3c_disasm/instr/shift.cpp

   1 /*   `Deep Thought', a softcore CPU implemented on a FPGA
   2
   3     Copyright (C) 2010 Markus Hofstaetter <markus.manrow@gmx.at>
   4     Copyright (C) 2010 Martin Perner <e0725782@student.tuwien.ac.at>
   5     Copyright (C) 2010 Stefan Rebernig <stefan.rebernig@gmail.com>
   6     Copyright (C) 2010 Manfred Schwarz <e0725898@student.tuwien.ac.at>
   7     Copyright (C) 2010 Bernhard Urban <lewurm@gmail.com>
   8
   9     This program is free software: you can redistribute it and/or modify
  10     it under the terms of the GNU General Public License as published by
  11     the Free Software Foundation, either version 3 of the License, or
  12     (at your option) any later version.
  13
  14     This program is distributed in the hope that it will be useful,
  15     but WITHOUT ANY WARRANTY; without even the implied warranty of
  16     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17     GNU General Public License for more details.
  18
  19     You should have received a copy of the GNU General Public License
  20     along with this program.  If not, see <http://www.gnu.org/licenses/>. */
  21
  22 #include "../Iinstr.hpp"
  23
  24 class Cshift : public Iinstr {
  25                 char m_typ;
  26         public:
  27                 Cshift();
  28                 void evalInstr();
  29                 void execInstr();
  30                 std::string toString();
  31                 Iinstr* getNew();
  32 };
  33
  34 /**
  35  * Name:      create_instruction
  36  * Purpose:   if compiled as shared library, this functions creates the
  37               instruction object
  38
  39  * Returns:   pointer to instruction object
  40  */
  41 extern "C" Iinstr* create_instruction() {
  42     return new Cshift();
  43 }
  44
  45 Iinstr* Cshift::getNew()
  46 {
  47         return new Cshift();
  48 }
  49 /**
  50  * Name:      destroy_instruction
  51  * Purpose:   if compiled as shared library, this functions destoys the
  52               instruction object
  53
  54  * Parameter: IInstruction - the instruction object to delete
  55  */
  56 extern "C" void destroy_instruction(Iinstr* p) {
  57     delete p;
  58 }
  59
  60 Cshift::Cshift() : m_typ(0)
  61 {
  62         opcode = B5(01010);
  63         name = "shift";
  64 }
  65
  66 void Cshift::evalInstr()
  67 {
  68         this->m_d = argbits[0];
  69         this->m_c = argbits[1];
  70         argbits >>= 2;
  71
  72         dynamic_bitset<> type = argbits;
  73         type.resize(2);
  74         this->m_typ = type.to_ulong();
  75
  76         switch(this->m_typ) {
  77                 case 1:
  78                         cerr << "INVALID shift type, using logic left shift!" << endl;
  79                         this->m_typ = 0;
  80                 case 0:
  81                         this->name = "lls";
  82                         break;
  83                 case 2:
  84                         this->name = "lrs";
  85                         break;
  86                 case 3:
  87                         this->name = "ars";
  88                         break;
  89                 default:
  90                         cerr << "What have you done? 2 bits that have more than 4 values?!" << endl;
  91         }
  92
  93         argbits >>= 8;
  94         dynamic_bitset<> immb = argbits;
  95         immb.resize(5);
  96         this->m_imm = immb.to_ulong();
  97         argbits >>= 5;
  98         m_ra = this->getRegister(argbits);
  99         argbits >>= 4;
 100         m_rd = this->getRegister(argbits);
 101 }
 102
 103 void Cshift::execInstr()
 104 {
 105         CDatd val = this->m_cpu->getRegister(m_ra);
 106         switch(this->m_typ) {
 107                 case 0:
 108                 case 1:
 109 //                      this->name = "lls";
 110                         for(unsigned int i = 0; i < m_imm; i++) {
 111                                 val = val << 1;
 112                         }
 113                         //carry
 114                         if(m_c) {
 115                                 this->m_cpu->updateCarry(((val >> BIT_LEN) & 0x1) != 0);
 116                         }
 117                         break;
 118                 case 2:
 119 //                      this->name = "lrs";
 120                         {
 121                                 bool carry = this->m_cpu->getCarry();
 122                                 for(unsigned int i = 0; i < m_imm; i++) {
 123                                         val = val >> 1;
 124
 125                                         //carry!
 126                                         //if user wants carry, and carry is set
 127                                         if(this->m_c && carry) {
 128                                                 //set highest bit 1
 129                                                 val |= (CDat)(1<<(BIT_LEN-1));
 130                                         }
 131                                         else {
 132                                                 //set highest bit 0
 133                                                 val &= (~(1<<(BIT_LEN-1)));
 134                                         }
 135                                 }
 136                         }
 137                         break;
 138                 case 3:
 139 //                      this->name = "ars";
 140                         //>> is a ars, but val is CDatd => we have to set the MSB manually
 141                         {
 142                                 bool msb = (val & (1<<(BIT_LEN-1)) >> (BIT_LEN-1));
 143                                 for(unsigned int i = 0; i < m_imm; i++) {
 144                                         val = val >> 1;
 145                                         if(msb) {
 146                                                 //set highest bit 1
 147                                                 val |= (CDat)(1<<(BIT_LEN-1));
 148                                         }
 149                                         else {
 150                                         //set highest bit 0
 151                                         val &= (~(1<<(BIT_LEN-1)));
 152                                         }
 153                                 }
 154                         }
 155                         break;
 156                 default:
 157                         cerr << "What have you done? 2 bits that have more than 4 values?!" << endl;
 158         }
 159         this->m_cpu->setRegister(m_rd, val);
 160 }
 161
 162 std::string Cshift::toString()
 163 {
 164         stringstream op;
 165         op << this->getName();
 166         if(m_c) op << "C";
 167         if(m_d) op << "D";
 168
 169         op << this->getConditionFlag();
 170         op << " r" << m_rd << ", r" << m_ra << ", " << m_imm;
 171         return op.str();
 172 }