Re: [patch 3/2] drivers/char/vt.c: remove unnecessary code

From: linux-os (linux-os_at_analogic.com)
Date: 02/28/05

  • Next message: Bartlomiej Zolnierkiewicz: "Re: [patch ide-dev 1/9] use struct ata_taskfile in ide_task_t" 
    Date:	Mon, 28 Feb 2005 08:33:24 -0500 (EST)
To: colbuse@ensisun.imag.fr

    On Mon, 28 Feb 2005 colbuse@ensisun.imag.fr wrote:

    > We could change an affectation into an incrementation by this patch, and,
    > so far I know, incrementing is quicker than or as quick as setting
    > a variable (depends on the architecture).
    >
    > Please _don't_ apply this, but tell me what you think about it.
    > Note that npar is unsigned.
    >
    > Signed-off-by: Emmanuel Colbus <emmanuel.colbus@ensimag.imag.fr>
    >

    Since it is common practice to write code as:
                    for(npar = 0 ; npar < NPAR ; npar++)
    ... it is quite likely that the compiler does a better job with
    that code than what you substitute. And, if you did a check
    of the code generation, it might be different between different
    compiler versions.

    This kind of "code optimization" won't optimize anything in
    the long-run.

    > --- old/drivers/char/vt.c 2004-12-24 22:35:25.000000000 +0100
    > +++ new/drivers/char/vt.c 2005-02-28 12:53:57.933256631 +0100
    > @@ -1655,9 +1655,9 @@
    > vc_state = ESnormal;
    > return;
    > case ESsquare:
    > - for(npar = 0 ; npar < NPAR ; npar++)
    > + for(npar = NPAR-1; npar < NPAR; npar--)
    > par[npar] = 0;
    > + npar++;
    > - npar = 0;
    > vc_state = ESgetpars;
    > if (c == '[') { /* Function key */
    > vc_state=ESfunckey;
    >
    >
    > --
    > Emmanuel Colbus
    > Club GNU/Linux
    > ENSIMAG - departement telecoms
    >

    Cheers,
    *** Johnson
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