https://gcc.gnu.org/bugzilla/show_bug.cgi?id=23970
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Unswitching does this as a separate transform now, the "hoist guards"
transform.
It's even done completely separate now:
unsigned int
tree_ssa_unswitch_loops (function *fun)
{
bool changed_unswitch = false;
bool changed_hoist = false;
auto_edge_flag ignored_edge_flag (fun);
ranger = enable_ranger (fun);
/* Go through all loops starting from innermost, hoisting guards. */
for (auto loop : loops_list (fun, LI_FROM_INNERMOST))
{
if (loop->inner)
changed_hoist |= tree_unswitch_outer_loop (loop);
}
/* Go through innermost loops, unswitching on invariant predicates
within those. */
...
the question is how we'd call the "cheap" unswitching transform. I guess
simply testing optimize > 2 || opt_enabled or so isn't quite desirable.
Note it's possible to separate this into an entirely separate pass as well.
