6894206: JVM needs a way to traverse method handle structures

Summary: We need a way to walk chained method handles in the JVM to call the right methods and to generate required bytecode adapters for the compilers.
Reviewed-by: kvn

src/cpu/x86/vm/methodHandles_x86.cpp

@@ -268,8 +268,9 @@ void MethodHandles::remove_arg_slots(MacroAssembler* _masm,
 }
 
 #ifndef PRODUCT
+extern "C" void print_method_handle(oop mh);
 void trace_method_handle_stub(const char* adaptername,
-                              oopDesc* mh,
+                              oop mh,
                               intptr_t* entry_sp,
                               intptr_t* saved_sp,
                               intptr_t* saved_bp) {
@@ -280,6 +281,7 @@ void trace_method_handle_stub(const char* adaptername,
          adaptername, (intptr_t)mh, (intptr_t)entry_sp, (intptr_t)(saved_sp - entry_sp), (intptr_t)(base_sp - last_sp), (intptr_t)saved_bp);
   if (last_sp != saved_sp)
     printf("*** last_sp="INTPTR_FORMAT"\n", (intptr_t)last_sp);
+  if (Verbose)  print_method_handle(mh);
 }
 #endif //PRODUCT
 

src/share/vm/classfile/javaClasses.cpp

@@ -2403,6 +2403,10 @@ oop java_dyn_MethodType::ptype(oop mt, int idx) {
   return ptypes(mt)->obj_at(idx);
 }
 
+int java_dyn_MethodType::ptype_count(oop mt) {
+  return ptypes(mt)->length();
+}
+
 
 
 // Support for java_dyn_MethodTypeForm

src/share/vm/classfile/javaClasses.hpp

@@ -1027,6 +1027,7 @@ class java_dyn_MethodType: AllStatic {
   static oop            form(oop mt);
 
   static oop            ptype(oop mt, int index);
+  static int            ptype_count(oop mt);
 
   static symbolOop      as_signature(oop mt, bool intern_if_not_found, TRAPS);
   static void           print_signature(oop mt, outputStream* st);

src/share/vm/classfile/vmSymbols.cpp

 /*
- * Copyright 1997-2008 Sun Microsystems, Inc.  All Rights Reserved.
+ * Copyright 1997-2009 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
@@ -70,6 +70,7 @@ static const char* vm_symbol_bodies = VM_SYMBOLS_DO(VM_SYMBOL_BODY, VM_ALIAS_IGN
 void vmSymbols::initialize(TRAPS) {
   assert((int)SID_LIMIT <= (1<<log2_SID_LIMIT), "must fit in this bitfield");
   assert((int)SID_LIMIT*5 > (1<<log2_SID_LIMIT), "make the bitfield smaller, please");
+  assert(vmIntrinsics::FLAG_LIMIT <= (1 << vmIntrinsics::log2_FLAG_LIMIT), "must fit in this bitfield");
 
   if (!UseSharedSpaces) {
     const char* string = &vm_symbol_bodies[0];
@@ -271,6 +272,44 @@ vmSymbols::SID vmSymbols::find_sid(symbolOop symbol) {
   return sid;
 }
 
