https://gcc.gnu.org/g:6ad7ca1bb905736c0f57688e93e9e77cbc71a325
commit r15-521-g6ad7ca1bb905736c0f57688e93e9e77cbc71a325
Author: Jakub Jelinek <ja...@redhat.com>
Date: Wed May 15 18:50:11 2024 +0200
c++: Optimize in maybe_clone_body aliases even when not at_eof [PR113208]
This patch reworks the cdtor alias optimization, such that we can create
aliases even when maybe_clone_body is called not at at_eof time, without
trying
to repeat it in maybe_optimize_cdtor.
2024-05-15 Jakub Jelinek <ja...@redhat.com>
Jason Merrill <ja...@redhat.com>
PR lto/113208
* cp-tree.h (maybe_optimize_cdtor): Remove.
* decl2.cc (tentative_decl_linkage): Call maybe_make_one_only
for implicit instantiations of maybe in charge ctors/dtors
declared inline.
(import_export_decl): Don't call maybe_optimize_cdtor.
(c_parse_final_cleanups): Formatting fixes.
* optimize.cc (can_alias_cdtor): Adjust condition, for
HAVE_COMDAT_GROUP && DECL_ONE_ONLY && DECL_WEAK return true even
if not DECL_INTERFACE_KNOWN.
(maybe_clone_body): Don't clear DECL_SAVED_TREE, instead set it
to void_node.
(maybe_clone_body): Remove.
* decl.cc (cxx_comdat_group): For DECL_CLONED_FUNCTION_P
functions if SUPPORTS_ONE_ONLY return DECL_COMDAT_GROUP if already
set.
* g++.dg/abi/comdat3.C: New test.
* g++.dg/abi/comdat4.C: New test.
Diff:
---
gcc/cp/cp-tree.h | 1 -
gcc/cp/decl.cc | 7 +++++
gcc/cp/decl2.cc | 32 ++++++++++---------
gcc/cp/optimize.cc | 63 ++------------------------------------
gcc/testsuite/g++.dg/abi/comdat3.C | 22 +++++++++++++
gcc/testsuite/g++.dg/abi/comdat4.C | 28 +++++++++++++++++
6 files changed, 78 insertions(+), 75 deletions(-)
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 9a8c86591573..ba9e848c177f 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7453,7 +7453,6 @@ extern bool handle_module_option (unsigned opt, const
char *arg, int value);
/* In optimize.cc */
extern tree clone_attrs (tree);
extern bool maybe_clone_body (tree);
-extern void maybe_optimize_cdtor (tree);
/* In parser.cc */
extern tree cp_convert_range_for (tree, tree, tree, cp_decomp *, bool,
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index a139b293e00c..6fcab615d55e 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -19287,6 +19287,13 @@ cxx_comdat_group (tree decl)
else
break;
}
+ /* If a ctor/dtor has already set the comdat group by
+ maybe_clone_body, don't override it. */
+ if (SUPPORTS_ONE_ONLY
+ && TREE_CODE (decl) == FUNCTION_DECL
+ && DECL_CLONED_FUNCTION_P (decl))
+ if (tree comdat = DECL_COMDAT_GROUP (decl))
+ return comdat;
}
return decl;
diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index 6913efa53552..7baff46a1921 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -3325,16 +3325,23 @@ tentative_decl_linkage (tree decl)
linkage of all functions, and as that causes writes to
the data mapped in from the PCH file, it's advantageous
to mark the functions at this point. */
- if (DECL_DECLARED_INLINE_P (decl)
- && (!DECL_IMPLICIT_INSTANTIATION (decl)
- || DECL_DEFAULTED_FN (decl)))
+ if (DECL_DECLARED_INLINE_P (decl))
{
- /* This function must have external linkage, as
- otherwise DECL_INTERFACE_KNOWN would have been
- set. */
- gcc_assert (TREE_PUBLIC (decl));
- comdat_linkage (decl);
- DECL_INTERFACE_KNOWN (decl) = 1;
+ if (!DECL_IMPLICIT_INSTANTIATION (decl)
+ || DECL_DEFAULTED_FN (decl))
+ {
+ /* This function must have external linkage, as
+ otherwise DECL_INTERFACE_KNOWN would have been
+ set. */
+ gcc_assert (TREE_PUBLIC (decl));
+ comdat_linkage (decl);
+ DECL_INTERFACE_KNOWN (decl) = 1;
+ }
+ else if (DECL_MAYBE_IN_CHARGE_CDTOR_P (decl))
+ /* For implicit instantiations of cdtors try to make
+ it comdat, so that maybe_clone_body can use aliases.
