https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115563
Bug ID: 115563
Summary: Unnecessary brackets prevent fortran vectorisation
Product: gcc
Version: 14.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: mjr19 at cam dot ac.uk
Target Milestone: ---
The code
subroutine foo(a,n)
complex (kind(1d0)) :: a(*)
integer :: i,n
!$OMP SIMD
do i=1,n
a(i)=(a(i)+(6d0,1d0))
enddo
end subroutine foo
compiled with
$ gfortran-14 -S -O3 -ffast-math -fopenmp-simd -mavx2 t3.f90
does not vectorise.
$ grep -c ymm t3.s
0
If the extra brackets are removed, so that the loop line reads
a(i)=a(i)+(6d0,1d0)
then it does.
$ grep -c ymm t3.s
3
It seems surprising that the code produced should differ depending on whether
the brackets are present, as I do not believe that they alter the meaning of
the code in any way. One can construct many similar examples, e.g. using a
complex variable in the place of the (6d0,1d0), or using a real constant, etc.
