1 /*
   2  * Copyright 2002 Sun Microsystems, Inc.  All Rights Reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 package sun.jvm.hotspot.asm.sparc;
  26 
  27 import sun.jvm.hotspot.asm.*;
  28 
  29 // basic instruction decoder class
  30 abstract class InstructionDecoder implements /* imports */ SPARCOpcodes , RTLDataTypes, RTLOperations {
  31     // some general utility functions - for format 2, 3 & 3A instructions
  32 
  33     static int extractSignedIntFromNBits(int value, int num_bits) {
  34         return (value << (32 - num_bits)) >> (32 - num_bits);
  35     }
  36 
  37     // "rs1"
  38     static int getSourceRegister1(int instruction) {
  39         return (instruction & RS1_MASK) >>> RS1_START_BIT;
  40     }
  41 
  42     // "rs2"
  43     static int getSourceRegister2(int instruction) {
  44         return (instruction & RS2_MASK);
  45     }
  46 
  47     // "rd"
  48     static int getDestinationRegister(int instruction) {
  49         return (instruction & RD_MASK) >>> RD_START_BIT;
  50     }
  51 
  52     static int getConditionCode(int instruction) {
  53         return (instruction & CONDITION_CODE_MASK) >>> CONDITION_CODE_START_BIT;
  54     }
  55 
  56     // "i" bit - used to indicate whether second component in an indirect
  57     // address is immediate value or a register. (format 3 & 3A).
  58 
  59     static boolean isIBitSet(int instruction) {
  60         return (instruction & I_MASK) != 0;
  61     }
  62 
  63     static ImmediateOrRegister getOperand2(int instruction) {
  64         boolean iBit = isIBitSet(instruction);
  65         ImmediateOrRegister operand2 = null;
  66         if (iBit) {
  67            operand2 = new Immediate(new Short((short)extractSignedIntFromNBits(instruction, 13)));
  68         } else {
  69            operand2 = SPARCRegisters.getRegister(getSourceRegister2(instruction));
  70         }
  71         return operand2;
  72     }
  73 
  74     // "opf" - floating point operation code.
  75     static int getOpf(int instruction) {
  76         return (instruction & OPF_MASK) >>> OPF_START_BIT;
  77     }
  78 
  79     abstract Instruction decode(int instruction, SPARCInstructionFactory factory);
  80 }