On 5/21/26 10:20 AM, Patrick Palka wrote:
When looking at the compile-time performance regression PR c++/125334
(caused by the dependent ADL patch r16-6311) I spotted some issues with
add_dependent_adl_entities:
1. Fix memory leak in add_dependent_adl_entities when it exits early.
2. Only consider type-dependent calls/operator expressions.
3. Fix early exit test for when all args are type-dependent.
4. Add assert verifying recursive name lookup does not happen with
tentative/dependent ADL since it avoids type completion.
Plugging the memory leak reduces max memory usage by 3% when building
the std module, besides that no significant effect towards the
regression.
gcc/cp/ChangeLog:
* module.c (dep_adl_info::args): Initializer to nullptr
instead of immediately allocating.
(depset::hash::add_dependent_adl_entities): Exit early
for non-type-dependent calls and operator expressions.
Only allocate dep_adl_info::args if we're not exiting early.
Correct all-type-dependent args test.
* name-lookup.cc (name_lookup::preserve_state): Replace
propagation of tentative flag with assert that it's not
set.
---
gcc/cp/module.cc | 30 ++++++++++++++++++++++--------
gcc/cp/name-lookup.cc | 3 ++-
2 files changed, 24 insertions(+), 9 deletions(-)
diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 02e53ef39697..c1a223925a37 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -2645,7 +2645,7 @@ public:
/* If not ERROR_MARK, a rewrite candidate for this operator. */
tree_code rewrite = ERROR_MARK;
/* Argument list for the call. */
- vec<tree, va_gc>* args = make_tree_vector ();
+ vec<tree, va_gc>* args = nullptr;
};
vec<dep_adl_info> dep_adl_entity_list;
@@ -15258,10 +15258,12 @@ depset::hash::add_dependent_adl_entities (tree expr)
return;
dep_adl_info info;
+ auto_vec<tree, 3> args;
switch (TREE_CODE (expr))
{
case CALL_EXPR:
- if (!KOENIG_LOOKUP_P (expr))
+ if (!KOENIG_LOOKUP_P (expr)
+ || !type_dependent_expression_p_push (expr))
return;
info.name = CALL_EXPR_FN (expr);
if (!info.name)
@@ -15273,7 +15275,7 @@ depset::hash::add_dependent_adl_entities (tree expr)
if (!identifier_p (info.name))
info.name = OVL_NAME (info.name);
for (int ix = 0; ix < call_expr_nargs (expr); ix++)
- vec_safe_push (info.args, CALL_EXPR_ARG (expr, ix));
+ args.safe_push (CALL_EXPR_ARG (expr, ix));
Perhaps we could only actually add to args if the arg is non-dependent...
break;
case LE_EXPR:
@@ -15310,10 +15312,12 @@ depset::hash::add_dependent_adl_entities (tree expr)
case TRUTH_ANDIF_EXPR:
case TRUTH_ORIF_EXPR:
overloadable_expr:
+ if (!type_dependent_expression_p_push (expr))
+ return;
info.name = ovl_op_identifier (TREE_CODE (expr));
gcc_checking_assert (tree_operand_length (expr) == 2);
- vec_safe_push (info.args, TREE_OPERAND (expr, 0));
- vec_safe_push (info.args, TREE_OPERAND (expr, 1));
+ args.safe_push (TREE_OPERAND (expr, 0));
+ args.safe_push (TREE_OPERAND (expr, 1));
break;
default:
@@ -15322,11 +15326,21 @@ depset::hash::add_dependent_adl_entities (tree expr)
/* If all arguments are type-dependent we don't need to do
anything further, we won't find new entities. */
- processing_template_decl_sentinel ptds;
- ++processing_template_decl;
- if (!any_type_dependent_arguments_p (info.args))
+ bool all_type_dependent = true;
+ for (tree arg : args)
+ if (!type_dependent_expression_p_push (arg))
+ {
+ all_type_dependent = false;
+ break;
+ }
+ if (all_type_dependent)
return;
...so this just checks whether args is empty? OK either way.
+ gcc_checking_assert (!info.args);
+ info.args = make_tree_vector ();
+ for (tree arg : args)
+ vec_safe_push (info.args, arg);
+
/* We need to defer name lookup until after walking, otherwise
we get confused by stray TREE_VISITEDs. */
dep_adl_entity_list.safe_push (info);
diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
index ef8440883819..6760c0e1f880 100644
--- a/gcc/cp/name-lookup.cc
+++ b/gcc/cp/name-lookup.cc
@@ -580,7 +580,8 @@ name_lookup::preserve_state ()
}
}
- tentative = previous->tentative;
+ /* We deliberately avoid instantiation during tentative ADL. */
+ gcc_checking_assert (!previous->tentative);
/* Unmark the outer partial lookup. */
if (previous->deduping)
