duke@435: /*
mikael@4153:  * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #ifndef SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_OBJECTSTARTARRAY_HPP
stefank@2314: #define SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_OBJECTSTARTARRAY_HPP
stefank@2314: 
stefank@2314: #include "gc_implementation/parallelScavenge/psVirtualspace.hpp"
stefank@2314: #include "memory/allocation.hpp"
stefank@2314: #include "memory/memRegion.hpp"
stefank@2314: #include "oops/oop.hpp"
stefank@2314: 
duke@435: //
duke@435: // This class can be used to locate the beginning of an object in the
duke@435: // covered region.
duke@435: //
duke@435: 
zgu@3900: class ObjectStartArray : public CHeapObj<mtGC> {
duke@435:  friend class VerifyObjectStartArrayClosure;
duke@435: 
duke@435:  private:
duke@435:   PSVirtualSpace  _virtual_space;
duke@435:   MemRegion       _reserved_region;
duke@435:   MemRegion       _covered_region;
duke@435:   MemRegion       _blocks_region;
duke@435:   jbyte*          _raw_base;
duke@435:   jbyte*          _offset_base;
duke@435: 
duke@435:  public:
duke@435: 
duke@435:   enum BlockValueConstants {
duke@435:     clean_block                  = -1
duke@435:   };
duke@435: 
duke@435:   enum BlockSizeConstants {
duke@435:     block_shift                  = 9,
duke@435:     block_size                   = 1 << block_shift,
duke@435:     block_size_in_words          = block_size / sizeof(HeapWord)
duke@435:   };
duke@435: 
duke@435:  protected:
duke@435: 
duke@435:   // Mapping from address to object start array entry
duke@435:   jbyte* block_for_addr(void* p) const {
duke@435:     assert(_covered_region.contains(p),
duke@435:            "out of bounds access to object start array");
duke@435:     jbyte* result = &_offset_base[uintptr_t(p) >> block_shift];
duke@435:     assert(_blocks_region.contains(result),
duke@435:            "out of bounds result in byte_for");
duke@435:     return result;
duke@435:   }
duke@435: 
duke@435:   // Mapping from object start array entry to address of first word
duke@435:   HeapWord* addr_for_block(jbyte* p) {
duke@435:     assert(_blocks_region.contains(p),
duke@435:            "out of bounds access to object start array");
duke@435:     size_t delta = pointer_delta(p, _offset_base, sizeof(jbyte));
duke@435:     HeapWord* result = (HeapWord*) (delta << block_shift);
duke@435:     assert(_covered_region.contains(result),
duke@435:            "out of bounds accessor from card marking array");
duke@435:     return result;
duke@435:   }
duke@435: 
duke@435:   // Mapping that includes the derived offset.
duke@435:   // If the block is clean, returns the last address in the covered region.
duke@435:   // If the block is < index 0, returns the start of the covered region.
duke@435:   HeapWord* offset_addr_for_block (jbyte* p) const {
duke@435:     // We have to do this before the assert
duke@435:     if (p < _raw_base) {
duke@435:       return _covered_region.start();
duke@435:     }
duke@435: 
duke@435:     assert(_blocks_region.contains(p),
duke@435:            "out of bounds access to object start array");
duke@435: 
duke@435:     if (*p == clean_block) {
duke@435:       return _covered_region.end();
duke@435:     }
duke@435: 
duke@435:     size_t delta = pointer_delta(p, _offset_base, sizeof(jbyte));
duke@435:     HeapWord* result = (HeapWord*) (delta << block_shift);
duke@435:     result += *p;
duke@435: 
duke@435:     assert(_covered_region.contains(result),
duke@435:            "out of bounds accessor from card marking array");
duke@435: 
duke@435:     return result;
duke@435:   }
duke@435: 
duke@435:  public:
duke@435: 
duke@435:   // This method is in lieu of a constructor, so that this class can be
duke@435:   // embedded inline in other classes.
duke@435:   void initialize(MemRegion reserved_region);
duke@435: 
duke@435:   void set_covered_region(MemRegion mr);
duke@435: 
duke@435:   void reset();
duke@435: 
duke@435:   MemRegion covered_region() { return _covered_region; }
duke@435: 
duke@435:   void allocate_block(HeapWord* p) {
duke@435:     assert(_covered_region.contains(p), "Must be in covered region");
duke@435:     jbyte* block = block_for_addr(p);
duke@435:     HeapWord* block_base = addr_for_block(block);
duke@435:     size_t offset = pointer_delta(p, block_base, sizeof(HeapWord*));
duke@435:     assert(offset < 128, "Sanity");
duke@435:     // When doing MT offsets, we can't assert this.
duke@435:     //assert(offset > *block, "Found backwards allocation");
duke@435:     *block = (jbyte)offset;
duke@435: 
duke@435:     // tty->print_cr("[%p]", p);
duke@435:   }
duke@435: 
duke@435:   // Optimized for finding the first object that crosses into
duke@435:   // a given block. The blocks contain the offset of the last
duke@435:   // object in that block. Scroll backwards by one, and the first
twisti@1040:   // object hit should be at the beginning of the block
duke@435:   HeapWord* object_start(HeapWord* addr) const {
duke@435:     assert(_covered_region.contains(addr), "Must be in covered region");
duke@435:     jbyte* block = block_for_addr(addr);
duke@435:     HeapWord* scroll_forward = offset_addr_for_block(block--);
duke@435:     while (scroll_forward > addr) {
duke@435:       scroll_forward = offset_addr_for_block(block--);
duke@435:     }
duke@435: 
duke@435:     HeapWord* next = scroll_forward;
duke@435:     while (next <= addr) {
duke@435:       scroll_forward = next;
duke@435:       next += oop(next)->size();
duke@435:     }
duke@435:     assert(scroll_forward <= addr, "wrong order for current and arg");
duke@435:     assert(addr <= next, "wrong order for arg and next");
duke@435:     return scroll_forward;
duke@435:   }
duke@435: 
duke@435:   bool is_block_allocated(HeapWord* addr) {
duke@435:     assert(_covered_region.contains(addr), "Must be in covered region");
duke@435:     jbyte* block = block_for_addr(addr);
duke@435:     if (*block == clean_block)
duke@435:       return false;
duke@435: 
duke@435:     return true;
duke@435:   }
duke@435: 
duke@435:   // Return true if an object starts in the range of heap addresses.
duke@435:   // If an object starts at an address corresponding to
duke@435:   // "start", the method will return true.
duke@435:   bool object_starts_in_range(HeapWord* start_addr, HeapWord* end_addr) const;
duke@435: };
stefank@2314: 
stefank@2314: #endif // SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_OBJECTSTARTARRAY_HPP