[gcc(refs/users/tnfchris/heads/gcc-14-early-break)] middle-end: Update loop form analysis to support early break

[gcc(refs/users/tnfchris/heads/gcc-14-early-break)] middle-end: Update loop form analysis to support early break

[Tamar Christina]

https://gcc.gnu.org/g:0bfccd4b6ba450f93c74440f98b325958af33830

commit 0bfccd4b6ba450f93c74440f98b325958af33830
Author: Tamar Christina <tamar.christina@arm.com>
Date:   Thu Nov 2 17:05:47 2023 +0000

    middle-end: Update loop form analysis to support early break

Diff:
---
 gcc/tree-vect-loop.cc | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index f406c59c2c3..cd83cc0a67a 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -1700,12 +1700,12 @@ vect_compute_single_scalar_iteration_cost (loop_vec_info loop_vinfo)
   loop_vinfo->scalar_costs->finish_cost (nullptr);
 }
 
-
 /* Function vect_analyze_loop_form.
 
    Verify that certain CFG restrictions hold, including:
    - the loop has a pre-header
-   - the loop has a single entry and exit
+   - the loop has a single entry
+   - nested loops can have only a single exit.
    - the loop exit condition is simple enough
    - the number of iterations can be analyzed, i.e, a countable loop.  The
      niter could be analyzed under some assumptions.  */
@@ -1841,10 +1841,14 @@ vect_analyze_loop_form (class loop *loop, vect_loop_form_info *info)
 				   "not vectorized: latch block not empty.\n");
 
   /* Make sure the exit is not abnormal.  */
-  if (exit_e->flags & EDGE_ABNORMAL)
-    return opt_result::failure_at (vect_location,
-				   "not vectorized:"
-				   " abnormal loop exit edge.\n");
+  auto_vec<edge> exits = get_loop_exit_edges (loop);
+  for (edge e : exits)
+    {
+      if (e->flags & EDGE_ABNORMAL)
+	return opt_result::failure_at (vect_location,
+				       "not vectorized:"
+				       " abnormal loop exit edge.\n");
+    }
 
   info->conds
     = vect_get_loop_niters (loop, exit_e, &info->assumptions,
@@ -1920,6 +1924,10 @@ vect_create_loop_vinfo (class loop *loop, vec_info_shared *shared,
 
   LOOP_VINFO_IV_EXIT (loop_vinfo) = info->loop_exit;
 
+  /* Check to see if we're vectorizing multiple exits.  */
+  LOOP_VINFO_EARLY_BREAKS (loop_vinfo)
+    = !LOOP_VINFO_LOOP_CONDS (loop_vinfo).is_empty ();
+
   if (info->inner_loop_cond)
     {
       stmt_vec_info inner_loop_cond_info
@@ -11691,7 +11699,7 @@ vect_transform_loop (loop_vec_info loop_vinfo, gimple *loop_vectorized_call)
   /* Make sure there exists a single-predecessor exit bb.  Do this before 
      versioning.   */
   edge e = LOOP_VINFO_IV_EXIT (loop_vinfo);
-  if (! single_pred_p (e->dest))
+  if (! single_pred_p (e->dest) && !LOOP_VINFO_EARLY_BREAKS (loop_vinfo))
     {
       split_loop_exit_edge (e, true);
       if (dump_enabled_p ())