6800154: Add comments to long_by_long_mulhi() for better understandability
Summary: This patch adds a comment pointing to the Hacker's Delight version of the algorithm plus a verbatim copy of it. Furthermore it adds inline comments.
Reviewed-by: kvn, jrose
/*
* Copyright 1997-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*
*/
// This file holds the platform specific parts of the StubRoutines
// definition. See stubRoutines.hpp for a description on how to
// extend it.
// So unfortunately c2 will call with a pc from a frame object
// (already adjusted) and a raw pc (unadjusted), so we need to check both.
// It didn't use to be like this before adapter removal.
static bool returns_to_call_stub(address return_pc) {
return ((return_pc + frame::pc_return_offset) == _call_stub_return_address) ||
(return_pc == _call_stub_return_address );
}
enum /* platform_dependent_constants */ {
// %%%%%%%% May be able to shrink this a lot
code_size1 = 20000, // simply increase if too small (assembler will crash if too small)
code_size2 = 20000 // simply increase if too small (assembler will crash if too small)
};
class Sparc {
friend class StubGenerator;
public:
enum { nof_instance_allocators = 10 };
// allocator lock values
enum {
unlocked = 0,
locked = 1
};
enum {
v8_oop_lock_ignore_bits = 2,
v8_oop_lock_bits = 4,
nof_v8_oop_lock_cache_entries = 1 << (v8_oop_lock_bits+v8_oop_lock_ignore_bits),
v8_oop_lock_mask = right_n_bits(v8_oop_lock_bits),
v8_oop_lock_mask_in_place = v8_oop_lock_mask << v8_oop_lock_ignore_bits
};
static int _v8_oop_lock_cache[nof_v8_oop_lock_cache_entries];
private:
static address _test_stop_entry;
static address _stop_subroutine_entry;
static address _flush_callers_register_windows_entry;
static int _atomic_memory_operation_lock;
static address _partial_subtype_check;
public:
// %%% global lock for everyone who needs to use atomic_compare_and_exchange
// %%% or atomic_increment -- should probably use more locks for more
// %%% scalability-- for instance one for each eden space or group of
// address of the lock for atomic_compare_and_exchange
static int* atomic_memory_operation_lock_addr() { return &_atomic_memory_operation_lock; }
// accessor and mutator for _atomic_memory_operation_lock
static int atomic_memory_operation_lock() { return _atomic_memory_operation_lock; }
static void set_atomic_memory_operation_lock(int value) { _atomic_memory_operation_lock = value; }
// test assembler stop routine by setting registers
static void (*test_stop_entry()) () { return CAST_TO_FN_PTR(void (*)(void), _test_stop_entry); }
// a subroutine for debugging assembler code
static address stop_subroutine_entry_address() { return (address)&_stop_subroutine_entry; }
// flushes (all but current) register window
static intptr_t* (*flush_callers_register_windows_func())() { return CAST_TO_FN_PTR(intptr_t* (*)(void), _flush_callers_register_windows_entry); }
static address partial_subtype_check() { return _partial_subtype_check; }
};