From: "Michel Dänzer" <michel@daenzer.net>
To: Steven Fuerst <svfuerst@gmail.com>
Cc: dri-devel@lists.freedesktop.org
Subject: Re: [Patch v2 1/4] Replace i2f() in r600_blit.c with an optimized version.
Date: Tue, 14 Aug 2012 12:33:29 +0200 [thread overview]
Message-ID: <1344940409.17900.503.camel@thor.local> (raw)
In-Reply-To: <1344706222-3018-1-git-send-email-svfuerst@gmail.com>
On Sam, 2012-08-11 at 10:30 -0700, Steven Fuerst wrote:
> We use __fls() to find the most significant bit. Using that, the
> loop can be avoided. A second trick is to use the behaviour of the
> rotate instructions to expand the range of the unsigned int to float
> conversion to the full 32 bits in a branchless way.
>
> The routine is now exact up to 2^24. Above that, we truncate which
> is equivalent to rounding towards zero.
>
> Signed-off-by: Steven Fuerst <svfuerst@gmail.com>
It might be better to reorder the series to use a shared int2float first
and then optimize that. Either way though, although I haven't really
looked into the floating point encoding aspects, the series is
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
--
Earthling Michel Dänzer | http://www.amd.com
Libre software enthusiast | Debian, X and DRI developer
prev parent reply other threads:[~2012-08-14 10:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-11 17:30 [Patch v2 1/4] Replace i2f() in r600_blit.c with an optimized version Steven Fuerst
2012-08-11 17:30 ` [Patch v2 2/4] Replace i2f() in r600_blit_kms.c " Steven Fuerst
2012-08-11 17:30 ` [Patch v2 3/4] Rename i2f() to int2float(), and make it global so one copy can be removed Steven Fuerst
2012-08-11 17:30 ` [Patch v2 4/4] Annotate int2float() as being a pure function Steven Fuerst
2012-08-14 10:33 ` Michel Dänzer [this message]
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