1 /*
2 * Copyright (c) 1997, 2018, 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 #ifndef SHARE_VM_ASM_ASSEMBLER_HPP
26 #define SHARE_VM_ASM_ASSEMBLER_HPP
27
28 #include "asm/codeBuffer.hpp"
29 #include "asm/register.hpp"
30 #include "code/oopRecorder.hpp"
31 #include "code/relocInfo.hpp"
32 #include "memory/allocation.hpp"
33 #include "runtime/vm_version.hpp"
34 #include "utilities/debug.hpp"
35 #include "utilities/growableArray.hpp"
36 #include "utilities/macros.hpp"
37
38 // This file contains platform-independent assembler declarations.
39
40 class MacroAssembler;
41 class AbstractAssembler;
42 class Label;
43
44 /**
45 * Labels represent destinations for control transfer instructions. Such
46 * instructions can accept a Label as their target argument. A Label is
47 * bound to the current location in the code stream by calling the
48 * MacroAssembler's 'bind' method, which in turn calls the Label's 'bind'
49 * method. A Label may be referenced by an instruction before it's bound
50 * (i.e., 'forward referenced'). 'bind' stores the current code offset
51 * in the Label object.
52 *
53 * If an instruction references a bound Label, the offset field(s) within
54 * the instruction are immediately filled in based on the Label's code
55 * offset. If an instruction references an unbound label, that
56 * instruction is put on a list of instructions that must be patched
57 * (i.e., 'resolved') when the Label is bound.
58 *
59 * 'bind' will call the platform-specific 'patch_instruction' method to
60 * fill in the offset field(s) for each unresolved instruction (if there
61 * are any). 'patch_instruction' lives in one of the
62 * cpu/<arch>/vm/assembler_<arch>* files.
63 *
64 * Instead of using a linked list of unresolved instructions, a Label has
65 * an array of unresolved instruction code offsets. _patch_index
66 * contains the total number of forward references. If the Label's array
67 * overflows (i.e., _patch_index grows larger than the array size), a
68 * GrowableArray is allocated to hold the remaining offsets. (The cache
69 * size is 4 for now, which handles over 99.5% of the cases)
70 *
71 * Labels may only be used within a single CodeSection. If you need
72 * to create references between code sections, use explicit relocations.
73 */
74 class Label {
75 private:
76 enum { PatchCacheSize = 4 };
77
78 // _loc encodes both the binding state (via its sign)
79 // and the binding locator (via its value) of a label.
80 //
81 // _loc >= 0 bound label, loc() encodes the target (jump) position
82 // _loc == -1 unbound label
83 int _loc;
84
85 // References to instructions that jump to this unresolved label.
86 // These instructions need to be patched when the label is bound
87 // using the platform-specific patchInstruction() method.
88 //
89 // To avoid having to allocate from the C-heap each time, we provide
90 // a local cache and use the overflow only if we exceed the local cache
91 int _patches[PatchCacheSize];
92 int _patch_index;
93 GrowableArray<int>* _patch_overflow;
94
95 Label(const Label&) { ShouldNotReachHere(); }
96 protected:
97
98 // The label will be bound to a location near its users.
99 bool _is_near;
100
101 public:
102
103 /**
104 * After binding, be sure 'patch_instructions' is called later to link
105 */
106 void bind_loc(int loc) {
107 assert(loc >= 0, "illegal locator");
108 assert(_loc == -1, "already bound");
109 _loc = loc;
110 }
111 void bind_loc(int pos, int sect) { bind_loc(CodeBuffer::locator(pos, sect)); }
112
113 #ifndef PRODUCT
114 // Iterates over all unresolved instructions for printing
115 void print_instructions(MacroAssembler* masm) const;
116 #endif // PRODUCT
117
118 /**
119 * Returns the position of the the Label in the code buffer
120 * The position is a 'locator', which encodes both offset and section.
121 */
122 int loc() const {
123 assert(_loc >= 0, "unbound label");
124 return _loc;
125 }
126 int loc_pos() const { return CodeBuffer::locator_pos(loc()); }
127 int loc_sect() const { return CodeBuffer::locator_sect(loc()); }
128
129 bool is_bound() const { return _loc >= 0; }
130 bool is_unbound() const { return _loc == -1 && _patch_index > 0; }
131 bool is_unused() const { return _loc == -1 && _patch_index == 0; }
132
133 // The label will be bound to a location near its users. Users can
134 // optimize on this information, e.g. generate short branches.
