ipa: Do not modify cgraph edges from thunk clones during inlining (PR116572)

In PR 116572 we hit an assert that a thunk which does not have a body
looks like it has one.  It does not, but the call_stmt of its outgoing
edge points to a statement, which should not.  In fact it has several
outgoing call graph edges, which cannot be.  The problem is that the
code updating the edges to reflect inlining into the master clone (an
ex-thunk, unlike the clone, which is still an unexpanded thunk) is
being updated during inling into the master clone.  This patch simply
makes the code to skip unexpanded thunk clones.

gcc/ChangeLog:

2025-03-13  Martin Jambor  <mjambor@suse.cz>

	PR ipa/116572
	* cgraph.cc (cgraph_update_edges_for_call_stmt): Do not update
	edges of clones that are unexpanded thunk.  Assert that the node
	passed as the parameter is not an unexpanded thunk.

gcc/testsuite/ChangeLog:

2025-03-13  Martin Jambor  <mjambor@suse.cz>

	PR ipa/116572
	* g++.dg/ipa/pr116572.C: New test.

(cherry picked from commit 075ec330307c5b1fe5ed166a633c718c06b01437)

diff --git a/gcc/cgraph.cc b/gcc/cgraph.cc
index 8226c7d96e058757e7576afc0f960cf3250f8db7..dc18a16f891758273b8f68b4113a84988e081414 100644 (file)
--- a/gcc/cgraph.cc
+++ b/gcc/cgraph.cc
@@ -1710,12 +1710,15 @@ cgraph_update_edges_for_call_stmt (gimple *old_stmt, tree old_decl,
   cgraph_node *node;
 
   gcc_checking_assert (orig);
+  gcc_assert (!orig->thunk);
   cgraph_update_edges_for_call_stmt_node (orig, old_stmt, old_decl, new_stmt);
   if (orig->clones)
     for (node = orig->clones; node != orig;)
       {
-       cgraph_update_edges_for_call_stmt_node (node, old_stmt, old_decl,
-                                               new_stmt);
+       /* Do not attempt to adjust bodies of yet unexpanded thunks.  */
+       if (!node->thunk)
+         cgraph_update_edges_for_call_stmt_node (node, old_stmt, old_decl,
+                                                 new_stmt);
        if (node->clones)
          node = node->clones;
        else if (node->next_sibling_clone)

diff --git a/gcc/testsuite/g++.dg/ipa/pr116572.C b/gcc/testsuite/g++.dg/ipa/pr116572.C
new file mode 100644 (file)
index 0000000..909568e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ipa/pr116572.C
@@ -0,0 +1,37 @@
+/* { dg-do compile } */
+/* { dg-options "-std=c++20 -O3 -fsanitize=undefined" } */
+
+long v;
+template <class> struct A;
+template <typename C, typename = A<C>, typename = C>
+class B;
+template <>
+struct A<char>
+{
+  static int foo(char *s, const char *t, long n) { return __builtin_memcmp(s, t, n); }
+};
+template <typename C, typename, typename>
+struct B {
+  long b;
+  B(const C *);
+  C *bar() const;
+  constexpr unsigned long baz(const C *, unsigned long, unsigned long) const noexcept;
+  void baz() { C c; baz(&c, 0, v); }
+};
+template <typename C, typename D, typename E>
+constexpr unsigned long
+B<C, D, E>::baz(const C *s, unsigned long, unsigned long n) const noexcept
+{
+  C *x = bar(); if (!x) return b; D::foo(x, s, n); return 0;
+}
+namespace {
+struct F { virtual ~F() {} };
+struct F2 { virtual void foo(B<char>) const; };
+struct F3 : F, F2 { void foo(B<char> s) const { s.baz(); } } f;
+}
+int
+main()
+{
+  F *p;
+  dynamic_cast<F2 *>(p)->foo("");
+}