[Bug target/16589] [3.5.0 regression] [m68k] segmentation fault on identical array accesses in the ?: operators' body

["wilson at specifixinc dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From wilson at specifixinc dot com  2004-09-02 03:39 -------
Subject: Re:  [3.5.0 regression] [m68k] segmentation fault
 on identical array accesses in the ?: operators' body

loki at inf dot u-szeged dot hu wrote:
> ------- Additional Comments From loki at inf dot u-szeged dot hu  2004-08-31 09:21 -------
> I have another testcase. Is it a similar problem?
> pr.i:6: internal compiler error: in output_348, at insn-output.c:3487

Yes, it is the same problem.

By the way, this problem goes away with my flag_trapping_math bug fix 
(it should be on by default but is not).  However, the underlying 
problem remains, and can still be triggered if you use the 
-fno-trapping-math option.

The underlying problem seems to be that we have two condition codes, one 
integer one and one FP one, and cc_status can only track one of them at 
a time.  If we clobber cc_status when CC_IN_68881 is set, then this 
problem will be fixed, but we won't be able to optimize away FP compares 
anymore, and hence there will be some performance loss.  However, the 
current code looks like it will handle negative-zero incorrectly, and 
probably also signalling NaNs, and maybe some other stuff too, so this 
may be a good idea anyways in order to fix some IEEE math correctness 
problems.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16589