[Bug fortran/32393] gfortran - incorrect run time results

["burnus at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #13 from burnus at gcc dot gnu dot org  2007-06-20 16:20 -------
> However, the problem that gfortran is having with the program is that it does 
> not take the full effect of the "equivalence (jt,tt)" into account. This is 
> where the real problem is and where I expected some disagreement.

I would not be surprised if some bug is lurking there, but my problem is that
if the program is invalid and produces different results with different
compilers, it is a bit difficult to pinpoint the problem.

What is actually the expected result? Depending on the compiler and compiler
setting, I get completely different results for the second triangular matrix.
(The first matrix remains always the same.)

NAG f95 -dusty refuses to compile the program.
gfortran with -O0 to -O3, sunf95 (default settings), g95 (-O0) and Intel's
ifort (-O1) give:
 row   1    0.1600E+02
 row   2    0.9000E+01  0.2000E+02
 row   3    0.1100E+02  0.1200E+02  0.2600E+02
ifort -O2 (= ifort w/ default settings) and gfortran -O3 -ffast-math give:
 row   1    0.0000E+00
 row   2    0.9000E+01  0.0000E+00
 row   3    0.1100E+02  0.1200E+02  0.0000E+00
g95 -O2 gives:
 row   1    0.8000E+01
 row   2    0.9000E+01  0.1000E+02
 row   3    0.1100E+02  0.1200E+02  0.1300E+02

Thus which compiler is right? Are all right? What exactly is the bug / expected
output? Is it fixed meanwhile as I get for -O3 w/o -ffast-math the same output
as for -O0?
Is it platform dependent? I use 4.3.0 20070620 (x86_64-unknown-linux-gnu) and
the unmodified version (or equivalently the version as modified by Dominique).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32393