Re: [PATCH] MIPS/glibc: soft-fp NaN representation corrections

["Joseph S. Myers" <joseph at codesourcery dot com>]

On Wed, 24 Apr 2013, Maciej W. Rozycki wrote:

>  These changes touch generic code, for the most part.  They are supposed 
> not to affect targets other than MIPS, however I think it would make sense 
> to test them at least on a selection of other targets glibc supports.  
> However I am not familiar enough with other targets to know how much 
> soft-fp is used across them; also I think automatic testing may have a 
> better value than manually poking at a function or three.  I will 
> therefore appreciate ideas as to how to test these changes, or any other 
> help with that indeed.

I have run powerpc-nofpu testing with this patch applied and not seen any 
NaN-related failures, and also confirmed that the generated libc/libm 
binaries are unchanged by the patch.

I would note that the test results would be better indicative of working 
NaN handling if Thomas's patch 
<http://sourceware.org/ml/libc-ports/2013-04/msg00008.html> to test sNaN 
inputs were checked in (minus the parts that as I noted were incorrect, 
and with appropriate conditionals, with comments referencing filed bugs, 
for cases that don't yet pass) - which it doesn't seem to be yet.

I believe this patch should fix at least one user-visible bug regarding 
sqrtl NaN handling (handling of input NaNs, and producing the correct sort 
of NaN as output for negative input) - and this should show up as an 
improvement on the test-ldouble results (although there will still be 
plenty of failures there arising from use of fp-bit in libgcc not 
supporting exceptions / rounding modes).  If that bug isn't already in 
Bugzilla, it should be filed there.  In any case, the appropriate [BZ #N] 
notation should be used in the ChangeLog entries (toplevel ChangeLog, and 
ports/ChangeLog.mips, not necessarily other ports/ChangeLog.<arch> files 
although it's harmless to include it there as well) to point to the bug, 
which should also be added to the list of fixed bugs in NEWS as part of 
the fixing commit.

The patch itself looks fine to me, but I think someone else should review 
it as well.

-- 
Joseph S. Myers
joseph@codesourcery.com