1 /*
2 * Copyright (c) 1997, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 // This file contains platform-independent 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 // A union type for code which has to assemble both constant and
144 // non-constant operands, when the distinction cannot be made
145 // statically.
146 class RegisterOrConstant VALUE_OBJ_CLASS_SPEC {
147 private:
148 Register _r;
149 intptr_t _c;
150
151 public:
152 RegisterOrConstant(): _r(noreg), _c(0) {}
153 RegisterOrConstant(Register r): _r(r), _c(0) {}
154 RegisterOrConstant(intptr_t c): _r(noreg), _c(c) {}
155
156 Register as_register() const { assert(is_register(),""); return _r; }
157 intptr_t as_constant() const { assert(is_constant(),""); return _c; }
158
159 Register register_or_noreg() const { return _r; }
160 intptr_t constant_or_zero() const { return _c; }
161
162 bool is_register() const { return _r != noreg; }
163 bool is_constant() const { return _r == noreg; }
164 };
165
166 // The Abstract Assembler: Pure assembler doing NO optimizations on the
167 // instruction level; i.e., what you write is what you get.
168 // The Assembler is generating code into a CodeBuffer.
169 class AbstractAssembler : public ResourceObj {
170 friend class Label;
171
172 protected:
173 CodeSection* _code_section; // section within the code buffer
174 address _code_begin; // first byte of code buffer
175 address _code_limit; // first byte after code buffer
176 address _code_pos; // current code generation position
177 OopRecorder* _oop_recorder; // support for relocInfo::oop_type
178
179 // Code emission & accessing
180 address addr_at(int pos) const { return _code_begin + pos; }
181
182 // This routine is called with a label is used for an address.
183 // Labels and displacements truck in offsets, but target must return a PC.
184 address target(Label& L); // return _code_section->target(L)
185
186 bool is8bit(int x) const { return -0x80 <= x && x < 0x80; }
187 bool isByte(int x) const { return 0 <= x && x < 0x100; }
188 bool isShiftCount(int x) const { return 0 <= x && x < 32; }
189
190 void emit_byte(int x); // emit a single byte
191 void emit_word(int x); // emit a 16-bit word (not a wordSize word!)
192 void emit_long(jint x); // emit a 32-bit word (not a longSize word!)
193 void emit_address(address x); // emit an address (not a longSize word!)
194
195 // Instruction boundaries (required when emitting relocatable values).
196 class InstructionMark: public StackObj {
197 private:
198 AbstractAssembler* _assm;
199
200 public:
201 InstructionMark(AbstractAssembler* assm) : _assm(assm) {
202 assert(assm->inst_mark() == NULL, "overlapping instructions");
203 _assm->set_inst_mark();
204 }
205 ~InstructionMark() {
206 _assm->clear_inst_mark();
207 }
208 };
209 friend class InstructionMark;
210 #ifdef ASSERT
211 // Make it return true on platforms which need to verify
212 // instruction boundaries for some operations.
213 inline static bool pd_check_instruction_mark();
214 #endif
215
216 // Label functions
217 void print(Label& L);
218
219 public:
220
221 // Creation
222 AbstractAssembler(CodeBuffer* code);
223
224 // save end pointer back to code buf.
225 void sync();
226
227 // ensure buf contains all code (call this before using/copying the code)
228 void flush();
229
230 // Accessors
231 CodeBuffer* code() const; // _code_section->outer()
232 CodeSection* code_section() const { return _code_section; }
233 int sect() const; // return _code_section->index()
234 address pc() const { return _code_pos; }
235 int offset() const { return _code_pos - _code_begin; }
236 int locator() const; // CodeBuffer::locator(offset(), sect())
237 OopRecorder* oop_recorder() const { return _oop_recorder; }
238 void set_oop_recorder(OopRecorder* r) { _oop_recorder = r; }
239
240 address inst_mark() const;
241 void set_inst_mark();
242 void clear_inst_mark();
243
244 // Constants in code
245 void a_byte(int x);
246 void a_long(jint x);
247 void relocate(RelocationHolder const& rspec, int format = 0);
248 void relocate( relocInfo::relocType rtype, int format = 0) {
249 if (rtype != relocInfo::none)
250 relocate(Relocation::spec_simple(rtype), format);
251 }
252
253 static int code_fill_byte(); // used to pad out odd-sized code buffers
254
255 // Associate a comment with the current offset. It will be printed
256 // along with the disassembly when printing nmethods. Currently
257 // only supported in the instruction section of the code buffer.