+static vmIntrinsics::ID wrapper_intrinsic(BasicType type, bool unboxing) {
+#define TYPE2(type, unboxing) ((int)(type)*2 + ((unboxing) ? 1 : 0))
+  switch (TYPE2(type, unboxing)) {
+#define BASIC_TYPE_CASE(type, box, unbox) \
+    case TYPE2(type, false):  return vmIntrinsics::box; \
+    case TYPE2(type, true):   return vmIntrinsics::unbox
+    BASIC_TYPE_CASE(T_BOOLEAN, _Boolean_valueOf,   _booleanValue);
+    BASIC_TYPE_CASE(T_BYTE,    _Byte_valueOf,      _byteValue);
+    BASIC_TYPE_CASE(T_CHAR,    _Character_valueOf, _charValue);
+    BASIC_TYPE_CASE(T_SHORT,   _Short_valueOf,     _shortValue);
+    BASIC_TYPE_CASE(T_INT,     _Integer_valueOf,   _intValue);
+    BASIC_TYPE_CASE(T_LONG,    _Long_valueOf,      _longValue);
+    BASIC_TYPE_CASE(T_FLOAT,   _Float_valueOf,     _floatValue);
+    BASIC_TYPE_CASE(T_DOUBLE,  _Double_valueOf,    _doubleValue);
+#undef BASIC_TYPE_CASE
+  }
+#undef TYPE2
+  return vmIntrinsics::_none;
+}
+
+vmIntrinsics::ID vmIntrinsics::for_boxing(BasicType type) {
+  return wrapper_intrinsic(type, false);
+}
+vmIntrinsics::ID vmIntrinsics::for_unboxing(BasicType type) {
+  return wrapper_intrinsic(type, true);
+}
+
+methodOop vmIntrinsics::method_for(vmIntrinsics::ID id) {
+  if (id == _none)  return NULL;
+  symbolOop cname = vmSymbols::symbol_at(class_for(id));
+  symbolOop mname = vmSymbols::symbol_at(name_for(id));
+  symbolOop msig  = vmSymbols::symbol_at(signature_for(id));
+  if (cname == NULL || mname == NULL || msig == NULL)  return NULL;
+  klassOop k = SystemDictionary::find_well_known_klass(cname);
+  if (k == NULL)  return NULL;
+  return instanceKlass::cast(k)->find_method(mname, msig);
+}
+
 
 #define VM_INTRINSIC_INITIALIZE(id, klass, name, sig, flags) #id "\0"
 static const char* vm_intrinsic_name_bodies =
@@ -330,12 +369,12 @@ inline bool match_F_RNY(jshort flags) {
 }
 
 // These are for forming case labels:
-#define ID3(x, y, z) (( jint)(z) +                                  \
-                      ((jint)(y) <<    vmSymbols::log2_SID_LIMIT) + \
-                      ((jint)(x) << (2*vmSymbols::log2_SID_LIMIT))  )
+#define ID3(x, y, z) (( jlong)(z) +                                  \
+                      ((jlong)(y) <<    vmSymbols::log2_SID_LIMIT) + \
+                      ((jlong)(x) << (2*vmSymbols::log2_SID_LIMIT))  )
 #define SID_ENUM(n) vmSymbols::VM_SYMBOL_ENUM_NAME(n)
 
-vmIntrinsics::ID vmIntrinsics::find_id(vmSymbols::SID holder,
+vmIntrinsics::ID vmIntrinsics::find_id_impl(vmSymbols::SID holder,
                                             vmSymbols::SID name,
                                             vmSymbols::SID sig,
                                             jshort flags) {
@@ -383,62 +422,50 @@ const char* vmIntrinsics::short_name_as_C_string(vmIntrinsics::ID id, char* buf,
 }
 
 
-// These are for friendly printouts of intrinsics:
+// These are to get information about intrinsics.
 
-vmSymbols::SID vmIntrinsics::class_for(vmIntrinsics::ID id) {
-#ifndef PRODUCT
-#define VM_INTRINSIC_CASE(id, klass, name, sig, fcode) \
-  case id: return SID_ENUM(klass);
+#define ID4(x, y, z, f) ((ID3(x, y, z) << vmIntrinsics::log2_FLAG_LIMIT) | (jlong) (f))
 
