1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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24
25 #ifndef SHARE_CLASSFILE_FIELDLAYOUTBUILDER_HPP
26 #define SHARE_CLASSFILE_FIELDLAYOUTBUILDER_HPP
27
28 #include "classfile/classFileParser.hpp"
29 #include "classfile/classLoaderData.hpp"
30 #include "memory/allocation.hpp"
31 #include "oops/fieldStreams.hpp"
32 #include "oops/inlineKlass.hpp"
33 #include "oops/instanceKlass.hpp"
34 #include "utilities/growableArray.hpp"
35
36 // Classes below are used to compute the field layout of classes.
37
38 // A LayoutRawBlock describes an element of a layout.
39 // Each field is represented by a LayoutRawBlock.
40 // LayoutRawBlocks can also represent elements injected by the JVM:
41 // padding, empty blocks, inherited fields, etc.
42 // All LayoutRawBlocks must have a size and an alignment. The size is the
43 // exact size of the field expressed in bytes. The alignment is
44 // the alignment constraint of the field (1 for byte, 2 for short,
45 // 4 for int, 8 for long, etc.)
46 //
47 // LayoutRawBlock are designed to be used in two data structures:
48 // - a linked list in a layout (using _next_block, _prev_block)
49 // - a GrowableArray in field group (the growable array contains pointers to LayoutRawBlocks)
50 //
51 // next/prev pointers are included in the LayoutRawBlock class to narrow
52 // the number of allocation required during the computation of a layout.
53 //
54
55 #define MAX_ATOMIC_OP_SIZE sizeof(uint64_t)
56
57 class LayoutRawBlock : public ResourceObj {
58 public:
59 // Some code relies on the order of values below.
60 enum Kind {
61 EMPTY, // empty slot, space is taken from this to allocate fields
62 RESERVED, // reserved for JVM usage (for instance object header)
63 PADDING, // padding (because of alignment constraints or @Contended)
64 REGULAR, // primitive or oop field (including not flat inline type fields)
65 FLAT, // flat field
66 INHERITED, // field(s) inherited from super classes
67 NULL_MARKER // stores the null marker for a flat field
68 };
69
70 private:
71 LayoutRawBlock* _next_block;
72 LayoutRawBlock* _prev_block;
73 InlineKlass* _inline_klass;
74 Kind _block_kind;
75 LayoutKind _layout_kind;
76 int _offset;
77 int _alignment;
78 int _size;
79 int _field_index;
80
81 public:
82 LayoutRawBlock(Kind kind, int size);
83
84 LayoutRawBlock(int index, Kind kind, int size, int alignment);
85 LayoutRawBlock* next_block() const { return _next_block; }
86 void set_next_block(LayoutRawBlock* next) { _next_block = next; }
87 LayoutRawBlock* prev_block() const { return _prev_block; }
88 void set_prev_block(LayoutRawBlock* prev) { _prev_block = prev; }
89 Kind block_kind() const { return _block_kind; }
90 void set_block_kind(LayoutRawBlock::Kind kind) { _block_kind = kind; } // Dangerous operation, is only used by remove_null_marker();
91 int offset() const {
92 assert(_offset >= 0, "Must be initialized");
93 return _offset;
94 }
95 void set_offset(int offset) { _offset = offset; }
96 int alignment() const { return _alignment; }
97 int size() const { return _size; }
98 void set_size(int size) { _size = size; }
99 int field_index() const {
100 assert(_field_index != -1, "Must be initialized");
101 return _field_index;
102 }
103 void set_field_index(int field_index) {
104 assert(_field_index == -1, "Must not be initialized");
105 _field_index = field_index;
106 }
107 InlineKlass* inline_klass() const {
108 assert(_inline_klass != nullptr, "Must be initialized");
109 return _inline_klass;
110 }
111 void set_inline_klass(InlineKlass* inline_klass) { _inline_klass = inline_klass; }
112
113 LayoutKind layout_kind() const { return _layout_kind; }
114 void set_layout_kind(LayoutKind kind) { _layout_kind = kind; }
115
116 bool fit(int size, int alignment);
117
118 static int compare_offset(LayoutRawBlock** x, LayoutRawBlock** y) { return (*x)->offset() - (*y)->offset(); }
119 // compare_size_inverted() returns the opposite of a regular compare method in order to
120 // sort fields in decreasing order.
