[gcc r13-1084] Restore bootstrap on ARM

[Eric Botcazou <ebotcazou@gcc.gnu.org>]

https://gcc.gnu.org/g:be6676286a0fad2d7fdb6a258befe9deb826690e

commit r13-1084-gbe6676286a0fad2d7fdb6a258befe9deb826690e
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Tue Jun 14 12:28:24 2022 +0200

    Restore bootstrap on ARM
    
    The -Wuse-after-free warning is explicitly disabled for destructors on ARM
    because of the special ABI and the previous change to the warning machinery
    uncovered another case where the warning data would be incorrectly erased.
    
    gcc/
            * warning-control.cc (copy_warning) [generic version]: Do not erase
            the warning data of the destination location when the no-warning
            bit is not set on the source.
            (copy_warning) [tree version]: Return early if TO is equal to FROM.
            (copy_warning) [gimple version]: Likewise.
    gcc/testsuite/
            * g++.dg/warn/Wuse-after-free5.C: New test.

Diff:
---
 gcc/testsuite/g++.dg/warn/Wuse-after-free5.C | 15 +++++++++++++++
 gcc/warning-control.cc                       |  8 ++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/g++.dg/warn/Wuse-after-free5.C b/gcc/testsuite/g++.dg/warn/Wuse-after-free5.C
new file mode 100644
index 00000000000..794cbfc44e7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wuse-after-free5.C
@@ -0,0 +1,15 @@
+// Check the suppression of -Wuse-after-free for destructors on ARM
+// { dg-do compile }
+// { dg-options "-Wuse-after-free" }
+
+struct range_label {
+  virtual ~range_label();
+};
+
+struct unpaired_bidi_rich_location {
+  struct custom_range_label : range_label {};
+  unpaired_bidi_rich_location(int);
+  custom_range_label m_custom_label;
+};
+
+void maybe_warn_bidi_on_close() { unpaired_bidi_rich_location(0); }
diff --git a/gcc/warning-control.cc b/gcc/warning-control.cc
index 0cbb4f079fa..7e9e701cfbe 100644
--- a/gcc/warning-control.cc
+++ b/gcc/warning-control.cc
@@ -191,7 +191,7 @@ void copy_warning (ToType to, FromType from)
 {
   const location_t to_loc = get_location (to);
 
-  bool supp = get_no_warning_bit (from);
+  const bool supp = get_no_warning_bit (from);
 
   nowarn_spec_t *from_spec = get_nowarn_spec (from);
   if (RESERVED_LOCATION_P (to_loc))
@@ -209,7 +209,7 @@ void copy_warning (ToType to, FromType from)
 	  nowarn_spec_t tem = *from_spec;
 	  nowarn_map->put (to_loc, tem);
 	}
-      else
+      else if (supp)
 	{
 	  if (nowarn_map)
 	    nowarn_map->remove (to_loc);
@@ -226,6 +226,8 @@ void copy_warning (ToType to, FromType from)
 void
 copy_warning (tree to, const_tree from)
 {
+  if (to == from)
+    return;
   copy_warning<tree, const_tree>(to, from);
 }
 
@@ -250,5 +252,7 @@ copy_warning (gimple *to, const_tree from)
 void
 copy_warning (gimple *to, const gimple *from)
 {
+  if (to == from)
+    return;
   copy_warning<gimple *, const gimple *>(to, from);
 }