HP 3000 Manuals

Writing Programs That Are Easily Optimized [ HP Pascal/iX Programmer's Guide ] MPE/iX 5.0 Documentation


HP Pascal/iX Programmer's Guide

Writing Programs That Are Easily Optimized 

To maximize the opportunities for optimization and the speed with which
your program is optimized, observe the following guidelines whenever
possible:

   *   Specify all possible assumptions with the ASSUME compiler option.

   *   Do not use system programming extensions (specify ASSUME
       'PASCAL_FEATURES').

   *   Use local variables and parameters instead of global variables
       (this helps the optimizer promote variables to registers).

   *   Don't use CRUNCHED, PACKED, or shortint variables.

   *   Don't put pointer fields in variant parts of records.

   *   Use unique types as often as possible (this helps the optimizer
       determine which variables are possible actual parameters for the
       formal parameters of routines).

   *   Make routines relatively small--approximately 50 executable lines
       maximum (this allows the optimizer to use registers more
       efficiently).

   *   Expand in-line any routine of fewer than five lines and any
       relatively small routine that your program calls only once (see
       "INLINE" in Chapter 8 ).

   *   Do not write a loop that contains only a routine call; put the
       loop in the routine instead, or use the INLINE compiler option.

   *   Design loops that terminate when their control values are zero or
       nil.

   *   Use WITH statements.

   *   Do not use the FORWARD and EXTERNAL directives without the ASSUME
       compiler option.

   *   Do not use the GOTO statement.



MPE/iX 5.0 Documentation