Programmer 7500/MAX_PROGRAMMERS.iso/INFO/C/NEWOPT88.ZIP/READ.ME

Text File | 1985-11-11 | 5.1 KB | 153 lines

        C88 Optimizer program instructions, notes, etc.

            (c) 1985, Harley H. Puthuff, Jr.

    The optimizer program (OPT88) is designed to process the
    assembler output of your C88 compiler.  This can be done
    either during the compilation process or as a separate
    stand-alone procedure.

    The optimizer program works with PC/MS-DOS versions 2.0
    or later and requires a minimum of RAM.  It will process
    approximately 65 assembly lines per second on a standard
    8088 PC.

    What the optimizer does is to scan the generated program
    for redundant instructions, unnecessary instructions, and
    instructions which can be changed to use less RAM or ex-
    ecute more efficiently.  For those familiar with 8086
    assembly language, some of the types of optimization
    performed are:

        - Elimination of redundant register loads where
          the value loaded already exists in the register

        - Replacement of 'MOV reg,xxx..x' with the
          instruction 'MOV reg,areg' where the xxx..x
          value exists in another (areg) register

        - Elimination of a 'CMP xxx..x,0' where it
          follows an arithmetic or logical instruction
          referencing the same datum

        - Replacement of a 'CMP reg,0' instruction with
          a 'OR reg,reg'

        - Replacement of a 'MOV reg,0' instruction with
          a 'XOR reg,reg'

        - Replacement of a 'ADD xxx..x,1' instruction
          with a 'INC xxx..x' instruction

        - Replacement of a 'SUB xxx..x,1' instruction
          with a 'DEC xxx..x' instruction

    The degree of optimization which can be performed for a
    particular application or program is, of course, dependent
    on the application and style of programming.  Typically,
    however, a code segment reduction of at least five percent
    is a reasonable expectation, along with an increase in the
    program's speed of execution.

    INSTALLATION:

    Simply copy the OPT88.EXE program to the disk directory
    (or diskette) where the C88 compiler and ASM88 assembler
    reside.

    STAND-ALONE OPERATION:

    The optimizer can be executed as a stand-alone process by
    entering the program command at the MS-DOS prompt.  Prior
    to execution, you should have generated the assembler
    input file by running the C88 compiler with the '-A'
    option.  Then type the following command:

    OPT88 filename [options]

    Where:

        filename    is an input file name which may
                include a drive and path as well
                as an extension.  The optimizer
                will supply the '.A' extension if
                missing, and replace any specified
                with '.A' if present.

        [options]    are one character program options
                which may or may not be preceeded
                by a minus [-] sign and are separ-
                ated by spaces.

    PROGRAM OPTIONS:

    The optimizer program supports the following options
    specifications using either upper or lower case:

    [-]S    Suppress all message output.  Normally the optim-
        izer produces a start message and a completion
        message which gives the number of lines processed
        and the approximate number of bytes saved in the
        output.

    [-]X    Diagnostic operation.  This results in more screen
        information about the optimizer run.  A period is
        displayed on the screen as each input statement is
        read, and additional statistics are displayed along
        with the ending message.

    [-]F    Create a separate output file.  Normally the optim-
        izer creates a new '.A' file and deletes the old
        one.  If you use the 'F' option, an output file
        with the same name as the input and an extension
        of '.OPT' is created and the input '.A' file is
        preserved.

    [-]N    Note the optimizer modifications.  This option
        results in the generation of assembly comments
        in the output file which indicate what changes
        were made.  These comments have no effect on
        your subsequent assembly.


    IN-LINE OPERATION:

    The optimizer may be incorporated into the compilation
    procedure by renaming a couple of programs.  Normally
    when the C88 compiler is executed (without the -A option)
    three separate programs are used:

        C88    -pre-compiler (#define & #include expan-
             sion).

        GEN    -generate assembly source code.

        ASM88    -assemble the final object code.

    In order to use the optimizer in-line, it needs to be run
    between the GEN and ASM88 programs.  This can be accomplished
    by selecting the directory where these programs (and OPT88)
    are present and entering the following commands:

        REN ASM88.EXE ASM88X.EXE
        REN OPT88.EXE ASM88.EXE

    The optimizer will then execute as part of the compilation
    and will not accept any options nor produce any messages.  In
    order to run the optimizer by itself, the command name is
    'ASM88' and in order to run the real assembler use 'ASM88X'.

    PROBLEMS, QUESTIONS, ETC.:

    The optimizer has been thoroughly tested against a variety of
    applications and should pose no problems.  If you do have a
    problem with it, first try your compilation and test the output
    without using the optimizer.  If the problem persists, it is
    probably a source program error.  If not, technical assist-
    ance is available from:

        Harley H. Puthuff, Jr.
        636 Santa Alicia Drive
        Rohnert Park, CA  94928
        [phone]