--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/code/dependencies.hpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,550 @@
+/*
+ * Copyright 2005-2006 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.
+ *
+ */
+
+//** Dependencies represent assertions (approximate invariants) within
+// the class hierarchy.  An example is an assertion that a given
+// method is not overridden; another example is that a type has only
+// one concrete subtype.  Compiled code which relies on such
+// assertions must be discarded if they are overturned by changes in
+// the class hierarchy.  We can think of these assertions as
+// approximate invariants, because we expect them to be overturned
+// very infrequently.  We are willing to perform expensive recovery
+// operations when they are overturned.  The benefit, of course, is
+// performing optimistic optimizations (!) on the object code.
+//
+// Changes in the class hierarchy due to dynamic linking or
+// class evolution can violate dependencies.  There is enough
+// indexing between classes and nmethods to make dependency
+// checking reasonably efficient.
+
+class ciEnv;
+class nmethod;
+class OopRecorder;
+class xmlStream;
+class CompileLog;
+class DepChange;
+class No_Safepoint_Verifier;
+
+class Dependencies: public ResourceObj {
+ public:
+  // Note: In the comments on dependency types, most uses of the terms
+  // subtype and supertype are used in a "non-strict" or "inclusive"
+  // sense, and are starred to remind the reader of this fact.
+  // Strict uses of the terms use the word "proper".
+  //
+  // Specifically, every class is its own subtype* and supertype*.
+  // (This trick is easier than continually saying things like "Y is a
+  // subtype of X or X itself".)
+  //
+  // Sometimes we write X > Y to mean X is a proper supertype of Y.
+  // The notation X > {Y, Z} means X has proper subtypes Y, Z.
+  // The notation X.m > Y means that Y inherits m from X, while
+  // X.m > Y.m means Y overrides X.m.  A star denotes abstractness,
+  // as *I > A, meaning (abstract) interface I is a super type of A,
+  // or A.*m > B.m, meaning B.m implements abstract method A.m.
+  //
+  // In this module, the terms "subtype" and "supertype" refer to
+  // Java-level reference type conversions, as detected by
+  // "instanceof" and performed by "checkcast" operations.  The method
+  // Klass::is_subtype_of tests these relations.  Note that "subtype"
+  // is richer than "subclass" (as tested by Klass::is_subclass_of),
+  // since it takes account of relations involving interface and array
+  // types.
+  //
+  // To avoid needless complexity, dependencies involving array types
+  // are not accepted.  If you need to make an assertion about an
+  // array type, make the assertion about its corresponding element
+  // types.  Any assertion that might change about an array type can
+  // be converted to an assertion about its element type.
+  //
+  // Most dependencies are evaluated over a "context type" CX, which
+  // stands for the set Subtypes(CX) of every Java type that is a subtype*
+  // of CX.  When the system loads a new class or interface N, it is
+  // responsible for re-evaluating changed dependencies whose context
+  // type now includes N, that is, all super types of N.
+  //
+  enum DepType {
+    end_marker = 0,
+
+    // An 'evol' dependency simply notes that the contents of the
+    // method were used.  If it evolves (is replaced), the nmethod
+    // must be recompiled.  No other dependencies are implied.
+    evol_method,
+    FIRST_TYPE = evol_method,
+
+    // A context type CX is a leaf it if has no proper subtype.
+    leaf_type,
+
+    // An abstract class CX has exactly one concrete subtype CC.
+    abstract_with_unique_concrete_subtype,
+
+    // The type CX is purely abstract, with no concrete subtype* at all.
+    abstract_with_no_concrete_subtype,
+
+    // The concrete CX is free of concrete proper subtypes.
+    concrete_with_no_concrete_subtype,
+
+    // Given a method M1 and a context class CX, the set MM(CX, M1) of
+    // "concrete matching methods" in CX of M1 is the set of every
+    // concrete M2 for which it is possible to create an invokevirtual
+    // or invokeinterface call site that can reach either M1 or M2.
+    // That is, M1 and M2 share a name, signature, and vtable index.
+    // We wish to notice when the set MM(CX, M1) is just {M1}, or
+    // perhaps a set of two {M1,M2}, and issue dependencies on this.
+
+    // The set MM(CX, M1) can be computed by starting with any matching
+    // concrete M2 that is inherited into CX, and then walking the
+    // subtypes* of CX looking for concrete definitions.
