[09/46] Add vec_info::lookup_single_use

[Richard Sandiford <richard.sandiford@arm.com>]

This patch adds a helper function for seeing whether there is a single
user of an SSA name, and whether that user has a stmt_vec_info.


2018-07-24  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vectorizer.h (vec_info::lookup_single_use): Declare.
	* tree-vectorizer.c (vec_info::lookup_single_use): New function.
	* tree-vect-loop.c (vectorizable_reduction): Use it instead of
	a single_imm_use-based sequence.
	* tree-vect-stmts.c (supportable_widening_operation): Likewise.

Index: gcc/tree-vectorizer.h
===================================================================
--- gcc/tree-vectorizer.h	2018-07-24 10:22:27.285336715 +0100
+++ gcc/tree-vectorizer.h	2018-07-24 10:22:30.401309046 +0100
@@ -220,6 +220,7 @@ struct vec_info {
   stmt_vec_info add_stmt (gimple *);
   stmt_vec_info lookup_stmt (gimple *);
   stmt_vec_info lookup_def (tree);
+  stmt_vec_info lookup_single_use (tree);
 
   /* The type of vectorization.  */
   vec_kind kind;
Index: gcc/tree-vectorizer.c
===================================================================
--- gcc/tree-vectorizer.c	2018-07-24 10:22:27.285336715 +0100
+++ gcc/tree-vectorizer.c	2018-07-24 10:22:30.401309046 +0100
@@ -548,6 +548,20 @@ vec_info::lookup_def (tree name)
   return NULL;
 }
 
+/* See whether there is a single non-debug statement that uses LHS and
+   whether that statement has an associated stmt_vec_info.  Return the
+   stmt_vec_info if so, otherwise return null.  */
+
+stmt_vec_info
+vec_info::lookup_single_use (tree lhs)
+{
+  use_operand_p dummy;
+  gimple *use_stmt;
+  if (single_imm_use (lhs, &dummy, &use_stmt))
+    return lookup_stmt (use_stmt);
+  return NULL;
+}
+
 /* A helper function to free scev and LOOP niter information, as well as
    clear loop constraint LOOP_C_FINITE.  */
 
Index: gcc/tree-vect-loop.c
===================================================================
--- gcc/tree-vect-loop.c	2018-07-24 10:22:27.277336786 +0100
+++ gcc/tree-vect-loop.c	2018-07-24 10:22:30.401309046 +0100
@@ -6138,6 +6138,7 @@ vectorizable_reduction (gimple *stmt, gi
 
   if (gimple_code (stmt) == GIMPLE_PHI)
     {
+      tree phi_result = gimple_phi_result (stmt);
       /* Analysis is fully done on the reduction stmt invocation.  */
       if (! vec_stmt)
 	{
@@ -6158,7 +6159,8 @@ vectorizable_reduction (gimple *stmt, gi
       if (STMT_VINFO_IN_PATTERN_P (vinfo_for_stmt (reduc_stmt)))
 	reduc_stmt = STMT_VINFO_RELATED_STMT (vinfo_for_stmt (reduc_stmt));
 
-      if (STMT_VINFO_VEC_REDUCTION_TYPE (vinfo_for_stmt (reduc_stmt))
+      stmt_vec_info reduc_stmt_info = vinfo_for_stmt (reduc_stmt);
+      if (STMT_VINFO_VEC_REDUCTION_TYPE (reduc_stmt_info)
 	  == EXTRACT_LAST_REDUCTION)
 	/* Leave the scalar phi in place.  */
 	return true;
@@ -6185,15 +6187,12 @@ vectorizable_reduction (gimple *stmt, gi
       else
 	ncopies = vect_get_num_copies (loop_vinfo, vectype_in);
 
-      use_operand_p use_p;
-      gimple *use_stmt;
+      stmt_vec_info use_stmt_info;
       if (ncopies > 1
-	  && (STMT_VINFO_RELEVANT (vinfo_for_stmt (reduc_stmt))
-	      <= vect_used_only_live)
-	  && single_imm_use (gimple_phi_result (stmt), &use_p, &use_stmt)
-	  && (use_stmt == reduc_stmt
-	      || (STMT_VINFO_RELATED_STMT (vinfo_for_stmt (use_stmt))
-		  == reduc_stmt)))
+	  && STMT_VINFO_RELEVANT (reduc_stmt_info) <= vect_used_only_live
+	  && (use_stmt_info = loop_vinfo->lookup_single_use (phi_result))
+	  && (use_stmt_info == reduc_stmt_info
+	      || STMT_VINFO_RELATED_STMT (use_stmt_info) == reduc_stmt))
 	single_defuse_cycle = true;
 
       /* Create the destination vector  */
@@ -6955,13 +6954,13 @@ vectorizable_reduction (gimple *stmt, gi
    This only works when we see both the reduction PHI and its only consumer
    in vectorizable_reduction and there are no intermediate stmts
    participating.  */
-  use_operand_p use_p;
-  gimple *use_stmt;
+  stmt_vec_info use_stmt_info;
+  tree reduc_phi_result = gimple_phi_result (reduc_def_stmt);
   if (ncopies > 1
       && (STMT_VINFO_RELEVANT (stmt_info) <= vect_used_only_live)
-      && single_imm_use (gimple_phi_result (reduc_def_stmt), &use_p, &use_stmt)
-      && (use_stmt == stmt
-	  || STMT_VINFO_RELATED_STMT (vinfo_for_stmt (use_stmt)) == stmt))
+      && (use_stmt_info = loop_vinfo->lookup_single_use (reduc_phi_result))
+      && (use_stmt_info == stmt_info
+	  || STMT_VINFO_RELATED_STMT (use_stmt_info) == stmt))
     {
       single_defuse_cycle = true;
       epilog_copies = 1;
Index: gcc/tree-vect-stmts.c
===================================================================
--- gcc/tree-vect-stmts.c	2018-07-24 10:22:27.281336751 +0100
+++ gcc/tree-vect-stmts.c	2018-07-24 10:22:30.401309046 +0100
@@ -10310,14 +10310,11 @@ supportable_widening_operation (enum tre
              same operation.  One such an example is s += a * b, where elements
              in a and b cannot be reordered.  Here we check if the vector defined
              by STMT is only directly used in the reduction statement.  */
-          tree lhs = gimple_assign_lhs (stmt);
-          use_operand_p dummy;
-          gimple *use_stmt;
-          stmt_vec_info use_stmt_info = NULL;
-          if (single_imm_use (lhs, &dummy, &use_stmt)
-              && (use_stmt_info = vinfo_for_stmt (use_stmt))
-              && STMT_VINFO_DEF_TYPE (use_stmt_info) == vect_reduction_def)
-            return true;
+	  tree lhs = gimple_assign_lhs (stmt);
+	  stmt_vec_info use_stmt_info = loop_info->lookup_single_use (lhs);
+	  if (use_stmt_info
+	      && STMT_VINFO_DEF_TYPE (use_stmt_info) == vect_reduction_def)
+	    return true;
         }
       c1 = VEC_WIDEN_MULT_LO_EXPR;
       c2 = VEC_WIDEN_MULT_HI_EXPR;