6924259: Remove String.count/String.offset

Summary: Allow a version of String class that doesn't have count and offset fields.
Reviewed-by: never, coleenp

12 files changed, 366 insertions, 192 deletions

diff --git a/src/cpu/sparc/vm/c1_LIRAssembler_sparc.cpp b/src/cpu/sparc/vm/c1_LIRAssembler_sparc.cpp
index 904489e3a..b2587e4d8 100644
--- a/src/cpu/sparc/vm/c1_LIRAssembler_sparc.cpp
+++ b/src/cpu/sparc/vm/c1_LIRAssembler_sparc.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2012, Oracle and/or its affiliates. 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
@@ -238,9 +238,12 @@ void LIR_Assembler::emit_string_compare(LIR_Opr left, LIR_Opr right, LIR_Opr dst
 
   Register result = dst->as_register();
   {
-    // Get a pointer to the first character of string0 in tmp0 and get string0.count in str0
-    // Get a pointer to the first character of string1 in tmp1 and get string1.count in str1
-    // Also, get string0.count-string1.count in o7 and get the condition code set
+    // Get a pointer to the first character of string0 in tmp0
+    //   and get string0.length() in str0
+    // Get a pointer to the first character of string1 in tmp1
+    //   and get string1.length() in str1
+    // Also, get string0.length()-string1.length() in
+    //   o7 and get the condition code set
     // Note: some instructions have been hoisted for better instruction scheduling
 
     Register tmp0 = L0;
@@ -248,27 +251,40 @@ void LIR_Assembler::emit_string_compare(LIR_Opr left, LIR_Opr right, LIR_Opr dst
     Register tmp2 = L2;
 
     int  value_offset = java_lang_String:: value_offset_in_bytes(); // char array
-    int offset_offset = java_lang_String::offset_offset_in_bytes(); // first character position
-    int  count_offset = java_lang_String:: count_offset_in_bytes();
-
-    __ load_heap_oop(str0, value_offset, tmp0);
-    __ ld(str0, offset_offset, tmp2);
-    __ add(tmp0, arrayOopDesc::base_offset_in_bytes(T_CHAR), tmp0);
-    __ ld(str0, count_offset, str0);
-    __ sll(tmp2, exact_log2(sizeof(jchar)), tmp2);
+    if (java_lang_String::has_offset_field()) {
+      int offset_offset = java_lang_String::offset_offset_in_bytes(); // first character position
+      int  count_offset = java_lang_String:: count_offset_in_bytes();
+      __ load_heap_oop(str0, value_offset, tmp0);
+      __ ld(str0, offset_offset, tmp2);
+      __ add(tmp0, arrayOopDesc::base_offset_in_bytes(T_CHAR), tmp0);
+      __ ld(str0, count_offset, str0);
+      __ sll(tmp2, exact_log2(sizeof(jchar)), tmp2);
+    } else {
+      __ load_heap_oop(str0, value_offset, tmp1);
+      __ add(tmp1, arrayOopDesc::base_offset_in_bytes(T_CHAR), tmp0);
+      __ ld(tmp1, arrayOopDesc::length_offset_in_bytes(), str0);
+    }
 
     // str1 may be null
     add_debug_info_for_null_check_here(info);
 
-    __ load_heap_oop(str1, value_offset, tmp1);
-    __ add(tmp0, tmp2, tmp0);
-
-    __ ld(str1, offset_offset, tmp2);
-    __ add(tmp1, arrayOopDesc::base_offset_in_bytes(T_CHAR), tmp1);
-    __ ld(str1, count_offset, str1);
-    __ sll(tmp2, exact_log2(sizeof(jchar)), tmp2);
+    if (java_lang_String::has_offset_field()) {
+      int offset_offset = java_lang_String::offset_offset_in_bytes(); // first character position
+      int  count_offset = java_lang_String:: count_offset_in_bytes();
+      __ load_heap_oop(str1, value_offset, tmp1);
+      __ add(tmp0, tmp2, tmp0);
+
+      __ ld(str1, offset_offset, tmp2);
+      __ add(tmp1, arrayOopDesc::base_offset_in_bytes(T_CHAR), tmp1);
+      __ ld(str1, count_offset, str1);
+      __ sll(tmp2, exact_log2(sizeof(jchar)), tmp2);
+      __ add(tmp1, tmp2, tmp1);
+    } else {
+      __ load_heap_oop(str1, value_offset, tmp2);
+      __ add(tmp2, arrayOopDesc::base_offset_in_bytes(T_CHAR), tmp1);
+      __ ld(tmp2, arrayOopDesc::length_offset_in_bytes(), str1);
+    }
     __ subcc(str0, str1, O7);
-    __ add(tmp1, tmp2, tmp1);
   }
 
   {
@@ -302,7 +318,7 @@ void LIR_Assembler::emit_string_compare(LIR_Opr left, LIR_Opr right, LIR_Opr dst
     // Shift base0 and base1 to the end of the arrays, negate limit
     __ add(base0, limit, base0);
     __ add(base1, limit, base1);
-    __ neg(limit);  // limit = -min{string0.count, strin1.count}
+    __ neg(limit);  // limit = -min{string0.length(), string1.length()}
 
     __ lduh(base0, limit, chr0);
     __ bind(Lloop);
diff --git a/src/cpu/x86/vm/c1_LIRAssembler_x86.cpp b/src/cpu/x86/vm/c1_LIRAssembler_x86.cpp
index a7cc42e49..4b2f8699e 100644
--- a/src/cpu/x86/vm/c1_LIRAssembler_x86.cpp
+++ b/src/cpu/x86/vm/c1_LIRAssembler_x86.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2012, Oracle and/or its affiliates. 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
@@ -505,19 +505,28 @@ void LIR_Assembler::emit_string_compare(LIR_Opr arg0, LIR_Opr arg1, LIR_Opr dst,
 
