Re: RFC: remove the "tile" architecture from glibc

[Joseph Myers <joseph@codesourcery.com>]

On Thu, 1 Feb 2018, Adhemerval Zanella wrote:

> However the math tests seems to shows a lot of corner cases issues which
> has been fixed in generic implementations. As I commented with Jason Duerstock,
> John Paul Adrian, and James Clarke in a private thread I think easier solution
> for 2.28 is we remove the arch-specific faulty ia64 math implementation and
> use the generic ones. If performance is an issue we reimplement and fixed
> them if it is the case.

(a) Note that various functions don't have a generic ldbl-96 
implementation, because all of x86_64, i386, ia64 and m68k have 
architecture-specific implementations.  So in those cases you can't simply 
remove the ia64 implementation because there isn't an alternative one.

(b) Where the issue is just errno setting, that code is often in C rather 
than ia64 assembly and so the existing implementation is probably easy to 
fix - indeed, there is a patch (from 2009) attached to bug 10163 to fix 
some such cases (including some where .S files are involved).  I've not 
checked whether that patch works, whether it applies to current sources, 
whether any of the issues there are already fixed or whether it's correct, 
but it's at least plausible for fixing some such bugs if it does indeed 
eliminate failures for the affected functions without introducing 
regressions.

(c) Of course, any fix, whether by removing an ia64-specific 
implementation or by fixing it, should have a bug filed in Bugzilla first 
stating what the actual bug is (we already have three such bugs).

(d) If you remove ia64-specific implementations you need to be careful not 
to introduce __*_finite symbols at old symbol versions (the ia64 
implementation doesn't have such symbols - it's probably not useful to add 
them piecemeal without having an ia64 bits/math-finite.h that would use 
them, but if added they should of course be at a new symbol version, not 
the version where they were originally added for other architectures).

-- 
Joseph S. Myers
joseph@codesourcery.com