3c_disasm/instr/branch.cpp

   1 #include "../Iinstr.hpp"
   2
   3 class Cbranch : public Iinstr {
   4         private:
   5                 bool m_taken;
   6                 char m_typ;
   7         public:
   8                 Cbranch();
   9                 void evalInstr();
  10                 void execInstr();
  11                 std::string toString();
  12                 Iinstr* getNew();
  13 };
  14
  15 /**
  16  * Name:      create_instruction
  17  * Purpose:   if compiled as shared library, this functions creates the
  18               instruction object
  19
  20  * Returns:   pointer to instruction object
  21  */
  22 extern "C" Iinstr* create_instruction() {
  23     return new Cbranch();
  24 }
  25
  26 Iinstr* Cbranch::getNew()
  27 {
  28         return new Cbranch();
  29 }
  30 /**
  31  * Name:      destroy_instruction
  32  * Purpose:   if compiled as shared library, this functions destoys the
  33               instruction object
  34
  35  * Parameter: IInstruction - the instruction object to delete
  36  */
  37 extern "C" void destroy_instruction(Iinstr* p) {
  38     delete p;
  39 }
  40
  41 Cbranch::Cbranch() : m_taken(1), m_typ(0)
  42 {
  43         opcode = B5(10110);
  44         name = "branch";
  45 }
  46
  47 void Cbranch::evalInstr()
  48 {
  49         this->m_s = argbits[0];
  50         this->m_taken = argbits[1];
  51
  52         argbits >>= 2;
  53
  54         dynamic_bitset<> type = argbits;
  55         type.resize(2);
  56         this->m_typ = type.to_ulong();
  57
  58         switch(this->m_typ) {
  59                 case 0:
  60                         this->name = "br";
  61                         break;
  62                 case 1:
  63                         this->name = "call";
  64                         break;
  65                 case 2:
  66                         this->name = "ret";
  67                         break;
  68                 case 3:
  69                         this->name = "reti";
  70                         break;
  71                 default:
  72                         cerr << "What have you done? 2 bits that have more than 4 values?!" << endl;
  73         }
  74
  75         argbits >>= 5;
  76
  77         dynamic_bitset<> immb = argbits;
  78         immb.resize(16);
  79         this->m_imm = this->generate16ImmSign(immb.to_ulong());
  80
  81 }
  82
  83 void Cbranch::execInstr()
  84 {
  85         //cout << "should exec " << this->toString() << endl;
  86         CDat pc = this->m_cpu->getCurPC();
  87         switch(this->m_typ) {
  88                 case 1:
  89                         {
  90                         CDat sp = this->m_cpu->getStack();
  91                         this->m_cpu->setRAM(sp, pc);
  92                         sp -= 4;
  93                         this->m_cpu->setStack(sp);
  94                         }
  95                 case 0:
  96                         this->m_cpu->setNextPC(pc+this->m_imm);
  97                         break;
  98                 case 2:
  99                 case 3:
 100                         this->m_cpu->setNextPC(this->m_cpu->getRAM(this->m_cpu->getStack()));
 101                         this->m_cpu->setStack(this->m_cpu->getStack()+4);
 102                         break;
 103                 default:
 104                         // nothing
 105                         this->m_cpu->setNextPC(400);
 106         }
 107 }
 108
 109 std::string Cbranch::toString()
 110 {
 111         stringstream op;
 112         op << this->getName();
 113
 114         if(m_s) op << 'S';
 115
 116         op << this->getConditionFlag() << (m_taken ? '+' : '-');
 117         if(m_typ < 2) {
 118                 op << " 0x" << std::hex << m_imm << "(" << std::dec << m_imm << ")";
 119         }
 120         return op.str();
 121 }