17

Machine-Independent Macro Processor Features---- Concatenation of Macro Parameters (cont.)

4. Macro Processors18

Machine-Independent Macro Processor Features---- Generation of unique labels

In general, the body of a macro instruction that contains 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 .

4. Macro Processors19

Machine-Independent Macro Processor Features---- Generation of unique labels (cont.)

4. Macro Processors20

Machine-Independent Macro Processor Features---- Generation of unique labels (cont.)

4. Macro Processors21

Machine-Independent Macro Processor Features---- Conditional Macro Expansion

For previous examples of macro instructions, these statements could be varied by the substitution of parameters, but the form of the statement, and the order in which they appeared, were unchanged.

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

4. Macro Processors22

Machine-Independent Macro Processor Features---- Conditional Macro Expansion (cont.)

4. Macro Processors23

Machine-Independent Macro Processor Features---- Conditional Macro Expansion (cont.)

Ps. &EORCK is a macro-time variable.

4. Macro Processors24

Machine-Independent Macro Processor Features---- Conditional Macro Expansion (cont.)

4. Macro Processors25

Machine-Independent Macro Processor Features---- Conditional Macro Expansion (cont.)

4. Macro Processors26

Machine-Independent Macro Processor Features---- Macro-time looping statements

4. Macro Processors27

Machine-Independent Macro Processor Features---- Macro-time looping statements (cont.)

4. Macro Processors28

Machine-Independent Macro Processor Features---- Keyword Macro Parameters

Positional parameter vs. Keyword parameter

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

GENER TYPE=DIRECT, CHANNEL=3.

4. Macro Processors29

Machine-Independent Macro Processor Features---- Keyword Macro Parameters (cont.)

4. Macro Processors30

Machine-Independent Macro Processor Features---- Keyword Macro Parameters (cont.)

4. Macro Processors31

Machine-Independent Macro Processor Features---- Keyword Macro Parameters (cont.)

4. Macro Processors32

Macro Processor Design Options---- Recursive Macro Expansion

The invocation of one macro, which is defined by another macro instruction.

Using a programming language that allows recursive calls to write the macro processor.

4. Macro Processors33