From: Jiri Slaby <jirislaby@gmail.com>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Andi Kleen <andi@firstfloor.org>,
"Robert P. J. Day" <rpjday@crashcourse.ca>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Make shr to divide by power of 2 (resend)
Date: Mon, 17 Aug 2009 09:15:20 +0200 [thread overview]
Message-ID: <4A890388.8070709@gmail.com> (raw)
In-Reply-To: <20090816091425.GB7968@localdomain.by>
On 08/16/2009 11:14 AM, Sergey Senozhatsky wrote:
> There are different shr/shl operations in bitblit.c. Like,
> #1
> cur_height = vc->vc_font.height >> 1
> cur_height = (vc->vc_font.height << 1)/3;
> c |= c >> 1;
> u32 idx = vc->vc_font.width >> 3;
> etc.
>
> So, should I convert it to something like:
Not at all. I was writing about about (X + 7) / 8 [or >> 3] which is
DIV_ROUND_UP(X, 8).
> #2
> cur_height = DIV_XXX(vc->vc_font.height, 2)
> cur_height = DIV_XXX( MUL_XXX(vc->vc_font.height, 2), 3); or cur_height = DIV_XXX( (vc->vc_font.height * 2), 3);
> c |= DIV_XXX(c, 1);
> u32 idx = DIV_XXX(vc->vc_font.width, 8);
>
> #1 is better-looking I think.
Agreed. I would write it without shifts though. But we were talking
about the roundup case not about the shifts all over the code.
next prev parent reply other threads:[~2009-08-17 7:15 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-15 13:43 [PATCH] Make shr to divide by power of 2 (resend) Sergey Senozhatsky
2009-08-15 13:48 ` Jiri Slaby
2009-08-15 13:49 ` Robert P. J. Day
2009-08-15 14:12 ` Sergey Senozhatsky
2009-08-15 20:42 ` Jiri Slaby
2009-08-16 9:14 ` Sergey Senozhatsky
2009-08-17 7:15 ` Jiri Slaby [this message]
2009-08-17 7:31 ` Sergey Senozhatsky
2009-08-17 7:48 ` [PATCH 1/1] VIDEO: console, use DIV_ROUND_UP Jiri Slaby
2009-08-17 8:00 ` Sergey Senozhatsky
2009-08-17 8:00 ` Jiri Slaby
2009-08-17 8:08 ` Sergey Senozhatsky
2009-08-17 8:11 ` Jiri Slaby
2009-08-15 14:26 ` [PATCH] Make shr to divide by power of 2 (resend) Sergey Senozhatsky
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