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src/hotspot/share/oops/compressedOops.cpp

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161 void CompressedOops::print_mode(outputStream* st) {
162   st->print("Heap address: " PTR_FORMAT ", size: " SIZE_FORMAT " MB",
163             p2i(_heap_address_range.start()), _heap_address_range.byte_size()/M);
164 
165   st->print(", Compressed Oops mode: %s", mode_to_string(mode()));
166 
167   if (base() != 0) {
168     st->print(": " PTR_FORMAT, p2i(base()));
169   }
170 
171   if (shift() != 0) {
172     st->print(", Oop shift amount: %d", shift());
173   }
174 
175   if (!use_implicit_null_checks()) {
176     st->print(", no protected page in front of the heap");
177   }
178   st->cr();
179 }
180 
181 // For UseCompressedClassPointers.
182 NarrowPtrStruct CompressedKlassPointers::_narrow_klass = { NULL, 0, true };
183 
184 // CompressedClassSpaceSize set to 1GB, but appear 3GB away from _narrow_ptrs_base during CDS dump.
185 // (Todo: we should #ifdef out CompressedKlassPointers for 32bit completely and fix all call sites which
186 //  are compiled for 32bit to LP64_ONLY).
187 size_t CompressedKlassPointers::_range = 0;
188 
189 
190 // Given an address range [addr, addr+len) which the encoding is supposed to
191 //  cover, choose base, shift and range.
192 //  The address range is the expected range of uncompressed Klass pointers we
193 //  will encounter (and the implicit promise that there will be no Klass
194 //  structures outside this range).
195 void CompressedKlassPointers::initialize(address addr, size_t len) {
196 #ifdef _LP64
197   assert(is_valid_base(addr), "Address must be a valid encoding base");
198   address const end = addr + len;
199 
200   address base;
201   int shift;
202   size_t range;
203 
204   if (UseSharedSpaces || DumpSharedSpaces) {
205 
206     // Special requirements if CDS is active:
207     // Encoding base and shift must be the same between dump and run time.
208     //   CDS takes care that the SharedBaseAddress and CompressedClassSpaceSize
209     //   are the same. Archive size will be probably different at runtime, but
210     //   it can only be smaller than at, never larger, since archives get
211     //   shrunk at the end of the dump process.
212     //   From that it follows that the range [addr, len) we are handed in at
213     //   runtime will start at the same address then at dumptime, and its len
214     //   may be smaller at runtime then it was at dump time.
215     //
216     // To be very careful here, we avoid any optimizations and just keep using
217     //  the same address and shift value. Specifically we avoid using zero-based
218     //  encoding. We also set the expected value range to 4G (encoding range
219     //  cannot be larger than that).
220 
221     base = addr;
222 
223     // JDK-8265705
224     // This is a temporary fix for aarch64: there, if the range-to-be-encoded is located
225     //  below 32g, either encoding base should be zero or base should be aligned to 4G
226     //  and shift should be zero. The simplest way to fix this for now is to force
227     //  shift to zero for both runtime and dumptime.
228     // Note however that this is not a perfect solution. Ideally this whole function
229     //  should be CDS agnostic, that would simplify it - and testing - a lot. See JDK-8267141
230     //  for details.
231     shift = 0;
232 
233     // This must be true since at dumptime cds+ccs is 4G, at runtime it can
234     //  only be smaller, see comment above.
235     assert(len <= 4 * G, "Encoding range cannot be larger than 4G");
236     range = 4 * G;
237 
238   } else {
239 
240     // Otherwise we attempt to use a zero base if the range fits in lower 32G.
241     if (end <= (address)KlassEncodingMetaspaceMax) {
242       base = 0;
243     } else {
244       base = addr;
245     }
246 
247     // Highest offset a Klass* can ever have in relation to base.
248     range = end - base;
249 
250     // We may not even need a shift if the range fits into 32bit:
251     const uint64_t UnscaledClassSpaceMax = (uint64_t(max_juint) + 1);
252     if (range < UnscaledClassSpaceMax) {
253       shift = 0;
254     } else {
255       shift = LogKlassAlignmentInBytes;
256     }
257 
258   }
259 
260   set_base(base);
261   set_shift(shift);
262   set_range(range);
263 #else
264   fatal("64bit only.");
265 #endif
266 }
267 
268 // Given an address p, return true if p can be used as an encoding base.
269 //  (Some platforms have restrictions of what constitutes a valid base address).
270 bool CompressedKlassPointers::is_valid_base(address p) {
271 #ifdef AARCH64
272   // Below 32G, base must be aligned to 4G.
273   // Above that point, base must be aligned to 32G
274   if (p < (address)(32 * G)) {
275     return is_aligned(p, 4 * G);
276   }
277   return is_aligned(p, (4 << LogKlassAlignmentInBytes) * G);
278 #else
279   return true;
280 #endif
281 }
282 
283 void CompressedKlassPointers::print_mode(outputStream* st) {
284   st->print_cr("Narrow klass base: " PTR_FORMAT ", Narrow klass shift: %d, "
285                "Narrow klass range: " SIZE_FORMAT_HEX, p2i(base()), shift(),
286                range());
287 }
288 
289 void CompressedKlassPointers::set_base(address base) {
290   assert(UseCompressedClassPointers, "no compressed klass ptrs?");
291   _narrow_klass._base   = base;
292 }
293 
294 void CompressedKlassPointers::set_shift(int shift)       {
295   assert(shift == 0 || shift == LogKlassAlignmentInBytes, "invalid shift for klass ptrs");
296   _narrow_klass._shift   = shift;
297 }
298 
299 void CompressedKlassPointers::set_range(size_t range) {
300   assert(UseCompressedClassPointers, "no compressed klass ptrs?");
301   _range = range;
302 }

161 void CompressedOops::print_mode(outputStream* st) {
162   st->print("Heap address: " PTR_FORMAT ", size: " SIZE_FORMAT " MB",
163             p2i(_heap_address_range.start()), _heap_address_range.byte_size()/M);
164 
165   st->print(", Compressed Oops mode: %s", mode_to_string(mode()));
166 
167   if (base() != 0) {
168     st->print(": " PTR_FORMAT, p2i(base()));
169   }
170 
171   if (shift() != 0) {
172     st->print(", Oop shift amount: %d", shift());
173   }
174 
175   if (!use_implicit_null_checks()) {
176     st->print(", no protected page in front of the heap");
177   }
178   st->cr();
179 }
180 


























































































































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