re PR tree-optimization/92173 (ICE in optab_for_tree_code, at optabs-tree.c:81)

2019-10-22  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/92173
	* tree-vect-loop.c (vectorizable_reduction): If
	vect_transform_reduction cannot handle code-generation try without
	the single-def-use-cycle optimization.  Pass optab_vector to
	optab_for_tree_code to get vector shifts as that's what we'd
	generate.

	* gcc.dg/torture/pr92173.c: New testcase.

From-SVN: r277286

gcc/ChangeLog

+2019-10-22  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/92173
+	* tree-vect-loop.c (vectorizable_reduction): If
+	vect_transform_reduction cannot handle code-generation try without
+	the single-def-use-cycle optimization.  Pass optab_vector to
+	optab_for_tree_code to get vector shifts as that's what we'd
+	generate.
+
 2019-10-22  Martin Liska  <mliska@suse.cz>
 
 	* diagnostic-format-json.cc (json_from_expanded_location):

gcc/testsuite/ChangeLog

+2019-10-22  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/92173
+	* gcc.dg/torture/pr92173.c: New testcase.
+
 2019-10-22  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* g++.dg/diagnostic/aka5.h: New test.

gcc/testsuite/gcc.dg/torture/pr92173.c

+/* { dg-do compile } */
+/* { dg-additional-options "-ftree-vectorize" } */
+
+unsigned int
+yo (unsigned int o0, signed char s1)
+{
+  for (s1 = 0; s1 < 1; s1 -= 2)
+    o0 += o0;
+
+  return o0 + s1;
+}

gcc/tree-vect-loop.c

@@ -6240,61 +6240,67 @@ vectorizable_reduction (stmt_vec_info stmt_info, slp_tree slp_node,
       && (!STMT_VINFO_IN_PATTERN_P (use_stmt_info)
 	  || !STMT_VINFO_PATTERN_DEF_SEQ (use_stmt_info))
       && vect_stmt_to_vectorize (use_stmt_info) == stmt_info)
-    STMT_VINFO_FORCE_SINGLE_CYCLE (reduc_info) = single_defuse_cycle = true;
+    single_defuse_cycle = true;
 
-  if (single_defuse_cycle
-      || code == DOT_PROD_EXPR
-      || code == WIDEN_SUM_EXPR
-      || code == SAD_EXPR)
+  bool lane_reduc_code_p
+    = (code == DOT_PROD_EXPR || code == WIDEN_SUM_EXPR || code == SAD_EXPR);
+  if (single_defuse_cycle || lane_reduc_code_p)
     {
       gcc_assert (code != COND_EXPR);
 
       /* 4. Supportable by target?  */
+      bool ok = true;
 
       /* 4.1. check support for the operation in the loop  */
-      optab optab = optab_for_tree_code (code, vectype_in, optab_default);
+      optab optab = optab_for_tree_code (code, vectype_in, optab_vector);
       if (!optab)
-        {
-          if (dump_enabled_p ())
+	{
+	  if (dump_enabled_p ())
 	    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
 			     "no optab.\n");
-
-          return false;
+	  ok = false;
         }
 
       machine_mode vec_mode = TYPE_MODE (vectype_in);
-      if (optab_handler (optab, vec_mode) == CODE_FOR_nothing)
+      if (ok && optab_handler (optab, vec_mode) == CODE_FOR_nothing)
         {
           if (dump_enabled_p ())
             dump_printf (MSG_NOTE, "op not supported by target.\n");
-
 	  if (maybe_ne (GET_MODE_SIZE (vec_mode), UNITS_PER_WORD)
 	      || !vect_worthwhile_without_simd_p (loop_vinfo, code))
-            return false;
-
-          if (dump_enabled_p ())
-	    dump_printf (MSG_NOTE, "proceeding using word mode.\n");
+	    ok = false;
+	  else
+	    if (dump_enabled_p ())
+	      dump_printf (MSG_NOTE, "proceeding using word mode.\n");
         }
 
       /* Worthwhile without SIMD support?  */
-      if (!VECTOR_MODE_P (TYPE_MODE (vectype_in))
+      if (ok
+	  && !VECTOR_MODE_P (TYPE_MODE (vectype_in))
 	  && !vect_worthwhile_without_simd_p (loop_vinfo, code))
         {
           if (dump_enabled_p ())
 	    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
 			     "not worthwhile without SIMD support.\n");
-
-          return false;
+	  ok = false;
         }
+
+      /* lane-reducing operations have to go through vect_transform_reduction.
+         For the other cases try without the single cycle optimization.  */
+      if (!ok)
+	{
+	  if (lane_reduc_code_p)
+	    return false;
+	  else
+	    single_defuse_cycle = false;
+	}
     }
+  STMT_VINFO_FORCE_SINGLE_CYCLE (reduc_info) = single_defuse_cycle;
 
   /* If the reduction stmt is one of the patterns that have lane
      reduction embedded we cannot handle the case of ! single_defuse_cycle.  */
-  if ((ncopies > 1
-       && ! single_defuse_cycle)
-      && (code == DOT_PROD_EXPR
-	  || code == WIDEN_SUM_EXPR
-	  || code == SAD_EXPR))
+  if ((ncopies > 1 && ! single_defuse_cycle)
+      && lane_reduc_code_p)
     {
       if (dump_enabled_p ())
 	dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,