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

linux-os
2005-02-28T13:37:39Z

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,
Dick Johnson
Penguin : Linux version 2.6.10 on an i686 machine (5537.79 BogoMips).
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