121 // Note: with line types, the comparison should include alignment constraint if sizes are equals
122 static int compare_size_inverted(LayoutRawBlock** x, LayoutRawBlock** y) {
123 int diff = (*y)->size() - (*x)->size();
124 // qsort() may reverse the order of fields with the same size.
125 // The extension is to ensure stable sort.
126 if (diff == 0) {
127 diff = (*x)->field_index() - (*y)->field_index();
128 }
129 return diff;
130 }
131 };
132
133 // A Field group represents a set of fields that have to be allocated together,
134 // this is the way the @Contended annotation is supported.
135 // Inside a FieldGroup, fields are sorted based on their kind: primitive,
136 // oop, or flat.
137 //
138 class FieldGroup : public ResourceObj {
139
140 private:
141 FieldGroup* _next;
142
143 GrowableArray<LayoutRawBlock*>* _small_primitive_fields;
144 GrowableArray<LayoutRawBlock*>* _big_primitive_fields;
145 GrowableArray<LayoutRawBlock*>* _oop_fields;
146 int _contended_group;
147 int _oop_count;
148 static const int INITIAL_LIST_SIZE = 16;
149
150 public:
151 FieldGroup(int contended_group = -1);
152
153 FieldGroup* next() const { return _next; }
154 void set_next(FieldGroup* next) { _next = next; }
155 GrowableArray<LayoutRawBlock*>* small_primitive_fields() const { return _small_primitive_fields; }
156 GrowableArray<LayoutRawBlock*>* big_primitive_fields() const { return _big_primitive_fields; }
157 GrowableArray<LayoutRawBlock*>* oop_fields() const { return _oop_fields; }
158 int contended_group() const { return _contended_group; }
159 int oop_count() const { return _oop_count; }
160
161 void add_primitive_field(int idx, BasicType type);
162 void add_oop_field(int idx);
163 void add_flat_field(int idx, InlineKlass* vk, LayoutKind lk, int size, int alignment);
164 void add_block(LayoutRawBlock** list, LayoutRawBlock* block);
165 void sort_by_size();
166 private:
167 void add_to_small_primitive_list(LayoutRawBlock* block);
168 void add_to_big_primitive_list(LayoutRawBlock* block);
169 };
170
171 // The FieldLayout class represents a set of fields organized
172 // in a layout.
173 // An instance of FieldLayout can either represent the layout
174 // of non-static fields (used in an instance object) or the
175 // layout of static fields (to be included in the class mirror).
176 //
177 // _block is a pointer to a list of LayoutRawBlock ordered by increasing
178 // offsets.
179 // _start points to the LayoutRawBlock with the first offset that can
180 // be used to allocate fields of the current class
181 // _last points to the last LayoutRawBlock of the list. In order to
182 // simplify the code, the LayoutRawBlock list always ends with an
183 // EMPTY block (the kind of LayoutRawBlock from which space is taken
184 // to allocate fields) with a size big enough to satisfy all
185 // field allocations.
