137 lines
4.7 KiB
C++
137 lines
4.7 KiB
C++
/*
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* Copyright 1998-2005 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*
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*/
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// Recording and retrieval of oop relocations in compiled code.
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class CodeBlob;
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class OopRecorder : public ResourceObj {
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public:
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// A two-way mapping from positive indexes to oop handles.
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// The zero index is reserved for a constant (sharable) null.
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// Indexes may not be negative.
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// Use the given arena to manage storage, if not NULL.
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// By default, uses the current ResourceArea.
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OopRecorder(Arena* arena = NULL);
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// Generate a new index on which CodeBlob::oop_addr_at will work.
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// allocate_index and find_index never return the same index,
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// and allocate_index never returns the same index twice.
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// In fact, two successive calls to allocate_index return successive ints.
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int allocate_index(jobject h) {
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return add_handle(h, false);
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}
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// For a given jobject, this will return the same index repeatedly.
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// The index can later be given to oop_at to retrieve the oop.
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// However, the oop must not be changed via CodeBlob::oop_addr_at.
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int find_index(jobject h) {
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int index = maybe_find_index(h);
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if (index < 0) { // previously unallocated
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index = add_handle(h, true);
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}
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return index;
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}
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// variant of find_index which does not allocate if not found (yields -1)
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int maybe_find_index(jobject h);
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// returns the size of the generated oop table, for sizing the CodeBlob.
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// must be called after all oops are allocated!
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int oop_size();
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// Retrieve the oop handle at a given index.
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jobject handle_at(int index);
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int element_count() {
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// there is always a NULL virtually present as first object
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return _handles->length() + first_index;
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}
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// copy the generated oop table to CodeBlob
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void copy_to(CodeBlob* code); // => code->copy_oops(_handles)
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bool is_unused() { return _handles == NULL && !_complete; }
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#ifdef ASSERT
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bool is_complete() { return _complete; }
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#endif
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private:
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// leaky hash table of handle => index, to help detect duplicate insertion
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class IndexCache: public ResourceObj {
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// This class is only used by the OopRecorder class.
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friend class OopRecorder;
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enum {
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_log_cache_size = 9,
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_cache_size = (1<<_log_cache_size),
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// Index entries are ints. The LSBit is a collision indicator.
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_collision_bit_shift = 0,
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_collision_bit = 1,
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_index_shift = _collision_bit_shift+1
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};
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int _cache[_cache_size];
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static juint cache_index(jobject handle) {
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juint ci = (int) (intptr_t) handle;
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ci ^= ci >> (BitsPerByte*2);
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ci += ci >> (BitsPerByte*1);
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return ci & (_cache_size-1);
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}
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int* cache_location(jobject handle) {
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return &_cache[ cache_index(handle) ];
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}
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static bool cache_location_collision(int* cloc) {
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return ((*cloc) & _collision_bit) != 0;
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}
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static int cache_location_index(int* cloc) {
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return (*cloc) >> _index_shift;
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}
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static void set_cache_location_index(int* cloc, int index) {
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int cval0 = (*cloc);
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int cval1 = (index << _index_shift);
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if (cval0 != 0 && cval1 != cval0) cval1 += _collision_bit;
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(*cloc) = cval1;
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}
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IndexCache();
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};
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// Helper function; returns false for NULL or Universe::non_oop_word().
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inline bool is_real_jobject(jobject h);
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void maybe_initialize();
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int add_handle(jobject h, bool make_findable);
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enum { null_index = 0, first_index = 1, index_cache_threshold = 20 };
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GrowableArray<jobject>* _handles; // ordered list (first is always NULL)
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GrowableArray<int>* _no_finds; // all unfindable indexes; usually empty
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IndexCache* _indexes; // map: jobject -> its probable index
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Arena* _arena;
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bool _complete;
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#ifdef ASSERT
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static int _find_index_calls, _hit_indexes, _missed_indexes;
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#endif
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};
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