https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65315
--- Comment #1 from Steve Ellcey <sje at gcc dot gnu.org> --- It might be easier to see this bug if you apply this patch: diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c index 7dfe1f6..7beb00e 100644 --- a/gcc/cfgexpand.c +++ b/gcc/cfgexpand.c @@ -973,6 +973,8 @@ expand_stack_vars (bool (*pred) (size_t), struct sta ck_vars_data *data) i = stack_vars_sorted[si]; alignb = stack_vars[i].alignb; + gcc_assert (alignb*BITS_PER_UNIT <= large_align); + /* Stop when we get to the first decl with "small" alignment. */ if (alignb * BITS_PER_UNIT <= MAX_SUPPORTED_STACK_ALIGNMENT) break; This way you get an ICE instead of just incorrectly aligned vectors.