+
+    // The parameters to this dependency are the method M1 and the
+    // context class CX.  M1 must be either inherited in CX or defined
+    // in a subtype* of CX.  It asserts that MM(CX, M1) is no greater
+    // than {M1}.
+    unique_concrete_method,       // one unique concrete method under CX
+
+    // An "exclusive" assertion concerns two methods or subtypes, and
+    // declares that there are at most two (or perhaps later N>2)
+    // specific items that jointly satisfy the restriction.
+    // We list all items explicitly rather than just giving their
+    // count, for robustness in the face of complex schema changes.
+
+    // A context class CX (which may be either abstract or concrete)
+    // has two exclusive concrete subtypes* C1, C2 if every concrete
+    // subtype* of CX is either C1 or C2.  Note that if neither C1 or C2
+    // are equal to CX, then CX itself must be abstract.  But it is
+    // also possible (for example) that C1 is CX (a concrete class)
+    // and C2 is a proper subtype of C1.
+    abstract_with_exclusive_concrete_subtypes_2,
+
+    // This dependency asserts that MM(CX, M1) is no greater than {M1,M2}.
+    exclusive_concrete_methods_2,
+
+    // This dependency asserts that no instances of class or it's
+    // subclasses require finalization registration.
+    no_finalizable_subclasses,
+
+    TYPE_LIMIT
+  };
+  enum {
+    LG2_TYPE_LIMIT = 4,  // assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT))
+
+    // handy categorizations of dependency types:
+    all_types      = ((1<<TYPE_LIMIT)-1) & ((-1)<<FIRST_TYPE),
+    non_ctxk_types = (1<<evol_method),
+    ctxk_types     = all_types & ~non_ctxk_types,
+
+    max_arg_count = 3,   // current maximum number of arguments (incl. ctxk)
+
+    // A "context type" is a class or interface that
+    // provides context for evaluating a dependency.
+    // When present, it is one of the arguments (dep_context_arg).
+    //
+    // If a dependency does not have a context type, there is a
+    // default context, depending on the type of the dependency.
+    // This bit signals that a default context has been compressed away.
+    default_context_type_bit = (1<<LG2_TYPE_LIMIT)
+  };
+
+  static const char* dep_name(DepType dept);
+  static int         dep_args(DepType dept);
+  static int  dep_context_arg(DepType dept) {
+    return dept_in_mask(dept, ctxk_types)? 0: -1;
+  }
+
+ private:
+  // State for writing a new set of dependencies:
+  GrowableArray<int>*       _dep_seen;  // (seen[h->ident] & (1<<dept))
+  GrowableArray<ciObject*>* _deps[TYPE_LIMIT];
+
+  static const char* _dep_name[TYPE_LIMIT];
+  static int         _dep_args[TYPE_LIMIT];
+
+  static bool dept_in_mask(DepType dept, int mask) {
+    return (int)dept >= 0 && dept < TYPE_LIMIT && ((1<<dept) & mask) != 0;
+  }
+
+  bool note_dep_seen(int dept, ciObject* x) {
+    assert(dept < BitsPerInt, "oob");
+    int x_id = x->ident();
+    assert(_dep_seen != NULL, "deps must be writable");
+    int seen = _dep_seen->at_grow(x_id, 0);
+    _dep_seen->at_put(x_id, seen | (1<<dept));
+    // return true if we've already seen dept/x
+    return (seen & (1<<dept)) != 0;
+  }
+
+  bool maybe_merge_ctxk(GrowableArray<ciObject*>* deps,
+                        int ctxk_i, ciKlass* ctxk);
+
+  void sort_all_deps();
+  size_t estimate_size_in_bytes();
+
+  // Initialize _deps, etc.
+  void initialize(ciEnv* env);
+
+  // State for making a new set of dependencies:
+  OopRecorder* _oop_recorder;
+
+  // Logging support
+  CompileLog* _log;
+
+  address  _content_bytes;  // everything but the oop references, encoded
+  size_t   _size_in_bytes;
+
+ public:
+  // Make a new empty dependencies set.
+  Dependencies(ciEnv* env) {
+    initialize(env);
+  }
+
+ private:
+  // Check for a valid context type.
+  // Enforce the restriction against array types.