   // Get addresses of first characters from both Strings
   __ load_heap_oop(rsi, Address(rax, java_lang_String::value_offset_in_bytes()));
-  __ movptr       (rcx, Address(rax, java_lang_String::offset_offset_in_bytes()));
-  __ lea          (rsi, Address(rsi, rcx, Address::times_2, arrayOopDesc::base_offset_in_bytes(T_CHAR)));
-
+  if (java_lang_String::has_offset_field()) {
+    __ movptr     (rcx, Address(rax, java_lang_String::offset_offset_in_bytes()));
+    __ movl       (rax, Address(rax, java_lang_String::count_offset_in_bytes()));
+    __ lea        (rsi, Address(rsi, rcx, Address::times_2, arrayOopDesc::base_offset_in_bytes(T_CHAR)));
+  } else {
+    __ movl       (rax, Address(rsi, arrayOopDesc::length_offset_in_bytes()));
+    __ lea        (rsi, Address(rsi, arrayOopDesc::base_offset_in_bytes(T_CHAR)));
+  }
 
   // rbx, may be NULL
   add_debug_info_for_null_check_here(info);
   __ load_heap_oop(rdi, Address(rbx, java_lang_String::value_offset_in_bytes()));
-  __ movptr       (rcx, Address(rbx, java_lang_String::offset_offset_in_bytes()));
-  __ lea          (rdi, Address(rdi, rcx, Address::times_2, arrayOopDesc::base_offset_in_bytes(T_CHAR)));
+  if (java_lang_String::has_offset_field()) {
+    __ movptr     (rcx, Address(rbx, java_lang_String::offset_offset_in_bytes()));
+    __ movl       (rbx, Address(rbx, java_lang_String::count_offset_in_bytes()));
+    __ lea        (rdi, Address(rdi, rcx, Address::times_2, arrayOopDesc::base_offset_in_bytes(T_CHAR)));
+  } else {
+    __ movl       (rbx, Address(rdi, arrayOopDesc::length_offset_in_bytes()));
+    __ lea        (rdi, Address(rdi, arrayOopDesc::base_offset_in_bytes(T_CHAR)));
+  }
 
   // compute minimum length (in rax) and difference of lengths (on top of stack)
-  __ movl  (rbx, Address(rbx, java_lang_String::count_offset_in_bytes()));
-  __ movl  (rax, Address(rax, java_lang_String::count_offset_in_bytes()));
   __ mov   (rcx, rbx);
   __ subptr(rbx, rax); // subtract lengths
   __ push  (rbx);      // result
diff --git a/src/share/vm/classfile/javaClasses.cpp b/src/share/vm/classfile/javaClasses.cpp
index b5e887f74..eab75e181 100644
--- a/src/share/vm/classfile/javaClasses.cpp
+++ b/src/share/vm/classfile/javaClasses.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2012, Oracle and/or its affiliates. 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
@@ -143,7 +143,27 @@ compute_optional_offset(int& dest_offset,
 }
 
 
+int java_lang_String::value_offset  = 0;
+int java_lang_String::offset_offset = 0;
+int java_lang_String::count_offset  = 0;
+int java_lang_String::hash_offset   = 0;
+
+bool java_lang_String::initialized  = false;
+
+void java_lang_String::compute_offsets() {
+  assert(!initialized, "offsets should be initialized only once");
+
+  klassOop k = SystemDictionary::String_klass();
+  compute_offset(value_offset,           k, vmSymbols::value_name(),  vmSymbols::char_array_signature());
+  compute_optional_offset(offset_offset, k, vmSymbols::offset_name(), vmSymbols::int_signature());
+  compute_optional_offset(count_offset,  k, vmSymbols::count_name(),  vmSymbols::int_signature());
+  compute_optional_offset(hash_offset,   k, vmSymbols::hash_name(),   vmSymbols::int_signature());
+
+  initialized = true;
+}
+
 Handle java_lang_String::basic_create(int length, bool tenured, TRAPS) {
+  assert(initialized, "Must be initialized");
   // Create the String object first, so there's a chance that the String
   // and the char array it points to end up in the same cache line.
   oop obj;
@@ -2837,10 +2857,6 @@ int java_lang_System::err_offset_in_bytes() {
 
 
 
-int java_lang_String::value_offset;
-int java_lang_String::offset_offset;
-int java_lang_String::count_offset;
-int java_lang_String::hash_offset;
 int java_lang_Class::_klass_offset;
 int java_lang_Class::_array_klass_offset;
 int java_lang_Class::_resolved_constructor_offset;
@@ -3000,12 +3016,6 @@ void JavaClasses::compute_hard_coded_offsets() {
   const int x = heapOopSize;
   const int header = instanceOopDesc::base_offset_in_bytes();
 
-  // Do the String Class
-  java_lang_String::value_offset  = java_lang_String::hc_value_offset  * x + header;
-  java_lang_String::offset_offset = java_lang_String::hc_offset_offset * x + header;
-  java_lang_String::count_offset  = java_lang_String::offset_offset + sizeof (jint);
-  java_lang_String::hash_offset   = java_lang_String::count_offset + sizeof (jint);
-
   // Throwable Class
   java_lang_Throwable::backtrace_offset  = java_lang_Throwable::hc_backtrace_offset  * x + header;
   java_lang_Throwable::detailMessage_offset = java_lang_Throwable::hc_detailMessage_offset * x + header;
@@ -3200,9 +3210,13 @@ void JavaClasses::check_offsets() {
   // java.lang.String
 
   CHECK_OFFSET("java/lang/String", java_lang_String, value, "[C");
-  CHECK_OFFSET("java/lang/String", java_lang_String, offset, "I");
-  CHECK_OFFSET("java/lang/String", java_lang_String, count, "I");
-  CHECK_OFFSET("java/lang/String", java_lang_String, hash, "I");
+  if (java_lang_String::has_offset_field()) {
+    CHECK_OFFSET("java/lang/String", java_lang_String, offset, "I");
+    CHECK_OFFSET("java/lang/String", java_lang_String, count, "I");
+  }
+  if (java_lang_String::has_hash_field()) {
+    CHECK_OFFSET("java/lang/String", java_lang_String, hash, "I");
+  }
 
