From: Marek Polacek <polacek@redhat.com>
To: Jason Merrill <jason@redhat.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>
Subject: [PATCH v2] c++: mark TARGET_EXPRs for function arguments eliding [PR114707]
Date: Thu, 23 May 2024 20:32:39 -0400 [thread overview]
Message-ID: <Zk_gJ8cpHNfRHVba@redhat.com> (raw)
In-Reply-To: <4bff239a-0437-488d-a295-09e218d4cb8d@redhat.com>
On Thu, May 23, 2024 at 04:04:13PM -0400, Jason Merrill wrote:
> On 5/23/24 10:41, Marek Polacek wrote:
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> >
> > -- >8 --
> > Coming back to our discussion in
> > <https://gcc.gnu.org/pipermail/gcc-patches/2024-April/649426.html>:
> > TARGET_EXPRs that initialize a function argument are not marked
> > TARGET_EXPR_ELIDING_P even though gimplify_arg drops such TARGET_EXPRs
> > on the floor.
>
> But only if TREE_TYPE (TARGET_EXPR_INITIAL is non-void, I think we should
> check that here too to be parallel.
Ah yes, definitely.
> Perhaps most/all affected TARGET_EXPRs will have been handled earlier in the
> function under the TREE_ADDRESSABLE check, but I wouldn't rely on that
> without an assert.
So like this or you want an assert somewhere too? dg.exp passed.
-- >8 --
Coming back to our discussion in
<https://gcc.gnu.org/pipermail/gcc-patches/2024-April/649426.html>:
TARGET_EXPRs that initialize a function argument are not marked
TARGET_EXPR_ELIDING_P even though gimplify_arg drops such TARGET_EXPRs
on the floor. To work around it, I added a pset to
replace_placeholders_for_class_temp_r, but it would be best to just rely
on TARGET_EXPR_ELIDING_P.
PR c++/114707
gcc/cp/ChangeLog:
* call.cc (convert_for_arg_passing): Call set_target_expr_eliding.
* typeck2.cc (replace_placeholders_for_class_temp_r): Don't use pset.
(digest_nsdmi_init): Call cp_walk_tree_without_duplicates instead of
cp_walk_tree.
---
gcc/cp/call.cc | 6 ++++++
gcc/cp/typeck2.cc | 20 ++++----------------
2 files changed, 10 insertions(+), 16 deletions(-)
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index ed68eb3c568..35c024f2c7c 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -9437,6 +9437,12 @@ convert_for_arg_passing (tree type, tree val, tsubst_flags_t complain)
if (complain & tf_warning)
warn_for_address_of_packed_member (type, val);
+ /* gimplify_arg elides TARGET_EXPRs that initialize a function argument. */
+ if (TREE_CODE (val) == TARGET_EXPR)
+ if (tree init = TARGET_EXPR_INITIAL (val))
+ if (!VOID_TYPE_P (TREE_TYPE (init)))
+ set_target_expr_eliding (val);
+
return val;
}
diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
index 06bad4d3303..7782f38da43 100644
--- a/gcc/cp/typeck2.cc
+++ b/gcc/cp/typeck2.cc
@@ -1409,16 +1409,14 @@ digest_init_flags (tree type, tree init, int flags, tsubst_flags_t complain)
in the context of guaranteed copy elision). */
static tree
-replace_placeholders_for_class_temp_r (tree *tp, int *, void *data)
+replace_placeholders_for_class_temp_r (tree *tp, int *, void *)
{
tree t = *tp;
- auto pset = static_cast<hash_set<tree> *>(data);
/* We're looking for a TARGET_EXPR nested in the whole expression. */
if (TREE_CODE (t) == TARGET_EXPR
/* That serves as temporary materialization, not an initializer. */
- && !TARGET_EXPR_ELIDING_P (t)
- && !pset->add (t))
+ && !TARGET_EXPR_ELIDING_P (t))
{
tree init = TARGET_EXPR_INITIAL (t);
while (TREE_CODE (init) == COMPOUND_EXPR)
@@ -1433,16 +1431,6 @@ replace_placeholders_for_class_temp_r (tree *tp, int *, void *data)
gcc_checking_assert (!find_placeholders (init));
}
}
- /* TARGET_EXPRs initializing function arguments are not marked as eliding,
- even though gimplify_arg drops them on the floor. Don't go replacing
- placeholders in them. */
- else if (TREE_CODE (t) == CALL_EXPR || TREE_CODE (t) == AGGR_INIT_EXPR)
- for (int i = 0; i < call_expr_nargs (t); ++i)
- {
- tree arg = get_nth_callarg (t, i);
- if (TREE_CODE (arg) == TARGET_EXPR && !TARGET_EXPR_ELIDING_P (arg))
- pset->add (arg);
- }
return NULL_TREE;
}
@@ -1490,8 +1478,8 @@ digest_nsdmi_init (tree decl, tree init, tsubst_flags_t complain)
temporary materialization does not occur when initializing an object
from a prvalue of the same type, therefore we must not replace the
placeholder with a temporary object so that it can be elided. */
- hash_set<tree> pset;
- cp_walk_tree (&init, replace_placeholders_for_class_temp_r, &pset, nullptr);
+ cp_walk_tree_without_duplicates (&init, replace_placeholders_for_class_temp_r,
+ nullptr);
return init;
}
base-commit: ee492101c2e51b58e926307448d35f539aec0b2c
--
2.45.1
next prev parent reply other threads:[~2024-05-24 0:32 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-23 14:41 [PATCH] " Marek Polacek
2024-05-23 20:04 ` Jason Merrill
2024-05-24 0:32 ` Marek Polacek [this message]
2024-05-24 14:01 ` [PATCH v2] " Jason Merrill
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