-  switch (id) {
-    VM_INTRINSICS_DO(VM_INTRINSIC_CASE,
-                     VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_ALIAS_IGNORE);
-  }
-#undef VM_INTRINSIC_CASE
-#endif //PRODUCT
-  return vmSymbols::NO_SID;
+static const jlong intrinsic_info_array[vmIntrinsics::ID_LIMIT+1] = {
+#define VM_INTRINSIC_INFO(ignore_id, klass, name, sig, fcode) \
+  ID4(SID_ENUM(klass), SID_ENUM(name), SID_ENUM(sig), vmIntrinsics::fcode),
+
+  0, VM_INTRINSICS_DO(VM_INTRINSIC_INFO,
+                     VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_ALIAS_IGNORE)
+    0
+#undef VM_INTRINSIC_INFO
+};
+
+inline jlong intrinsic_info(vmIntrinsics::ID id) {
+  return intrinsic_info_array[vmIntrinsics::ID_from((int)id)];
 }
 
-vmSymbols::SID vmIntrinsics::name_for(vmIntrinsics::ID id) {
-#ifndef PRODUCT
-#define VM_INTRINSIC_CASE(id, klass, name, sig, fcode) \
-  case id: return SID_ENUM(name);
+vmSymbols::SID vmIntrinsics::class_for(vmIntrinsics::ID id) {
+  jlong info = intrinsic_info(id);
+  int shift = 2*vmSymbols::log2_SID_LIMIT + log2_FLAG_LIMIT, mask = right_n_bits(vmSymbols::log2_SID_LIMIT);
+  assert(((ID4(1021,1022,1023,15) >> shift) & mask) == 1021, "");
+  return vmSymbols::SID( (info >> shift) & mask );
+}
 
-  switch (id) {
-    VM_INTRINSICS_DO(VM_INTRINSIC_CASE,
-                     VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_ALIAS_IGNORE);
-  }
-#undef VM_INTRINSIC_CASE
-#endif //PRODUCT
-  return vmSymbols::NO_SID;
+vmSymbols::SID vmIntrinsics::name_for(vmIntrinsics::ID id) {
+  jlong info = intrinsic_info(id);
+  int shift = vmSymbols::log2_SID_LIMIT + log2_FLAG_LIMIT, mask = right_n_bits(vmSymbols::log2_SID_LIMIT);
+  assert(((ID4(1021,1022,1023,15) >> shift) & mask) == 1022, "");
+  return vmSymbols::SID( (info >> shift) & mask );
 }
 
 vmSymbols::SID vmIntrinsics::signature_for(vmIntrinsics::ID id) {
-#ifndef PRODUCT
-#define VM_INTRINSIC_CASE(id, klass, name, sig, fcode) \
-  case id: return SID_ENUM(sig);
-
-  switch (id) {
-    VM_INTRINSICS_DO(VM_INTRINSIC_CASE,
-                     VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_ALIAS_IGNORE);
-  }
-#undef VM_INTRINSIC_CASE
-#endif //PRODUCT
-  return vmSymbols::NO_SID;
+  jlong info = intrinsic_info(id);
+  int shift = log2_FLAG_LIMIT, mask = right_n_bits(vmSymbols::log2_SID_LIMIT);
+  assert(((ID4(1021,1022,1023,15) >> shift) & mask) == 1023, "");
+  return vmSymbols::SID( (info >> shift) & mask );
 }
 
 vmIntrinsics::Flags vmIntrinsics::flags_for(vmIntrinsics::ID id) {
-#ifndef PRODUCT
-#define VM_INTRINSIC_CASE(id, klass, name, sig, fcode) \
-  case id: return fcode;
-
-  switch (id) {
-    VM_INTRINSICS_DO(VM_INTRINSIC_CASE,
-                     VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_SYMBOL_IGNORE, VM_ALIAS_IGNORE);
-  }
-#undef VM_INTRINSIC_CASE
-#endif //PRODUCT
-  return F_none;
+  jlong info = intrinsic_info(id);
+  int shift = 0, mask = right_n_bits(log2_FLAG_LIMIT);
+  assert(((ID4(1021,1022,1023,15) >> shift) & mask) == 15, "");
+  return Flags( (info >> shift) & mask );
 }
 
