[Bug math/3976] libm rounding modes do not work correctly for many archs

["joseph at codesourcery dot com" <sourceware-bugzilla at sourceware dot org>]

------- Additional Comments From joseph at codesourcery dot com  2008-10-27 12:42 -------
Subject: Re:  libm rounding modes do not work correctly for
 many archs

On Mon, 27 Oct 2008, vincent+libc at vinc17 dot org wrote:

> So, this just means that an implementation doesn't need to return a result
> rounded to the correct direction (this is implementation-defined). Still it
> should return an approximate value whatever the rounding direction mode is, and
> not behave erratically.

Furthermore, some functions whose implementations only work in 
round-to-nearest mode do save the mode then set round-to-nearest using 
feholdexcept and fesetround (e.g. sysdeps/ieee754/dbl-64/e_exp2.c).  I 
think this is the best thing to do in such cases.  (Regarding the issue of 
rounding modes in signal handlers, I think the best thing is for ABI 
documents to make explicit that library functions may temporarily save and 
restore rounding modes; that's what is being done in the Power 
Architecture ABI document being worked on, to document what the de facto 
ABI is right now.)



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http://sourceware.org/bugzilla/show_bug.cgi?id=3976

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