From: Harald Anlauf <anlauf@gmx.de>
To: gcc-patches@gcc.gnu.org
Cc: fortran@gcc.gnu.org
Subject: Re: [PATCH] Fortran: fix passing array component to polymorphic argument [PR105658]
Date: Fri, 16 Feb 2024 22:19:48 +0100 [thread overview]
Message-ID: <cdf24a94-0edd-46c3-8ef6-c3289a992419@gmx.de> (raw)
Message-ID: <20240216211948.6W6R4J1_GAf10kPmzaPZ82HX0PqqwHCCOe8FbolG1Hk@z> (raw)
In-Reply-To: <CAFmps265e6DURKbU2+nMJBtSvb+-w-RHnFE_0ozqDWE0fzRFPQ@mail.gmail.com>
Hi Peter,
thanks for your contribution to gfortran! You've found indeed
a solution for a potentially annoying bug.
Am 15.02.24 um 18:50 schrieb Peter Hill:
> Dear all,
>
> The attached patch fixes PR105658 by forcing an array temporary to be
> created. This is required when passing an array component, but this
> didn't happen if the dummy argument was an unlimited polymorphic type.
>
> The problem bit of code is in `gfc_conv_expr_descriptor`, near L7828:
>
> subref_array_target = (is_subref_array (expr)
> && (se->direct_byref
> || expr->ts.type == BT_CHARACTER));
> need_tmp = (gfc_ref_needs_temporary_p (expr->ref)
> && !subref_array_target);
>
> where `need_tmp` is being evaluated to 0. The logic here isn't clear
> to me, and this function is used in several places, which is why I
> went with setting `parmse.force_tmp = 1` in `gfc_conv_procedure_call`
> and using the same conditional as the later branch for the
> non-polymorphic case (near the call to `gfc_conv_subref_array_arg`)
>
> If this patch is ok, please could someone commit it for me? This is my
> first patch for GCC, so apologies in advance if the commit message is
> missing something.
Your patch mostly does the right thing. Note that when fsym is
an unlimited polymorphic, some of its attributes are buried deep
within its internal representation. I would also prefer to move
the code to gfc_conv_intrinsic_to_class where it seems to fit better,
like:
diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index a0593b76f18..db906caa52e 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -1019,6 +1019,14 @@ gfc_conv_intrinsic_to_class (gfc_se *parmse,
gfc_expr *e,
tmp = gfc_typenode_for_spec (&class_ts);
var = gfc_create_var (tmp, "class");
+ /* Force a temporary for component or substring references. */
+ if (unlimited_poly
+ && class_ts.u.derived->components->attr.dimension
+ && !class_ts.u.derived->components->attr.class_pointer
+ && !class_ts.u.derived->components->attr.allocatable
+ && is_subref_array (e))
+ parmse->force_tmp = 1;
+
/* Set the vptr. */
ctree = gfc_class_vptr_get (var);
(I am not entirely sure whether we need to exclude pointer and
allocatable attributes here explicitly, given the constraints
in F2023:15.5.2.6, but other may have an opinion, too.
The above should be safe anyway.)
> Tested on x86_64-pc-linux-gnu.
>
> The bug is present in gfortran back to 4.9, so should it also be backported?
I think we'll target 14-mainline and might consider a backport to
13-branch.
> Cheers,
> Peter
>
> PR fortran/105658
>
> gcc/fortran/ChangeLog
>
> * trans-expr.cc (gfc_conv_procedure_call): When passing an
> array component reference of intrinsic type to a procedure
> with an unlimited polymorphic dummy argument, a temporary
> should be created.
>
> gcc/testsuite/ChangeLog
>
> * gfortran.dg/PR105658.f90: New test.
