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.

diff --git a/gcc/cgraph.cc b/gcc/cgraph.cc
index d0b19ad850e02307ade7bf91e5efb17407e9713d..6ae6a97f6f56cdc07b19c680a3636bd8cd9a7318 100644 (file)
--- a/gcc/cgraph.cc
+++ b/gcc/cgraph.cc
@@ -1708,12 +1708,15 @@ 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("");
+}