135 bool is_near() { return _is_near; }
136
137 /**
138 * Adds a reference to an unresolved displacement instruction to
139 * this unbound label
140 *
141 * @param cb the code buffer being patched
142 * @param branch_loc the locator of the branch instruction in the code buffer
143 */
144 void add_patch_at(CodeBuffer* cb, int branch_loc);
145
146 /**
147 * Iterate over the list of patches, resolving the instructions
148 * Call patch_instruction on each 'branch_loc' value
149 */
150 void patch_instructions(MacroAssembler* masm);
151
152 void init() {
153 _loc = -1;
154 _patch_index = 0;
155 _patch_overflow = NULL;
156 _is_near = false;
157 }
158
159 Label() {
160 init();
161 }
162
163 ~Label() {
164 assert(is_bound() || is_unused(), "Label was never bound to a location, but it was used as a jmp target");
165 }
166 };
167
168 // A NearLabel must be bound to a location near its users. Users can
169 // optimize on this information, e.g. generate short branches.
170 class NearLabel : public Label {
171 public:
172 NearLabel() : Label() { _is_near = true; }
173 };
174
175 // A union type for code which has to assemble both constant and
176 // non-constant operands, when the distinction cannot be made
177 // statically.
178 class RegisterOrConstant {
179 private:
180 Register _r;
181 intptr_t _c;
182
183 public:
184 RegisterOrConstant(): _r(noreg), _c(0) {}
185 RegisterOrConstant(Register r): _r(r), _c(0) {}
186 RegisterOrConstant(intptr_t c): _r(noreg), _c(c) {}
187
188 Register as_register() const { assert(is_register(),""); return _r; }
189 intptr_t as_constant() const { assert(is_constant(),""); return _c; }
190
191 Register register_or_noreg() const { return _r; }
192 intptr_t constant_or_zero() const { return _c; }
193
194 bool is_register() const { return _r != noreg; }
195 bool is_constant() const { return _r == noreg; }
196 };
197
198 // The Abstract Assembler: Pure assembler doing NO optimizations on the
199 // instruction level; i.e., what you write is what you get.
200 // The Assembler is generating code into a CodeBuffer.
201 class AbstractAssembler : public ResourceObj {
202 friend class Label;
203
204 protected:
205 CodeSection* _code_section; // section within the code buffer
206 OopRecorder* _oop_recorder; // support for relocInfo::oop_type
207
208 public:
209 // Code emission & accessing
210 address addr_at(int pos) const { return code_section()->start() + pos; }
211
212 protected:
213 // This routine is called with a label is used for an address.
214 // Labels and displacements truck in offsets, but target must return a PC.
215 address target(Label& L) { return code_section()->target(L, pc()); }
216
217 bool is8bit(int x) const { return -0x80 <= x && x < 0x80; }
218 bool isByte(int x) const { return 0 <= x && x < 0x100; }
219 bool isShiftCount(int x) const { return 0 <= x && x < 32; }
220
221 // Instruction boundaries (required when emitting relocatable values).
222 class InstructionMark: public StackObj {
223 private:
224 AbstractAssembler* _assm;
225
226 public:
227 InstructionMark(AbstractAssembler* assm) : _assm(assm) {
228 assert(assm->inst_mark() == NULL, "overlapping instructions");
229 _assm->set_inst_mark();
230 }
231 ~InstructionMark() {
232 _assm->clear_inst_mark();
233 }
234 };
235 friend class InstructionMark;
236 #ifdef ASSERT
237 // Make it return true on platforms which need to verify
238 // instruction boundaries for some operations.
239 static bool pd_check_instruction_mark();
240
241 // Add delta to short branch distance to verify that it still fit into imm8.
