[FFmpeg-devel] Input requested on floating point decomposition for AAC Main

Jason Garrett-Glaser darkshikari
Tue Nov 11 11:21:15 CET 2008

On Mon, Nov 10, 2008 at 10:39 PM, Alex Converse <alex.converse at gmail.com> wrote:
> To do 16-bit floating point rounding for AAC-Main, I need a function
> that will decompose a float into a normalized scheme and it's
> exponent. Conveniently there exists the x87 instruction FXTRACT for
> this very purpose.

Are you sure this is a good idea?  FXTRACT takes 170 clock cycles on
Core 2, according to Agner, making it the single slowest floating
point operation in x86 history, perhaps competing with FBSTP.

Dark Shikari

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