https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105562
--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index d4d0aba880c..9f7f12846cb 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -2593,6 +2593,11 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void
*data_,
bool lhs_ref_ok = false;
poly_int64 copy_size;
+ /* We can optimistically disambiguate against CLOBBERs, when there
+ is any overlap it would be undefined behavior. */
+ if (gimple_clobber_p (def_stmt))
+ return NULL;
+
/* First try to disambiguate after value-replacing in the definitions LHS.
*/
if (is_gimple_assign (def_stmt))
{
avoids the diagnostics.
