1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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 "utilities/growableArray.hpp"
33
34 // Classes below are used to compute the field layout of classes.
35
36
37 // A LayoutRawBlock describes an element of a layout.
38 // Each field is represented by a LayoutRawBlock.
39 // LayoutRawBlocks can also represent elements injected by the JVM:
40 // padding, empty blocks, inherited fields, etc.
41 // All LayoutRawBlocks must have a size and an alignment. The size is the
42 // exact size of the field expressed in bytes. The alignment is
43 // the alignment constraint of the field (1 for byte, 2 for short,
44 // 4 for int, 8 for long, etc.)
45 //
46 // LayoutRawBlock are designed to be used in two data structures:
47 // - a linked list in a layout (using _next_block, _prev_block)
48 // - a GrowableArray in field group (the growable array contains pointers to LayoutRawBlocks)
49 //
50 // next/prev pointers are included in the LayoutRawBlock class to narrow
51 // the number of allocation required during the computation of a layout.
52 //
53 class LayoutRawBlock : public ResourceObj {
54 public:
55 // Some code relies on the order of values below.
56 enum Kind {
57 EMPTY, // empty slot, space is taken from this to allocate fields
58 RESERVED, // reserved for JVM usage (for instance object header)
59 PADDING, // padding (because of alignment constraints or @Contended)
60 REGULAR, // primitive or oop field (including non-flattened inline fields)
61 FLATTENED, // flattened field
62 INHERITED // field(s) inherited from super classes
63 };
64
65 private:
66 LayoutRawBlock* _next_block;
67 LayoutRawBlock* _prev_block;
68 Kind _kind;
69 int _offset;
70 int _alignment;
71 int _size;
72 int _field_index;
73 bool _is_reference;
74
75 public:
76 LayoutRawBlock(Kind kind, int size);
77 LayoutRawBlock(int index, Kind kind, int size, int alignment, bool is_reference = false);
78 LayoutRawBlock* next_block() const { return _next_block; }
79 void set_next_block(LayoutRawBlock* next) { _next_block = next; }
80 LayoutRawBlock* prev_block() const { return _prev_block; }
81 void set_prev_block(LayoutRawBlock* prev) { _prev_block = prev; }
82 Kind kind() const { return _kind; }
83 int offset() const {
84 assert(_offset >= 0, "Must be initialized");
85 return _offset;
86 }
87 void set_offset(int offset) { _offset = offset; }
88 int alignment() const { return _alignment; }
89 int size() const { return _size; }
90 void set_size(int size) { _size = size; }
91 int field_index() const {
92 assert(_field_index != -1, "Must be initialized");
93 return _field_index;
94 }
95 bool is_reference() const { return _is_reference; }
96
97 bool fit(int size, int alignment);
98
99 static int compare_offset(LayoutRawBlock** x, LayoutRawBlock** y) { return (*x)->offset() - (*y)->offset(); }
100 // compare_size_inverted() returns the opposite of a regular compare method in order to
101 // sort fields in decreasing order.
102 // Note: with line types, the comparison should include alignment constraint if sizes are equals
103 static int compare_size_inverted(LayoutRawBlock** x, LayoutRawBlock** y) {
104 int diff = (*y)->size() - (*x)->size();
105 // qsort() may reverse the order of fields with the same size.
106 // The extension is to ensure stable sort.
107 if (diff == 0) {
108 diff = (*x)->field_index() - (*y)->field_index();
109 }
110 return diff;
111 }
112
113 };
114
115 // A Field group represents a set of fields that have to be allocated together,
116 // this is the way the @Contended annotation is supported.
117 // Inside a FieldGroup, fields are sorted based on their kind: primitive,
118 // oop, or flattened.
119 //
120 class FieldGroup : public ResourceObj {
121
122 private:
123 FieldGroup* _next;
124 GrowableArray<LayoutRawBlock*>* _primitive_fields;
125 GrowableArray<LayoutRawBlock*>* _oop_fields;
126 int _contended_group;
127 int _oop_count;
128 static const int INITIAL_LIST_SIZE = 16;
129
130 public:
131 FieldGroup(int contended_group = -1);
132
133 FieldGroup* next() const { return _next; }
134 void set_next(FieldGroup* next) { _next = next; }
135 GrowableArray<LayoutRawBlock*>* primitive_fields() const { return _primitive_fields; }
136 GrowableArray<LayoutRawBlock*>* oop_fields() const { return _oop_fields; }
137 int contended_group() const { return _contended_group; }
138 int oop_count() const { return _oop_count; }
139
140 void add_primitive_field(int idx, BasicType type);
141 void add_oop_field(int idx);
142 void sort_by_size();
143 };
144
145 // The FieldLayout class represents a set of fields organized
146 // in a layout.
147 // An instance of FieldLayout can either represent the layout
148 // of non-static fields (used in an instance object) or the
149 // layout of static fields (to be included in the class mirror).