+  static void check_ctxk(ciKlass* ctxk) {
+    assert(ctxk->is_instance_klass(), "java types only");
+  }
+  static void check_ctxk_concrete(ciKlass* ctxk) {
+    assert(is_concrete_klass(ctxk->as_instance_klass()), "must be concrete");
+  }
+  static void check_ctxk_abstract(ciKlass* ctxk) {
+    check_ctxk(ctxk);
+    assert(!is_concrete_klass(ctxk->as_instance_klass()), "must be abstract");
+  }
+
+  void assert_common_1(DepType dept, ciObject* x);
+  void assert_common_2(DepType dept, ciKlass* ctxk, ciObject* x);
+  void assert_common_3(DepType dept, ciKlass* ctxk, ciObject* x, ciObject* x2);
+
+ public:
+  // Adding assertions to a new dependency set at compile time:
+  void assert_evol_method(ciMethod* m);
+  void assert_leaf_type(ciKlass* ctxk);
+  void assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck);
+  void assert_abstract_with_no_concrete_subtype(ciKlass* ctxk);
+  void assert_concrete_with_no_concrete_subtype(ciKlass* ctxk);
+  void assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm);
+  void assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2);
+  void assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2);
+  void assert_has_no_finalizable_subclasses(ciKlass* ctxk);
+
+  // Define whether a given method or type is concrete.
+  // These methods define the term "concrete" as used in this module.
+  // For this module, an "abstract" class is one which is non-concrete.
+  //
+  // Future optimizations may allow some classes to remain
+  // non-concrete until their first instantiation, and allow some
+  // methods to remain non-concrete until their first invocation.
+  // In that case, there would be a middle ground between concrete
+  // and abstract (as defined by the Java language and VM).
+  static bool is_concrete_klass(klassOop k);    // k is instantiable
+  static bool is_concrete_method(methodOop m);  // m is invocable
+  static Klass* find_finalizable_subclass(Klass* k);
+
+  // These versions of the concreteness queries work through the CI.
+  // The CI versions are allowed to skew sometimes from the VM
+  // (oop-based) versions.  The cost of such a difference is a
+  // (safely) aborted compilation, or a deoptimization, or a missed
+  // optimization opportunity.
+  //
+  // In order to prevent spurious assertions, query results must
+  // remain stable within any single ciEnv instance.  (I.e., they must
+  // not go back into the VM to get their value; they must cache the
+  // bit in the CI, either eagerly or lazily.)
+  static bool is_concrete_klass(ciInstanceKlass* k); // k appears instantiable
+  static bool is_concrete_method(ciMethod* m);       // m appears invocable
+  static bool has_finalizable_subclass(ciInstanceKlass* k);
+
+  // As a general rule, it is OK to compile under the assumption that
+  // a given type or method is concrete, even if it at some future
+  // point becomes abstract.  So dependency checking is one-sided, in
+  // that it permits supposedly concrete classes or methods to turn up
+  // as really abstract.  (This shouldn't happen, except during class
+  // evolution, but that's the logic of the checking.)  However, if a
+  // supposedly abstract class or method suddenly becomes concrete, a
+  // dependency on it must fail.
+
+  // Checking old assertions at run-time (in the VM only):
+  static klassOop check_evol_method(methodOop m);
+  static klassOop check_leaf_type(klassOop ctxk);
+  static klassOop check_abstract_with_unique_concrete_subtype(klassOop ctxk, klassOop conck,
+                                                              DepChange* changes = NULL);
+  static klassOop check_abstract_with_no_concrete_subtype(klassOop ctxk,
+                                                          DepChange* changes = NULL);
+  static klassOop check_concrete_with_no_concrete_subtype(klassOop ctxk,
+                                                          DepChange* changes = NULL);
+  static klassOop check_unique_concrete_method(klassOop ctxk, methodOop uniqm,
+                                               DepChange* changes = NULL);
+  static klassOop check_abstract_with_exclusive_concrete_subtypes(klassOop ctxk, klassOop k1, klassOop k2,
+                                                                  DepChange* changes = NULL);
+  static klassOop check_exclusive_concrete_methods(klassOop ctxk, methodOop m1, methodOop m2,
+                                                   DepChange* changes = NULL);
+  static klassOop check_has_no_finalizable_subclasses(klassOop ctxk,
+                                                      DepChange* changes = NULL);
+  // A returned klassOop is NULL if the dependency assertion is still
+  // valid.  A non-NULL klassOop is a 'witness' to the assertion
+  // failure, a point in the class hierarchy where the assertion has
+  // been proven false.  For example, if check_leaf_type returns
+  // non-NULL, the value is a subtype of the supposed leaf type.  This
+  // witness value may be useful for logging the dependency failure.