 

src/share/vm/classfile/vmSymbols.hpp

@@ -346,9 +346,14 @@
                                                                                                   \
   /* common signatures names */                                                                   \
   template(void_method_signature,                     "()V")                                      \
+  template(void_boolean_signature,                    "()Z")                                      \
+  template(void_byte_signature,                       "()B")                                      \
+  template(void_char_signature,                       "()C")                                      \
+  template(void_short_signature,                      "()S")                                      \
   template(void_int_signature,                        "()I")                                      \
   template(void_long_signature,                       "()J")                                      \
-  template(void_boolean_signature,                    "()Z")                                      \
+  template(void_float_signature,                      "()F")                                      \
+  template(void_double_signature,                     "()D")                                      \
   template(int_void_signature,                        "(I)V")                                     \
   template(int_int_signature,                         "(I)I")                                     \
   template(int_bool_signature,                        "(I)Z")                                     \
@@ -853,6 +858,46 @@
                                                                                                                           \
   do_intrinsic(_invoke,                   java_lang_reflect_Method, invoke_name, object_array_object_object_signature, F_R) \
   /*   (symbols invoke_name and invoke_signature defined above) */                                                      \
+  do_intrinsic(_checkSpreadArgument,      sun_dyn_MethodHandleImpl, checkSpreadArgument_name, checkSpreadArgument_signature, F_S) \
+   do_name(    checkSpreadArgument_name,       "checkSpreadArgument")                                                   \
+   do_name(    checkSpreadArgument_signature,  "(Ljava/lang/Object;I)V")                                                \
+                                                                                                                        \
+  /* unboxing methods: */                                                                                               \
+  do_intrinsic(_booleanValue,             java_lang_Boolean,      booleanValue_name, void_boolean_signature, F_R)       \
+   do_name(     booleanValue_name,       "booleanValue")                                                                \
+  do_intrinsic(_byteValue,                java_lang_Byte,         byteValue_name, void_byte_signature, F_R)             \
+   do_name(     byteValue_name,          "byteValue")                                                                   \
+  do_intrinsic(_charValue,                java_lang_Character,    charValue_name, void_char_signature, F_R)             \
+   do_name(     charValue_name,          "charValue")                                                                   \
+  do_intrinsic(_shortValue,               java_lang_Short,        shortValue_name, void_short_signature, F_R)           \
+   do_name(     shortValue_name,         "shortValue")                                                                  \
+  do_intrinsic(_intValue,                 java_lang_Integer,      intValue_name, void_int_signature, F_R)               \
+   do_name(     intValue_name,           "intValue")                                                                    \
+  do_intrinsic(_longValue,                java_lang_Long,         longValue_name, void_long_signature, F_R)             \
+   do_name(     longValue_name,          "longValue")                                                                   \
+  do_intrinsic(_floatValue,               java_lang_Float,        floatValue_name, void_float_signature, F_R)           \
+   do_name(     floatValue_name,         "floatValue")                                                                  \
+  do_intrinsic(_doubleValue,              java_lang_Double,       doubleValue_name, void_double_signature, F_R)         \
+   do_name(     doubleValue_name,        "doubleValue")                                                                 \
+                                                                                                                        \
+  /* boxing methods: */                                                                                                 \
+   do_name(    valueOf_name,              "valueOf")                                                                    \
+  do_intrinsic(_Boolean_valueOf,          java_lang_Boolean,      valueOf_name, Boolean_valueOf_signature, F_S)         \
+   do_name(     Boolean_valueOf_signature,                       "(Z)Ljava/lang/Boolean;")                              \
+  do_intrinsic(_Byte_valueOf,             java_lang_Byte,         valueOf_name, Byte_valueOf_signature, F_S)            \
+   do_name(     Byte_valueOf_signature,                          "(B)Ljava/lang/Byte;")                                 \
+  do_intrinsic(_Character_valueOf,        java_lang_Character,    valueOf_name, Character_valueOf_signature, F_S)       \
+   do_name(     Character_valueOf_signature,                     "(C)Ljava/lang/Character;")                            \
+  do_intrinsic(_Short_valueOf,            java_lang_Short,        valueOf_name, Short_valueOf_signature, F_S)           \
+   do_name(     Short_valueOf_signature,                         "(S)Ljava/lang/Short;")                                \
+  do_intrinsic(_Integer_valueOf,          java_lang_Integer,      valueOf_name, Integer_valueOf_signature, F_S)         \
+   do_name(     Integer_valueOf_signature,                       "(I)Ljava/lang/Integer;")                              \
+  do_intrinsic(_Long_valueOf,             java_lang_Long,         valueOf_name, Long_valueOf_signature, F_S)            \
+   do_name(     Long_valueOf_signature,                          "(J)Ljava/lang/Long;")                                 \
+  do_intrinsic(_Float_valueOf,            java_lang_Float,        valueOf_name, Float_valueOf_signature, F_S)           \
+   do_name(     Float_valueOf_signature,                         "(F)Ljava/lang/Float;")                                \
+  do_intrinsic(_Double_valueOf,           java_lang_Double,       valueOf_name, Double_valueOf_signature, F_S)          \
+   do_name(     Double_valueOf_signature,                        "(D)Ljava/lang/Double;")                               \
                                                                                                                         \
     /*end*/
 
