1 /*
2 * Copyright (c) 2018, 2023, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2020, Red Hat, Inc. and/or its affiliates.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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8 * published by the Free Software Foundation.
9 *
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11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
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25
26 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHMARKBITMAP_HPP
27 #define SHARE_GC_SHENANDOAH_SHENANDOAHMARKBITMAP_HPP
28
29 #include "memory/memRegion.hpp"
30 #include "runtime/atomic.hpp"
31 #include "utilities/globalDefinitions.hpp"
32
33 class ShenandoahMarkBitMap {
34 public:
35 typedef size_t idx_t; // Type used for bit and word indices.
36 typedef uintptr_t bm_word_t; // Element type of array that represents the
37 // bitmap, with BitsPerWord bits per element.
38
39 private:
40 // Values for get_next_bit_impl flip parameter.
41 static const bm_word_t find_ones_flip = 0;
42 static const bm_word_t find_zeros_flip = ~(bm_word_t)0;
43
44 int const _shift;
45 MemRegion _covered;
46
47 bm_word_t* _map; // First word in bitmap
48 idx_t _size; // Size of bitmap (in bits)
49
50 // Threshold for performing small range operation, even when large range
51 // operation was requested. Measured in words.
52 static const size_t small_range_words = 32;
53
54 static bool is_small_range_of_words(idx_t beg_full_word, idx_t end_full_word);
55
56 inline size_t address_to_index(const HeapWord* addr) const;
57 inline HeapWord* index_to_address(size_t offset) const;
58
59 void check_mark(HeapWord* addr) const NOT_DEBUG_RETURN;
60
61 // Return a mask that will select the specified bit, when applied to the word
62 // containing the bit.
63 static bm_word_t bit_mask(idx_t bit) { return (bm_word_t)1 << bit_in_word(bit); }
64
65 // Return the bit number of the first bit in the specified word.
66 static idx_t bit_index(idx_t word) { return word << LogBitsPerWord; }
67
68 // Return the position of bit within the word that contains it (e.g., if
69 // bitmap words are 32 bits, return a number 0 <= n <= 31).
70 static idx_t bit_in_word(idx_t bit) { return bit & (BitsPerWord - 1); }
71
72 bm_word_t* map() { return _map; }
73 const bm_word_t* map() const { return _map; }
74 bm_word_t map(idx_t word) const { return _map[word]; }
75
76 // Return a pointer to the word containing the specified bit.
77 bm_word_t* word_addr(idx_t bit) {
78 return map() + to_words_align_down(bit);
79 }
80
81 const bm_word_t* word_addr(idx_t bit) const {
82 return map() + to_words_align_down(bit);
83 }
84
85 bool at(idx_t index) const {
86 verify_index(index);
87 return (*word_addr(index) & bit_mask(index)) != 0;
88 }
89
90 // Assumes relevant validity checking for bit has already been done.
91 static idx_t raw_to_words_align_up(idx_t bit) {
92 return raw_to_words_align_down(bit + (BitsPerWord - 1));
93 }
94
95 // Assumes relevant validity checking for bit has already been done.
96 static idx_t raw_to_words_align_down(idx_t bit) {
97 return bit >> LogBitsPerWord;
98 }
99
100 // Word-aligns bit and converts it to a word offset.
101 // precondition: bit <= size()
102 idx_t to_words_align_up(idx_t bit) const {
103 verify_limit(bit);
104 return raw_to_words_align_up(bit);
105 }
106
107 // Word-aligns bit and converts it to a word offset.
108 // precondition: bit <= size()
109 inline idx_t to_words_align_down(idx_t bit) const {
110 verify_limit(bit);
111 return raw_to_words_align_down(bit);
112 }
113
114 // Helper for get_next_{zero,one}_bit variants.
115 // - flip designates whether searching for 1s or 0s. Must be one of
116 // find_{zeros,ones}_flip.
117 // - aligned_right is true if r_index is a priori on a bm_word_t boundary.
118 template<bm_word_t flip, bool aligned_right>
119 inline idx_t get_next_bit_impl(idx_t l_index, idx_t r_index) const;
120
121 inline idx_t get_next_one_offset (idx_t l_index, idx_t r_index) const;
122
123 void clear_large_range (idx_t beg, idx_t end);
124
125 // Verify bit is less than size().
126 void verify_index(idx_t bit) const NOT_DEBUG_RETURN;
127 // Verify bit is not greater than size().
128 void verify_limit(idx_t bit) const NOT_DEBUG_RETURN;
129 // Verify [beg,end) is a valid range, e.g. beg <= end <= size().
130 void verify_range(idx_t beg, idx_t end) const NOT_DEBUG_RETURN;
131
132 public:
133 static size_t compute_size(size_t heap_size);
134 // Returns the amount of bytes on the heap between two marks in the bitmap.
135 static size_t mark_distance();
136 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
137 // mark bitmap corresponds to. This is the same as the mark distance above.
138 static size_t heap_map_factor() {
139 return mark_distance();
140 }
141
142 ShenandoahMarkBitMap(MemRegion heap, MemRegion storage);
143
144 // Mark word as 'strong' if it hasn't been marked strong yet.
145 // Return true if the word has been marked strong, false if it has already been
146 // marked strong or if another thread has beat us by marking it
147 // strong.
148 // Words that have been marked final before or by a concurrent thread will be
149 // upgraded to strong. In this case, this method also returns true.
150 inline bool mark_strong(HeapWord* w, bool& was_upgraded);
151
152 // Mark word as 'weak' if it hasn't been marked weak or strong yet.
153 // Return true if the word has been marked weak, false if it has already been
154 // marked strong or weak or if another thread has beat us by marking it
155 // strong or weak.
156 inline bool mark_weak(HeapWord* heap_addr);
157
158 inline bool is_marked(HeapWord* addr) const;
159 inline bool is_marked_strong(HeapWord* w) const;
160 inline bool is_marked_weak(HeapWord* addr) const;
161
162 // Return the address corresponding to the next marked bit at or after
163 // "addr", and before "limit", if "limit" is non-null. If there is no
164 // such bit, returns "limit" if that is non-null, or else "endWord()".
165 HeapWord* get_next_marked_addr(const HeapWord* addr,
166 const HeapWord* limit) const;
167
168 bm_word_t inverted_bit_mask_for_range(idx_t beg, idx_t end) const;
169 void clear_range_within_word (idx_t beg, idx_t end);
170 void clear_range (idx_t beg, idx_t end);
171 void clear_range_large(MemRegion mr);
172
173 void clear_range_of_words(idx_t beg, idx_t end);
174 void clear_large_range_of_words(idx_t beg, idx_t end);
175 static void clear_range_of_words(bm_word_t* map, idx_t beg, idx_t end);
176
177 };
178
179 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHMARKBITMAP_HPP