https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84960
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Slightly better one without the weird __builtin_prefetch.
/* PR tree-optimization/84960 */
/* { dg-do compile } */
/* { dg-options "-O2 -fwrapv" } */
void
foo (int a, float b, void *c)
{
lab:
if ((b - (a %= 0) < 1) * -1)
;
else
{
long f = a;
__builtin_unreachable ();
c = &&lab;
}
goto *c;
}
Seems ssa_redirect_edges attempts to redirect ENTRY -> 2 edge to some other
basic block and the bb 2, which contains a forced label is then removed as
unreachable and removing unreachable blocks implies:
if (label_stmt
&& (FORCED_LABEL (gimple_label_label (label_stmt))
|| DECL_NONLOCAL (gimple_label_label (label_stmt))))
{
basic_block new_bb;
gimple_stmt_iterator new_gsi;
/* A non-reachable non-local label may still be referenced.
But it no longer needs to carry the extra semantics of
non-locality. */
if (DECL_NONLOCAL (gimple_label_label (label_stmt)))
{
DECL_NONLOCAL (gimple_label_label (label_stmt)) = 0;
FORCED_LABEL (gimple_label_label (label_stmt)) = 1;
}
new_bb = bb->prev_bb;
new_gsi = gsi_start_bb (new_bb);
gsi_remove (&i, false);
gsi_insert_before (&new_gsi, stmt, GSI_NEW_STMT);
}
but here bb->prev_bb is ENTRY_BLOCK, into which we obviously can't insert
anything.
