Fast-float (FFloat) library for 56F83xx and CW

dynode — Wed, 01 Aug 2007 23:53:26 GMT

Hi,

Last fall we found that the built-in software floating point library in CodeWarrior was too slow for our robot project, and that we couldn't make controller code changes fast enough with fixed point - too many bugs.

So we wrote our own floating-point package in assembly, kind of like the Fast-Float for the AD Blackfin. It isn't IEEE compliant, it has a 16-bit mantissa (fraction) and 8-bit exponent. Not as much resolution, but much faster. It is written mostly in assembly for the 56F83xx, and uses instructions not recognized by the 56F80x, so probably not compatible without significant rework.

Below is a list of the functions so far, and processor cycle counts. (Cycle counts were done using the CW 7 software simulator, with IEEE single float and int for comparison.) Let me know if there is any interest. I don't know how it would be made available at this point, but if enough people want to use it I'll see what I can do. If you're from Freescale, is there any chance this could be integrated in some way with CodeWarrior? The main problem with it now is that all the operations have to be done as function calls, which gets cumbersome for complicated equations. And, constants have to be pre-converted and written in hex (although macros can help).

Function Name Cycle Count float cycle count int cycle count

FFadd 53 254 6

FFsub 64 264 6

FFmult 41 230 8

FFdiv 87 335 40

FFsin 1061

FFcos 1050

FFatan 808

FFgt 46 157 18

FFgte 46 141 12

FFgtz 22

FFlt 46 164 12

FFlte 46 148 12

FFltz 22

FFeqz 21

S16int2FFloat 22

FFloatRnd2S16int 29

FFloatTrunc2S16int 29

S32int2FFloat 25

U32int2FFloat 27

IEEE2FFloat 50

FFloat2IEEE

FFneg 35

FFabs 35

Re: Fast-float (FFloat) library for 56F83xx and CW

trytohelp — Thu, 02 Aug 2007 18:55:44 GMT

Hi,

Thanks for the feedback.

If you meet a problem with our library on the DSC because it was too slow, some other users will meet the same problem.

Can I suggest you to log this issue in the Technical Support via the web interface ?

See below for details.

For Technical Support Issues please use Freescale on line support web page.
- Go to following URL: http://www.freescale.com/TechSupport
- Click on Submit a Service Request. You will come to a login page.
- You can submit your request through the web from there.

See below for details.

It would be interresting for our compiler team to have your feedback.

With a Service Request, it will be more easy for you and us to investigate the problem.

Thanks.

Pascal

Classic/Legacy CodeWarriorのトピックRe: Fast-float (FFloat) library for 56F83xx and CW

Fast-float (FFloat) library for 56F83xx and CW

Re: Fast-float (FFloat) library for 56F83xx and CW