+ See PR113208. */
+ maybe_make_one_only (decl);
}
}
else if (VAR_P (decl))
@@ -3604,9 +3611,6 @@ import_export_decl (tree decl)
}
DECL_INTERFACE_KNOWN (decl) = 1;
-
- if (DECL_CLONED_FUNCTION_P (decl))
- maybe_optimize_cdtor (decl);
}
/* Return an expression that performs the destruction of DECL, which
@@ -5331,7 +5335,7 @@ c_parse_final_cleanups (void)
node = node->get_alias_target ();
node->call_for_symbol_thunks_and_aliases (clear_decl_external,
- NULL, true);
+ NULL, true);
/* If we mark !DECL_EXTERNAL one of the symbols in some comdat
group, we need to mark all symbols in the same comdat group
that way. */
@@ -5341,7 +5345,7 @@ c_parse_final_cleanups (void)
next != node;
next = dyn_cast<cgraph_node *> (next->same_comdat_group))
next->call_for_symbol_thunks_and_aliases (clear_decl_external,
- NULL, true);
+ NULL, true);
}
/* If we're going to need to write this function out, and
diff --git a/gcc/cp/optimize.cc b/gcc/cp/optimize.cc
index 7147f5e00f13..b8791d8a9635 100644
--- a/gcc/cp/optimize.cc
+++ b/gcc/cp/optimize.cc
@@ -220,10 +220,8 @@ can_alias_cdtor (tree fn)
gcc_assert (DECL_MAYBE_IN_CHARGE_CDTOR_P (fn));
/* Don't use aliases for weak/linkonce definitions unless we can put both
symbols in the same COMDAT group. */
- return (DECL_INTERFACE_KNOWN (fn)
- && (SUPPORTS_ONE_ONLY || !DECL_WEAK (fn))
- && (!DECL_ONE_ONLY (fn)
- || (HAVE_COMDAT_GROUP && DECL_WEAK (fn))));
+ return (DECL_WEAK (fn) ? (HAVE_COMDAT_GROUP && DECL_ONE_ONLY (fn))
+ : (DECL_INTERFACE_KNOWN (fn) && !DECL_ONE_ONLY (fn)));
}
/* FN is a [cd]tor, fns is a pointer to an array of length 3. Fill fns
@@ -712,7 +710,7 @@ maybe_clone_body (tree fn)
if (expand_or_defer_fn_1 (clone))
emit_associated_thunks (clone);
/* We didn't generate a body, so remove the empty one. */
- DECL_SAVED_TREE (clone) = NULL_TREE;
+ DECL_SAVED_TREE (clone) = void_node;
}
else
expand_or_defer_fn (clone);
@@ -723,58 +721,3 @@ maybe_clone_body (tree fn)
/* We don't need to process the original function any further. */
return 1;
}
-
-/* If maybe_clone_body is called while the cdtor is still tentative,
- DECL_ONE_ONLY will be false and so will be can_alias_cdtor (fn).
