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/*
* Copyright (c) 1998, 2010, 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
* 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#ifndef SHARE_VM_CODE_OOPRECORDER_HPP
#define SHARE_VM_CODE_OOPRECORDER_HPP
#include "runtime/handles.hpp"
#include "utilities/growableArray.hpp"
// Recording and retrieval of oop relocations in compiled code.
class CodeBlob;
class OopRecorder : public ResourceObj {
public:
// A two-way mapping from positive indexes to oop handles.
// The zero index is reserved for a constant (sharable) null.
// Indexes may not be negative.
// Use the given arena to manage storage, if not NULL.
// By default, uses the current ResourceArea.
OopRecorder(Arena* arena = NULL);
// Generate a new index on which CodeBlob::oop_addr_at will work.
// allocate_index and find_index never return the same index,
// and allocate_index never returns the same index twice.
// In fact, two successive calls to allocate_index return successive ints.
int allocate_index(jobject h) {
return add_handle(h, false);
}
// For a given jobject, this will return the same index repeatedly.
// The index can later be given to oop_at to retrieve the oop.
// However, the oop must not be changed via CodeBlob::oop_addr_at.
int find_index(jobject h) {
int index = maybe_find_index(h);
if (index < 0) { // previously unallocated
index = add_handle(h, true);
}
return index;
}
// variant of find_index which does not allocate if not found (yields -1)
int maybe_find_index(jobject h);
// returns the size of the generated oop table, for sizing the CodeBlob.
// must be called after all oops are allocated!
int oop_size();
// Retrieve the oop handle at a given index.
jobject handle_at(int index);
int element_count() {
// there is always a NULL virtually present as first object
return _handles->length() + first_index;
}
// copy the generated oop table to nmethod
void copy_to(nmethod* nm); // => nm->copy_oops(_handles)
bool is_unused() { return _handles == NULL && !_complete; }
#ifdef ASSERT
bool is_complete() { return _complete; }
#endif
private:
// leaky hash table of handle => index, to help detect duplicate insertion
class IndexCache: public ResourceObj {
// This class is only used by the OopRecorder class.
friend class OopRecorder;
enum {
_log_cache_size = 9,
_cache_size = (1<<_log_cache_size),
// Index entries are ints. The LSBit is a collision indicator.
_collision_bit_shift = 0,
_collision_bit = 1,
_index_shift = _collision_bit_shift+1
};
int _cache[_cache_size];
static juint cache_index(jobject handle) {
juint ci = (int) (intptr_t) handle;
ci ^= ci >> (BitsPerByte*2);
ci += ci >> (BitsPerByte*1);
return ci & (_cache_size-1);
}
int* cache_location(jobject handle) {
return &_cache[ cache_index(handle) ];
}
static bool cache_location_collision(int* cloc) {
return ((*cloc) & _collision_bit) != 0;
}
static int cache_location_index(int* cloc) {
return (*cloc) >> _index_shift;
}
static void set_cache_location_index(int* cloc, int index) {
int cval0 = (*cloc);
int cval1 = (index << _index_shift);
if (cval0 != 0 && cval1 != cval0) cval1 += _collision_bit;
(*cloc) = cval1;
}
IndexCache();
};
// Helper function; returns false for NULL or Universe::non_oop_word().
inline bool is_real_jobject(jobject h);
void maybe_initialize();
int add_handle(jobject h, bool make_findable);
enum { null_index = 0, first_index = 1, index_cache_threshold = 20 };
GrowableArray<jobject>* _handles; // ordered list (first is always NULL)
GrowableArray<int>* _no_finds; // all unfindable indexes; usually empty
IndexCache* _indexes; // map: jobject -> its probable index
Arena* _arena;
bool _complete;
#ifdef ASSERT
static int _find_index_calls, _hit_indexes, _missed_indexes;
#endif
};
#endif // SHARE_VM_CODE_OOPRECORDER_HPP
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