--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/tree-ssa/strlenopt-1.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,42 @@
+/* PR tree-optimization/92765 - wrong code for strcmp of a union member
+   { dg-do run }
+   { dg-options "-O2 -Wall" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+inline void* operator new (size_t, void *p)
+{
+  return p;
+}
+
+struct A { char a2[2]; };
+struct B { char a4[4]; };
+
+__attribute__((noipa)) void
+sink (void*) { }
+
+__attribute__((noipa)) void
+copy (char *d, const char *s)
+{
+  while ((*d++ = *s++));
+}
+
+__attribute__((noipa)) void
+store_and_compare (void *p)
+{
+  A *a = new (p) A;
+  sink (a->a2);
+
+  B *b = new (p) B;
+  char *q = (char *) b->a4;
+  copy (q, "abc");
+
+  if (__builtin_strcmp (q, "abc"))
+    __builtin_abort ();
+}
+
+int main ()
+{
+  char a [sizeof (A) > sizeof (B) ? sizeof (A) : sizeof (B)];
+  store_and_compare (a);
+}