middle-end: Refactor vectorizer loop conditionals and separate out IV to new variables

This is extracted out of the patch series to support early break vectorization
in order to simplify the review of that patch series.

The goal of this one is to separate out the refactoring from the new
functionality.

This first patch separates out the vectorizer's definition of an exit to their
own values inside loop_vinfo.  During vectorization we can have three separate
copies for each loop: scalar, vectorized, epilogue.  The scalar loop can also be
the versioned loop before peeling.

Because of this we track 3 different exits inside loop_vinfo corresponding to
each of these loops.  Additionally each function that uses an exit, when not
obviously clear which exit is needed will now take the exit explicitly as an
argument.

This is because often times the callers switch the loops being passed around.
While the caller knows which loops it is, the callee does not.

For now the loop exits are simply initialized to same value as before determined
by single_exit (..).

No change in functionality is expected throughout this patch series.

gcc/ChangeLog:

	* tree-loop-distribution.cc (copy_loop_before): Pass exit explicitly.
	(loop_distribution::distribute_loop): Bail out of not single exit.
	* tree-scalar-evolution.cc (get_loop_exit_condition): New.
	* tree-scalar-evolution.h (get_loop_exit_condition): New.
	* tree-vect-data-refs.cc (vect_enhance_data_refs_alignment): Pass exit
	explicitly.
	* tree-vect-loop-manip.cc (vect_set_loop_condition_partial_vectors,
	vect_set_loop_condition_partial_vectors_avx512,
	vect_set_loop_condition_normal, vect_set_loop_condition): Explicitly
	take exit.
	(slpeel_tree_duplicate_loop_to_edge_cfg): Explicitly take exit and
	return new peeled corresponding peeled exit.
	(slpeel_can_duplicate_loop_p): Explicitly take exit.
	(find_loop_location): Handle not knowing an explicit exit.
	(vect_update_ivs_after_vectorizer, vect_gen_vector_loop_niters_mult_vf,
	find_guard_arg, slpeel_update_phi_nodes_for_loops,
	slpeel_update_phi_nodes_for_guard2): Use new exits.
	(vect_do_peeling): Update bookkeeping to keep track of exits.
	* tree-vect-loop.cc (vect_get_loop_niters): Explicitly take exit to
	analyze.
	(vec_init_loop_exit_info): New.
	(_loop_vec_info::_loop_vec_info): Initialize vec_loop_iv,
	vec_epilogue_loop_iv, scalar_loop_iv.
	(vect_analyze_loop_form): Initialize exits.
	(vect_create_loop_vinfo): Set main exit.
	(vect_create_epilog_for_reduction, vectorizable_live_operation,
	vect_transform_loop): Use it.
	(scale_profile_for_vect_loop): Explicitly take exit to scale.
	* tree-vectorizer.cc (set_uid_loop_bbs): Initialize loop exit.
	* tree-vectorizer.h (LOOP_VINFO_IV_EXIT, LOOP_VINFO_EPILOGUE_IV_EXIT,
	LOOP_VINFO_SCALAR_IV_EXIT): New.
	(struct loop_vec_info): Add vec_loop_iv, vec_epilogue_loop_iv,
	scalar_loop_iv.
	(vect_set_loop_condition, slpeel_can_duplicate_loop_p,
	slpeel_tree_duplicate_loop_to_edge_cfg): Take explicit exits.
	(vec_init_loop_exit_info): New.
	(struct vect_loop_form_info): Add loop_exit.

1 files changed, 22 insertions, 4 deletions

diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index f315292..a521608 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -925,10 +925,24 @@ public:
      analysis.  */
   vec<_loop_vec_info *> epilogue_vinfos;
 
+  /* The controlling loop IV for the current loop when vectorizing.  This IV
+     controls the natural exits of the loop.  */
+  edge vec_loop_iv_exit;
+
+  /* The controlling loop IV for the epilogue loop when vectorizing.  This IV
+     controls the natural exits of the loop.  */
+  edge vec_epilogue_loop_iv_exit;
+
+  /* The controlling loop IV for the scalar loop being vectorized.  This IV
+     controls the natural exits of the loop.  */
+  edge scalar_loop_iv_exit;
 } *loop_vec_info;
 
 /* Access Functions.  */
 #define LOOP_VINFO_LOOP(L)                 (L)->loop
+#define LOOP_VINFO_IV_EXIT(L)              (L)->vec_loop_iv_exit
+#define LOOP_VINFO_EPILOGUE_IV_EXIT(L)     (L)->vec_epilogue_loop_iv_exit
+#define LOOP_VINFO_SCALAR_IV_EXIT(L)       (L)->scalar_loop_iv_exit
 #define LOOP_VINFO_BBS(L)                  (L)->bbs
 #define LOOP_VINFO_NITERSM1(L)             (L)->num_itersm1
 #define LOOP_VINFO_NITERS(L)               (L)->num_iters
@@ -2161,11 +2175,13 @@ class auto_purge_vect_location
 
 /* Simple loop peeling and versioning utilities for vectorizer's purposes -
    in tree-vect-loop-manip.cc.  */
-extern void vect_set_loop_condition (class loop *, loop_vec_info,
+extern void vect_set_loop_condition (class loop *, edge, loop_vec_info,
 				     tree, tree, tree, bool);
-extern bool slpeel_can_duplicate_loop_p (const class loop *, const_edge);
-class loop *slpeel_tree_duplicate_loop_to_edge_cfg (class loop *,
-						     class loop *, edge);
+extern bool slpeel_can_duplicate_loop_p (const class loop *, const_edge,
+					 const_edge);
+class loop *slpeel_tree_duplicate_loop_to_edge_cfg (class loop *, edge,
+						    class loop *, edge,
+						    edge, edge *);
 class loop *vect_loop_versioning (loop_vec_info, gimple *);
 extern class loop *vect_do_peeling (loop_vec_info, tree, tree,
 				    tree *, tree *, tree *, int, bool, bool,
@@ -2175,6 +2191,7 @@ extern void vect_prepare_for_masked_peels (loop_vec_info);
 extern dump_user_location_t find_loop_location (class loop *);
 extern bool vect_can_advance_ivs_p (loop_vec_info);
 extern void vect_update_inits_of_drs (loop_vec_info, tree, tree_code);
+extern edge vec_init_loop_exit_info (class loop *);
 
 /* In tree-vect-stmts.cc.  */
 extern tree get_related_vectype_for_scalar_type (machine_mode, tree,
@@ -2364,6 +2381,7 @@ struct vect_loop_form_info
   tree assumptions;
   gcond *loop_cond;
   gcond *inner_loop_cond;
+  edge loop_exit;
 };
 extern opt_result vect_analyze_loop_form (class loop *, vect_loop_form_info *);
 extern loop_vec_info vect_create_loop_vinfo (class loop *, vec_info_shared *,