https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91236
--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> --- Ooops (double-oops, see 2nd hunk...). Testing the following: Index: gcc/tree-ssa-sccvn.c =================================================================== --- gcc/tree-ssa-sccvn.c (revision 273758) +++ gcc/tree-ssa-sccvn.c (working copy) @@ -1818,7 +1870,7 @@ vn_walk_cb_data::push_partial_def (const if (TREE_CODE (pd.rhs) == CONSTRUCTOR) /* Empty CONSTRUCTOR. */ memset (buffer + MAX (0, pd.offset), - 0, MIN ((HOST_WIDE_INT)sizeof (buffer), + 0, MIN ((HOST_WIDE_INT)sizeof (buffer) - MAX (0, pd.offset), pd.size + MIN (0, pd.offset))); else { @@ -1833,7 +1885,7 @@ vn_walk_cb_data::push_partial_def (const pad = GET_MODE_SIZE (mode) - pd.size; } len = native_encode_expr (pd.rhs, buffer + MAX (0, pd.offset), - sizeof (buffer - MAX (0, pd.offset)), + sizeof (buffer) - MAX (0, pd.offset), MAX (0, -pd.offset) + pad); if (len <= 0 || len < (pd.size - MAX (0, -pd.offset))) {