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comparison src/share/vm/asm/assembler.hpp @ 0:a61af66fc99e jdk7-b24

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
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1 /*
2 * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 // This file contains platform-independant assembler declarations.
26
27 class CodeBuffer;
28 class MacroAssembler;
29 class AbstractAssembler;
30 class Label;
31
32 /**
33 * Labels represent destinations for control transfer instructions. Such
34 * instructions can accept a Label as their target argument. A Label is
35 * bound to the current location in the code stream by calling the
36 * MacroAssembler's 'bind' method, which in turn calls the Label's 'bind'
37 * method. A Label may be referenced by an instruction before it's bound
38 * (i.e., 'forward referenced'). 'bind' stores the current code offset
39 * in the Label object.
40 *
41 * If an instruction references a bound Label, the offset field(s) within
42 * the instruction are immediately filled in based on the Label's code
43 * offset. If an instruction references an unbound label, that
44 * instruction is put on a list of instructions that must be patched
45 * (i.e., 'resolved') when the Label is bound.
46 *
47 * 'bind' will call the platform-specific 'patch_instruction' method to
48 * fill in the offset field(s) for each unresolved instruction (if there
49 * are any). 'patch_instruction' lives in one of the
50 * cpu/<arch>/vm/assembler_<arch>* files.
51 *
52 * Instead of using a linked list of unresolved instructions, a Label has
53 * an array of unresolved instruction code offsets. _patch_index
54 * contains the total number of forward references. If the Label's array
55 * overflows (i.e., _patch_index grows larger than the array size), a
56 * GrowableArray is allocated to hold the remaining offsets. (The cache
57 * size is 4 for now, which handles over 99.5% of the cases)
58 *
59 * Labels may only be used within a single CodeSection. If you need
60 * to create references between code sections, use explicit relocations.
61 */
62 class Label VALUE_OBJ_CLASS_SPEC {
63 private:
64 enum { PatchCacheSize = 4 };
65
66 // _loc encodes both the binding state (via its sign)
67 // and the binding locator (via its value) of a label.
68 //
69 // _loc >= 0 bound label, loc() encodes the target (jump) position
70 // _loc == -1 unbound label
71 int _loc;
72
73 // References to instructions that jump to this unresolved label.
74 // These instructions need to be patched when the label is bound
75 // using the platform-specific patchInstruction() method.
76 //
77 // To avoid having to allocate from the C-heap each time, we provide
78 // a local cache and use the overflow only if we exceed the local cache
79 int _patches[PatchCacheSize];
80 int _patch_index;
81 GrowableArray<int>* _patch_overflow;
82
83 Label(const Label&) { ShouldNotReachHere(); }
84
85 public:
86
87 /**
88 * After binding, be sure 'patch_instructions' is called later to link
89 */
90 void bind_loc(int loc) {
91 assert(loc >= 0, "illegal locator");
92 assert(_loc == -1, "already bound");
93 _loc = loc;
94 }
95 void bind_loc(int pos, int sect); // = bind_loc(locator(pos, sect))
96
97 #ifndef PRODUCT
98 // Iterates over all unresolved instructions for printing
99 void print_instructions(MacroAssembler* masm) const;
100 #endif // PRODUCT
101
102 /**
103 * Returns the position of the the Label in the code buffer
104 * The position is a 'locator', which encodes both offset and section.
105 */
106 int loc() const {
107 assert(_loc >= 0, "unbound label");
108 return _loc;
109 }
110 int loc_pos() const; // == locator_pos(loc())
111 int loc_sect() const; // == locator_sect(loc())
112
113 bool is_bound() const { return _loc >= 0; }
114 bool is_unbound() const { return _loc == -1 && _patch_index > 0; }
115 bool is_unused() const { return _loc == -1 && _patch_index == 0; }
116
117 /**
118 * Adds a reference to an unresolved displacement instruction to
119 * this unbound label
120 *
121 * @param cb the code buffer being patched
122 * @param branch_loc the locator of the branch instruction in the code buffer
123 */
124 void add_patch_at(CodeBuffer* cb, int branch_loc);
125
126 /**
127 * Iterate over the list of patches, resolving the instructions
128 * Call patch_instruction on each 'branch_loc' value
129 */
130 void patch_instructions(MacroAssembler* masm);
131
132 void init() {
133 _loc = -1;
134 _patch_index = 0;
135 _patch_overflow = NULL;
136 }
137
138 Label() {
139 init();
140 }
141 };
142
143
144 // The Abstract Assembler: Pure assembler doing NO optimizations on the
145 // instruction level; i.e., what you write is what you get.
146 // The Assembler is generating code into a CodeBuffer.
147 class AbstractAssembler : public ResourceObj {
148 friend class Label;
149
150 protected:
151 CodeSection* _code_section; // section within the code buffer
152 address _code_begin; // first byte of code buffer
153 address _code_limit; // first byte after code buffer
154 address _code_pos; // current code generation position
155 OopRecorder* _oop_recorder; // support for relocInfo::oop_type
156
157 // Code emission & accessing
158 address addr_at(int pos) const { return _code_begin + pos; }
159
160 // This routine is called with a label is used for an address.
161 // Labels and displacements truck in offsets, but target must return a PC.
