1 /*
2 * Copyright (c) 1998, 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 # include "incls/_precompiled.incl"
26 # include "incls/_rewriter.cpp.incl"
27
28 // Computes a CPC map (new_index -> original_index) for constant pool entries
29 // that are referred to by the interpreter at runtime via the constant pool cache.
30 // Also computes a CP map (original_index -> new_index).
31 // Marks entries in CP which require additional processing.
32 void Rewriter::compute_index_maps() {
33 const int length = _pool->length();
34 init_cp_map(length);
35 jint tag_mask = 0;
36 for (int i = 0; i < length; i++) {
37 int tag = _pool->tag_at(i).value();
38 tag_mask |= (1 << tag);
39 switch (tag) {
40 case JVM_CONSTANT_InterfaceMethodref:
41 case JVM_CONSTANT_Fieldref : // fall through
42 case JVM_CONSTANT_Methodref : // fall through
43 case JVM_CONSTANT_MethodHandle : // fall through
44 case JVM_CONSTANT_MethodType : // fall through
45 case JVM_CONSTANT_InvokeDynamic : // fall through
46 add_cp_cache_entry(i);
47 break;
48 }
49 }
50
51 guarantee((int)_cp_cache_map.length()-1 <= (int)((u2)-1),
52 "all cp cache indexes fit in a u2");
53
54 _have_invoke_dynamic = ((tag_mask & (1 << JVM_CONSTANT_InvokeDynamic)) != 0);
55 }
56
57
58 // Creates a constant pool cache given a CPC map
59 // This creates the constant pool cache initially in a state
60 // that is unsafe for concurrent GC processing but sets it to
61 // a safe mode before the constant pool cache is returned.
62 void Rewriter::make_constant_pool_cache(TRAPS) {
63 const int length = _cp_cache_map.length();
64 constantPoolCacheOop cache =
65 oopFactory::new_constantPoolCache(length, methodOopDesc::IsUnsafeConc, CHECK);
66 cache->initialize(_cp_cache_map);
67
68 // Don't bother to the next pass if there is no JVM_CONSTANT_InvokeDynamic.
69 if (_have_invoke_dynamic) {
70 for (int i = 0; i < length; i++) {
71 int pool_index = cp_cache_entry_pool_index(i);
72 if (pool_index >= 0 &&
73 _pool->tag_at(pool_index).is_invoke_dynamic()) {
74 int bsm_index = _pool->invoke_dynamic_bootstrap_method_ref_index_at(pool_index);
75 if (bsm_index != 0) {
76 assert(_pool->tag_at(bsm_index).is_method_handle(), "must be a MH constant");
77 // There is a CP cache entry holding the BSM for these calls.
78 int bsm_cache_index = cp_entry_to_cp_cache(bsm_index);
79 cache->entry_at(i)->initialize_bootstrap_method_index_in_cache(bsm_cache_index);
80 } else {
81 // There is no CP cache entry holding the BSM for these calls.
82 // We will need to look for a class-global BSM, later.
83 guarantee(AllowTransitionalJSR292, "");
84 }
85 }
86 }
87 }
88
89 _pool->set_cache(cache);
90 cache->set_constant_pool(_pool());
91 }
92
93
94
95 // The new finalization semantics says that registration of
96 // finalizable objects must be performed on successful return from the
97 // Object.<init> constructor. We could implement this trivially if
98 // <init> were never rewritten but since JVMTI allows this to occur, a
99 // more complicated solution is required. A special return bytecode
100 // is used only by Object.<init> to signal the finalization
101 // registration point. Additionally local 0 must be preserved so it's
102 // available to pass to the registration function. For simplicty we
103 // require that local 0 is never overwritten so it's available as an
104 // argument for registration.
105
106 void Rewriter::rewrite_Object_init(methodHandle method, TRAPS) {
107 RawBytecodeStream bcs(method);
108 while (!bcs.is_last_bytecode()) {
109 Bytecodes::Code opcode = bcs.raw_next();
110 switch (opcode) {
111 case Bytecodes::_return: *bcs.bcp() = Bytecodes::_return_register_finalizer; break;
112
113 case Bytecodes::_istore:
114 case Bytecodes::_lstore:
115 case Bytecodes::_fstore:
116 case Bytecodes::_dstore:
117 case Bytecodes::_astore:
118 if (bcs.get_index() != 0) continue;
119
120 // fall through
121 case Bytecodes::_istore_0:
122 case Bytecodes::_lstore_0:
123 case Bytecodes::_fstore_0:
124 case Bytecodes::_dstore_0:
125 case Bytecodes::_astore_0:
126 THROW_MSG(vmSymbols::java_lang_IncompatibleClassChangeError(),
127 "can't overwrite local 0 in Object.<init>");
128 break;
129 }
130 }
131 }
132
133
134 // Rewrite a classfile-order CP index into a native-order CPC index.
