tree-optimization/116982 - analyze scalar loop exit early

The following makes sure to discover the scalar loop IV exit during
analysis as failure to do so (if DCE and friends are disabled this
can happen due to if-conversion doing DCE and FRE on the if-converted
loop) would ICE later.

I refrained from larger refactoring to be able to eventually backport.

	PR tree-optimization/116982
	* tree-vectorizer.h (vect_analyze_loop): Pass in .LOOP_VECTORIZED
	call.
	(vect_analyze_loop_form): Likewise.
	* tree-vect-loop.cc (vect_analyze_loop_form): Reject loops where we
	cannot determine a IV exit for the scalar loop.
	(vect_analyze_loop): Adjust.
	* tree-vectorizer.cc (try_vectorize_loop_1): Likewise.
	* tree-parloops.cc (gather_scalar_reductions): Likewise.

4 files changed, 27 insertions, 9 deletions

diff --git a/gcc/tree-parloops.cc b/gcc/tree-parloops.cc
index f446865..6a1249b 100644
--- a/gcc/tree-parloops.cc
+++ b/gcc/tree-parloops.cc
@@ -3305,7 +3305,7 @@ gather_scalar_reductions (loop_p loop, reduction_info_table_type *reduction_list
 
   vec_info_shared shared;
   vect_loop_form_info info;
-  if (!vect_analyze_loop_form (loop, &info))
+  if (!vect_analyze_loop_form (loop, NULL, &info))
     goto gather_done;
 
   simple_loop_info = vect_create_loop_vinfo (loop, &shared, &info);
@@ -3347,7 +3347,7 @@ gather_scalar_reductions (loop_p loop, reduction_info_table_type *reduction_list
     {
       vec_info_shared shared;
       vect_loop_form_info info;
-      if (vect_analyze_loop_form (loop->inner, &info))
+      if (vect_analyze_loop_form (loop->inner, NULL, &info))
 	{
 	  simple_loop_info
 	    = vect_create_loop_vinfo (loop->inner, &shared, &info);
diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index f1b3fb2..bbadf21 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -1737,7 +1737,8 @@ vect_compute_single_scalar_iteration_cost (loop_vec_info loop_vinfo)
      niter could be analyzed under some assumptions.  */
 
 opt_result
-vect_analyze_loop_form (class loop *loop, vect_loop_form_info *info)
+vect_analyze_loop_form (class loop *loop, gimple *loop_vectorized_call,
+			vect_loop_form_info *info)
 {
   DUMP_VECT_SCOPE ("vect_analyze_loop_form");
 
@@ -1747,6 +1748,18 @@ vect_analyze_loop_form (class loop *loop, vect_loop_form_info *info)
 				   "not vectorized:"
 				   " could not determine main exit from"
 				   " loop with multiple exits.\n");
+  if (loop_vectorized_call)
+    {
+      tree arg = gimple_call_arg (loop_vectorized_call, 1);
+      class loop *scalar_loop = get_loop (cfun, tree_to_shwi (arg));
+      edge scalar_exit_e = vec_init_loop_exit_info (scalar_loop);
+      if (!scalar_exit_e)
+	return opt_result::failure_at (vect_location,
+				       "not vectorized:"
+				       " could not determine main exit from"
+				       " loop with multiple exits.\n");
+    }
+
   info->loop_exit = exit_e;
   if (dump_enabled_p ())
       dump_printf_loc (MSG_NOTE, vect_location,
@@ -1819,7 +1832,7 @@ vect_analyze_loop_form (class loop *loop, vect_loop_form_info *info)
 
       /* Analyze the inner-loop.  */
       vect_loop_form_info inner;
-      opt_result res = vect_analyze_loop_form (loop->inner, &inner);
+      opt_result res = vect_analyze_loop_form (loop->inner, NULL, &inner);
       if (!res)
 	{
 	  if (dump_enabled_p ())
@@ -3520,7 +3533,8 @@ vect_analyze_loop_1 (class loop *loop, vec_info_shared *shared,
    for it.  The different analyses will record information in the
    loop_vec_info struct.  */
 opt_loop_vec_info
-vect_analyze_loop (class loop *loop, vec_info_shared *shared)
+vect_analyze_loop (class loop *loop, gimple *loop_vectorized_call,
+		   vec_info_shared *shared)
 {
   DUMP_VECT_SCOPE ("analyze_loop_nest");
 
@@ -3538,7 +3552,8 @@ vect_analyze_loop (class loop *loop, vec_info_shared *shared)
 
   /* Analyze the loop form.  */
   vect_loop_form_info loop_form_info;
-  opt_result res = vect_analyze_loop_form (loop, &loop_form_info);
+  opt_result res = vect_analyze_loop_form (loop, loop_vectorized_call,
+					   &loop_form_info);
   if (!res)
     {
       if (dump_enabled_p ())
diff --git a/gcc/tree-vectorizer.cc b/gcc/tree-vectorizer.cc
index d4ab473..fed12c4 100644
--- a/gcc/tree-vectorizer.cc
+++ b/gcc/tree-vectorizer.cc
@@ -1067,7 +1067,8 @@ try_vectorize_loop_1 (hash_table<simduid_to_vf> *&simduid_to_vf_htab,
 		 LOCATION_LINE (vect_location.get_location_t ()));
 
   /* Try to analyze the loop, retaining an opt_problem if dump_enabled_p.  */
-  opt_loop_vec_info loop_vinfo = vect_analyze_loop (loop, &shared);
+  opt_loop_vec_info loop_vinfo = vect_analyze_loop (loop, loop_vectorized_call,
+						    &shared);
   loop->aux = loop_vinfo;
 
   if (!loop_vinfo)
diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index 490061a..73bccb5 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -2460,7 +2460,8 @@ extern bool check_reduction_path (dump_user_location_t, loop_p, gphi *, tree,
 				  enum tree_code);
 extern bool needs_fold_left_reduction_p (tree, code_helper);
 /* Drive for loop analysis stage.  */
-extern opt_loop_vec_info vect_analyze_loop (class loop *, vec_info_shared *);
+extern opt_loop_vec_info vect_analyze_loop (class loop *, gimple *,
+					    vec_info_shared *);
 extern tree vect_build_loop_niters (loop_vec_info, bool * = NULL);
 extern void vect_gen_vector_loop_niters (loop_vec_info, tree, tree *,
 					 tree *, bool);
@@ -2495,7 +2496,8 @@ struct vect_loop_form_info
   gcond *inner_loop_cond;
   edge loop_exit;
 };
-extern opt_result vect_analyze_loop_form (class loop *, vect_loop_form_info *);
+extern opt_result vect_analyze_loop_form (class loop *, gimple *,
+					  vect_loop_form_info *);
 extern loop_vec_info vect_create_loop_vinfo (class loop *, vec_info_shared *,
 					     const vect_loop_form_info *,
 					     loop_vec_info = nullptr);