Support vectorisation with mixed vector sizes

After previous patches, it's now possible to make the vectoriser
support multiple vector sizes in the same vector region, using
related_vector_mode to pick the right vector mode for a given
element mode.  No port yet takes advantage of this, but I have
a follow-on patch for AArch64.

This patch also seemed like a good opportunity to add some more dump
messages: one to make it clear which vector size/mode was being used
when analysis passed or failed, and another to say when we've decided
to skip a redundant vector size/mode.

2019-11-14  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* machmode.h (opt_machine_mode::operator==): New function.
	(opt_machine_mode::operator!=): Likewise.
	* tree-vectorizer.h (vec_info::vector_mode): Update comment.
	(get_related_vectype_for_scalar_type): Delete.
	(get_vectype_for_scalar_type_and_size): Declare.
	* tree-vect-slp.c (vect_slp_bb_region): Print dump messages to say
	whether analysis passed or failed, and with what vector modes.
	Use related_vector_mode to check whether trying a particular
	vector mode would be redundant with the autodetected mode,
	and print a dump message if we decide to skip it.
	* tree-vect-loop.c (vect_analyze_loop): Likewise.
	(vect_create_epilog_for_reduction): Use
	get_related_vectype_for_scalar_type instead of
	get_vectype_for_scalar_type_and_size.
	* tree-vect-stmts.c (get_vectype_for_scalar_type_and_size): Replace
	with...
	(get_related_vectype_for_scalar_type): ...this new function.
	Take a starting/"prevailing" vector mode rather than a vector size.
	Take an optional nunits argument, with the same meaning as for
	related_vector_mode.  Use related_vector_mode when not
	auto-detecting a mode, falling back to mode_for_vector if no
	target mode exists.
	(get_vectype_for_scalar_type): Update accordingly.
	(get_same_sized_vectype): Likewise.
	* tree-vectorizer.c (get_vec_alignment_for_array_type): Likewise.

From-SVN: r278240

1 files changed, 29 insertions, 4 deletions

diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index 3885d9cbe4a..1e00db5a326 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -3203,7 +3203,12 @@ vect_slp_bb_region (gimple_stmt_iterator region_begin,
 	  && dbg_cnt (vect_slp))
 	{
 	  if (dump_enabled_p ())
-	    dump_printf_loc (MSG_NOTE, vect_location, "SLPing BB part\n");
+	    {
+	      dump_printf_loc (MSG_NOTE, vect_location,
+			       "***** Analysis succeeded with vector mode"
+			       " %s\n", GET_MODE_NAME (bb_vinfo->vector_mode));
+	      dump_printf_loc (MSG_NOTE, vect_location, "SLPing BB part\n");
+	    }
 
 	  bb_vinfo->shared->check_datarefs ();
 	  vect_schedule_slp (bb_vinfo);
@@ -3223,6 +3228,13 @@ vect_slp_bb_region (gimple_stmt_iterator region_begin,
 
 	  vectorized = true;
 	}
+      else
+	{
+	  if (dump_enabled_p ())
+	    dump_printf_loc (MSG_NOTE, vect_location,
+			     "***** Analysis failed with vector mode %s\n",
+			     GET_MODE_NAME (bb_vinfo->vector_mode));
+	}
 
       if (mode_i == 0)
 	autodetected_vector_mode = bb_vinfo->vector_mode;
@@ -3230,9 +3242,22 @@ vect_slp_bb_region (gimple_stmt_iterator region_begin,
       delete bb_vinfo;
 
       if (mode_i < vector_modes.length ()
-	  && known_eq (GET_MODE_SIZE (vector_modes[mode_i]),
-		       GET_MODE_SIZE (autodetected_vector_mode)))
-	mode_i += 1;
+	  && VECTOR_MODE_P (autodetected_vector_mode)
+	  && (related_vector_mode (vector_modes[mode_i],
+				   GET_MODE_INNER (autodetected_vector_mode))
+	      == autodetected_vector_mode)
+	  && (related_vector_mode (autodetected_vector_mode,
+				   GET_MODE_INNER (vector_modes[mode_i]))
+	      == vector_modes[mode_i]))
+	{
+	  if (dump_enabled_p ())
+	    dump_printf_loc (MSG_NOTE, vect_location,
+			     "***** Skipping vector mode %s, which would"
+			     " repeat the analysis for %s\n",
+			     GET_MODE_NAME (vector_modes[mode_i]),
+			     GET_MODE_NAME (autodetected_vector_mode));
+	  mode_i += 1;
+	}
 
       if (vectorized
 	  || mode_i == vector_modes.length ()