@@ -983,7 +1028,12 @@ class vmIntrinsics: AllStatic {
     F_Y,                        // !static ?native  synchronized
     F_RN,                       // !static  native !synchronized
     F_SN,                       //  static  native !synchronized
-    F_RNY                       // !static  native  synchronized
+    F_RNY,                      // !static  native  synchronized
+
+    FLAG_LIMIT
+  };
+  enum {
+    log2_FLAG_LIMIT = 4         // checked by an assert at start-up
   };
 
 public:
@@ -995,15 +1045,32 @@ public:
 
   static const char* name_at(ID id);
 
+private:
+  static ID find_id_impl(vmSymbols::SID holder,
+                         vmSymbols::SID name,
+                         vmSymbols::SID sig,
+                         jshort flags);
+
+public:
   // Given a method's class, name, signature, and access flags, report its ID.
   static ID find_id(vmSymbols::SID holder,
                     vmSymbols::SID name,
                     vmSymbols::SID sig,
-                    jshort flags);
+                    jshort flags) {
+    ID id = find_id_impl(holder, name, sig, flags);
+#ifdef ASSERT
+    // ID _none does not hold the following asserts.
+    if (id == _none)  return id;
+#endif
+    assert(    class_for(id) == holder, "correct id");
+    assert(     name_for(id) == name,   "correct id");
+    assert(signature_for(id) == sig,    "correct id");
+    return id;
+  }
 
   static void verify_method(ID actual_id, methodOop m) PRODUCT_RETURN;
 
-  // No need for these in the product:
+  // Find out the symbols behind an intrinsic:
   static vmSymbols::SID     class_for(ID id);
   static vmSymbols::SID      name_for(ID id);
   static vmSymbols::SID signature_for(ID id);
@@ -1013,4 +1080,8 @@ public:
 
   // Access to intrinsic methods:
   static methodOop method_for(ID id);
+
+  // Wrapper object methods:
+  static ID for_boxing(BasicType type);
+  static ID for_unboxing(BasicType type);
 };

src/share/vm/includeDB_core

@@ -2814,6 +2814,10 @@ methodDataOop.hpp                       oop.hpp
 methodDataOop.hpp                       orderAccess.hpp
 methodDataOop.hpp                       universe.hpp
 