- In that case we wouldn't try to optimize using an alias and instead
- would emit separate base and complete cdtor. The following function
- attempts to still optimize that case when we import_export_decl
- is called first time on one of the clones. */
-
-void
-maybe_optimize_cdtor (tree orig_decl)
-{
- tree fns[3];
- tree fn = DECL_CLONED_FUNCTION (orig_decl);
- gcc_checking_assert (DECL_MAYBE_IN_CHARGE_CDTOR_P (fn));
- if (DECL_INTERFACE_KNOWN (fn)
- || !TREE_ASM_WRITTEN (fn)
- || !DECL_ONE_ONLY (orig_decl)
- || symtab->global_info_ready)
- return;
-
- populate_clone_array (fn, fns);
-
- if (!fns[0] || !fns[1])
- return;
- for (int i = 2 - !fns[2]; i >= 0; --i)
- if (fns[i] != orig_decl && DECL_INTERFACE_KNOWN (fns[i]))
- return;
- DECL_INTERFACE_KNOWN (fn) = 1;
- comdat_linkage (fn);
- if (!can_alias_cdtor (fn))
- return;
- /* For comdat base and complete cdtors put them into the same,
- *[CD]5* comdat group instead of *[CD][12]*. */
- auto n0 = cgraph_node::get_create (fns[0]);
- auto n1 = cgraph_node::get_create (fns[1]);
- auto n2 = fns[2] ? cgraph_node::get_create (fns[1]) : NULL;
- if (n0->lowered || n1->lowered || (n2 && n2->lowered))
- return;
- import_export_decl (fns[0]);
- n1->definition = false;
- if (!n0->create_same_body_alias (fns[1], fns[0]))
- return;
-
- tree comdat_group = cdtor_comdat_group (fns[1], fns[0]);
- n1 = cgraph_node::get (fns[1]);
- n0->set_comdat_group (comdat_group);
- if (n1->same_comdat_group)
- n1->remove_from_same_comdat_group ();
- n1->add_to_same_comdat_group (n0);
- if (fns[2])
- n2->add_to_same_comdat_group (n0);
- import_export_decl (fns[1]);
- /* Remove the body now that it is an alias. */
- release_function_body (fns[1]);
-}
diff --git a/gcc/testsuite/g++.dg/abi/comdat3.C
b/gcc/testsuite/g++.dg/abi/comdat3.C
new file mode 100644
index 000000000000..2ea14d0abddd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/abi/comdat3.C
@@ -0,0 +1,22 @@
+// PR lto/113208
+// { dg-do compile { target { c++11 && { *-*-*gnu* } } } }
+// { dg-additional-options "-O2" }
+// { dg-final { scan-assembler "_ZN1M1SINS_1P1TELN1N1LE2EEC5Ev,comdat" } }
+// { dg-final { scan-assembler-not "_ZN1M1SINS_1P1TELN1N1LE2EEC1Ev,comdat" } }
+// { dg-final { scan-assembler-not "_ZN1M1SINS_1P1TELN1N1LE2EEC2Ev,comdat" } }
+
+namespace N { enum L { L1, L2, L3 } const O = L3; }
+namespace M {
+ using N::O;
+ using N::L;
+ template <typename, L = O>
+ struct S { constexpr S () {} };
+ namespace P {
+ struct T;
+ struct U { S<T> u; };
+ void foo () { U (); }
+ }
+ extern template class S<P::T>;
+}
+namespace p = M::P;
+template class M::S<p::T>;
diff --git a/gcc/testsuite/g++.dg/abi/comdat4.C
b/gcc/testsuite/g++.dg/abi/comdat4.C
new file mode 100644
index 000000000000..8669f153e39d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/abi/comdat4.C
@@ -0,0 +1,28 @@
+// PR lto/113208
+// { dg-do compile { target { c++11 && { *-*-*gnu* } } } }
+// { dg-additional-options "-O2" }
+// { dg-final { scan-assembler "_ZN1BI1CEC5ERKS1_,comdat" } }
+// { dg-final { scan-assembler-not "_ZN1BI1CEC1ERKS1_,comdat" } }
+// { dg-final { scan-assembler-not "_ZN1BI1CEC2ERKS1_,comdat" } }
+
+template <typename T>
+struct A {
+ int foo () const;
+ A (int, int);
+};
+template <typename T>
+struct B : A<T> {
+ constexpr B (const B &x) : A<T> (1, x.foo ()) {}
+ B () : A<T> (1, 2) {}
+};
+struct C;
+struct D : B<C> {};
+void bar (D);
+
+void
+baz (D x)
+{
+ bar (x);
+}
+
+template struct B<C>;
