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[Bug tree-optimization/43716] [4.6/4.7/4.8 Regression] Revision 158105 miscompiles doduc.f90


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43716

--- Comment #47 from Uros Bizjak <ubizjak at gmail dot com> 2013-01-08 19:23:41 UTC ---
(In reply to comment #44)
> Can't reproduce on x86_64-linux with current trunk at -O3 -g -ffast-math, both
> with LRA and when LRA is disabled.  From what I understood, this bug used to be
> present on darwin, but went away two years ago, then it got reopened for
> x86_64-linux in July and apparently doesn't reproduce anymore either.  So, is
> this broken anywhere now?

Sorry for late answer, the NaN is still generated with current mainline, as can
be proved with:

"-g -O3 -ffast-math -ffpe-trap=invalid"

$ ./a.out
 MAIN : FIN S00002
 MAIN : FIN S00001
 MAIN : FIN S00011
 MAIN : FIN S00022

Program received signal SIGFPE: Floating-point exception - erroneous arithmetic
operation.

Backtrace for this error:
#0  0x7F9A9AF66FD7
#1  0x7F9A9AF675A4
#2  0x346B2359AF
#3  0x40AAA6 in s00017_ at doduc.f90:1852
#4  0x41B9E9 in MAIN__ at doduc.f90:186
Floating point exception

*However*, --ffast-math implies -fno-signaling-nans, and this contradicts with
-ffpe-trap=invalid.

Going a bit further:

"-g -O3 -ffast-math -fsignaling-nans -ffpe-trap=invalid"

works as expected, without FP exceptions.

So, as far as I'm concerned, "--fast-math -ffpe-trap=invalid" combination of
options (and the whole issue with NaNs on x86_64 as dubiously raised in comment
#34) is invalid.


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