The final loop IV use after the loop has that not in LC SSA
(and inserts not simplified _2 = _3 - 0 stmts). In particular
since it splits the exit edge when there's a virtual PHI in the
destination it breaks virtual LC SSA form (but likely also
non-virtual).
The following properly inserts LC PHIs instead.
Bootstrap & regtest pending on x86_64-unknown-linux-gnu.
OK if that succeeds?
Thanks,
Richard.
2022-07-04 Richard Biener <rguent...@suse.de>
* tree-vect-loop-manip.cc (vect_set_loop_condition_normal):
Maintain LC SSA.
---
gcc/tree-vect-loop-manip.cc | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index 895957472c9..eba71c50428 100644
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -920,9 +920,22 @@ vect_set_loop_condition_normal (class loop *loop, tree
niters, tree step,
if (final_iv)
{
- gassign *assign = gimple_build_assign (final_iv, MINUS_EXPR,
- indx_after_incr, init);
- gsi_insert_on_edge_immediate (single_exit (loop), assign);
+ gassign *assign;
+ edge exit = single_exit (loop);
+ gcc_assert (single_pred_p (exit->dest));
+ tree phi_dest
+ = integer_zerop (init) ? final_iv : copy_ssa_name (indx_after_incr);
+ /* Make sure to maintain LC SSA form here and elide the subtraction
+ if the value is zero. */
+ gphi *phi = create_phi_node (phi_dest, exit->dest);
+ add_phi_arg (phi, indx_after_incr, exit, UNKNOWN_LOCATION);
+ if (!integer_zerop (init))
+ {
+ assign = gimple_build_assign (final_iv, MINUS_EXPR,
+ phi_dest, init);
+ gimple_stmt_iterator gsi = gsi_after_labels (exit->dest);
+ gsi_insert_before (&gsi, assign, GSI_SAME_STMT);
+ }
}
return cond_stmt;
--
2.35.3
