4. macro processors1 chapter iv: macro processors overview: r to study the design and implementation...
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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)
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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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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: NAMTAB 、 DEFTAB 、 and ARGTAB.
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Macro processor algorithm and data structures (cont.)
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Macro processor algorithm and data structures
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Macro processor algorithm and data structures (cont.)
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Macro processor algorithm and data structures (cont.)
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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)
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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 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 .
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Machine-Independent Macro Processor Features---- Generation of unique labels (cont.)
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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, 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.
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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.)
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 parameter vs. 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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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 by another macro instruction.
Using a programming language that allows recursive calls to write the macro processor.
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