162 address target(Label& L); // return _code_section->target(L)
163
164 bool is8bit(int x) const { return -0x80 <= x && x < 0x80; }
165 bool isByte(int x) const { return 0 <= x && x < 0x100; }
166 bool isShiftCount(int x) const { return 0 <= x && x < 32; }
167
168 void emit_byte(int x); // emit a single byte
169 void emit_word(int x); // emit a 16-bit word (not a wordSize word!)
170 void emit_long(jint x); // emit a 32-bit word (not a longSize word!)
171 void emit_address(address x); // emit an address (not a longSize word!)
172
173 // Instruction boundaries (required when emitting relocatable values).
174 class InstructionMark: public StackObj {
175 private:
176 AbstractAssembler* _assm;
177
178 public:
179 InstructionMark(AbstractAssembler* assm) : _assm(assm) {
180 assert(assm->inst_mark() == NULL, "overlapping instructions");
181 _assm->set_inst_mark();
182 }
183 ~InstructionMark() {
184 _assm->clear_inst_mark();
185 }
186 };
187 friend class InstructionMark;
188 #ifdef ASSERT
189 // Make it return true on platforms which need to verify
190 // instruction boundaries for some operations.
191 inline static bool pd_check_instruction_mark();
192 #endif
193
194 // Label functions
195 void print(Label& L);
196
197 public:
198
199 // Creation
200 AbstractAssembler(CodeBuffer* code);
201
202 // save end pointer back to code buf.
203 void sync();
204
205 // ensure buf contains all code (call this before using/copying the code)
206 void flush();
207
208 // Accessors
209 CodeBuffer* code() const; // _code_section->outer()
210 CodeSection* code_section() const { return _code_section; }
211 int sect() const; // return _code_section->index()
212 address pc() const { return _code_pos; }
213 int offset() const { return _code_pos - _code_begin; }
214 int locator() const; // CodeBuffer::locator(offset(), sect())
215 OopRecorder* oop_recorder() const { return _oop_recorder; }
216 void set_oop_recorder(OopRecorder* r) { _oop_recorder = r; }
217
218 address inst_mark() const;
219 void set_inst_mark();
220 void clear_inst_mark();
221
222 // Constants in code
223 void a_byte(int x);
224 void a_long(jint x);
225 void relocate(RelocationHolder const& rspec, int format = 0);
226 void relocate( relocInfo::relocType rtype, int format = 0) {
227 if (rtype != relocInfo::none)
228 relocate(Relocation::spec_simple(rtype), format);
229 }
230
231 static int code_fill_byte(); // used to pad out odd-sized code buffers
232
233 // Associate a comment with the current offset. It will be printed
234 // along with the disassembly when printing nmethods. Currently
235 // only supported in the instruction section of the code buffer.
236 void block_comment(const char* comment);
237
238 // Label functions
239 void bind(Label& L); // binds an unbound label L to the current code position
240
241 // Move to a different section in the same code buffer.
242 void set_code_section(CodeSection* cs);
243
244 // Inform assembler when generating stub code and relocation info
245 address start_a_stub(int required_space);
246 void end_a_stub();
247 // Ditto for constants.
248 address start_a_const(int required_space, int required_align = sizeof(double));
249 void end_a_const();
250
251 // fp constants support
252 address double_constant(jdouble c) {
253 address ptr = start_a_const(sizeof(c), sizeof(c));
254 if (ptr != NULL) {
255 *(jdouble*)ptr = c;
256 _code_pos = ptr + sizeof(c);
257 end_a_const();
258 }
259 return ptr;
260 }
261 address float_constant(jfloat c) {
262 address ptr = start_a_const(sizeof(c), sizeof(c));
263 if (ptr != NULL) {
264 *(jfloat*)ptr = c;
265 _code_pos = ptr + sizeof(c);
266 end_a_const();
267 }
268 return ptr;
269 }
270 address address_constant(address c, RelocationHolder const& rspec) {
271 address ptr = start_a_const(sizeof(c), sizeof(c));
272 if (ptr != NULL) {
273 relocate(rspec);
274 *(address*)ptr = c;
275 _code_pos = ptr + sizeof(c);
276 end_a_const();
277 }
278 return ptr;
279 }
280 inline address address_constant(Label& L);
281 inline address address_table_constant(GrowableArray<Label*> label);
282
283 // Bang stack to trigger StackOverflowError at a safe location
284 // implementation delegates to machine-specific bang_stack_with_offset
285 void generate_stack_overflow_check( int frame_size_in_bytes );
286 virtual void bang_stack_with_offset(int offset) = 0;
287
288
289 /**
290 * A platform-dependent method to patch a jump instruction that refers
291 * to this label.
292 *
293 * @param branch the location of the instruction to patch
294 * @param masm the assembler which generated the branch
295 */
296 void pd_patch_instruction(address branch, address target);
297
298 #ifndef PRODUCT
299 /**
300 * Platform-dependent method of printing an instruction that needs to be
301 * patched.
302 *
303 * @param branch the instruction to be patched in the buffer.
304 */
305 static void pd_print_patched_instruction(address branch);
306 #endif // PRODUCT
307 };
308
309 #include "incls/_assembler_pd.hpp.incl"