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 "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 #ifdef _WINDOWS
105 // qsort() on Windows reverse the order of fields with the same size
106 // the extension of the comparison function below preserves this order
107 int diff = (*y)->size() - (*x)->size();
108 if (diff == 0) {
109 diff = (*x)->field_index() - (*y)->field_index();
110 }
111 return diff;
112 #else
113 return (*y)->size() - (*x)->size();
114 #endif // _WINDOWS
115 }
116
117 };
118
119 // A Field group represents a set of fields that have to be allocated together,
120 // this is the way the @Contended annotation is supported.
121 // Inside a FieldGroup, fields are sorted based on their kind: primitive,
122 // oop, or flattened.
123 //
124 class FieldGroup : public ResourceObj {
125
126 private:
127 FieldGroup* _next;
128 GrowableArray<LayoutRawBlock*>* _primitive_fields;
129 GrowableArray<LayoutRawBlock*>* _oop_fields;
130 int _contended_group;
131 int _oop_count;
132 static const int INITIAL_LIST_SIZE = 16;
133
134 public:
135 FieldGroup(int contended_group = -1);
136
137 FieldGroup* next() const { return _next; }
138 void set_next(FieldGroup* next) { _next = next; }
139 GrowableArray<LayoutRawBlock*>* primitive_fields() const { return _primitive_fields; }
140 GrowableArray<LayoutRawBlock*>* oop_fields() const { return _oop_fields; }
141 int contended_group() const { return _contended_group; }
142 int oop_count() const { return _oop_count; }
143
144 void add_primitive_field(int idx, BasicType type);
145 void add_oop_field(int idx);
146 void sort_by_size();
147 };
148
149 // The FieldLayout class represents a set of fields organized
150 // in a layout.
151 // An instance of FieldLayout can either represent the layout
152 // of non-static fields (used in an instance object) or the
153 // layout of static fields (to be included in the class mirror).
154 //
155 // _block is a pointer to a list of LayoutRawBlock ordered by increasing
156 // offsets.
157 // _start points to the LayoutRawBlock with the first offset that can
158 // be used to allocate fields of the current class
159 // _last points to the last LayoutRawBlock of the list. In order to
160 // simplify the code, the LayoutRawBlock list always ends with an
161 // EMPTY block (the kind of LayoutRawBlock from which space is taken
162 // to allocate fields) with a size big enough to satisfy all
163 // field allocations.
164 //
165 class FieldLayout : public ResourceObj {
166 private:
167 GrowableArray<FieldInfo>* _field_info;
168 ConstantPool* _cp;
169 LayoutRawBlock* _blocks; // the layout being computed
170 LayoutRawBlock* _start; // points to the first block where a field can be inserted
171 LayoutRawBlock* _last; // points to the last block of the layout (big empty block)
172
173 public:
174 FieldLayout(GrowableArray<FieldInfo>* field_info, ConstantPool* cp);
175 void initialize_static_layout();
176 void initialize_instance_layout(const InstanceKlass* ik);
177
178 LayoutRawBlock* first_empty_block() {
179 LayoutRawBlock* block = _start;
180 while (block->kind() != LayoutRawBlock::EMPTY) {
181 block = block->next_block();
182 }
183 return block;
184 }
185
186 LayoutRawBlock* start() { return _start; }
187 void set_start(LayoutRawBlock* start) { _start = start; }
188 LayoutRawBlock* last_block() { return _last; }
189
190 LayoutRawBlock* first_field_block();
191 void add(GrowableArray<LayoutRawBlock*>* list, LayoutRawBlock* start = nullptr);
192 void add_field_at_offset(LayoutRawBlock* blocks, int offset, LayoutRawBlock* start = nullptr);
193 void add_contiguously(GrowableArray<LayoutRawBlock*>* list, LayoutRawBlock* start = nullptr);
194 LayoutRawBlock* insert_field_block(LayoutRawBlock* slot, LayoutRawBlock* block);
195 bool reconstruct_layout(const InstanceKlass* ik);
196 void fill_holes(const InstanceKlass* ik);
197 LayoutRawBlock* insert(LayoutRawBlock* slot, LayoutRawBlock* block);
198 void remove(LayoutRawBlock* block);
199 void print(outputStream* output, bool is_static, const InstanceKlass* super);
200 };
201
202
203 // FieldLayoutBuilder is the main entry point for layout computation.
204 // This class has three methods to generate layout: one for regular classes
205 // and two for classes with hard coded offsets (java,lang.ref.Reference
206 // and the boxing classes). The rationale for having multiple methods
207 // is that each kind of class has a different set goals regarding
208 // its layout, so instead of mixing several layout strategies into a
209 // single method, each kind has its own method (see comments below
210 // for more details about the allocation strategies).
211 //
212 // Computing the layout of a class always goes through 4 steps:
213 // 1 - Prologue: preparation of data structure and gathering of
214 // layout information inherited from super classes
215 // 2 - Field sorting: fields are sorted according to their
216 // kind (oop, primitive, inline class) and their contention
217 // annotation (if any)
218 // 3 - Layout is computed from the set of lists generated during
219 // step 2
220 // 4 - Epilogue: oopmaps are generated, layout information is
221 // prepared so other VM components can use it (instance size,
222 // static field size, non-static field size, etc.)
223 //
224 // Steps 1 and 4 are common to all layout computations. Step 2 and 3
225 // can vary with the allocation strategy.
226 //
227 class FieldLayoutBuilder : public ResourceObj {
228 private:
229
230 const Symbol* _classname;
231 const InstanceKlass* _super_klass;
232 ConstantPool* _constant_pool;
233 GrowableArray<FieldInfo>* _field_info;
234 FieldLayoutInfo* _info;
235 FieldGroup* _root_group;
236 GrowableArray<FieldGroup*> _contended_groups;
237 FieldGroup* _static_fields;
238 FieldLayout* _layout;
239 FieldLayout* _static_layout;
240 int _nonstatic_oopmap_count;
241 int _alignment;
242 bool _has_nonstatic_fields;
243 bool _is_contended; // is a contended class?
244
245 public:
246 FieldLayoutBuilder(const Symbol* classname, const InstanceKlass* super_klass, ConstantPool* constant_pool,
247 GrowableArray<FieldInfo>* field_info, bool is_contended, FieldLayoutInfo* info);
248
249 int get_alignment() {
250 assert(_alignment != -1, "Uninitialized");
251 return _alignment;
252 }
253
254 void build_layout();
255 void compute_regular_layout();
256 void insert_contended_padding(LayoutRawBlock* slot);
257
258 private:
259 void prologue();
260 void epilogue();
261 void regular_field_sorting();
262 FieldGroup* get_or_create_contended_group(int g);
263 };
264
265 #endif // SHARE_CLASSFILE_FIELDLAYOUTBUILDER_HPP