+methodHandleWalk.hpp                    methodHandles.hpp
+
+methodHandleWalk.cpp                    methodHandleWalk.hpp
+
 methodHandles.hpp                       frame.inline.hpp
 methodHandles.hpp                       globals.hpp
 methodHandles.hpp                       interfaceSupport.hpp

src/share/vm/prims/methodHandleWalk.hpp

+/*
+ * Copyright 2008-2010 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.
+ *
+ */
+
+// Low-level parser for method handle chains.
+class MethodHandleChain : StackObj {
+public:
+  typedef MethodHandles::EntryKind EntryKind;
+
+private:
+  Handle        _root;          // original target
+  Handle        _method_handle; // current target
+  bool          _is_last;       // final guy in chain
+  bool          _is_bound;      // has a bound argument
+  BasicType     _arg_type;      // if is_bound, the bound argument type
+  int           _arg_slot;      // if is_bound or is_adapter, affected argument slot
+  jint          _conversion;    // conversion field of AMH or -1
+  methodHandle  _last_method;   // if is_last, which method we target
+  Bytecodes::Code _last_invoke; // if is_last, type of invoke
+  const char*   _lose_message;  // saved argument to lose()
+
+  void set_method_handle(Handle target, TRAPS);
+  void set_last_method(oop target, TRAPS);
+  static BasicType compute_bound_arg_type(oop target, methodOop m, int arg_slot, TRAPS);
+
+  oop MethodHandle_type_oop()     { return java_dyn_MethodHandle::type(method_handle_oop()); }
+  oop MethodHandle_vmtarget_oop() { return java_dyn_MethodHandle::vmtarget(method_handle_oop()); }
+  int MethodHandle_vmslots()      { return java_dyn_MethodHandle::vmslots(method_handle_oop()); }
+  int DirectMethodHandle_vmindex()     { return sun_dyn_DirectMethodHandle::vmindex(method_handle_oop()); }
+  oop BoundMethodHandle_argument_oop() { return sun_dyn_BoundMethodHandle::argument(method_handle_oop()); }
+  int BoundMethodHandle_vmargslot()    { return sun_dyn_BoundMethodHandle::vmargslot(method_handle_oop()); }
+  int AdapterMethodHandle_conversion() { return sun_dyn_AdapterMethodHandle::conversion(method_handle_oop()); }
+
+public:
+  MethodHandleChain(Handle root, TRAPS)
+    : _root(root)
+  { set_method_handle(root, THREAD); }
+
+  bool is_adapter()             { return _conversion != -1; }
+  bool is_bound()               { return _is_bound; }
+  bool is_last()                { return _is_last; }
+
+  void next(TRAPS) {
+    assert(!is_last(), "");
+    set_method_handle(MethodHandle_vmtarget_oop(), THREAD);
+  }
+
+  Handle method_handle()        { return _method_handle; }
+  oop    method_handle_oop()    { return _method_handle(); }
+  oop    method_type_oop()      { return MethodHandle_type_oop(); }
+
+  jint adapter_conversion()     { assert(is_adapter(), ""); return _conversion; }
+  int  adapter_conversion_op()  { return MethodHandles::adapter_conversion_op(adapter_conversion()); }
+  BasicType adapter_conversion_src_type()
+                                { return MethodHandles::adapter_conversion_src_type(adapter_conversion()); }
+  BasicType adapter_conversion_dest_type()
+                                { return MethodHandles::adapter_conversion_dest_type(adapter_conversion()); }
+  int  adapter_conversion_stack_move()
+                                { return MethodHandles::adapter_conversion_stack_move(adapter_conversion()); }
+  int  adapter_conversion_stack_pushes()
+                                { return adapter_conversion_stack_move() / MethodHandles::stack_move_unit(); }