+  // Note that, when a dependency fails, there may be several possible
+  // witnesses to the failure.  The value returned from the check_foo
+  // method is chosen arbitrarily.
+
+  // The 'changes' value, if non-null, requests a limited spot-check
+  // near the indicated recent changes in the class hierarchy.
+  // It is used by DepStream::spot_check_dependency_at.
+
+  // Detecting possible new assertions:
+  static klassOop  find_unique_concrete_subtype(klassOop ctxk);
+  static methodOop find_unique_concrete_method(klassOop ctxk, methodOop m);
+  static int       find_exclusive_concrete_subtypes(klassOop ctxk, int klen, klassOop k[]);
+  static int       find_exclusive_concrete_methods(klassOop ctxk, int mlen, methodOop m[]);
+
+  // Create the encoding which will be stored in an nmethod.
+  void encode_content_bytes();
+
+  address content_bytes() {
+    assert(_content_bytes != NULL, "encode it first");
+    return _content_bytes;
+  }
+  size_t size_in_bytes() {
+    assert(_content_bytes != NULL, "encode it first");
+    return _size_in_bytes;
+  }
+
+  OopRecorder* oop_recorder() { return _oop_recorder; }
+  CompileLog*  log()          { return _log; }
+
+  void copy_to(nmethod* nm);
+
+  void log_all_dependencies();
+  void log_dependency(DepType dept, int nargs, ciObject* args[]) {
+    write_dependency_to(log(), dept, nargs, args);
+  }
+  void log_dependency(DepType dept,
+                      ciObject* x0,
+                      ciObject* x1 = NULL,
+                      ciObject* x2 = NULL) {
+    if (log() == NULL)  return;
+    ciObject* args[max_arg_count];
+    args[0] = x0;
+    args[1] = x1;
+    args[2] = x2;
+    assert(2 < max_arg_count, "");
+    log_dependency(dept, dep_args(dept), args);
+  }
+
+  static void write_dependency_to(CompileLog* log,
+                                  DepType dept,
+                                  int nargs, ciObject* args[],
+                                  klassOop witness = NULL);
+  static void write_dependency_to(CompileLog* log,
+                                  DepType dept,
+                                  int nargs, oop args[],
+                                  klassOop witness = NULL);
+  static void write_dependency_to(xmlStream* xtty,
+                                  DepType dept,
+                                  int nargs, oop args[],
+                                  klassOop witness = NULL);
+  static void print_dependency(DepType dept,
+                               int nargs, oop args[],
+                               klassOop witness = NULL);
+
+ private:
+  // helper for encoding common context types as zero:
+  static ciKlass* ctxk_encoded_as_null(DepType dept, ciObject* x);
+
+  static klassOop ctxk_encoded_as_null(DepType dept, oop x);
+
+ public:
+  // Use this to iterate over an nmethod's dependency set.
+  // Works on new and old dependency sets.
+  // Usage:
+  //
+  // ;
+  // Dependencies::DepType dept;
+  // for (Dependencies::DepStream deps(nm); deps.next(); ) {
+  //   ...
+  // }
+  //
+  // The caller must be in the VM, since oops are not wrapped in handles.
