1 /*
2 * Copyright (c) 1997, 2013, 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 #include "precompiled.hpp"
26 #include "asm/macroAssembler.hpp"
27 #include "asm/macroAssembler.inline.hpp"
28 #include "asm/codeBuffer.hpp"
29 #include "runtime/atomic.inline.hpp"
30 #include "runtime/icache.hpp"
31 #include "runtime/os.hpp"
32
33
34 // Implementation of AbstractAssembler
35 //
36 // The AbstractAssembler is generating code into a CodeBuffer. To make code generation faster,
37 // the assembler keeps a copy of the code buffers boundaries & modifies them when
38 // emitting bytes rather than using the code buffers accessor functions all the time.
39 // The code buffer is updated via set_code_end(...) after emitting a whole instruction.
40
41 AbstractAssembler::AbstractAssembler(CodeBuffer* code) {
42 if (code == NULL) return;
43 CodeSection* cs = code->insts();
44 cs->clear_mark(); // new assembler kills old mark
45 if (cs->start() == NULL) {
46 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, err_msg("CodeCache: no room for %s",
47 code->name()));
48 }
49 _code_section = cs;
50 _oop_recorder= code->oop_recorder();
51 DEBUG_ONLY( _short_branch_delta = 0; )
52 }
53
54 void AbstractAssembler::set_code_section(CodeSection* cs) {
55 assert(cs->outer() == code_section()->outer(), "sanity");
56 assert(cs->is_allocated(), "need to pre-allocate this section");
57 cs->clear_mark(); // new assembly into this section kills old mark
58 _code_section = cs;
59 }
60
61 // Inform CodeBuffer that incoming code and relocation will be for stubs
62 address AbstractAssembler::start_a_stub(int required_space) {
63 CodeBuffer* cb = code();
64 CodeSection* cs = cb->stubs();
65 assert(_code_section == cb->insts(), "not in insts?");
66 if (cs->maybe_expand_to_ensure_remaining(required_space)
67 && cb->blob() == NULL) {
68 return NULL;
69 }
70 set_code_section(cs);
71 return pc();
72 }
73
74 // Inform CodeBuffer that incoming code and relocation will be code
75 // Should not be called if start_a_stub() returned NULL
76 void AbstractAssembler::end_a_stub() {
77 assert(_code_section == code()->stubs(), "not in stubs?");
78 set_code_section(code()->insts());
79 }
80
81 // Inform CodeBuffer that incoming code and relocation will be for stubs
82 address AbstractAssembler::start_a_const(int required_space, int required_align) {
83 CodeBuffer* cb = code();
84 CodeSection* cs = cb->consts();
85 assert(_code_section == cb->insts() || _code_section == cb->stubs(), "not in insts/stubs?");
86 address end = cs->end();
87 int pad = -(intptr_t)end & (required_align-1);
88 if (cs->maybe_expand_to_ensure_remaining(pad + required_space)) {
89 if (cb->blob() == NULL) return NULL;
90 end = cs->end(); // refresh pointer
91 }
92 if (pad > 0) {
93 while (--pad >= 0) { *end++ = 0; }
94 cs->set_end(end);
95 }
96 set_code_section(cs);
97 return end;
98 }
99
100 // Inform CodeBuffer that incoming code and relocation will be code
101 // in section cs (insts or stubs).
102 void AbstractAssembler::end_a_const(CodeSection* cs) {
103 assert(_code_section == code()->consts(), "not in consts?");
104 set_code_section(cs);
105 }
106
107 void AbstractAssembler::flush() {
108 ICache::invalidate_range(addr_at(0), offset());
109 }
110
111 void AbstractAssembler::bind(Label& L) {
112 if (L.is_bound()) {
113 // Assembler can bind a label more than once to the same place.