242 int _short_branch_delta;
243
244 int short_branch_delta() const { return _short_branch_delta; }
245 void set_short_branch_delta() { _short_branch_delta = 32; }
246 void clear_short_branch_delta() { _short_branch_delta = 0; }
247
248 class ShortBranchVerifier: public StackObj {
249 private:
250 AbstractAssembler* _assm;
251
252 public:
253 ShortBranchVerifier(AbstractAssembler* assm) : _assm(assm) {
254 assert(assm->short_branch_delta() == 0, "overlapping instructions");
255 _assm->set_short_branch_delta();
256 }
257 ~ShortBranchVerifier() {
258 _assm->clear_short_branch_delta();
259 }
260 };
261 #else
262 // Dummy in product.
263 class ShortBranchVerifier: public StackObj {
264 public:
265 ShortBranchVerifier(AbstractAssembler* assm) {}
266 };
267 #endif
268
269 public:
270
271 // Creation
272 AbstractAssembler(CodeBuffer* code);
273
274 // ensure buf contains all code (call this before using/copying the code)
275 void flush();
276
277 void emit_int8( int8_t x) { code_section()->emit_int8( x); }
278 void emit_int16( int16_t x) { code_section()->emit_int16( x); }
279 void emit_int32( int32_t x) { code_section()->emit_int32( x); }
280 void emit_int64( int64_t x) { code_section()->emit_int64( x); }
281
282 void emit_float( jfloat x) { code_section()->emit_float( x); }
283 void emit_double( jdouble x) { code_section()->emit_double( x); }
284 void emit_address(address x) { code_section()->emit_address(x); }
285
286 // min and max values for signed immediate ranges
287 static int min_simm(int nbits) { return -(intptr_t(1) << (nbits - 1)) ; }
288 static int max_simm(int nbits) { return (intptr_t(1) << (nbits - 1)) - 1; }
289
290 // Define some:
291 static int min_simm10() { return min_simm(10); }
292 static int min_simm13() { return min_simm(13); }
293 static int min_simm16() { return min_simm(16); }
294
295 // Test if x is within signed immediate range for nbits
296 static bool is_simm(intptr_t x, int nbits) { return min_simm(nbits) <= x && x <= max_simm(nbits); }
297
298 // Define some:
299 static bool is_simm5( intptr_t x) { return is_simm(x, 5 ); }
300 static bool is_simm8( intptr_t x) { return is_simm(x, 8 ); }
301 static bool is_simm10(intptr_t x) { return is_simm(x, 10); }
302 static bool is_simm11(intptr_t x) { return is_simm(x, 11); }
303 static bool is_simm12(intptr_t x) { return is_simm(x, 12); }
304 static bool is_simm13(intptr_t x) { return is_simm(x, 13); }
305 static bool is_simm16(intptr_t x) { return is_simm(x, 16); }
306 static bool is_simm26(intptr_t x) { return is_simm(x, 26); }
307 static bool is_simm32(intptr_t x) { return is_simm(x, 32); }
308
309 // Accessors
310 CodeSection* code_section() const { return _code_section; }
311 CodeBuffer* code() const { return code_section()->outer(); }
312 int sect() const { return code_section()->index(); }
313 address pc() const { return code_section()->end(); }
314 int offset() const { return code_section()->size(); }
315 int locator() const { return CodeBuffer::locator(offset(), sect()); }
316
317 OopRecorder* oop_recorder() const { return _oop_recorder; }
318 void set_oop_recorder(OopRecorder* r) { _oop_recorder = r; }
319
320 address inst_mark() const { return code_section()->mark(); }
321 void set_inst_mark() { code_section()->set_mark(); }
322 void clear_inst_mark() { code_section()->clear_mark(); }
323
324 // Constants in code
325 void relocate(RelocationHolder const& rspec, int format = 0) {
326 assert(!pd_check_instruction_mark()
327 || inst_mark() == NULL || inst_mark() == code_section()->end(),
328 "call relocate() between instructions");
329 code_section()->relocate(code_section()->end(), rspec, format);
330 }
331 void relocate( relocInfo::relocType rtype, int format = 0) {
332 code_section()->relocate(code_section()->end(), rtype, format);
333 }
334
335 static int code_fill_byte(); // used to pad out odd-sized code buffers
336
337 // Associate a comment with the current offset. It will be printed
338 // along with the disassembly when printing nmethods. Currently
339 // only supported in the instruction section of the code buffer.