135 void Rewriter::rewrite_member_reference(address bcp, int offset) {
136 address p = bcp + offset;
137 int cp_index = Bytes::get_Java_u2(p);
138 int cache_index = cp_entry_to_cp_cache(cp_index);
139 Bytes::put_native_u2(p, cache_index);
140 }
141
142
143 void Rewriter::rewrite_invokedynamic(address bcp, int offset) {
144 address p = bcp + offset;
145 assert(p[-1] == Bytecodes::_invokedynamic, "");
146 int cp_index = Bytes::get_Java_u2(p);
147 int cpc = maybe_add_cp_cache_entry(cp_index); // add lazily
148 int cpc2 = add_secondary_cp_cache_entry(cpc);
149
150 // Replace the trailing four bytes with a CPC index for the dynamic
151 // call site. Unlike other CPC entries, there is one per bytecode,
152 // not just one per distinct CP entry. In other words, the
153 // CPC-to-CP relation is many-to-one for invokedynamic entries.
154 // This means we must use a larger index size than u2 to address
155 // all these entries. That is the main reason invokedynamic
156 // must have a five-byte instruction format. (Of course, other JVM
157 // implementations can use the bytes for other purposes.)
158 Bytes::put_native_u4(p, constantPoolCacheOopDesc::encode_secondary_index(cpc2));
159 // Note: We use native_u4 format exclusively for 4-byte indexes.
160 }
161
162
163 // Rewrite some ldc bytecodes to _fast_aldc
164 void Rewriter::maybe_rewrite_ldc(address bcp, int offset, bool is_wide) {
165 assert((*bcp) == (is_wide ? Bytecodes::_ldc_w : Bytecodes::_ldc), "");
166 address p = bcp + offset;
167 int cp_index = is_wide ? Bytes::get_Java_u2(p) : (u1)(*p);
168 constantTag tag = _pool->tag_at(cp_index).value();
169 if (tag.is_method_handle() || tag.is_method_type()) {
170 int cache_index = cp_entry_to_cp_cache(cp_index);
171 if (is_wide) {
172 (*bcp) = Bytecodes::_fast_aldc_w;
173 assert(cache_index == (u2)cache_index, "");
174 Bytes::put_native_u2(p, cache_index);
175 } else {
176 (*bcp) = Bytecodes::_fast_aldc;
177 assert(cache_index == (u1)cache_index, "");
178 (*p) = (u1)cache_index;
179 }
180 }
181 }
182
183
184 // Rewrites a method given the index_map information
185 void Rewriter::scan_method(methodOop method) {
186
187 int nof_jsrs = 0;
188 bool has_monitor_bytecodes = false;
189
190 {
191 // We cannot tolerate a GC in this block, because we've
192 // cached the bytecodes in 'code_base'. If the methodOop
193 // moves, the bytecodes will also move.
194 No_Safepoint_Verifier nsv;
195 Bytecodes::Code c;
196
197 // Bytecodes and their length
198 const address code_base = method->code_base();
199 const int code_length = method->code_size();
200
201 int bc_length;
202 for (int bci = 0; bci < code_length; bci += bc_length) {
203 address bcp = code_base + bci;
204 int prefix_length = 0;
205 c = (Bytecodes::Code)(*bcp);
206
207 // Since we have the code, see if we can get the length
208 // directly. Some more complicated bytecodes will report
209 // a length of zero, meaning we need to make another method
210 // call to calculate the length.
211 bc_length = Bytecodes::length_for(c);
212 if (bc_length == 0) {
213 bc_length = Bytecodes::length_at(bcp);
214
215 // length_at will put us at the bytecode after the one modified
216 // by 'wide'. We don't currently examine any of the bytecodes
217 // modified by wide, but in case we do in the future...
218 if (c == Bytecodes::_wide) {
219 prefix_length = 1;
220 c = (Bytecodes::Code)bcp[1];
221 }
222 }
223
224 assert(bc_length != 0, "impossible bytecode length");
225
226 switch (c) {
227 case Bytecodes::_lookupswitch : {
228 #ifndef CC_INTERP
229 Bytecode_lookupswitch* bc = Bytecode_lookupswitch_at(bcp);
230 (*bcp) = (
231 bc->number_of_pairs() < BinarySwitchThreshold
232 ? Bytecodes::_fast_linearswitch
233 : Bytecodes::_fast_binaryswitch
234 );
235 #endif
236 break;
237 }
238 case Bytecodes::_getstatic : // fall through
239 case Bytecodes::_putstatic : // fall through
240 case Bytecodes::_getfield : // fall through
241 case Bytecodes::_putfield : // fall through
242 case Bytecodes::_invokevirtual : // fall through
243 case Bytecodes::_invokespecial : // fall through
244 case Bytecodes::_invokestatic :
245 case Bytecodes::_invokeinterface:
246 rewrite_member_reference(bcp, prefix_length+1);
247 break;
248 case Bytecodes::_invokedynamic:
249 rewrite_invokedynamic(bcp, prefix_length+1);
250 break;
251 case Bytecodes::_ldc:
252 maybe_rewrite_ldc(bcp, prefix_length+1, false);
253 break;
254 case Bytecodes::_ldc_w:
255 maybe_rewrite_ldc(bcp, prefix_length+1, true);
256 break;
257 case Bytecodes::_jsr : // fall through
258 case Bytecodes::_jsr_w : nof_jsrs++; break;
259 case Bytecodes::_monitorenter : // fall through
260 case Bytecodes::_monitorexit : has_monitor_bytecodes = true; break;
261 }
262 }
263 }
264
265 // Update access flags
266 if (has_monitor_bytecodes) {
267 method->set_has_monitor_bytecodes();
268 }
269
270 // The present of a jsr bytecode implies that the method might potentially
271 // have to be rewritten, so we run the oopMapGenerator on the method
272 if (nof_jsrs > 0) {
273 method->set_has_jsrs();
274 // Second pass will revisit this method.
