Re: [Patch v2 1/4] Replace i2f() in r600_blit.c with an optimized version.

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