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 2000-2006 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.
*
*/
private:
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//
// Sparc load/store emission
//
// The sparc ld/st instructions cannot accomodate displacements > 13 bits long.
// The following "pseudo" sparc instructions (load/store) make it easier to use the indexed addressing mode
// by allowing 32 bit displacements:
//
// When disp <= 13 bits long, a single load or store instruction is emitted with (disp + [d]).
// When disp > 13 bits long, code is emitted to set the displacement into the O7 register,
// and then a load or store is emitted with ([O7] + [d]).
//
// some load/store variants return the code_offset for proper positioning of debug info for null checks
// load/store with 32 bit displacement
int load(Register s, int disp, Register d, BasicType ld_type, CodeEmitInfo* info = NULL);
void store(Register value, Register base, int offset, BasicType type, CodeEmitInfo *info = NULL);
// loadf/storef with 32 bit displacement
void load(Register s, int disp, FloatRegister d, BasicType ld_type, CodeEmitInfo* info = NULL);
void store(FloatRegister d, Register s1, int disp, BasicType st_type, CodeEmitInfo* info = NULL);
// convienence methods for calling load/store with an Address
void load(const Address& a, Register d, BasicType ld_type, CodeEmitInfo* info = NULL, int offset = 0);
void store(Register d, const Address& a, BasicType st_type, CodeEmitInfo* info = NULL, int offset = 0);
void load(const Address& a, FloatRegister d, BasicType ld_type, CodeEmitInfo* info = NULL, int offset = 0);
void store(FloatRegister d, const Address& a, BasicType st_type, CodeEmitInfo* info = NULL, int offset = 0);
// convienence methods for calling load/store with an LIR_Address
void load(LIR_Address* a, Register d, BasicType ld_type, CodeEmitInfo* info = NULL);
void store(Register d, LIR_Address* a, BasicType st_type, CodeEmitInfo* info = NULL);
void load(LIR_Address* a, FloatRegister d, BasicType ld_type, CodeEmitInfo* info = NULL);
void store(FloatRegister d, LIR_Address* a, BasicType st_type, CodeEmitInfo* info = NULL);
int store(LIR_Opr from_reg, Register base, int offset, BasicType type, bool unaligned = false);
int store(LIR_Opr from_reg, Register base, Register disp, BasicType type);
int load(Register base, int offset, LIR_Opr to_reg, BasicType type, bool unaligned = false);
int load(Register base, Register disp, LIR_Opr to_reg, BasicType type);
void monitorexit(LIR_Opr obj_opr, LIR_Opr lock_opr, Register hdr, int monitor_no);
int shift_amount(BasicType t);
static bool is_single_instruction(LIR_Op* op);
public:
void pack64( Register rs, Register rd );
void unpack64( Register rd );
enum {
#ifdef _LP64
call_stub_size = 68,
#else
call_stub_size = 20,
#endif // _LP64
exception_handler_size = DEBUG_ONLY(1*K) NOT_DEBUG(10*4),
deopt_handler_size = DEBUG_ONLY(1*K) NOT_DEBUG(10*4) };