275 assert(method->has_jsrs(), "");
276 }
277 }
278
279 // After constant pool is created, revisit methods containing jsrs.
280 methodHandle Rewriter::rewrite_jsrs(methodHandle method, TRAPS) {
281 ResolveOopMapConflicts romc(method);
282 methodHandle original_method = method;
283 method = romc.do_potential_rewrite(CHECK_(methodHandle()));
284 if (method() != original_method()) {
285 // Insert invalid bytecode into original methodOop and set
286 // interpreter entrypoint, so that a executing this method
287 // will manifest itself in an easy recognizable form.
288 address bcp = original_method->bcp_from(0);
289 *bcp = (u1)Bytecodes::_shouldnotreachhere;
290 int kind = Interpreter::method_kind(original_method);
291 original_method->set_interpreter_kind(kind);
292 }
293
294 // Update monitor matching info.
295 if (romc.monitor_safe()) {
296 method->set_guaranteed_monitor_matching();
297 }
298
299 return method;
300 }
301
302
303 void Rewriter::rewrite(instanceKlassHandle klass, TRAPS) {
304 ResourceMark rm(THREAD);
305 Rewriter rw(klass, klass->constants(), klass->methods(), CHECK);
306 // (That's all, folks.)
307 }
308
309
310 void Rewriter::rewrite(instanceKlassHandle klass, constantPoolHandle cpool, objArrayHandle methods, TRAPS) {
311 ResourceMark rm(THREAD);
312 Rewriter rw(klass, cpool, methods, CHECK);
313 // (That's all, folks.)
314 }
315
316
317 Rewriter::Rewriter(instanceKlassHandle klass, constantPoolHandle cpool, objArrayHandle methods, TRAPS)
318 : _klass(klass),
319 _pool(cpool),
320 _methods(methods)
321 {
322 assert(_pool->cache() == NULL, "constant pool cache must not be set yet");
323
324 // determine index maps for methodOop rewriting
325 compute_index_maps();
326
327 if (RegisterFinalizersAtInit && _klass->name() == vmSymbols::java_lang_Object()) {
328 bool did_rewrite = false;
329 int i = _methods->length();
330 while (i-- > 0) {
331 methodOop method = (methodOop)_methods->obj_at(i);
332 if (method->intrinsic_id() == vmIntrinsics::_Object_init) {
333 // rewrite the return bytecodes of Object.<init> to register the
334 // object for finalization if needed.
335 methodHandle m(THREAD, method);
336 rewrite_Object_init(m, CHECK);
337 did_rewrite = true;
338 break;
339 }
340 }
341 assert(did_rewrite, "must find Object::<init> to rewrite it");
342 }
343
344 // rewrite methods, in two passes
345 int i, len = _methods->length();
346
347 for (i = len; --i >= 0; ) {
348 methodOop method = (methodOop)_methods->obj_at(i);
349 scan_method(method);
350 }
351
352 // allocate constant pool cache, now that we've seen all the bytecodes
353 make_constant_pool_cache(CHECK);
354
355 for (i = len; --i >= 0; ) {
356 methodHandle m(THREAD, (methodOop)_methods->obj_at(i));
357
358 if (m->has_jsrs()) {
359 m = rewrite_jsrs(m, CHECK);
360 // Method might have gotten rewritten.
361 _methods->obj_at_put(i, m());
362 }
363
364 // Set up method entry points for compiler and interpreter.
365 m->link_method(m, CHECK);
366
367 #ifdef ASSERT
368 if (StressMethodComparator) {
369 static int nmc = 0;
370 for (int j = i; j >= 0 && j >= i-4; j--) {
371 if ((++nmc % 1000) == 0) tty->print_cr("Have run MethodComparator %d times...", nmc);
372 bool z = MethodComparator::methods_EMCP(m(), (methodOop)_methods->obj_at(j));
373 if (j == i && !z) {
374 tty->print("MethodComparator FAIL: "); m->print(); m->print_codes();
375 assert(z, "method must compare equal to itself");
376 }
377 }
378 }
379 #endif //ASSERT
380 }
381 }