https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97656
Bug ID: 97656
Summary: Specify that there is no address arithmetic on a
pointer
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: tkoenig at gcc dot gnu.org
Target Milestone: ---
This involves Fortran, but possibly also other languages.
Consider
$ cat alias.f90
program main
interface
subroutine foo(a)
integer, intent(inout) :: a
end subroutine foo
end interface
integer, dimension(2) :: x
x(1) = 42
x(2) = 42
call foo(x(1))
if (x(2) /= 42) stop "Error!"
end program main
This program specifies that foo has a scalar argument, passed by reference.
It is forbidden by Fortran's rules foo could access the element x(2),
therefore the call to stop could be optimized away, but it isn't:
$ gfortran -O3 -S alias.f90
$ grep _gfortran_stop alias.s
call _gfortran_stop_string
$
It would be good if there was a TREE_NO_POINTER_ARITHMETC (or simlar) flag
that could be set by the Fortran front end.
