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/*
* Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#ifndef SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_OBJECTSTARTARRAY_HPP
#define SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_OBJECTSTARTARRAY_HPP
#include "gc_implementation/parallelScavenge/psVirtualspace.hpp"
#include "memory/allocation.hpp"
#include "memory/memRegion.hpp"
#include "oops/oop.hpp"
//
// This class can be used to locate the beginning of an object in the
// covered region.
//
class ObjectStartArray : public CHeapObj {
friend class VerifyObjectStartArrayClosure;
private:
PSVirtualSpace _virtual_space;
MemRegion _reserved_region;
MemRegion _covered_region;
MemRegion _blocks_region;
jbyte* _raw_base;
jbyte* _offset_base;
public:
enum BlockValueConstants {
clean_block = -1
};
enum BlockSizeConstants {
block_shift = 9,
block_size = 1 << block_shift,
block_size_in_words = block_size / sizeof(HeapWord)
};
protected:
// Mapping from address to object start array entry
jbyte* block_for_addr(void* p) const {
assert(_covered_region.contains(p),
"out of bounds access to object start array");
jbyte* result = &_offset_base[uintptr_t(p) >> block_shift];
assert(_blocks_region.contains(result),
"out of bounds result in byte_for");
return result;
}
// Mapping from object start array entry to address of first word
HeapWord* addr_for_block(jbyte* p) {
assert(_blocks_region.contains(p),
"out of bounds access to object start array");
size_t delta = pointer_delta(p, _offset_base, sizeof(jbyte));
HeapWord* result = (HeapWord*) (delta << block_shift);
assert(_covered_region.contains(result),
"out of bounds accessor from card marking array");
return result;
}
// Mapping that includes the derived offset.
// If the block is clean, returns the last address in the covered region.
// If the block is < index 0, returns the start of the covered region.
HeapWord* offset_addr_for_block (jbyte* p) const {
// We have to do this before the assert
if (p < _raw_base) {
return _covered_region.start();
}
assert(_blocks_region.contains(p),
"out of bounds access to object start array");
if (*p == clean_block) {
return _covered_region.end();
}
size_t delta = pointer_delta(p, _offset_base, sizeof(jbyte));
HeapWord* result = (HeapWord*) (delta << block_shift);
result += *p;
assert(_covered_region.contains(result),
"out of bounds accessor from card marking array");
return result;
}
public:
// This method is in lieu of a constructor, so that this class can be
// embedded inline in other classes.
void initialize(MemRegion reserved_region);
void set_covered_region(MemRegion mr);
void reset();
MemRegion covered_region() { return _covered_region; }
void allocate_block(HeapWord* p) {
assert(_covered_region.contains(p), "Must be in covered region");
jbyte* block = block_for_addr(p);
HeapWord* block_base = addr_for_block(block);
size_t offset = pointer_delta(p, block_base, sizeof(HeapWord*));
assert(offset < 128, "Sanity");
// When doing MT offsets, we can't assert this.
//assert(offset > *block, "Found backwards allocation");
*block = (jbyte)offset;
// tty->print_cr("[%p]", p);
}
// Optimized for finding the first object that crosses into
// a given block. The blocks contain the offset of the last
// object in that block. Scroll backwards by one, and the first
// object hit should be at the beginning of the block
HeapWord* object_start(HeapWord* addr) const {
assert(_covered_region.contains(addr), "Must be in covered region");
jbyte* block = block_for_addr(addr);
HeapWord* scroll_forward = offset_addr_for_block(block--);
while (scroll_forward > addr) {
scroll_forward = offset_addr_for_block(block--);
}
HeapWord* next = scroll_forward;
while (next <= addr) {
scroll_forward = next;
next += oop(next)->size();
}
assert(scroll_forward <= addr, "wrong order for current and arg");
assert(addr <= next, "wrong order for arg and next");
return scroll_forward;
}
bool is_block_allocated(HeapWord* addr) {
assert(_covered_region.contains(addr), "Must be in covered region");
jbyte* block = block_for_addr(addr);
if (*block == clean_block)
return false;
return true;
}
// Return true if an object starts in the range of heap addresses.
// If an object starts at an address corresponding to
// "start", the method will return true.
bool object_starts_in_range(HeapWord* start_addr, HeapWord* end_addr) const;
};
#endif // SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_OBJECTSTARTARRAY_HPP
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