https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61607
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Like with
Index: gcc/tree-ssa-threadupdate.c
===================================================================
--- gcc/tree-ssa-threadupdate.c (revision 211969)
+++ gcc/tree-ssa-threadupdate.c (working copy)
@@ -764,6 +764,14 @@ ssa_redirect_edges (struct redirection_d
if ((*path)[1]->type != EDGE_COPY_SRC_JOINER_BLOCK)
EDGE_SUCC (rd->dup_blocks[0], 0)->count += e->count;
+ /* If we redirect a loop latch edge cancel its loop. */
+ if (e->src == e->src->loop_father->latch)
+ {
+ e->src->loop_father->header = NULL;
+ e->src->loop_father->latch = NULL;
+ loops_state_set (LOOPS_NEED_FIXUP);
+ }
+
/* Redirect the incoming edge (possibly to the joiner block) to the
appropriate duplicate block. */
e2 = redirect_edge_and_branch (e, rd->dup_blocks[0]);
@@ -853,32 +861,6 @@ thread_block_1 (basic_block bb, bool nol
redirection_data
= new hash_table<struct redirection_data> (EDGE_COUNT (bb->succs));
- /* If we thread the latch of the loop to its exit, the loop ceases to
- exist. Make sure we do not restrict ourselves in order to preserve
- this loop. */
- if (loop->header == bb)
- {
- e = loop_latch_edge (loop);
- vec<jump_thread_edge *> *path = THREAD_PATH (e);
-
- if (path
- && (((*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK && joiners)
- || ((*path)[1]->type == EDGE_COPY_SRC_BLOCK && !joiners)))
- {
- for (unsigned int i = 1; i < path->length (); i++)
- {
- edge e2 = (*path)[i]->e;
-
- if (loop_exit_edge_p (loop, e2))
- {
- loop->header = NULL;
- loop->latch = NULL;
- loops_state_set (LOOPS_NEED_FIXUP);
- }
- }
- }
- }
-
/* Record each unique threaded destination into a hash table for
efficient lookups. */
FOR_EACH_EDGE (e, ei, bb->preds)