+  int  adapter_conversion_vminfo()
+                                { return MethodHandles::adapter_conversion_vminfo(adapter_conversion()); }
+  int adapter_arg_slot()        { assert(is_adapter(), ""); return _arg_slot; }
+  oop adapter_arg_oop()         { assert(is_adapter(), ""); return BoundMethodHandle_argument_oop(); }
+
+  BasicType bound_arg_type()    { assert(is_bound(), ""); return _arg_type; }
+  int       bound_arg_slot()    { assert(is_bound(), ""); return _arg_slot; }
+  oop       bound_arg_oop()     { assert(is_bound(), ""); return BoundMethodHandle_argument_oop(); }
+
+  methodOop last_method_oop()   { assert(is_last(), ""); return _last_method(); }
+  Bytecodes::Code last_invoke_code() { assert(is_last(), ""); return _last_invoke; }
+
+  void lose(const char* msg, TRAPS);
+  const char* lose_message()    { return _lose_message; }
+};
+
+
+// Structure walker for method handles.
+// Does abstract interpretation on top of low-level parsing.
+// You supply the tokens shuffled by the abstract interpretation.
+class MethodHandleWalker : StackObj {
+public:
+  struct _ArgToken { };  // dummy struct
+  typedef _ArgToken* ArgToken;
+
+  // Abstract interpretation state:
+  struct SlotState {
+    BasicType _type;
+    ArgToken  _arg;
+    SlotState() : _type(), _arg() {}
+  };
+  static SlotState make_state(BasicType type, ArgToken arg) {
+    SlotState ss;
+    ss._type = type; ss._arg = arg;
+    return ss;
+  }
+
+private:
+  MethodHandleChain _chain;
+
+  GrowableArray<SlotState> _outgoing;  // current outgoing parameter slots
+  int                      _outgoing_argc;  // # non-empty outgoing slots
+
+  // Replace a value of type old_type at slot (and maybe slot+1) with the new value.
+  // If old_type != T_VOID, remove the old argument at that point.
+  // If new_type != T_VOID, insert the new argument at that point.
+  // Insert or delete a second empty slot as needed.
+  void change_argument(BasicType old_type, int slot, BasicType new_type, ArgToken new_arg);
+
+  SlotState* slot_state(int slot) {
+    if (slot < 0 || slot >= _outgoing.length())
+      return NULL;
+    return _outgoing.adr_at(slot);
+  }
+  BasicType slot_type(int slot) {
+    SlotState* ss = slot_state(slot);
+    if (ss == NULL)
+      return T_ILLEGAL;
+    return ss->_type;
+  }
+  bool slot_has_argument(int slot) {
+    return slot_type(slot) < T_VOID;
+  }
+
+#ifdef ASSERT
+  int argument_count_slow();
+#endif
+
+  // Return a bytecode for converting src to dest, if one exists.
+  Bytecodes::Code conversion_code(BasicType src, BasicType dest);
+
+  void walk_incoming_state(TRAPS);
+
+public:
+  MethodHandleWalker(Handle root, TRAPS)
+    : _chain(root, THREAD),
+      _outgoing(THREAD, 10),
+      _outgoing_argc(0)
+  { }
+
+  MethodHandleChain& chain() { return _chain; }
+
+  // plug-in abstract interpretation steps:
+  virtual ArgToken make_parameter( BasicType type, klassOop tk, int argnum, TRAPS ) = 0;
+  virtual ArgToken make_prim_constant( BasicType type, jvalue* con, TRAPS ) = 0;
+  virtual ArgToken make_oop_constant( oop con, TRAPS ) = 0;
+  virtual ArgToken make_conversion( BasicType type, klassOop tk, Bytecodes::Code op, ArgToken src, TRAPS ) = 0;
+  virtual ArgToken make_fetch( BasicType type, klassOop tk, Bytecodes::Code op, ArgToken base, ArgToken offset, TRAPS ) = 0;
+  virtual ArgToken make_invoke( methodOop m, vmIntrinsics::ID iid, Bytecodes::Code op, bool tailcall, int argc, ArgToken* argv, TRAPS ) = 0;
