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hotspot/src/share/vm/interpreter/oopMapCache.hpp

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+/*
+ * Copyright 1997-2006 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.
+ *
+ */
+
+// A Cache for storing (method, bci) -> oopMap.
+// The memory management system uses the cache when locating object
+// references in an interpreted frame.
+//
+// OopMapCache's are allocated lazily per instanceKlass.
+
+// The oopMap (InterpreterOopMap) is stored as a bit mask. If the
+// bit_mask can fit into two words it is stored in
+// the _bit_mask array, otherwise it is allocated on the heap.
+// For OopMapCacheEntry the bit_mask is allocated in the C heap
+// because these entries persist between garbage collections.
+// For InterpreterOopMap the bit_mask is allocated in
+// a resource area for better performance.  InterpreterOopMap
+// should only be created and deleted during same garbage collection.
+//
+// If ENABBLE_ZAP_DEAD_LOCALS is defined, two bits are used
+// per entry instead of one. In all cases,
+// the first bit is set to indicate oops as opposed to other
+// values. If the second bit is available,
+// it is set for dead values. We get the following encoding:
+//
+// 00 live value
+// 01 live oop
+// 10 dead value
+// 11 <unused>                                   (we cannot distinguish between dead oops or values with the current oop map generator)
+
+
+class OffsetClosure  {
+ public:
+  virtual void offset_do(int offset) = 0;
+};
+
+
+class InterpreterOopMap: ResourceObj {
+  friend class OopMapCache;
+
+ public:
+  enum {
+    N                = 2,                // the number of words reserved
+                                         // for inlined mask storage
+    small_mask_limit = N * BitsPerWord,  // the maximum number of bits
+                                         // available for small masks,
+                                         // small_mask_limit can be set to 0
+                                         // for testing bit_mask allocation
+
+#ifdef ENABLE_ZAP_DEAD_LOCALS
+    bits_per_entry   = 2,
+    dead_bit_number  = 1,
+#else
+    bits_per_entry   = 1,
+#endif
+    oop_bit_number   = 0
+  };
+
+ private:
+  methodOop      _method;         // the method for which the mask is valid
+  unsigned short _bci;            // the bci    for which the mask is valid
+  int            _mask_size;      // the mask size in bits
+  int            _expression_stack_size; // the size of the expression stack in slots
+
+ protected:
+  intptr_t       _bit_mask[N];    // the bit mask if
+                                  // mask_size <= small_mask_limit,
+                                  // ptr to bit mask otherwise
+                                  // "protected" so that sub classes can
+                                  // access it without using trickery in
+                                  // methd bit_mask().
+#ifdef ASSERT
+  bool _resource_allocate_bit_mask;
+#endif
+
+  // access methods
+  methodOop      method() const                  { return _method; }
+  void           set_method(methodOop v)         { _method = v; }
+  int            bci() const                     { return _bci; }
+  void           set_bci(int v)                  { _bci = v; }
+  int            mask_size() const               { return _mask_size; }
+  void           set_mask_size(int v)            { _mask_size = v; }
+  int            number_of_entries() const       { return mask_size() / bits_per_entry; }
+  // Test bit mask size and return either the in-line bit mask or allocated
+  // bit mask.
+  uintptr_t*  bit_mask()                         { return (uintptr_t*)(mask_size() <= small_mask_limit ? (intptr_t)_bit_mask : _bit_mask[0]); }
+
+  // return the word size of_bit_mask.  mask_size() <= 4 * MAX_USHORT
+  size_t mask_word_size() {
+    return (mask_size() + BitsPerWord - 1) / BitsPerWord;
+  }
+
+  uintptr_t entry_at(int offset)            { int i = offset * bits_per_entry; return bit_mask()[i / BitsPerWord] >> (i % BitsPerWord); }
+
+  void set_expression_stack_size(int sz)    { _expression_stack_size = sz; }
+
+#ifdef ENABLE_ZAP_DEAD_LOCALS
+  bool is_dead(int offset)                       { return (entry_at(offset) & (1 << dead_bit_number)) != 0; }
+#endif
+
+  // Lookup
+  bool match(methodHandle method, int bci)       { return _method == method() && _bci == bci; }
+  bool is_empty();
+
+  // Initialization
+  void initialize();
+
+ public:
+  InterpreterOopMap();
+  ~InterpreterOopMap();
+
+  // Copy the OopMapCacheEntry in parameter "from" into this
+  // InterpreterOopMap.  If the _bit_mask[0] in "from" points to
+  // allocated space (i.e., the bit mask was to large to hold
+  // in-line), allocate the space from a Resource area.
+  void resource_copy(OopMapCacheEntry* from);
+
+  void iterate_oop(OffsetClosure* oop_closure);
+  void oop_iterate(OopClosure * blk);
+  void oop_iterate(OopClosure * blk, MemRegion mr);
+  void verify();
+  void print();
+
+  bool is_oop  (int offset)                      { return (entry_at(offset) & (1 << oop_bit_number )) != 0; }
+
+  int expression_stack_size()                    { return _expression_stack_size; }
+
+#ifdef ENABLE_ZAP_DEAD_LOCALS
+  void iterate_all(OffsetClosure* oop_closure, OffsetClosure* value_closure, OffsetClosure* dead_closure);
+#endif
+};
+
+class OopMapCache : public CHeapObj {
+ private:
+  enum { _size        = 32,     // Use fixed size for now
+         _probe_depth = 3       // probe depth in case of collisions
+  };
+
+  OopMapCacheEntry* _array;
+
+  unsigned int hash_value_for(methodHandle method, int bci);
+  OopMapCacheEntry* entry_at(int i) const;
+
+  Mutex _mut;
+
+  void flush();
+
+ public:
+  OopMapCache();
+  ~OopMapCache();                                // free up memory
+
+  // flush cache entry is occupied by an obsolete method
+  void flush_obsolete_entries();
+
+  // Returns the oopMap for (method, bci) in parameter "entry".
+  // Returns false if an oop map was not found.
+  void lookup(methodHandle method, int bci, InterpreterOopMap* entry);
+
+  // Compute an oop map without updating the cache or grabbing any locks (for debugging)
+  static void compute_one_oop_map(methodHandle method, int bci, InterpreterOopMap* entry);
+
+  // Helpers
+  // Iterate over the entries in the cached OopMapCacheEntry's
+  void oop_iterate(OopClosure *blk);
+  void oop_iterate(OopClosure *blk, MemRegion mr);
+  void verify();
+
+  // Returns total no. of bytes allocated as part of OopMapCache's
+  static long memory_usage()                     PRODUCT_RETURN0;
+};