186 //
187 class FieldLayout : public ResourceObj {
188 private:
189 GrowableArray<FieldInfo>* _field_info;
190 Array<InlineLayoutInfo>* _inline_layout_info_array;
191 ConstantPool* _cp;
192 LayoutRawBlock* _blocks; // the layout being computed
193 LayoutRawBlock* _start; // points to the first block where a field can be inserted
194 LayoutRawBlock* _last; // points to the last block of the layout (big empty block)
195 int _super_first_field_offset;
196 int _super_alignment;
197 int _super_min_align_required;
198 int _null_reset_value_offset; // offset of the reset value in class mirror, only for static layout of inline classes
199 bool _super_has_fields;
200 bool _has_inherited_fields;
201
202 public:
203 FieldLayout(GrowableArray<FieldInfo>* field_info, Array<InlineLayoutInfo>* inline_layout_info_array, ConstantPool* cp);
204 void initialize_static_layout();
205 void initialize_instance_layout(const InstanceKlass* ik, bool& super_ends_with_oop);
206
207 LayoutRawBlock* first_empty_block() {
208 LayoutRawBlock* block = _start;
209 while (block->block_kind() != LayoutRawBlock::EMPTY) {
210 block = block->next_block();
211 }
212 return block;
213 }
214
215 LayoutRawBlock* blocks() const { return _blocks; }
216
217 LayoutRawBlock* start() const { return _start; }
218 void set_start(LayoutRawBlock* start) { _start = start; }
219 LayoutRawBlock* last_block() const { return _last; }
220 int super_first_field_offset() const { return _super_first_field_offset; }
221 int super_alignment() const { return _super_alignment; }
222 int super_min_align_required() const { return _super_min_align_required; }
223 int null_reset_value_offset() const {
224 assert(_null_reset_value_offset != -1, "Must have been set");
225 return _null_reset_value_offset;
226 }
227 bool super_has_fields() const { return _super_has_fields; }
228 bool has_inherited_fields() const { return _has_inherited_fields; }
229
230 LayoutRawBlock* first_field_block();
231 void add(GrowableArray<LayoutRawBlock*>* list, LayoutRawBlock* start = nullptr);
232 void add_field_at_offset(LayoutRawBlock* blocks, int offset, LayoutRawBlock* start = nullptr);
233 void add_contiguously(GrowableArray<LayoutRawBlock*>* list, LayoutRawBlock* start = nullptr);
234 LayoutRawBlock* insert_field_block(LayoutRawBlock* slot, LayoutRawBlock* block);
235 void reconstruct_layout(const InstanceKlass* ik, bool& has_instance_fields, bool& ends_with_oop);
236 void fill_holes(const InstanceKlass* ik);
237 LayoutRawBlock* insert(LayoutRawBlock* slot, LayoutRawBlock* block);
238 void remove(LayoutRawBlock* block);
239 void shift_fields(int shift);
240 LayoutRawBlock* find_null_marker();
241 void remove_null_marker();
242 void print(outputStream* output, bool is_static, const InstanceKlass* super, Array<InlineLayoutInfo>* inline_fields);
243 };
244
245
246 // FieldLayoutBuilder is the main entry point for layout computation.
247 // This class has two methods to generate layout: one for identity classes
248 // and one for inline classes. The rational for having two methods
249 // is that each kind of classes has a different set goals regarding
250 // its layout, so instead of mixing two layout strategies into a
251 // single method, each kind has its own method (see comments below
252 // for more details about the allocation strategies).
253 //
254 // Computing the layout of a class always goes through 4 steps:
255 // 1 - Prologue: preparation of data structure and gathering of
256 // layout information inherited from super classes
257 // 2 - Field sorting: fields are sorted according to their
258 // kind (oop, primitive, inline class) and their contention
259 // annotation (if any)
260 // 3 - Layout is computed from the set of lists generated during
261 // step 2
262 // 4 - Epilogue: oopmaps are generated, layout information is
263 // prepared so other VM components can use it (instance size,
264 // static field size, non-static field size, etc.)
265 //
266 // Steps 1 and 4 are common to all layout computations. Step 2 and 3
267 // differ for inline classes and identity classes.