   // java.lang.Class
 
diff --git a/src/share/vm/classfile/javaClasses.hpp b/src/share/vm/classfile/javaClasses.hpp
index 2a32801fc..708ea4f54 100644
--- a/src/share/vm/classfile/javaClasses.hpp
+++ b/src/share/vm/classfile/javaClasses.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2012, Oracle and/or its affiliates. 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
@@ -52,26 +52,36 @@
 
 class java_lang_String : AllStatic {
  private:
-  enum {
-    hc_value_offset  = 0,
-    hc_offset_offset = 1
-    //hc_count_offset = 2  -- not a word-scaled offset
-    //hc_hash_offset  = 3  -- not a word-scaled offset
-  };
-
   static int value_offset;
   static int offset_offset;
   static int count_offset;
   static int hash_offset;
 
+  static bool initialized;
+
   static Handle basic_create(int length, bool tenured, TRAPS);
   static Handle basic_create_from_unicode(jchar* unicode, int length, bool tenured, TRAPS);
 
-  static void set_value( oop string, typeArrayOop buffer) { string->obj_field_put(value_offset,  (oop)buffer); }
-  static void set_offset(oop string, int offset)          { string->int_field_put(offset_offset, offset); }
-  static void set_count( oop string, int count)           { string->int_field_put(count_offset,  count);  }
+  static void set_value( oop string, typeArrayOop buffer) {
+    assert(initialized, "Must be initialized");
+    string->obj_field_put(value_offset,  (oop)buffer);
+  }
+  static void set_offset(oop string, int offset) {
+    assert(initialized, "Must be initialized");
+    if (offset_offset > 0) {
+      string->int_field_put(offset_offset, offset);
+    }
+  }
+  static void set_count( oop string, int count) {
+    assert(initialized, "Must be initialized");
+    if (count_offset > 0) {
+      string->int_field_put(count_offset,  count);
+    }
+  }
 
  public:
+  static void compute_offsets();
+
   // Instance creation
   static Handle create_from_unicode(jchar* unicode, int len, TRAPS);
   static Handle create_tenured_from_unicode(jchar* unicode, int len, TRAPS);
@@ -82,23 +92,61 @@ class java_lang_String : AllStatic {
   static Handle create_from_platform_dependent_str(const char* str, TRAPS);
   static Handle char_converter(Handle java_string, jchar from_char, jchar to_char, TRAPS);
 
-  static int value_offset_in_bytes()  { return value_offset;  }
-  static int count_offset_in_bytes()  { return count_offset;  }
-  static int offset_offset_in_bytes() { return offset_offset; }
-  static int hash_offset_in_bytes()   { return hash_offset;   }
+  static bool has_offset_field()  {
+    assert(initialized, "Must be initialized");
+    return (offset_offset > 0);
+  }
+
+  static bool has_count_field()  {
+    assert(initialized, "Must be initialized");
+    return (count_offset > 0);
+  }
+
+  static bool has_hash_field()  {
+    assert(initialized, "Must be initialized");
+    return (hash_offset > 0);
+  }
+
+  static int value_offset_in_bytes()  {
+    assert(initialized && (value_offset > 0), "Must be initialized");
+    return value_offset;
+  }
+  static int count_offset_in_bytes()  {
+    assert(initialized && (count_offset > 0), "Must be initialized");
+    return count_offset;
+  }
+  static int offset_offset_in_bytes() {
+    assert(initialized && (offset_offset > 0), "Must be initialized");
+    return offset_offset;
+  }
+  static int hash_offset_in_bytes()   {
+    assert(initialized && (hash_offset > 0), "Must be initialized");
+    return hash_offset;
+  }
 
   // Accessors
   static typeArrayOop value(oop java_string) {
+    assert(initialized && (value_offset > 0), "Must be initialized");
     assert(is_instance(java_string), "must be java_string");
     return (typeArrayOop) java_string->obj_field(value_offset);
   }
   static int offset(oop java_string) {
+    assert(initialized, "Must be initialized");
     assert(is_instance(java_string), "must be java_string");
-    return java_string->int_field(offset_offset);
+    if (offset_offset > 0) {
+      return java_string->int_field(offset_offset);
+    } else {
+      return 0;
+    }
   }
   static int length(oop java_string) {
+    assert(initialized, "Must be initialized");
     assert(is_instance(java_string), "must be java_string");
-    return java_string->int_field(count_offset);
+    if (count_offset > 0) {
+      return java_string->int_field(count_offset);
+    } else {
+      return ((typeArrayOop)java_string->obj_field(value_offset))->length();
+    }
   }
   static int utf8_length(oop java_string);
 
diff --git a/src/share/vm/classfile/systemDictionary.cpp b/src/share/vm/classfile/systemDictionary.cpp
index 04bb9d9f5..0bdc16de6 100644
--- a/src/share/vm/classfile/systemDictionary.cpp
+++ b/src/share/vm/classfile/systemDictionary.cpp
@@ -1971,6 +1971,9 @@ void SystemDictionary::initialize_preloaded_classes(TRAPS) {
   // first do Object, String, Class
   initialize_wk_klasses_through(WK_KLASS_ENUM_NAME(Class_klass), scan, CHECK);
 
+  // Calculate offsets for String and Class classes since they are loaded and
+  // can be used after this point.
+  java_lang_String::compute_offsets();
   java_lang_Class::compute_offsets();
 