114 guarantee(L.loc() == locator(), "attempt to redefine label");
115 return;
116 }
117 L.bind_loc(locator());
118 L.patch_instructions((MacroAssembler*)this);
119 }
120
121 void AbstractAssembler::generate_stack_overflow_check(int frame_size_in_bytes) {
122 if (UseStackBanging) {
123 // Each code entry causes one stack bang n pages down the stack where n
124 // is configurable by StackShadowPages. The setting depends on the maximum
125 // depth of VM call stack or native before going back into java code,
126 // since only java code can raise a stack overflow exception using the
127 // stack banging mechanism. The VM and native code does not detect stack
128 // overflow.
129 // The code in JavaCalls::call() checks that there is at least n pages
130 // available, so all entry code needs to do is bang once for the end of
131 // this shadow zone.
132 // The entry code may need to bang additional pages if the framesize
133 // is greater than a page.
134
135 const int page_size = os::vm_page_size();
136 int bang_end = StackShadowPages * page_size;
137
138 // This is how far the previous frame's stack banging extended.
139 const int bang_end_safe = bang_end;
140
141 if (frame_size_in_bytes > page_size) {
142 bang_end += frame_size_in_bytes;
143 }
144
145 int bang_offset = bang_end_safe;
146 while (bang_offset <= bang_end) {
147 // Need at least one stack bang at end of shadow zone.
148 bang_stack_with_offset(bang_offset);
149 bang_offset += page_size;
150 }
151 } // end (UseStackBanging)
152 }
153
154 void Label::add_patch_at(CodeBuffer* cb, int branch_loc) {
155 assert(_loc == -1, "Label is unbound");
156 if (_patch_index < PatchCacheSize) {
157 _patches[_patch_index] = branch_loc;
158 } else {
159 if (_patch_overflow == NULL) {
160 _patch_overflow = cb->create_patch_overflow();
161 }
162 _patch_overflow->push(branch_loc);
163 }
164 ++_patch_index;
165 }
166
167 void Label::patch_instructions(MacroAssembler* masm) {
168 assert(is_bound(), "Label is bound");
169 CodeBuffer* cb = masm->code();
170 int target_sect = CodeBuffer::locator_sect(loc());
171 address target = cb->locator_address(loc());
172 while (_patch_index > 0) {
173 --_patch_index;
174 int branch_loc;
175 if (_patch_index >= PatchCacheSize) {
176 branch_loc = _patch_overflow->pop();
177 } else {
178 branch_loc = _patches[_patch_index];
179 }
180 int branch_sect = CodeBuffer::locator_sect(branch_loc);
181 address branch = cb->locator_address(branch_loc);
182 if (branch_sect == CodeBuffer::SECT_CONSTS) {
183 // The thing to patch is a constant word.
184 *(address*)branch = target;
185 continue;
186 }
187
188 #ifdef ASSERT
189 // Cross-section branches only work if the
190 // intermediate section boundaries are frozen.
191 if (target_sect != branch_sect) {
192 for (int n = MIN2(target_sect, branch_sect),
193 nlimit = (target_sect + branch_sect) - n;
194 n < nlimit; n++) {
195 CodeSection* cs = cb->code_section(n);
196 assert(cs->is_frozen(), "cross-section branch needs stable offsets");
197 }
198 }
199 #endif //ASSERT
200
201 // Push the target offset into the branch instruction.
202 masm->pd_patch_instruction(branch, target);
203 }
204 }
205
206 struct DelayedConstant {
207 typedef void (*value_fn_t)();
208 BasicType type;
209 intptr_t value;
210 value_fn_t value_fn;
211 // This limit of 20 is generous for initial uses.
212 // The limit needs to be large enough to store the field offsets
213 // into classes which do not have statically fixed layouts.
214 // (Initial use is for method handle object offsets.)
215 // Look for uses of "delayed_value" in the source code
216 // and make sure this number is generous enough to handle all of them.