268 //
269 class FieldLayoutBuilder : public ResourceObj {
270
271 private:
272 const Symbol* _classname;
273 ClassLoaderData* _loader_data;
274 const InstanceKlass* _super_klass;
275 ConstantPool* _constant_pool;
276 GrowableArray<FieldInfo>* _field_info;
277 FieldLayoutInfo* _info;
278 Array<InlineLayoutInfo>* _inline_layout_info_array;
279 FieldGroup* _root_group;
280 GrowableArray<FieldGroup*> _contended_groups;
281 FieldGroup* _static_fields;
282 FieldLayout* _layout;
283 FieldLayout* _static_layout;
284 int _nonstatic_oopmap_count;
285 int _payload_alignment;
286 int _payload_offset;
287 int _null_marker_offset; // if any, -1 means no internal null marker
288 int _payload_size_in_bytes;
289 int _non_atomic_layout_size_in_bytes;
290 int _non_atomic_layout_alignment;
291 int _atomic_layout_size_in_bytes;
292 int _nullable_layout_size_in_bytes;
293 int _fields_size_sum;
294 int _declared_non_static_fields_count;
295 bool _has_non_naturally_atomic_fields;
296 bool _is_naturally_atomic;
297 bool _must_be_atomic;
298 bool _has_nonstatic_fields;
299 bool _has_inline_type_fields;
300 bool _is_contended;
301 bool _super_ends_with_oop;
302 bool _is_inline_type;
303 bool _is_abstract_value;
304 bool _has_flattening_information;
305 bool _is_empty_inline_class;
306
307 FieldGroup* get_or_create_contended_group(int g);
308
309 public:
310 FieldLayoutBuilder(const Symbol* classname, ClassLoaderData* loader_data, const InstanceKlass* super_klass, ConstantPool* constant_pool,
311 GrowableArray<FieldInfo>* field_info, bool is_contended, bool is_inline_type, bool is_abstract_value,
312 bool must_be_atomic, FieldLayoutInfo* info, Array<InlineLayoutInfo>* inline_layout_info_array);
313
314 int payload_offset() const { assert(_payload_offset != -1, "Uninitialized"); return _payload_offset; }
315 int payload_layout_size_in_bytes() const { return _payload_size_in_bytes; }
316 int payload_layout_alignment() const { assert(_payload_alignment != -1, "Uninitialized"); return _payload_alignment; }
317 bool has_non_atomic_flat_layout() const { return _non_atomic_layout_size_in_bytes != -1; }
318 int non_atomic_layout_size_in_bytes() const { return _non_atomic_layout_size_in_bytes; }
319 int non_atomic_layout_alignment() const { return _non_atomic_layout_alignment; }
320 bool has_atomic_layout() const { return _atomic_layout_size_in_bytes != -1; }
321 int atomic_layout_size_in_bytes() const { return _atomic_layout_size_in_bytes; }
322 bool has_nullable_atomic_layout() const { return _nullable_layout_size_in_bytes != -1; }
323 int nullable_layout_size_in_bytes() const { return _nullable_layout_size_in_bytes; }
324 int null_marker_offset() const { return _null_marker_offset; }
325 bool is_empty_inline_class() const { return _is_empty_inline_class; }
326
327 void build_layout();
328 void compute_regular_layout();
329 void compute_inline_class_layout();
330 void insert_contended_padding(LayoutRawBlock* slot);
331
332 protected:
333 void prologue();
334 void epilogue();
335 void regular_field_sorting();
336 void inline_class_field_sorting();
337 void add_flat_field_oopmap(OopMapBlocksBuilder* nonstatic_oop_map, InlineKlass* vk, int offset);
338 void register_embedded_oops_from_list(OopMapBlocksBuilder* nonstatic_oop_maps, GrowableArray<LayoutRawBlock*>* list);
339 void register_embedded_oops(OopMapBlocksBuilder* nonstatic_oop_maps, FieldGroup* group);
340 };
341
342 #endif // SHARE_CLASSFILE_FIELDLAYOUTBUILDER_HPP