https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108665
Bug ID: 108665
Summary: Depenency checking: Run-time loop reversal instead of
creating a temporary
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: tkoenig at gcc dot gnu.org
Target Milestone: ---
In the Fortran front end, we could sometimes reverse loops at runtime if
dependency analysis shows that either a forward or a backward loop would have
no dependencies.
Example code:
module x
implicit none
contains
subroutine foo(a,i,j,n)
integer, intent(in) :: i, j, n
real, dimension(:), intent(inout) :: a
a(i:i+n-1) = a(j:j+n-1) + 10.
end subroutine foo
subroutine bar(a,i,j,n)
real, dimension(:), intent(inout) :: a
integer,intent(in) :: i, j, n
integer :: k
if (i <= j) then
do k=0, n-1, 1
a(i+k) = a(j+k) + 10.
end do
else
do k=n-1,0,-1
a(i+k) = a(j+k) + 10.
end do
end if
end subroutine bar
end module x
where we create a temporary in foo.