   // Fixup mirrors for classes loaded before java.lang.Class.
diff --git a/src/share/vm/classfile/vmSymbols.hpp b/src/share/vm/classfile/vmSymbols.hpp
index 9cee5ac04..b0d014575 100644
--- a/src/share/vm/classfile/vmSymbols.hpp
+++ b/src/share/vm/classfile/vmSymbols.hpp
@@ -340,6 +340,9 @@
   template(park_event_name,                           "nativeParkEventPointer")                   \
   template(cache_field_name,                          "cache")                                    \
   template(value_name,                                "value")                                    \
+  template(offset_name,                               "offset")                                   \
+  template(count_name,                                "count")                                    \
+  template(hash_name,                                 "hash")                                     \
   template(frontCacheEnabled_name,                    "frontCacheEnabled")                        \
   template(stringCacheEnabled_name,                   "stringCacheEnabled")                       \
   template(numberOfLeadingZeros_name,                 "numberOfLeadingZeros")                     \
diff --git a/src/share/vm/memory/dump.cpp b/src/share/vm/memory/dump.cpp
index af1d7928d..e91d33135 100644
--- a/src/share/vm/memory/dump.cpp
+++ b/src/share/vm/memory/dump.cpp
@@ -78,8 +78,8 @@ public:
   void do_oop(oop* p) {
     if (p != NULL) {
       oop obj = *p;
-      if (obj->klass() == SystemDictionary::String_klass()) {
-
+      if (obj->klass() == SystemDictionary::String_klass() &&
+          java_lang_String::has_hash_field()) {
         int hash = java_lang_String::hash_string(obj);
         obj->int_field_put(hash_offset, hash);
       }
diff --git a/src/share/vm/opto/graphKit.cpp b/src/share/vm/opto/graphKit.cpp
index 61d922760..b3dca9531 100644
--- a/src/share/vm/opto/graphKit.cpp
+++ b/src/share/vm/opto/graphKit.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2012, Oracle and/or its affiliates. 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
@@ -3748,3 +3748,81 @@ void GraphKit::g1_write_barrier_post(Node* oop_store,
   final_sync(ideal);
 }
 #undef __
+
+
+
+Node* GraphKit::load_String_offset(Node* ctrl, Node* str) {
+  if (java_lang_String::has_offset_field()) {
+    int offset_offset = java_lang_String::offset_offset_in_bytes();
+    const TypeInstPtr* string_type = TypeInstPtr::make(TypePtr::NotNull, C->env()->String_klass(),
+                                                       false, NULL, 0);
+    const TypePtr* offset_field_type = string_type->add_offset(offset_offset);
+    int offset_field_idx = C->get_alias_index(offset_field_type);
+    return make_load(ctrl,
+                     basic_plus_adr(str, str, offset_offset),
+                     TypeInt::INT, T_INT, offset_field_idx);
+  } else {
+    return intcon(0);
+  }
+}
+
+Node* GraphKit::load_String_length(Node* ctrl, Node* str) {
+  if (java_lang_String::has_count_field()) {
+    int count_offset = java_lang_String::count_offset_in_bytes();
+    const TypeInstPtr* string_type = TypeInstPtr::make(TypePtr::NotNull, C->env()->String_klass(),
+                                                       false, NULL, 0);
+    const TypePtr* count_field_type = string_type->add_offset(count_offset);
+    int count_field_idx = C->get_alias_index(count_field_type);
+    return make_load(ctrl,
+                     basic_plus_adr(str, str, count_offset),
+                     TypeInt::INT, T_INT, count_field_idx);
+  } else {
+    return load_array_length(load_String_value(ctrl, str));
+  }
+}
+
+Node* GraphKit::load_String_value(Node* ctrl, Node* str) {
+  int value_offset = java_lang_String::value_offset_in_bytes();
+  const TypeInstPtr* string_type = TypeInstPtr::make(TypePtr::NotNull, C->env()->String_klass(),
+                                                     false, NULL, 0);
+  const TypePtr* value_field_type = string_type->add_offset(value_offset);
+  const TypeAryPtr*  value_type = TypeAryPtr::make(TypePtr::NotNull,
+                                                   TypeAry::make(TypeInt::CHAR,TypeInt::POS),
+                                                   ciTypeArrayKlass::make(T_CHAR), true, 0);
+  int value_field_idx = C->get_alias_index(value_field_type);
+  return make_load(ctrl, basic_plus_adr(str, str, value_offset),
+                   value_type, T_OBJECT, value_field_idx);
+}
+
+void GraphKit::store_String_offset(Node* ctrl, Node* str, Node* value) {
+  int offset_offset = java_lang_String::offset_offset_in_bytes();
+  const TypeInstPtr* string_type = TypeInstPtr::make(TypePtr::NotNull, C->env()->String_klass(),
+                                                     false, NULL, 0);
+  const TypePtr* offset_field_type = string_type->add_offset(offset_offset);
+  int offset_field_idx = C->get_alias_index(offset_field_type);
+  store_to_memory(ctrl, basic_plus_adr(str, offset_offset),
+                  value, T_INT, offset_field_idx);
+}
+
+void GraphKit::store_String_value(Node* ctrl, Node* str, Node* value) {
+  int value_offset = java_lang_String::value_offset_in_bytes();
+  const TypeInstPtr* string_type = TypeInstPtr::make(TypePtr::NotNull, C->env()->String_klass(),
+                                                     false, NULL, 0);
+  const TypePtr* value_field_type = string_type->add_offset(value_offset);
+  const TypeAryPtr*  value_type = TypeAryPtr::make(TypePtr::NotNull,
+                                                   TypeAry::make(TypeInt::CHAR,TypeInt::POS),
+                                                   ciTypeArrayKlass::make(T_CHAR), true, 0);
+  int value_field_idx = C->get_alias_index(value_field_type);
+  store_to_memory(ctrl, basic_plus_adr(str, value_offset),
+                  value, T_OBJECT, value_field_idx);
+}
+
+void GraphKit::store_String_length(Node* ctrl, Node* str, Node* value) {
+  int count_offset = java_lang_String::count_offset_in_bytes();
+  const TypeInstPtr* string_type = TypeInstPtr::make(TypePtr::NotNull, C->env()->String_klass(),
+                                                     false, NULL, 0);
+  const TypePtr* count_field_type = string_type->add_offset(count_offset);
+  int count_field_idx = C->get_alias_index(count_field_type);
+  store_to_memory(ctrl, basic_plus_adr(str, count_offset),
+                  value, T_INT, count_field_idx);
+}
diff --git a/src/share/vm/opto/graphKit.hpp b/src/share/vm/opto/graphKit.hpp
index bffebc879..723e65e3b 100644
--- a/src/share/vm/opto/graphKit.hpp
+++ b/src/share/vm/opto/graphKit.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2012, Oracle and/or its affiliates. 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
@@ -781,6 +781,14 @@ class GraphKit : public Phase {
   Node* new_array(Node* klass_node, Node* count_val, int nargs,
                   Node* *return_size_val = NULL);
 
