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.RTLDataTypes;
  28 
  29 class RegisterDecoder implements /* imports */ RTLDataTypes {
  30     // refer to page 40 - section 5.1.4.1 - Floating-point Register Number Encoding
  31     private static SPARCFloatRegister decodeDouble(int num) {
  32         // 6 bit double precision registers are encoded in 5 bits as
  33         // b<4> b<3> b<2> b<1> b<5>.
  34 
  35         boolean lsb = (0x1 & num) != 0;
  36         if (lsb)
  37             num |= 0x20;  // 10000b
  38 
  39         if ((num % 2) != 0)
  40             return null;
  41 
  42         return SPARCFloatRegisters.getRegister(num);
  43     }
  44 
  45     private static SPARCFloatRegister decodeQuad(int num) {
  46         // 6 bit quad precision registers are encoded in 5 bits as
  47         // b<4> b<3> b<2> 0 b<5>
  48 
  49         boolean lsb = (0x1 & num) != 0;
  50         if (lsb)
  51             num |= 0x20; // 10000b
  52 
  53         if ((num % 4) != 0)
  54             return null;
  55 
  56         return SPARCFloatRegisters.getRegister(num);
  57     }
  58 
  59     static SPARCRegister decode(int dataType, int regNum) {
  60         regNum &= 0x1F; // mask out all but lsb 5 bits
  61         SPARCRegister result = null;
  62         switch (dataType) {
  63             case RTLDT_FL_SINGLE:
  64                 result = SPARCFloatRegisters.getRegister(regNum);
  65                 break;
  66 
  67             case RTLDT_FL_DOUBLE:
  68                 result = decodeDouble(regNum);
  69                 break;
  70 
  71             case RTLDT_FL_QUAD:
  72                 result = decodeQuad(regNum);
  73                 break;
  74 
  75             case RTLDT_UNKNOWN:
  76                 result = null;
  77                 break;
  78 
  79             default: // some integer register
  80                 result = SPARCRegisters.getRegister(regNum);
  81                 break;
  82         }
  83         return result;
  84     }
  85 }