[Bug rtl-optimization/49847] [4.7/4.8/4.9 Regression] NULL deref in fold_rtx (prev_insn_cc0 == NULL)

["rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49847

--- Comment #35 from rguenther at suse dot de <rguenther at suse dot de> ---
On Tue, 25 Feb 2014, law at redhat dot com wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49847
> 
> --- Comment #34 from Jeffrey A. Law <law at redhat dot com> ---
> OK.  Then I suggest two immediate things to do.
> 
> 1. Fix the documentation for cc0 targets to indicate that the setter/user no
> longer have to be consecutive, particularly in the presence of
> flag_trapping_math.

Sounds good.  I'd document that they still should be consecutive
instructions (if interpreting 'consecutive' as following a
fallthru path).  And say the cc0 setter may be the source of
EH edges.

> 2. Fault in fixes.  While a review of every bit of HAVE_cc0 code is warranted,
> I'm not terribly inclined as HAVE_cc0 targets simply aren't that important
> anymore.

I suppose fixing things as they arise is good enough.  But yes, HAVE_cc0
should be phased out - but I suppose it's unlikely to get existing ports
to convert ...