L.S.,
This code:
SUBROUTINE S(N)
INTEGER N
COMMON /COM/ A(100)
REAL A
REAL B(N), C(N), D(N)
DO I = 1, N
B(I) = D(I)
ENDDO
DO I = 1, N
A(I) = B(I)
ENDDO
CALL S1(C(1))
END
when compiled thusly:
$ gfortran -g -S -O3 -ftree-vectorize -ftree-vectorizer-verbose=2 -msse2 vect4.f
draws the following "not vectorized" message:
vecta.f:6: note: LOOP VECTORIZED.
vecta.f:9: note: not vectorized: can't determine dependence between
(*b_15)[D.928_29] and com.a[D.928_29]
vecta.f:9: note: vectorized 1 loops in function.
This cannot be right. According to the Fortran Standards that have been,
that are, and that will be, A (which resides in common) and B (which is
a local array) cannot have *any* storage in common. They're disjoint - they
won't unite no matter what.
So where does the compiler lose this valuable information ?
This is a hunt for the more advance vector-sorcerer. Note that removing
the (1) from the CALL in the last-but-one line makes the compiler
recall the ever important Fortran alias rules.
[ Sprinkle the above with :-) liberally ]
Kind regards,
--
Toon Moene - e-mail: [EMAIL PROTECTED] - phone: +31 346 214290
Saturnushof 14, 3738 XG Maartensdijk, The Netherlands
A maintainer of GNU Fortran 95: http://gcc.gnu.org/fortran/