+  class DepStream {
+  private:
+    nmethod*              _code;   // null if in a compiler thread
+    Dependencies*         _deps;   // null if not in a compiler thread
+    CompressedReadStream  _bytes;
+#ifdef ASSERT
+    size_t                _byte_limit;
+#endif
+
+    // iteration variables:
+    DepType               _type;
+    int                   _xi[max_arg_count+1];
+
+    void initial_asserts(size_t byte_limit) NOT_DEBUG({});
+
+    inline oop recorded_oop_at(int i);
+        // => _code? _code->oop_at(i): *_deps->_oop_recorder->handle_at(i)
+
+    klassOop check_dependency_impl(DepChange* changes);
+
+  public:
+    DepStream(Dependencies* deps)
+      : _deps(deps),
+        _code(NULL),
+        _bytes(deps->content_bytes())
+    {
+      initial_asserts(deps->size_in_bytes());
+    }
+    DepStream(nmethod* code)
+      : _deps(NULL),
+        _code(code),
+        _bytes(code->dependencies_begin())
+    {
+      initial_asserts(code->dependencies_size());
+    }
+
+    bool next();
+
+    DepType type()               { return _type; }
+    int argument_count()         { return dep_args(type()); }
+    int argument_index(int i)    { assert(0 <= i && i < argument_count(), "oob");
+                                   return _xi[i]; }
+    oop argument(int i);         // => recorded_oop_at(argument_index(i))
+    klassOop context_type();
+
+    methodOop method_argument(int i) {
+      oop x = argument(i);
+      assert(x->is_method(), "type");
+      return (methodOop) x;
+    }
+    klassOop type_argument(int i) {
+      oop x = argument(i);
+      assert(x->is_klass(), "type");
+      return (klassOop) x;
+    }
+
+    // The point of the whole exercise:  Is this dep is still OK?
+    klassOop check_dependency() {
+      return check_dependency_impl(NULL);
+    }
+    // A lighter version:  Checks only around recent changes in a class
+    // hierarchy.  (See Universe::flush_dependents_on.)
+    klassOop spot_check_dependency_at(DepChange& changes);
+
+    // Log the current dependency to xtty or compilation log.
+    void log_dependency(klassOop witness = NULL);
+
+    // Print the current dependency to tty.
+    void print_dependency(klassOop witness = NULL, bool verbose = false);
+  };
+  friend class Dependencies::DepStream;
+
+  static void print_statistics() PRODUCT_RETURN;
+};
+
+// A class hierarchy change coming through the VM (under the Compile_lock).
+// The change is structured as a single new type with any number of supers
+// and implemented interface types.  Other than the new type, any of the
+// super types can be context types for a relevant dependency, which the
+// new type could invalidate.
+class DepChange : public StackObj {
+ private:
+  enum ChangeType {
+    NO_CHANGE = 0,              // an uninvolved klass
+    Change_new_type,            // a newly loaded type
+    Change_new_sub,             // a super with a new subtype
+    Change_new_impl,            // an interface with a new implementation
+    CHANGE_LIMIT,
+    Start_Klass = CHANGE_LIMIT  // internal indicator for ContextStream
+  };
+
+  // each change set is rooted in exactly one new type (at present):
+  KlassHandle _new_type;
+
+  void initialize();
+
+ public:
+  // notes the new type, marks it and all its super-types
+  DepChange(KlassHandle new_type)
+    : _new_type(new_type)
+  {
+    initialize();
+  }
+
+  // cleans up the marks
+  ~DepChange();
+
+  klassOop new_type()                   { return _new_type(); }
+
+  // involves_context(k) is true if k is new_type or any of the super types
+  bool involves_context(klassOop k);
+
+  // Usage:
+  // for (DepChange::ContextStream str(changes); str.next(); ) {
+  //   klassOop k = str.klass();
+  //   switch (str.change_type()) {
+  //     ...
+  //   }
+  // }
+  class ContextStream : public StackObj {
+   private:
+    DepChange&       _changes;
+    friend class DepChange;
+
+    // iteration variables:
+    ChangeType            _change_type;
+    klassOop              _klass;
+    objArrayOop           _ti_base;    // i.e., transitive_interfaces
+    int                   _ti_index;
+    int                   _ti_limit;
+
+    // start at the beginning:
+    void start() {
+      klassOop new_type = _changes.new_type();
+      _change_type = (new_type == NULL ? NO_CHANGE: Start_Klass);
+      _klass = new_type;
+      _ti_base = NULL;
+      _ti_index = 0;
+      _ti_limit = 0;
+    }
+
+    ContextStream(DepChange& changes)
+      : _changes(changes)
+    { start(); }
+
+   public:
+    ContextStream(DepChange& changes, No_Safepoint_Verifier& nsv)
+      : _changes(changes)
+      // the nsv argument makes it safe to hold oops like _klass
+    { start(); }
+
+    bool next();
+
+    klassOop   klass()           { return _klass; }
+  };
+  friend class DepChange::ContextStream;
+
+  void print();
+};