340 void block_comment(const char* comment);
341 // Copy str to a buffer that has the same lifetime as the CodeBuffer
342 const char* code_string(const char* str);
343
344 // Label functions
345 void bind(Label& L); // binds an unbound label L to the current code position
346
347 // Move to a different section in the same code buffer.
348 void set_code_section(CodeSection* cs);
349
350 // Inform assembler when generating stub code and relocation info
351 address start_a_stub(int required_space);
352 void end_a_stub();
353 // Ditto for constants.
354 address start_a_const(int required_space, int required_align = sizeof(double));
355 void end_a_const(CodeSection* cs); // Pass the codesection to continue in (insts or stubs?).
356
357 // constants support
358 //
359 // We must remember the code section (insts or stubs) in c1
360 // so we can reset to the proper section in end_a_const().
361 address int_constant(jint c) {
362 CodeSection* c1 = _code_section;
363 address ptr = start_a_const(sizeof(c), sizeof(c));
364 if (ptr != NULL) {
365 emit_int32(c);
366 end_a_const(c1);
367 }
368 return ptr;
369 }
370 address long_constant(jlong c) {
371 CodeSection* c1 = _code_section;
372 address ptr = start_a_const(sizeof(c), sizeof(c));
373 if (ptr != NULL) {
374 emit_int64(c);
375 end_a_const(c1);
376 }
377 return ptr;
378 }
379 address double_constant(jdouble c) {
380 CodeSection* c1 = _code_section;
381 address ptr = start_a_const(sizeof(c), sizeof(c));
382 if (ptr != NULL) {
383 emit_double(c);
384 end_a_const(c1);
385 }
386 return ptr;
387 }
388 address float_constant(jfloat c) {
389 CodeSection* c1 = _code_section;
390 address ptr = start_a_const(sizeof(c), sizeof(c));
391 if (ptr != NULL) {
392 emit_float(c);
393 end_a_const(c1);
394 }
395 return ptr;
396 }
397 address address_constant(address c) {
398 CodeSection* c1 = _code_section;
399 address ptr = start_a_const(sizeof(c), sizeof(c));
400 if (ptr != NULL) {
401 emit_address(c);
402 end_a_const(c1);
403 }
404 return ptr;
405 }
406 address address_constant(address c, RelocationHolder const& rspec) {
407 CodeSection* c1 = _code_section;
408 address ptr = start_a_const(sizeof(c), sizeof(c));
409 if (ptr != NULL) {
410 relocate(rspec);
411 emit_address(c);
412 end_a_const(c1);
413 }
414 return ptr;
415 }
416
417 // Bootstrapping aid to cope with delayed determination of constants.
418 // Returns a static address which will eventually contain the constant.
419 // The value zero (NULL) stands instead of a constant which is still uncomputed.
420 // Thus, the eventual value of the constant must not be zero.
421 // This is fine, since this is designed for embedding object field
422 // offsets in code which must be generated before the object class is loaded.
423 // Field offsets are never zero, since an object's header (mark word)
424 // is located at offset zero.
425 RegisterOrConstant delayed_value(int(*value_fn)(), Register tmp, int offset = 0);
426 RegisterOrConstant delayed_value(address(*value_fn)(), Register tmp, int offset = 0);
427 virtual RegisterOrConstant delayed_value_impl(intptr_t* delayed_value_addr, Register tmp, int offset) = 0;
428 // Last overloading is platform-dependent; look in assembler_<arch>.cpp.
429 static intptr_t* delayed_value_addr(int(*constant_fn)());
430 static intptr_t* delayed_value_addr(address(*constant_fn)());
431 static void update_delayed_values();
432
433 // Bang stack to trigger StackOverflowError at a safe location
434 // implementation delegates to machine-specific bang_stack_with_offset
435 void generate_stack_overflow_check( int frame_size_in_bytes );
436 virtual void bang_stack_with_offset(int offset) = 0;
437
438
439 /**
440 * A platform-dependent method to patch a jump instruction that refers
441 * to this label.
442 *
443 * @param branch the location of the instruction to patch
444 * @param masm the assembler which generated the branch
445 */
446 void pd_patch_instruction(address branch, address target);
447
448 };
449
450 #include CPU_HEADER(assembler)
451
452 #endif // SHARE_VM_ASM_ASSEMBLER_HPP