https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121202
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
(gdb) p debug_gimple_stmt (last_stmt)
vect__9.23_46 = { 1, 1, 1, 1 } << a.2_1;
$4 = void
(gdb) p debug_gimple_stmt (stmt)
# VUSE <.MEM_14>
a.2_1 = a;
$5 = void
(gdb) p debug_bb_n (3)
<bb 3> [local count: 105119322]:
a.2_1 = a;
vect__9.23_46 = { 1, 1, 1, 1 } << a.2_1;
if (a.2_1 <= 1)
so there's proper dominance. But
(gdb) p gimple_uid (last_stmt)
$8 = 0
(gdb) p gimple_uid (stmt)
$7 = 4294967295
and we hit
if (gimple_uid (gsi_stmt (gsi1)) == -1u)
return false;
this is because the stmts are externals and those do not get initialized
UIDs (aka stmt_vec_info).
This usually works but what breaks it is the -1 UID on the condition stmt.
We should have inserted the vect__9.23_46 = { 1, 1, 1, 1 } << a.2_1; in
the preheader, so that's arguably what triggers the issue here - and,
of course, that we have an invariant stmt inside of the loop.
