[3/n] PR85694: Fix dummy assignment handling in vectorizable_call

vectorizable_call stubs out the original scalar statement with
a dummy assignment to the same lhs, so that we don't leave any bogus
scalar calls around.  If the call is actually a pattern statement,
the code rightly took the lhs of the original bb statement:

  if (is_pattern_stmt_p (stmt_info))
    lhs = gimple_call_lhs (STMT_VINFO_RELATED_STMT (stmt_info));
  else
    lhs = gimple_call_lhs (stmt);

But it then associated the new statement with the stmt_vec_info of the
pattern statement rather than the bb statement, which meant we had two
stmt_vec_infos assigning to the same lhs.  This seems to be latent at
the moment but caused problems further into the series.

2018-06-20  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vect-stmts.c (vectorizable_call): Make sure that we
	use the stmt_vec_info of the original bb statement for the
	new zero assignment, even if the call is part of a pattern.

From-SVN: r261786

gcc/ChangeLog

 2018-06-20  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* tree-vect-stmts.c (vectorizable_call): Make sure that we
+	use the stmt_vec_info of the original bb statement for the
+	new zero assignment, even if the call is part of a pattern.
+
+2018-06-20  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* tree-vectorizer.h (_stmt_vec_info): Note above pattern_def_seq
 	that the sequence is attached to the original statement rather
 	than the pattern statement.

gcc/tree-vect-stmts.c

@@ -3605,13 +3605,12 @@ vectorizable_call (gimple *gs, gimple_stmt_iterator *gsi, gimple **vec_stmt,
 
   type = TREE_TYPE (scalar_dest);
   if (is_pattern_stmt_p (stmt_info))
-    lhs = gimple_call_lhs (STMT_VINFO_RELATED_STMT (stmt_info));
-  else
-    lhs = gimple_call_lhs (stmt);
+    stmt_info = vinfo_for_stmt (STMT_VINFO_RELATED_STMT (stmt_info));
+  lhs = gimple_get_lhs (stmt_info->stmt);
 
   new_stmt = gimple_build_assign (lhs, build_zero_cst (type));
   set_vinfo_for_stmt (new_stmt, stmt_info);
-  set_vinfo_for_stmt (stmt, NULL);
+  set_vinfo_for_stmt (stmt_info->stmt, NULL);
   STMT_VINFO_STMT (stmt_info) = new_stmt;
   gsi_replace (gsi, new_stmt, false);