[Bug fortran/103023] ICE (Segmentation fault) with !$OMP DECLARE SIMD(func) linear(ref(u))

["bartoldeman at users dot sourceforge.net" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103023

--- Comment #2 from bartoldeman at users dot sourceforge.net ---
Yes this is about the ICE mainly.

It was stripped down from this, which HAS uniform.

subroutine func(u,f,ndim)
  !$OMP DECLARE SIMD(func) uniform(ndim) linear(ref(f,u):1)
  integer, intent(in) :: ndim
  double precision, intent(in) :: u(ndim)
  double precision, intent(out) :: f(ndim)
  f(1) = u(1) + u(2)
  f(2) = u(1) - u(2)
end subroutine func

subroutine main(u,f)
  double precision, intent(in) :: u(8)
  double precision, intent(out) :: f(8)
!$OMP SIMD
  do i=1,8,2
     call func(u(i),f(i),2)
  enddo
end subroutine main

If I leave out ndim and hardcode "2" in func (:: u(2) and :: f(2)), or let the
auto-vectorizer and inliner do its work this produces good code (though it
would be better with u and f transposed, as basically the code transposes it to
two ymm registers in the asm output.

With general "ndim" that could still work, e.g. with ndim=3 and 3 equations for
u(1:3) -> f(1:3), you'd work with 3 vector registers.

Now you may wonder why "ndim" here, since we know it's "2": this comes from
feeding a user-defined function into a larger program (that processes e.g.
maps) where that same user needs to specify ndim as a parameter.

Intel (ifort) doesn't like this at all from what I can see:

openfun.f90(1): error #6080: Only scalar variables may be referenced in a
LINEAR or MONOTONIC clause.   [U]
subroutine func(u,f)
----------------^
openfun.f90(1): error #6080: Only scalar variables may be referenced in a
LINEAR or MONOTONIC clause.   [F]
subroutine func(u,f)
------------------^
compilation aborted for openfun.f90 (code 1)