> ---
> gcc/fortran/trans-expr.cc | 8 ++++++++
> gcc/testsuite/gfortran.dg/PR105658.f90 | 25 +++++++++++++++++++++++++
> 2 files changed, 33 insertions(+)
> create mode 100644 gcc/testsuite/gfortran.dg/PR105658.f90
>
> diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
> index a0593b76f18..7fd3047c4e9 100644
> --- a/gcc/fortran/trans-expr.cc
> +++ b/gcc/fortran/trans-expr.cc
> @@ -6439,6 +6439,14 @@ gfc_conv_procedure_call (gfc_se * se, gfc_symbol * sym,
> CLASS object for the unlimited polymorphic formal. */
> gfc_find_vtab (&e->ts);
> gfc_init_se (&parmse, se);
> + /* The actual argument is a component reference to an array
> + of derived types, so we need to force creation of a
> + temporary */
> + if (e->expr_type == EXPR_VARIABLE
> + && is_subref_array (e)
> + && !(fsym && fsym->attr.pointer))
> + parmse.force_tmp = 1;
> +
> gfc_conv_intrinsic_to_class (&parmse, e, fsym->ts);
>
> }
> diff --git a/gcc/testsuite/gfortran.dg/PR105658.f90
> b/gcc/testsuite/gfortran.dg/PR105658.f90
> new file mode 100644
> index 00000000000..407ee25f77c
> --- /dev/null
> +++ b/gcc/testsuite/gfortran.dg/PR105658.f90
> @@ -0,0 +1,25 @@
> +! { dg-do compile }
> +! { dg-options "-Warray-temporaries" }
> +! Test fix for incorrectly passing array component to unlimited
> polymorphic procedure
> +
> +module test_PR105658_mod
> + implicit none
> + type :: foo
> + integer :: member1
> + integer :: member2
> + end type foo
> +contains
> + subroutine print_poly(array)
> + class(*), dimension(:), intent(in) :: array
> + select type(array)
> + type is (integer)
> + print*, array
> + end select
> + end subroutine print_poly
> +
> + subroutine do_print(thing)
> + type(foo), dimension(3), intent(in) :: thing
> + call print_poly(thing%member1) ! { dg-warning "array temporary" }
> + end subroutine do_print
> +
> +end module test_PR105658_mod
One could extend this testcase to cover substrings as well:
module test_PR105658_mod
implicit none
type :: foo
integer :: member1
integer :: member2
end type foo
contains
subroutine print_poly(array)
class(*), dimension(:), intent(in) :: array
select type(array)
type is (integer)
print*, array
type is (character(*))
print *, array
end select
end subroutine print_poly
subroutine do_print(thing)
type(foo), dimension(3), intent(in) :: thing
type(foo), parameter :: y(3) = [foo(1,2),foo(3,4),foo(5,6)]
integer :: i, j, uu(5,6)
call print_poly(thing%member1) ! { dg-warning "array temporary" }
call print_poly(y%member2) ! { dg-warning "array temporary" }
call print_poly(y(1::2)%member2) ! { dg-warning "array temporary" }
! The following array sections work without temporaries
uu = reshape([(((10*i+j),i=1,5),j=1,6)],[5,6])
print *, uu(2,2::2)
call print_poly (uu(2,2::2)) ! no temp needed!
print *, uu(1::2,6)
call print_poly (uu(1::2,6)) ! no temp needed!
end subroutine do_print
subroutine do_print2(thing2)
class(foo), dimension(:), intent(in) :: thing2
call print_poly (thing2% member2) ! { dg-warning "array temporary" }
end subroutine do_print2
subroutine do_print3 ()
character(3) :: c(3) = ["abc","def","ghi"]
call print_poly (c(1::2)) ! no temp needed!
call print_poly (c(1::2)(2:3)) ! { dg-warning "array temporary" }
end subroutine do_print3
end module test_PR105658_mod
If you like, you can repackage the patch and sign it
(see https://gcc.gnu.org/dco.html), and one of us will
then commit it for you.
Thanks!
Harald
next prev parent reply other threads:[~2024-02-16 21:19 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-15 17:50 Peter Hill
2024-02-16 21:19 ` Harald Anlauf [this message]
2024-02-16 21:19 ` Harald Anlauf
2024-02-19 15:19 ` Peter Hill
2024-02-19 19:52 ` Harald Anlauf
2024-02-19 19:52 ` Harald Anlauf
2024-02-20 19:53 ` Harald Anlauf
2024-02-20 19:53 ` Harald Anlauf
2024-02-20 20:09 ` Steve Kargl
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