+  // java.lang.String helpers
+  Node* load_String_offset(Node* ctrl, Node* str);
+  Node* load_String_length(Node* ctrl, Node* str);
+  Node* load_String_value(Node* ctrl, Node* str);
+  void store_String_offset(Node* ctrl, Node* str, Node* value);
+  void store_String_length(Node* ctrl, Node* str, Node* value);
+  void store_String_value(Node* ctrl, Node* str, Node* value);
+
   // Handy for making control flow
   IfNode* create_and_map_if(Node* ctrl, Node* tst, float prob, float cnt) {
     IfNode* iff = new (C, 2) IfNode(ctrl, tst, prob, cnt);// New IfNode's
diff --git a/src/share/vm/opto/library_call.cpp b/src/share/vm/opto/library_call.cpp
index 13c3a4327..e0f5f9591 100644
--- a/src/share/vm/opto/library_call.cpp
+++ b/src/share/vm/opto/library_call.cpp
@@ -147,7 +147,8 @@ class LibraryCallKit : public GraphKit {
     return generate_method_call(method_id, true, false);
   }
 
-  Node* make_string_method_node(int opcode, Node* str1, Node* cnt1, Node* str2, Node* cnt2);
+  Node* make_string_method_node(int opcode, Node* str1_start, Node* cnt1, Node* str2_start, Node* cnt2);
+  Node* make_string_method_node(int opcode, Node* str1, Node* str2);
   bool inline_string_compareTo();
   bool inline_string_indexOf();
   Node* string_indexOf(Node* string_object, ciTypeArray* target_array, jint offset, jint cache_i, jint md2_i);
@@ -873,48 +874,76 @@ Node* LibraryCallKit::generate_current_thread(Node* &tls_output) {
 
 
 //------------------------------make_string_method_node------------------------
-// Helper method for String intrinsic finctions.
-Node* LibraryCallKit::make_string_method_node(int opcode, Node* str1, Node* cnt1, Node* str2, Node* cnt2) {
-  const int value_offset  = java_lang_String::value_offset_in_bytes();
-  const int count_offset  = java_lang_String::count_offset_in_bytes();
-  const int offset_offset = java_lang_String::offset_offset_in_bytes();
-
+// Helper method for String intrinsic functions. This version is called
+// with str1 and str2 pointing to String object nodes.
+//
+Node* LibraryCallKit::make_string_method_node(int opcode, Node* str1, Node* str2) {
   Node* no_ctrl = NULL;
 
-  ciInstanceKlass* klass = env()->String_klass();
-  const TypeOopPtr* string_type = TypeOopPtr::make_from_klass(klass);
-
-  const TypeAryPtr* value_type =
-        TypeAryPtr::make(TypePtr::NotNull,
-                         TypeAry::make(TypeInt::CHAR,TypeInt::POS),
-                         ciTypeArrayKlass::make(T_CHAR), true, 0);
-
-  // Get start addr of string and substring
-  Node* str1_valuea  = basic_plus_adr(str1, str1, value_offset);
-  Node* str1_value   = make_load(no_ctrl, str1_valuea, value_type, T_OBJECT, string_type->add_offset(value_offset));
-  Node* str1_offseta = basic_plus_adr(str1, str1, offset_offset);
-  Node* str1_offset  = make_load(no_ctrl, str1_offseta, TypeInt::INT, T_INT, string_type->add_offset(offset_offset));
+  // Get start addr of string
+  Node* str1_value   = load_String_value(no_ctrl, str1);
+  Node* str1_offset  = load_String_offset(no_ctrl, str1);
   Node* str1_start   = array_element_address(str1_value, str1_offset, T_CHAR);
 
-  Node* str2_valuea  = basic_plus_adr(str2, str2, value_offset);
-  Node* str2_value   = make_load(no_ctrl, str2_valuea, value_type, T_OBJECT, string_type->add_offset(value_offset));
-  Node* str2_offseta = basic_plus_adr(str2, str2, offset_offset);
-  Node* str2_offset  = make_load(no_ctrl, str2_offseta, TypeInt::INT, T_INT, string_type->add_offset(offset_offset));
+  // Get length of string 1
+  Node* str1_len  = load_String_length(no_ctrl, str1);
+
+  Node* str2_value   = load_String_value(no_ctrl, str2);
+  Node* str2_offset  = load_String_offset(no_ctrl, str2);
   Node* str2_start   = array_element_address(str2_value, str2_offset, T_CHAR);
 
