On Tue, Oct 1, 2024 at 12:01 PM Eric Botcazou <botca...@adacore.com> wrote:
>
> Hi,
>
> the attached Ada testcase compiled with -O -flto exhibits a wrong code issue
> when the 3 optimizations NRV + RSO + inlining are applied to the same call: if
> the LHS of the call is marked write-only before inlining, then it will keep
> the mark after inlining although it may be read in GIMPLE from that point on.
>
> The proposed fix is to apply the removal of the store that would have been
> applied by execute_fixup_cfg if the call was not inlined:
>
> /* For calls we can simply remove LHS when it is known
> to be write-only. */
> if (is_gimple_call (stmt)
> && gimple_get_lhs (stmt))
> {
> tree lhs = get_base_address (gimple_get_lhs (stmt));
>
> if (VAR_P (lhs)
> && (TREE_STATIC (lhs) || DECL_EXTERNAL (lhs))
> && varpool_node::get (lhs)->writeonly)
> {
> gimple_call_set_lhs (stmt, NULL);
> update_stmt (stmt);
> todo |= TODO_update_ssa | TODO_cleanup_cfg;
> }
> }
>
> right before inlining, which will prevent the problematic references to the
> LHS from being generated during inlining.
>
> Tested on x86-64/Linux, OK for the mainline?
Nice solution - OK.
Thanks,
Richard.
>
> 2024-10-01 Eric Botcazou <ebotca...@adacore.com>
>
> * tree-inline.cc (expand_call_inline): Remove the store to the
> return slot if it is a global variable that is only written to.
>
>
> 2024-10-01 Eric Botcazou <ebotca...@adacore.com>
>
> * gnat.dg/lto28.adb: New test.
> * gnat.dg/lto28_pkg1.ads: New helper.
> * gnat.dg/lto28_pkg2.ads: Likewise.
> * gnat.dg/lto28_pkg2.adb: Likewise.
> * gnat.dg/lto28_pkg3.ads: Likewise.
>
> --
> Eric Botcazou