217 enum { DC_LIMIT = 20 };
218 static DelayedConstant delayed_constants[DC_LIMIT];
219 static DelayedConstant* add(BasicType type, value_fn_t value_fn);
220 bool match(BasicType t, value_fn_t cfn) {
221 return type == t && value_fn == cfn;
222 }
223 static void update_all();
224 };
225
226 DelayedConstant DelayedConstant::delayed_constants[DC_LIMIT];
227 // Default C structure initialization rules have the following effect here:
228 // = { { (BasicType)0, (intptr_t)NULL }, ... };
229
230 DelayedConstant* DelayedConstant::add(BasicType type,
231 DelayedConstant::value_fn_t cfn) {
232 for (int i = 0; i < DC_LIMIT; i++) {
233 DelayedConstant* dcon = &delayed_constants[i];
234 if (dcon->match(type, cfn))
235 return dcon;
236 if (dcon->value_fn == NULL) {
237 // (cmpxchg not because this is multi-threaded but because I'm paranoid)
238 if (Atomic::cmpxchg_ptr(CAST_FROM_FN_PTR(void*, cfn), &dcon->value_fn, NULL) == NULL) {
239 dcon->type = type;
240 return dcon;
241 }
242 }
243 }
244 // If this assert is hit (in pre-integration testing!) then re-evaluate
245 // the comment on the definition of DC_LIMIT.
246 guarantee(false, "too many delayed constants");
247 return NULL;
248 }
249
250 void DelayedConstant::update_all() {
251 for (int i = 0; i < DC_LIMIT; i++) {
252 DelayedConstant* dcon = &delayed_constants[i];
253 if (dcon->value_fn != NULL && dcon->value == 0) {
254 typedef int (*int_fn_t)();
255 typedef address (*address_fn_t)();
256 switch (dcon->type) {
257 case T_INT: dcon->value = (intptr_t) ((int_fn_t) dcon->value_fn)(); break;
258 case T_ADDRESS: dcon->value = (intptr_t) ((address_fn_t)dcon->value_fn)(); break;
259 }
260 }
261 }
262 }
263
264 RegisterOrConstant AbstractAssembler::delayed_value(int(*value_fn)(), Register tmp, int offset) {
265 intptr_t val = (intptr_t) (*value_fn)();
266 if (val != 0) return val + offset;
267 return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);
268 }
269 RegisterOrConstant AbstractAssembler::delayed_value(address(*value_fn)(), Register tmp, int offset) {
270 intptr_t val = (intptr_t) (*value_fn)();
271 if (val != 0) return val + offset;
272 return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);
273 }
274 intptr_t* AbstractAssembler::delayed_value_addr(int(*value_fn)()) {
275 DelayedConstant* dcon = DelayedConstant::add(T_INT, (DelayedConstant::value_fn_t) value_fn);
276 return &dcon->value;
277 }
278 intptr_t* AbstractAssembler::delayed_value_addr(address(*value_fn)()) {
279 DelayedConstant* dcon = DelayedConstant::add(T_ADDRESS, (DelayedConstant::value_fn_t) value_fn);
280 return &dcon->value;
281 }
282 void AbstractAssembler::update_delayed_values() {
283 DelayedConstant::update_all();
284 }
285
286 void AbstractAssembler::block_comment(const char* comment) {
287 if (sect() == CodeBuffer::SECT_INSTS) {
288 code_section()->outer()->block_comment(offset(), comment);
289 }
290 }
291
292 const char* AbstractAssembler::code_string(const char* str) {
293 if (sect() == CodeBuffer::SECT_INSTS || sect() == CodeBuffer::SECT_STUBS) {
294 return code_section()->outer()->code_string(str);
295 }
296 return NULL;
297 }
298
299 bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {
300 // Exception handler checks the nmethod's implicit null checks table
301 // only when this method returns false.
302 #ifdef _LP64
303 if (UseCompressedOops && Universe::narrow_oop_base() != NULL) {
304 assert (Universe::heap() != NULL, "java heap should be initialized");
305 // The first page after heap_base is unmapped and
306 // the 'offset' is equal to [heap_base + offset] for
307 // narrow oop implicit null checks.
308 uintptr_t base = (uintptr_t)Universe::narrow_oop_base();
309 if ((uintptr_t)offset >= base) {
310 // Normalize offset for the next check.
311 offset = (intptr_t)(pointer_delta((void*)offset, (void*)base, 1));
312 }
313 }
314 #endif
315 return offset < 0 || os::vm_page_size() <= offset;
316 }