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 1997-2006 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.
*
*/
#include "incls/_precompiled.incl"
#include "incls/_icBuffer_sparc.cpp.incl"
int InlineCacheBuffer::ic_stub_code_size() {
#ifdef _LP64
if (TraceJumps) return 600 * wordSize;
return (NativeMovConstReg::instruction_size + // sethi;add
NativeJump::instruction_size + // sethi; jmp; delay slot
(1*BytesPerInstWord) + 1); // flush + 1 extra byte
#else
if (TraceJumps) return 300 * wordSize;
return (2+2+ 1) * wordSize + 1; // set/jump_to/nop + 1 byte so that code_end can be set in CodeBuffer
#endif
}
void InlineCacheBuffer::assemble_ic_buffer_code(address code_begin, oop cached_oop, address entry_point) {
ResourceMark rm;
CodeBuffer code(code_begin, ic_stub_code_size());
MacroAssembler* masm = new MacroAssembler(&code);
// note: even though the code contains an embedded oop, we do not need reloc info
// because
// (1) the oop is old (i.e., doesn't matter for scavenges)
// (2) these ICStubs are removed *before* a GC happens, so the roots disappear
assert(cached_oop == NULL || cached_oop->is_perm(), "must be old oop");
Address cached_oop_addr(G5_inline_cache_reg, address(cached_oop));
// Force the sethi to generate the fixed sequence so next_instruction_address works
masm->sethi(cached_oop_addr, true /* ForceRelocatable */ );
masm->add(cached_oop_addr, G5_inline_cache_reg);
assert(G3_scratch != G5_method, "Do not clobber the method oop in the transition stub");
assert(G3_scratch != G5_inline_cache_reg, "Do not clobber the inline cache register in the transition stub");
Address entry(G3_scratch, entry_point);
masm->JUMP(entry, 0);
masm->delayed()->nop();
masm->flush();
}
address InlineCacheBuffer::ic_buffer_entry_point(address code_begin) {
NativeMovConstReg* move = nativeMovConstReg_at(code_begin); // creation also verifies the object
NativeJump* jump = nativeJump_at(move->next_instruction_address());
return jump->jump_destination();
}
oop InlineCacheBuffer::ic_buffer_cached_oop(address code_begin) {
NativeMovConstReg* move = nativeMovConstReg_at(code_begin); // creation also verifies the object
NativeJump* jump = nativeJump_at(move->next_instruction_address());
return (oop)move->data();
}