258 void block_comment(const char* comment);
259
260 // Label functions
261 void bind(Label& L); // binds an unbound label L to the current code position
262
263 // Move to a different section in the same code buffer.
264 void set_code_section(CodeSection* cs);
265
266 // Inform assembler when generating stub code and relocation info
267 address start_a_stub(int required_space);
268 void end_a_stub();
269 // Ditto for constants.
270 address start_a_const(int required_space, int required_align = sizeof(double));
271 void end_a_const();
272
273 // constants support
274 address long_constant(jlong c) {
275 address ptr = start_a_const(sizeof(c), sizeof(c));
276 if (ptr != NULL) {
277 *(jlong*)ptr = c;
278 _code_pos = ptr + sizeof(c);
279 end_a_const();
280 }
281 return ptr;
282 }
283 address double_constant(jdouble c) {
284 address ptr = start_a_const(sizeof(c), sizeof(c));
285 if (ptr != NULL) {
286 *(jdouble*)ptr = c;
287 _code_pos = ptr + sizeof(c);
288 end_a_const();
289 }
290 return ptr;
291 }
292 address float_constant(jfloat c) {
293 address ptr = start_a_const(sizeof(c), sizeof(c));
294 if (ptr != NULL) {
295 *(jfloat*)ptr = c;
296 _code_pos = ptr + sizeof(c);
297 end_a_const();
298 }
299 return ptr;
300 }
301 address address_constant(address c) {
302 address ptr = start_a_const(sizeof(c), sizeof(c));
303 if (ptr != NULL) {
304 *(address*)ptr = c;
305 _code_pos = ptr + sizeof(c);
306 end_a_const();
307 }
308 return ptr;
309 }
310 address address_constant(address c, RelocationHolder const& rspec) {
311 address ptr = start_a_const(sizeof(c), sizeof(c));
312 if (ptr != NULL) {
313 relocate(rspec);
314 *(address*)ptr = c;
315 _code_pos = ptr + sizeof(c);
316 end_a_const();
317 }
318 return ptr;
319 }
320
321 // Bootstrapping aid to cope with delayed determination of constants.
322 // Returns a static address which will eventually contain the constant.
323 // The value zero (NULL) stands instead of a constant which is still uncomputed.
324 // Thus, the eventual value of the constant must not be zero.
325 // This is fine, since this is designed for embedding object field
326 // offsets in code which must be generated before the object class is loaded.
327 // Field offsets are never zero, since an object's header (mark word)
328 // is located at offset zero.
329 RegisterOrConstant delayed_value(int(*value_fn)(), Register tmp, int offset = 0) {
330 return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);
331 }
332 RegisterOrConstant delayed_value(address(*value_fn)(), Register tmp, int offset = 0) {
333 return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);
334 }
335 virtual RegisterOrConstant delayed_value_impl(intptr_t* delayed_value_addr, Register tmp, int offset) = 0;
336 // Last overloading is platform-dependent; look in assembler_<arch>.cpp.
337 static intptr_t* delayed_value_addr(int(*constant_fn)());
338 static intptr_t* delayed_value_addr(address(*constant_fn)());
339 static void update_delayed_values();
340
341 // Bang stack to trigger StackOverflowError at a safe location
342 // implementation delegates to machine-specific bang_stack_with_offset
343 void generate_stack_overflow_check( int frame_size_in_bytes );
344 virtual void bang_stack_with_offset(int offset) = 0;
345
346
347 /**
348 * A platform-dependent method to patch a jump instruction that refers
349 * to this label.
350 *
351 * @param branch the location of the instruction to patch
352 * @param masm the assembler which generated the branch
353 */
354 void pd_patch_instruction(address branch, address target);
355
356 #ifndef PRODUCT
357 /**
358 * Platform-dependent method of printing an instruction that needs to be
359 * patched.
360 *
361 * @param branch the instruction to be patched in the buffer.
362 */
363 static void pd_print_patched_instruction(address branch);
364 #endif // PRODUCT
365 };
366
367 #include "incls/_assembler_pd.hpp.incl"