[patch][0/5] powerpc: Add support to fully comply with IEEE-754standard

[Zhu Ebony-r57400]

> -----Original Message-----
> From: Segher Boessenkool [mailto:segher at kernel.crashing.org] 
> Sent: 2007年1月12日 20:04
> To: Zhu Ebony-r57400
> Cc: Paul Mackerras; linuxppc-dev at ozlabs.org
> Subject: Re: [patch][0/5] powerpc: Add support to fully 
> comply with IEEE-754standard
> 
> > When floating-point underflow exceptions are disabled 
> (SPEFSCR[FUNFE] 
> > is cleared) and the result of a floating-point operation 
> underflows, a 
> > signed zero result is produced.
> 
> You probably want to make at least this one tweakable 
> per-process; on some important algorithms (some FFTs
> etc.) the results are perfectly acceptable with underflow- 
> to-zero and the performance difference is huge.  AltiVec can 
> do this per-process too, for example -- it has a user 
> register for setting this, you need some other interface though.
> 
> 
> Segher

Do you mean we can make a switch in order to let user choose
whether to enable exception handling or just use default value? If so,
a separate CONFIG_SPE_MATH_EMU in Kconfig is reasonable...

Ebony