/*

 * 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

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#include "gc/parallel/objectStartArray.hpp"

// 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* ObjectStartArray::object_start(HeapWord* addr) const {

  assert_covered_region_contains(addr);

  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;

}