This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
RE: Gcc builtin review: isinf, insnan ...
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Wilco Dijkstra <wdijkstr at arm dot com>
- Cc: 'Ondřej Bílka' <neleai at seznam dot cz>, <libc-alpha at sourceware dot org>, <pinskia at gmail dot com>
- Date: Fri, 29 May 2015 11:46:50 +0000
- Subject: RE: Gcc builtin review: isinf, insnan ...
- Authentication-results: sourceware.org; auth=none
- References: <A610E03AD50BFC4D95529A36D37FA55E769AD3FAC3 at GEORGE dot Emea dot Arm dot com> <000e01d0988d$686514d0$392f3e70$ at com> <alpine dot DEB dot 2 dot 10 dot 1505281736460 dot 16930 at digraph dot polyomino dot org dot uk> <001001d09a04$46a68810$d3f39830$ at com>
On Fri, 29 May 2015, Wilco Dijkstra wrote:
> > It's certainly the case that substantial GCC work is needed to make
> > floating-point properly follow even C99/C11 Annex F regarding exceptions /
> > rounding modes, let alone make signaling NaNs follow TS 18661-1, though
> > the signaling NaNs fixes would probably be more straightforward (reviewing
> > lots of code and making local changes, rather than any tricky design
> > issues involved for other floating-point areas). While I think such
> > support would be desirable, it also seems there's limited demand for it.
>
> IMHO support for different rounding modes, trapping exceptions and signalling
> NaNs are not required by many (most ARM CPUs don't even support FP traps...),
-ftrapping-math (default) is nothing to do with traps in the sense of
SIGFPE or change of flow of control, only about the raising of exception
flags that can be tested with <fenv.h> interfaces. Annex F and TS 18661
also have nothing to with the traps (part 5 deals with alternate exception
handling, but I doubt processor-level traps will be particularly useful in
implementing it). -frounding-math and -fsignaling-nans are not enabled by
default.
--
Joseph S. Myers
joseph@codesourcery.com