6892658: C2 should optimize some stringbuilder patterns

Reviewed-by: kvn, twisti

hotspot/src/share/vm/opto/stringopts.hpp

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2009 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+class StringConcat;
+
+class PhaseStringOpts : public Phase {
+  friend class StringConcat;
+
+ private:
+  PhaseGVN* _gvn;
+
+  // List of dead nodes to clean up aggressively at the end
+  Unique_Node_List dead_worklist;
+
+  // Memory slices needed for code gen
+  int char_adr_idx;
+  int value_field_idx;
+  int count_field_idx;
+  int offset_field_idx;
+
+  // Integer.sizeTable - used for int to String conversion
+  ciField* size_table_field;
+
+  // A set for use by various stages
+  VectorSet _visited;
+
+  // Collect a list of all SB.toString calls
+  Node_List collect_toString_calls();
+
+  // Examine the use of the SB alloc to see if it can be replace with
+  // a single string construction.
+  StringConcat* build_candidate(CallStaticJavaNode* call);
+
+  // Replace all the SB calls in concat with an optimization String allocation
+  void replace_string_concat(StringConcat* concat);
+
+  // Load the value of a static field, performing any constant folding.
+  Node* fetch_static_field(GraphKit& kit, ciField* field);
+
+  // Compute the number of characters required to represent the int value
+  Node* int_stringSize(GraphKit& kit, Node* value);
+
+  // Copy the characters representing value into char_array starting at start
+  void int_getChars(GraphKit& kit, Node* value, Node* char_array, Node* start, Node* end);
+
+  // Copy of the contents of the String str into char_array starting at index start.
+  Node* copy_string(GraphKit& kit, Node* str, Node* char_array, Node* start);
+
+  // Clean up any leftover nodes
+  void record_dead_node(Node* node);
+  void remove_dead_nodes();
+
+  PhaseGVN* gvn() { return _gvn; }
+
+  enum {
+    // max length of constant string copy unrolling in copy_string
+    unroll_string_copy_length = 6
+  };
+
+ public:
+  PhaseStringOpts(PhaseGVN* gvn, Unique_Node_List* worklist);
+};