+  Node* str2_len = NULL;
+  Node* result = NULL;
+
+  switch (opcode) {
+  case Op_StrIndexOf:
+    // Get length of string 2
+    str2_len = load_String_length(no_ctrl, str2);
+
+    result = new (C, 6) StrIndexOfNode(control(), memory(TypeAryPtr::CHARS),
+                                 str1_start, str1_len, str2_start, str2_len);
+    break;
+  case Op_StrComp:
+    // Get length of string 2
+    str2_len = load_String_length(no_ctrl, str2);
+
+    result = new (C, 6) StrCompNode(control(), memory(TypeAryPtr::CHARS),
+                                 str1_start, str1_len, str2_start, str2_len);
+    break;
+  case Op_StrEquals:
+    result = new (C, 5) StrEqualsNode(control(), memory(TypeAryPtr::CHARS),
+                               str1_start, str2_start, str1_len);
+    break;
+  default:
+    ShouldNotReachHere();
+    return NULL;
+  }
+
+  // All these intrinsics have checks.
+  C->set_has_split_ifs(true); // Has chance for split-if optimization
+
+  return _gvn.transform(result);
+}
+
+// Helper method for String intrinsic functions. This version is called
+// with str1 and str2 pointing to char[] nodes, with cnt1 and cnt2 pointing
+// to Int nodes containing the lenghts of str1 and str2.
+//
+Node* LibraryCallKit::make_string_method_node(int opcode, Node* str1_start, Node* cnt1, Node* str2_start, Node* cnt2) {
+
   Node* result = NULL;
   switch (opcode) {
   case Op_StrIndexOf:
     result = new (C, 6) StrIndexOfNode(control(), memory(TypeAryPtr::CHARS),
-                                       str1_start, cnt1, str2_start, cnt2);
+                                 str1_start, cnt1, str2_start, cnt2);
     break;
   case Op_StrComp:
     result = new (C, 6) StrCompNode(control(), memory(TypeAryPtr::CHARS),
-                                    str1_start, cnt1, str2_start, cnt2);
+                                 str1_start, cnt1, str2_start, cnt2);
     break;
   case Op_StrEquals:
     result = new (C, 5) StrEqualsNode(control(), memory(TypeAryPtr::CHARS),
-                                      str1_start, str2_start, cnt1);
+                                 str1_start, str2_start, cnt1);
     break;
   default:
     ShouldNotReachHere();
@@ -932,10 +961,6 @@ bool LibraryCallKit::inline_string_compareTo() {
 
   if (!Matcher::has_match_rule(Op_StrComp)) return false;
 
-  const int value_offset = java_lang_String::value_offset_in_bytes();
-  const int count_offset = java_lang_String::count_offset_in_bytes();
-  const int offset_offset = java_lang_String::offset_offset_in_bytes();
-
   _sp += 2;
   Node *argument = pop();  // pop non-receiver first:  it was pushed second
   Node *receiver = pop();
@@ -952,18 +977,7 @@ bool LibraryCallKit::inline_string_compareTo() {
     return true;
   }
 
-  ciInstanceKlass* klass = env()->String_klass();
-  const TypeOopPtr* string_type = TypeOopPtr::make_from_klass(klass);
-  Node* no_ctrl = NULL;
-
-  // Get counts for string and argument
-  Node* receiver_cnta = basic_plus_adr(receiver, receiver, count_offset);
-  Node* receiver_cnt  = make_load(no_ctrl, receiver_cnta, TypeInt::INT, T_INT, string_type->add_offset(count_offset));
-
-  Node* argument_cnta = basic_plus_adr(argument, argument, count_offset);
-  Node* argument_cnt  = make_load(no_ctrl, argument_cnta, TypeInt::INT, T_INT, string_type->add_offset(count_offset));
-
-  Node* compare = make_string_method_node(Op_StrComp, receiver, receiver_cnt, argument, argument_cnt);
+  Node* compare = make_string_method_node(Op_StrComp, receiver, argument);
   push(compare);
   return true;
 }
@@ -973,10 +987,6 @@ bool LibraryCallKit::inline_string_equals() {
 
   if (!Matcher::has_match_rule(Op_StrEquals)) return false;
 
-  const int value_offset = java_lang_String::value_offset_in_bytes();
-  const int count_offset = java_lang_String::count_offset_in_bytes();
-  const int offset_offset = java_lang_String::offset_offset_in_bytes();
-
   int nargs = 2;
   _sp += nargs;
   Node* argument = pop();  // pop non-receiver first:  it was pushed second
@@ -1030,24 +1040,31 @@ bool LibraryCallKit::inline_string_equals() {
     }
   }
 
-  const TypeOopPtr* string_type = TypeOopPtr::make_from_klass(klass);
-
-  Node* no_ctrl = NULL;
-  Node* receiver_cnt;
-  Node* argument_cnt;
-
   if (!stopped()) {
+    const TypeOopPtr* string_type = TypeOopPtr::make_from_klass(klass);
+
     // Properly cast the argument to String
     argument = _gvn.transform(new (C, 2) CheckCastPPNode(control(), argument, string_type));
     // This path is taken only when argument's type is String:NotNull.
     argument = cast_not_null(argument, false);
 
-    // Get counts for string and argument
-    Node* receiver_cnta = basic_plus_adr(receiver, receiver, count_offset);
-    receiver_cnt  = make_load(no_ctrl, receiver_cnta, TypeInt::INT, T_INT, string_type->add_offset(count_offset));
+    Node* no_ctrl = NULL;
+
+    // Get start addr of receiver
+    Node* receiver_val    = load_String_value(no_ctrl, receiver);
+    Node* receiver_offset = load_String_offset(no_ctrl, receiver);
+    Node* receiver_start = array_element_address(receiver_val, receiver_offset, T_CHAR);
+
+    // Get length of receiver
+    Node* receiver_cnt  = load_String_length(no_ctrl, receiver);
 
-    Node* argument_cnta = basic_plus_adr(argument, argument, count_offset);
-    argument_cnt  = make_load(no_ctrl, argument_cnta, TypeInt::INT, T_INT, string_type->add_offset(count_offset));
+    // Get start addr of argument
+    Node* argument_val   = load_String_value(no_ctrl, argument);
+    Node* argument_offset = load_String_offset(no_ctrl, argument);
+    Node* argument_start = array_element_address(argument_val, argument_offset, T_CHAR);
+
+    // Get length of argument
+    Node* argument_cnt  = load_String_length(no_ctrl, argument);
 
     // Check for receiver count != argument count
     Node* cmp = _gvn.transform( new(C, 3) CmpINode(receiver_cnt, argument_cnt) );
@@ -1057,14 +1074,14 @@ bool LibraryCallKit::inline_string_equals() {
       phi->init_req(4, intcon(0));
       region->init_req(4, if_ne);
     }
-  }
 
-  // Check for count == 0 is done by mach node StrEquals.
+    // Check for count == 0 is done by assembler code for StrEquals.
 
