Hi!
The following testcase is miscompiled, because build_trivial_dtor_call
handles the case when instance is a pointer by adding a clobber to what
the pointer points to (which is desirable e.g. for delete) rather than the
pointer itself. That is I think always desirable behavior for references,
but for pointers for the pseudo dtor case it is not.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?
2020-08-24 Jakub Jelinek <ja...@redhat.com>
PR c++/96721
* cp-tree.h (build_trivial_dtor_call): Add bool argument defaulted
to false.
* call.c (build_trivial_dtor_call): Add NO_PTR_DEREF argument. If
instance is a pointer and NO_PTR_DEREF is true, clobber the pointer
rather than what it points to.
* semantics.c (finish_call_expr): Call build_trivial_dtor_call with
true as NO_PTR_DEREF.
* g++.dg/opt/flifetime-dse8.C: New test.
--- gcc/cp/cp-tree.h.jj 2020-08-24 10:00:01.383257572 +0200
+++ gcc/cp/cp-tree.h 2020-08-24 12:28:02.698410896 +0200
@@ -6248,7 +6248,7 @@ extern bool null_member_pointer_value_p
extern bool sufficient_parms_p (const_tree);
extern tree type_decays_to (tree);
extern tree extract_call_expr (tree);
-extern tree build_trivial_dtor_call (tree);
+extern tree build_trivial_dtor_call (tree, bool = false);
extern tree build_user_type_conversion (tree, tree, int,
tsubst_flags_t);
extern tree build_new_function_call (tree, vec<tree, va_gc> **,
--- gcc/cp/call.c.jj 2020-08-18 07:50:18.564922335 +0200
+++ gcc/cp/call.c 2020-08-24 12:30:55.211961352 +0200
@@ -8430,10 +8430,12 @@ conv_binds_ref_to_prvalue (conversion *c
}
/* Call the trivial destructor for INSTANCE, which can be either an lvalue of
- class type or a pointer to class type. */
+ class type or a pointer to class type. If NO_PTR_DEREF is true and
+ INSTANCE has pointer type, clobber the pointer rather than what it points
+ to. */
tree
-build_trivial_dtor_call (tree instance)
+build_trivial_dtor_call (tree instance, bool no_ptr_deref)
{
gcc_assert (!is_dummy_object (instance));
@@ -8443,7 +8445,8 @@ build_trivial_dtor_call (tree instance)
return fold_convert (void_type_node, instance);
}
- if (INDIRECT_TYPE_P (TREE_TYPE (instance)))
+ if (INDIRECT_TYPE_P (TREE_TYPE (instance))
+ && (!no_ptr_deref || TYPE_REF_P (TREE_TYPE (instance))))
{
if (VOID_TYPE_P (TREE_TYPE (TREE_TYPE (instance))))
goto no_clobber;
--- gcc/cp/semantics.c.jj 2020-08-18 07:50:18.653921086 +0200
+++ gcc/cp/semantics.c 2020-08-24 12:31:06.564800148 +0200
@@ -2713,7 +2713,7 @@ finish_call_expr (tree fn, vec<tree, va_
denoted by the object expression of the class member access. */
tree ob = TREE_OPERAND (fn, 0);
if (obvalue_p (ob))
- result = build_trivial_dtor_call (ob);
+ result = build_trivial_dtor_call (ob, true);
else
/* No location to clobber. */
result = convert_to_void (ob, ICV_STATEMENT, complain);
--- gcc/testsuite/g++.dg/opt/flifetime-dse8.C.jj 2020-08-24
12:36:24.585285134 +0200
+++ gcc/testsuite/g++.dg/opt/flifetime-dse8.C 2020-08-24 12:36:20.341345380
+0200
@@ -0,0 +1,12 @@
+// PR c++/96721
+// { dg-do run }
+// { dg-options "-O2 -flifetime-dse" }
+
+typedef int *T;
+
+int
+main ()
+{
+ T a = T ();
+ a.~T ();
+}
Jakub
