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                         this->clockcount = 3;
  68                         break;
  69                 case 3:
  70                         this->name = "reti";
  71                         this->clockcount = 3;
  72                         break;
  73                 default:
  74                         cerr << "What have you done? 2 bits that have more than 4 values?!" << endl;
  75         }
  76
  77         argbits >>= 5;
  78
  79         dynamic_bitset<> immb = argbits;
  80         immb.resize(16);
  81         this->m_imm = this->generate16ImmSign(immb.to_ulong())*4;
  82
  83 }
  84
  85 void Cbranch::execInstr()
  86 {
  87         //cout << "should exec " << this->toString() << endl;
  88         CDat pc = this->m_cpu->getCurPC();
  89         switch(this->m_typ) {
  90                 case 1:
  91                         {
  92                         CDat sp = this->m_cpu->getStack();
  93                         sp -= 4;
  94                         this->m_cpu->setRAM(sp, this->m_cpu->getNextPC());
  95                         this->m_cpu->setStack(sp);
  96                         }
  97                         /* fall through */
  98                 case 0:
  99                         this->m_cpu->setNextPC(pc+(this->m_imm));
 100                         break;
 101                 case 2:
 102                 case 3:
 103                         this->m_cpu->setNextPC(this->m_cpu->getRAM(this->m_cpu->getStack()));
 104                         this->m_cpu->setStack(this->m_cpu->getStack()+4);
 105                         break;
 106                 default:
 107                         // nothing
 108                         this->m_cpu->setNextPC(400);
 109         }
 110 }
 111
 112 std::string Cbranch::toString()
 113 {
 114         stringstream op;
 115         op << this->getName();
 116
 117         if(m_s) op << 'S';
 118
 119         op << this->getConditionFlag() << (m_taken ? '+' : '-');
 120         if(m_typ < 2) {
 121                 op << " 0x" << std::hex << m_imm << "(" << std::dec << m_imm << ", " << (int) m_imm << ")";
 122         }
 123         return op.str();
 124 }