+
+  // For make_invoke, the methodOop can be NULL if the intrinsic ID
+  // is something other than vmIntrinsics::_none.
+
+  // and in case anyone cares to related the previous actions to the chain:
+  virtual void set_method_handle(oop mh) { }
+
+  void lose(const char* msg, TRAPS) { chain().lose(msg, THREAD); }
+  const char* lose_message()        { return chain().lose_message(); }
+
+  ArgToken walk(TRAPS);
+};
+
+
+// An abstract interpreter for method handle chains.
+// Produces an account of the semantics of a chain, in terms of a static IR.
+// The IR happens to be JVM bytecodes.
+class MethodHandleCompiler : public MethodHandleWalker {
+private:
+  Thread* _thread;
+
+  struct PrimCon {
+    BasicType _type;
+    jvalue    _value;
+  };
+
+  // Accumulated compiler state:
+  stringStream _bytes;
+  GrowableArray<Handle>   _constant_oops;
+  GrowableArray<PrimCon*> _constant_prims;
+  int _max_stack;
+  int _num_params;
+  int _max_locals;
+  int _name_index;
+  int _signature_index;
+
+  // Stack values:
+  enum TokenType {
+    tt_void,
+    tt_parameter,
+    tt_temporary,
+    tt_constant
+  };
+
+  ArgToken make_stack_value(TokenType tt, BasicType type, int id) {
+    return ArgToken( ((intptr_t)id << 8) | ((intptr_t)type << 4) | (intptr_t)tt );
+  }
+
+public:
+  virtual ArgToken make_parameter(BasicType type, klassOop tk, int argnum, TRAPS) {
+    return make_stack_value(tt_parameter, type, argnum);
+  }
+  virtual ArgToken make_oop_constant(oop con, TRAPS) {
+    return make_stack_value(tt_constant, T_OBJECT, find_oop_constant(con));
+  }
+  virtual ArgToken make_prim_constant(BasicType type, jvalue* con, TRAPS) {
+    return make_stack_value(tt_constant, type, find_prim_constant(type, con));
+  }
+  virtual ArgToken make_conversion(BasicType type, klassOop tk, Bytecodes::Code op, ArgToken src, TRAPS);
+  virtual ArgToken make_fetch(BasicType type, klassOop tk, Bytecodes::Code op, ArgToken base, ArgToken offset, TRAPS);
+  virtual ArgToken make_invoke(methodOop m, vmIntrinsics::ID iid, Bytecodes::Code op, bool tailcall, int argc, ArgToken* argv, TRAPS);
+
+  int find_oop_constant(oop con);
+  int find_prim_constant(BasicType type, jvalue* con);
+
+public:
+  MethodHandleCompiler(Handle root, TRAPS)
+    : MethodHandleWalker(root, THREAD),
+      _thread(THREAD),
+      _bytes(50),
+      _constant_oops(THREAD, 10),
+      _constant_prims(THREAD, 10),
+      _max_stack(0), _max_locals(0),
+      _name_index(0), _signature_index(0)
+  { }
+  const char* bytes()         { return _bytes.as_string(); }
+  int constant_length()       { return _constant_oops.length(); }
+  int max_stack()             { return _max_stack; }
+  int max_locals()            { return _max_locals; }
+  int name_index()            { return _name_index; }
+  int signature_index()       { return _signature_index; }
+  symbolHandle name()         { return symbolHandle(_thread, (symbolOop)constant_oop_at(_name_index)()); }
+  symbolHandle signature()    { return symbolHandle(_thread, (symbolOop)constant_oop_at(_signature_index)()); }
+
+  bool constant_is_oop_at(int i) {
+    return (_constant_prims.at(i) == NULL);
+  }
+  Handle constant_oop_at(int i) {
+    assert(constant_is_oop_at(i), "");
+    return _constant_oops.at(i);
+  }
+  PrimCon* constant_prim_at(int i) {
+    assert(!constant_is_oop_at(i), "");
+    return _constant_prims.at(i);
+  }
+
+  // Compile the given MH chain into bytecode.
+  void compile(TRAPS);
+};