-  if (!stopped()) {
-    Node* equals = make_string_method_node(Op_StrEquals, receiver, receiver_cnt, argument, argument_cnt);
-    phi->init_req(1, equals);
-    region->init_req(1, control());
+    if (!stopped()) {
+      Node* equals = make_string_method_node(Op_StrEquals, receiver_start, receiver_cnt, argument_start, argument_cnt);
+      phi->init_req(1, equals);
+      region->init_req(1, control());
+    }
   }
 
   // post merge
@@ -1162,20 +1179,9 @@ Node* LibraryCallKit::string_indexOf(Node* string_object, ciTypeArray* target_ar
 
   const int nargs = 2; // number of arguments to push back for uncommon trap in predicate
 
-  const int value_offset  = java_lang_String::value_offset_in_bytes();
-  const int count_offset  = java_lang_String::count_offset_in_bytes();
-  const int offset_offset = java_lang_String::offset_offset_in_bytes();
-
-  ciInstanceKlass* klass = env()->String_klass();
-  const TypeOopPtr* string_type = TypeOopPtr::make_from_klass(klass);
-  const TypeAryPtr*  source_type = TypeAryPtr::make(TypePtr::NotNull, TypeAry::make(TypeInt::CHAR,TypeInt::POS), ciTypeArrayKlass::make(T_CHAR), true, 0);
-
-  Node* sourceOffseta = basic_plus_adr(string_object, string_object, offset_offset);
-  Node* sourceOffset  = make_load(no_ctrl, sourceOffseta, TypeInt::INT, T_INT, string_type->add_offset(offset_offset));
-  Node* sourceCounta  = basic_plus_adr(string_object, string_object, count_offset);
-  Node* sourceCount   = make_load(no_ctrl, sourceCounta, TypeInt::INT, T_INT, string_type->add_offset(count_offset));
-  Node* sourcea       = basic_plus_adr(string_object, string_object, value_offset);
-  Node* source        = make_load(no_ctrl, sourcea, source_type, T_OBJECT, string_type->add_offset(value_offset));
+  Node* source        = load_String_value(no_ctrl, string_object);
+  Node* sourceOffset  = load_String_offset(no_ctrl, string_object);
+  Node* sourceCount   = load_String_length(no_ctrl, string_object);
 
   Node* target = _gvn.transform( makecon(TypeOopPtr::make_from_constant(target_array, true)) );
   jint target_length = target_array->length();
@@ -1243,10 +1249,6 @@ Node* LibraryCallKit::string_indexOf(Node* string_object, ciTypeArray* target_ar
 //------------------------------inline_string_indexOf------------------------
 bool LibraryCallKit::inline_string_indexOf() {
 
-  const int value_offset  = java_lang_String::value_offset_in_bytes();
-  const int count_offset  = java_lang_String::count_offset_in_bytes();
-  const int offset_offset = java_lang_String::offset_offset_in_bytes();
-
   _sp += 2;
   Node *argument = pop();  // pop non-receiver first:  it was pushed second
   Node *receiver = pop();
@@ -1280,12 +1282,21 @@ bool LibraryCallKit::inline_string_indexOf() {
     Node*       result_phi = new (C, 4) PhiNode(result_rgn, TypeInt::INT);
     Node* no_ctrl  = NULL;
 
-    // Get counts for string and substr
-    Node* source_cnta = basic_plus_adr(receiver, receiver, count_offset);
-    Node* source_cnt  = make_load(no_ctrl, source_cnta, TypeInt::INT, T_INT, string_type->add_offset(count_offset));
+    // Get start addr of source string
+    Node* source = load_String_value(no_ctrl, receiver);
+    Node* source_offset = load_String_offset(no_ctrl, receiver);
+    Node* source_start = array_element_address(source, source_offset, T_CHAR);
+
+    // Get length of source string
+    Node* source_cnt  = load_String_length(no_ctrl, receiver);
+
+    // Get start addr of substring
+    Node* substr = load_String_value(no_ctrl, argument);
+    Node* substr_offset = load_String_offset(no_ctrl, argument);
+    Node* substr_start = array_element_address(substr, substr_offset, T_CHAR);
 
-    Node* substr_cnta = basic_plus_adr(argument, argument, count_offset);
-    Node* substr_cnt  = make_load(no_ctrl, substr_cnta, TypeInt::INT, T_INT, string_type->add_offset(count_offset));
+    // Get length of source string
+    Node* substr_cnt  = load_String_length(no_ctrl, argument);
 
     // Check for substr count > string count
     Node* cmp = _gvn.transform( new(C, 3) CmpINode(substr_cnt, source_cnt) );
@@ -1308,7 +1319,7 @@ bool LibraryCallKit::inline_string_indexOf() {
     }
 
     if (!stopped()) {
-      result = make_string_method_node(Op_StrIndexOf, receiver, source_cnt, argument, substr_cnt);
+      result = make_string_method_node(Op_StrIndexOf, source_start, source_cnt, substr_start, substr_cnt);
       result_phi->init_req(1, result);
       result_rgn->init_req(1, control());
     }
@@ -1333,11 +1344,19 @@ bool LibraryCallKit::inline_string_indexOf() {
     ciInstance* str = str_const->as_instance();
     assert(str != NULL, "must be instance");
 
