[Bug fortran/56937] Unnecessarily temporary with array-vector assignments

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56937

--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2013-04-12 20:56:36 UTC ---
Is the following code valid?

integer :: i, idx(4), r(4), p(4)
p = [1,2,3,4]
idx = [2,2,2,2]
r = 0
r(idx) = p
print *, sum(r)
r = 0
do i = 1, 4
  r(idx(i)) = p(i)
end do
print *, sum(r)
r = 0
do i = 4, 1, -1
  r(idx(i)) = p(i)
end do
print *, sum(r)

end

The output is

           4
           4
           1

i.e., the value of r(2) depends on the way the assignment is scalarized: my
rule of thumb for missing temporary and/or invalid code.