150 //
151 // _block is a pointer to a list of LayoutRawBlock ordered by increasing
152 // offsets.
153 // _start points to the LayoutRawBlock with the first offset that can
154 // be used to allocate fields of the current class
155 // _last points to the last LayoutRawBlock of the list. In order to
156 // simplify the code, the LayoutRawBlock list always ends with an
157 // EMPTY block (the kind of LayoutRawBlock from which space is taken
158 // to allocate fields) with a size big enough to satisfy all
159 // field allocations.
160 //
161 class FieldLayout : public ResourceObj {
162 private:
163 GrowableArray<FieldInfo>* _field_info;
164 ConstantPool* _cp;
165 LayoutRawBlock* _blocks; // the layout being computed
166 LayoutRawBlock* _start; // points to the first block where a field can be inserted
167 LayoutRawBlock* _last; // points to the last block of the layout (big empty block)
168
169 public:
170 FieldLayout(GrowableArray<FieldInfo>* field_info, ConstantPool* cp);
171 void initialize_static_layout();
172 void initialize_instance_layout(const InstanceKlass* ik);
173
174 LayoutRawBlock* first_empty_block() {
175 LayoutRawBlock* block = _start;
176 while (block->kind() != LayoutRawBlock::EMPTY) {
177 block = block->next_block();
178 }
179 return block;
180 }
181
182 LayoutRawBlock* start() { return _start; }
183 void set_start(LayoutRawBlock* start) { _start = start; }
184 LayoutRawBlock* last_block() { return _last; }
185
186 LayoutRawBlock* first_field_block();
187 void add(GrowableArray<LayoutRawBlock*>* list, LayoutRawBlock* start = nullptr);
188 void add_field_at_offset(LayoutRawBlock* blocks, int offset, LayoutRawBlock* start = nullptr);
189 void add_contiguously(GrowableArray<LayoutRawBlock*>* list, LayoutRawBlock* start = nullptr);
190 LayoutRawBlock* insert_field_block(LayoutRawBlock* slot, LayoutRawBlock* block);
191 bool reconstruct_layout(const InstanceKlass* ik);
192 void fill_holes(const InstanceKlass* ik);
193 LayoutRawBlock* insert(LayoutRawBlock* slot, LayoutRawBlock* block);
194 void remove(LayoutRawBlock* block);
195 void print(outputStream* output, bool is_static, const InstanceKlass* super);
196 };
197
198
199 // FieldLayoutBuilder is the main entry point for layout computation.
200 // This class has three methods to generate layout: one for regular classes
201 // and two for classes with hard coded offsets (java,lang.ref.Reference
202 // and the boxing classes). The rationale for having multiple methods
203 // is that each kind of class has a different set goals regarding
204 // its layout, so instead of mixing several layout strategies into a
205 // single method, each kind has its own method (see comments below
206 // for more details about the allocation strategies).
207 //
208 // Computing the layout of a class always goes through 4 steps:
209 // 1 - Prologue: preparation of data structure and gathering of
210 // layout information inherited from super classes
211 // 2 - Field sorting: fields are sorted according to their
212 // kind (oop, primitive, inline class) and their contention
213 // annotation (if any)
214 // 3 - Layout is computed from the set of lists generated during
215 // step 2
216 // 4 - Epilogue: oopmaps are generated, layout information is
217 // prepared so other VM components can use it (instance size,
218 // static field size, non-static field size, etc.)
219 //
220 // Steps 1 and 4 are common to all layout computations. Step 2 and 3
221 // can vary with the allocation strategy.
222 //
223 class FieldLayoutBuilder : public ResourceObj {
224 private:
225
226 const Symbol* _classname;
227 const InstanceKlass* _super_klass;
228 ConstantPool* _constant_pool;
229 GrowableArray<FieldInfo>* _field_info;
230 FieldLayoutInfo* _info;
231 FieldGroup* _root_group;
232 GrowableArray<FieldGroup*> _contended_groups;
233 FieldGroup* _static_fields;
234 FieldLayout* _layout;
235 FieldLayout* _static_layout;
236 int _nonstatic_oopmap_count;
237 int _alignment;
238 bool _has_nonstatic_fields;
239 bool _is_contended; // is a contended class?
240
241 public:
242 FieldLayoutBuilder(const Symbol* classname, const InstanceKlass* super_klass, ConstantPool* constant_pool,
243 GrowableArray<FieldInfo>* field_info, bool is_contended, FieldLayoutInfo* info);
244
245 int get_alignment() {
246 assert(_alignment != -1, "Uninitialized");
247 return _alignment;
248 }
249
250 void build_layout();
251 void compute_regular_layout();
252 void insert_contended_padding(LayoutRawBlock* slot);
253
254 private:
255 void prologue();
256 void epilogue();
257 void regular_field_sorting();
258 FieldGroup* get_or_create_contended_group(int g);
259 };
260
261 #endif // SHARE_CLASSFILE_FIELDLAYOUTBUILDER_HPP