-    ciObject* v = str->field_value_by_offset(value_offset).as_object();
-    int       o = str->field_value_by_offset(offset_offset).as_int();
-    int       c = str->field_value_by_offset(count_offset).as_int();
+    ciObject* v = str->field_value_by_offset(java_lang_String::value_offset_in_bytes()).as_object();
     ciTypeArray* pat = v->as_type_array(); // pattern (argument) character array
 
+    int o;
+    int c;
+    if (java_lang_String::has_offset_field()) {
+      o = str->field_value_by_offset(java_lang_String::offset_offset_in_bytes()).as_int();
+      c = str->field_value_by_offset(java_lang_String::count_offset_in_bytes()).as_int();
+    } else {
+      o = 0;
+      c = pat->length();
+    }
+
     // constant strings have no offset and count == length which
     // simplifies the resulting code somewhat so lets optimize for that.
     if (o != 0 || c != pat->length()) {
diff --git a/src/share/vm/opto/stringopts.cpp b/src/share/vm/opto/stringopts.cpp
index 496e7a883..99498ea95 100644
--- a/src/share/vm/opto/stringopts.cpp
+++ b/src/share/vm/opto/stringopts.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2009, 2012, Oracle and/or its affiliates. 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
@@ -528,16 +528,6 @@ PhaseStringOpts::PhaseStringOpts(PhaseGVN* gvn, Unique_Node_List*):
   }
 
   // Collect the types needed to talk about the various slices of memory
-  const TypeInstPtr* string_type = TypeInstPtr::make(TypePtr::NotNull, C->env()->String_klass(),
-                                                     false, NULL, 0);
-
-  const TypePtr* value_field_type = string_type->add_offset(java_lang_String::value_offset_in_bytes());
-  const TypePtr* offset_field_type = string_type->add_offset(java_lang_String::offset_offset_in_bytes());
-  const TypePtr* count_field_type = string_type->add_offset(java_lang_String::count_offset_in_bytes());
-
-  value_field_idx = C->get_alias_index(value_field_type);
-  count_field_idx = C->get_alias_index(count_field_type);
-  offset_field_idx = C->get_alias_index(offset_field_type);
   char_adr_idx = C->get_alias_index(TypeAryPtr::CHARS);
 
   // For each locally allocated StringBuffer see if the usages can be
@@ -1174,18 +1164,9 @@ void PhaseStringOpts::int_getChars(GraphKit& kit, Node* arg, Node* char_array, N
 
 Node* PhaseStringOpts::copy_string(GraphKit& kit, Node* str, Node* char_array, Node* start) {
   Node* string = str;
-  Node* offset = kit.make_load(kit.control(),
-                               kit.basic_plus_adr(string, string, java_lang_String::offset_offset_in_bytes()),
-                               TypeInt::INT, T_INT, offset_field_idx);
-  Node* count = kit.make_load(kit.control(),
-                              kit.basic_plus_adr(string, string, java_lang_String::count_offset_in_bytes()),
-                              TypeInt::INT, T_INT, count_field_idx);
-  const TypeAryPtr*  value_type = TypeAryPtr::make(TypePtr::NotNull,
-                                                   TypeAry::make(TypeInt::CHAR,TypeInt::POS),
-                                                   ciTypeArrayKlass::make(T_CHAR), true, 0);
-  Node* value = kit.make_load(kit.control(),
-                              kit.basic_plus_adr(string, string, java_lang_String::value_offset_in_bytes()),
-                              value_type, T_OBJECT, value_field_idx);
+  Node* offset = kit.load_String_offset(kit.control(), string);
+  Node* count  = kit.load_String_length(kit.control(), string);
+  Node* value  = kit.load_String_value (kit.control(), string);
 
   // copy the contents
   if (offset->is_Con() && count->is_Con() && value->is_Con() && count->get_int() < unroll_string_copy_length) {
@@ -1342,10 +1323,9 @@ void PhaseStringOpts::replace_string_concat(StringConcat* sc) {
           arg = phi;
           sc->set_argument(argi, arg);
         }
-        //         Node* offset = kit.make_load(NULL, kit.basic_plus_adr(arg, arg, offset_offset),
-        //                                      TypeInt::INT, T_INT, offset_field_idx);
-        Node* count = kit.make_load(kit.control(), kit.basic_plus_adr(arg, arg, java_lang_String::count_offset_in_bytes()),
-                                    TypeInt::INT, T_INT, count_field_idx);
+
+        Node* count = kit.load_String_length(kit.control(), arg);
+
         length = __ AddI(length, count);
         string_sizes->init_req(argi, NULL);
         break;
@@ -1436,12 +1416,11 @@ void PhaseStringOpts::replace_string_concat(StringConcat* sc) {
   }
 
   // Intialize the string
-  kit.store_to_memory(kit.control(), kit.basic_plus_adr(result, java_lang_String::offset_offset_in_bytes()),
-                      __ intcon(0), T_INT, offset_field_idx);
-  kit.store_to_memory(kit.control(), kit.basic_plus_adr(result, java_lang_String::count_offset_in_bytes()),
-                      length, T_INT, count_field_idx);
-  kit.store_to_memory(kit.control(), kit.basic_plus_adr(result, java_lang_String::value_offset_in_bytes()),
-                      char_array, T_OBJECT, value_field_idx);
+  if (java_lang_String::has_offset_field()) {
+    kit.store_String_offset(kit.control(), result, __ intcon(0));
+    kit.store_String_length(kit.control(), result, length);
+  }
+  kit.store_String_value(kit.control(), result, char_array);
 
   // hook up the outgoing control and result
   kit.replace_call(sc->end(), result);
diff --git a/src/share/vm/opto/stringopts.hpp b/src/share/vm/opto/stringopts.hpp
index 1ffe6c309..0fb1ed70f 100644
--- a/src/share/vm/opto/stringopts.hpp
+++ b/src/share/vm/opto/stringopts.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2009, 2012, Oracle and/or its affiliates. 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
@@ -41,9 +41,6 @@ class PhaseStringOpts : public Phase {
 
   // 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;