internal void DataOpHandleSetFlagsAWC_NonCMP(uint opcode, uint Rd, AWCResult awcResult)
{
if (Rd == GeneralPurposeRegisters.PCRegisterIndex)
{
CPSR.RestoreCPUMode();
}
else
{
DataOpHandleSetFlagsAWC_CMP(opcode, Rd, awcResult);
}
}
internal void DataOpHandleSetFlagsLogical_NonCMP(uint opcode, uint Rd, uint result, bool shift_carry)
{
if (Rd == GeneralPurposeRegisters.PCRegisterIndex)
{
CPSR.RestoreCPUMode();
}
else
{
DataOpHandleSetFlagsLogical_CMP(opcode, Rd, result, shift_carry);
}
}
/*----------------------------------------------------------------------------*/
//----------------------------------------------------------------------------
internal uint normal_data_op(uint op_code, uint operation)
{
//extract the S bit value from the opcode
bool SBit = ((op_code & s_mask) != 0);
//extract destination register from opcode
uint Rd = ((op_code & rd_mask) >> 12);
//extract operand register and get first operand
uint Rn = ((op_code & rn_mask) >> 16);
uint a = get_reg(Rn);
bool shift_carry = false;
uint b;
if ((op_code & imm_mask) == 0)
{
b = b_reg(op_code & op2_mask, ref shift_carry);
}
else
{
b = b_immediate(op_code & op2_mask, ref shift_carry);
}
uint rd = 0;
switch (operation) /* R15s @@?! */
{
case 0x0: rd = a & b; break; //AND
case 0x1: rd = a ^ b; break; //EOR
case 0x2: rd = a - b; break; //SUB
case 0x3: rd = b - a; break; //RSB
case 0x4: rd = a + b; break; //ADD
case 0x5: rd = a + b; //ADC
if (CPSR.cf)
{
++rd;
}
break;
case 0x6: rd = a - b - 1; //SBC
if (CPSR.cf)
{
++rd;
}
break;
case 0x7: rd = b - a - 1; //RSC
if (CPSR.cf)
{
++rd;
}
break;
case 0x8: rd = a & b; break; //TST
case 0x9: rd = a ^ b; break; //TEQ
case 0xa: rd = a - b; break; //CMP
case 0xb: rd = a + b; break; //CMN
case 0xc: rd = a | b; break; //ORR
case 0xd: rd = b; break; //MOV
case 0xe: rd = a & ~b; break; //BIC
case 0xf: rd = ~b; break; //MVN
}//switch
if ((operation & 0xc) != 0x8) //Return result unless a compare
{
//write result into destination register
mGPR[Rd] = rd;
//if S bit is set and if the destination register is r15(pc) then this instruction has
//special meaning. We are returning from a non-user mode to user-mode.
//ie movs pc,r14
if (SBit && (Rd == GeneralPurposeRegisters.PCRegisterIndex))
{
CPSR.RestoreCPUMode();
return(1);
} //if
} //if
//if S bit is not set, we do not need to set any cpu flags, so we are done here
if (!SBit)
{
return(1);
}
switch (operation)
{ //LOGICALs
case 0x0: //AND
case 0x1: //EOR
case 0x8: //TST
case 0x9: //TEQ
case 0xc: //ORR
case 0xd: //MOV
case 0xe: //BIC
case 0xf: //MVN
CPSR.set_NZ(rd);
CPSR.cf = shift_carry;
break;
case 0x2: //SUB
case 0xa: //CMP
CPSR.set_flags_sub(a, b, rd, true);
break;
case 0x6: //SBC
CPSR.set_flags_sub(a, b, rd, CPSR.cf);
break;
case 0x3: //RSB
CPSR.set_flags_sub(b, a, rd, true);
break;
case 0x7: //RSC
CPSR.set_flags_sub(b, a, rd, CPSR.cf);
break;
case 0x4: //ADD
case 0xb: //CMN
CPSR.set_flags_add(a, b, rd, false);
break;
case 0x5: //ADC
CPSR.set_flags_add(a, b, rd, CPSR.cf);
break;
default: break;
} //switch
return(1);
} //normal_data_op
} //stm
/// <summary>
/// LDM - perform a multi-register load from memory
/// </summary>
/// <returns>Number of clock cycles executed</returns>
internal uint ldm(uint opcode)
{
uint mode = (opcode & 0x01800000) >> 23; //isolate PU bits
uint Rn = (opcode & rn_mask) >> 16; //get base register
uint reg_list = opcode & 0x0000ffff; //get the register list
bool writeback = (opcode & write_back_mask) != 0; //determine writeback flag
bool userModeLoad = ((opcode & 0x00400000) != 0); //get user mode load flag
uint address = Utils.valid_address(get_reg(Rn)); //make sure it is word aligned.
int first_reg;
uint count = bit_count(reg_list, out first_reg);
bool includesPC = ((reg_list & 0x00008000) != 0);
uint new_base;
switch (mode)
{
case 0: new_base = address - 4 * count; address = new_base + 4; break; //DA (Decrement After)
case 1: new_base = address + 4 * count; break; //IA (Increment After)
case 2: new_base = address - 4 * count; address = new_base; break; //DB (Decrement Before)
case 3: new_base = address + 4 * count; address = address + 4; break; //IB (Increment Before)
default: return(0);
} //switch
if (writeback)
{
mGPR[Rn] = new_base;
}
uint reg = 0;
uint extraCycles = 0;
//check
while (reg_list != 0)
{
if (Utils.lsb(reg_list))
{
uint data = this.GetMemory(address, ARMPluginInterfaces.MemorySize.Word);
if (reg == GeneralPurposeRegisters.PCRegisterIndex)
{ //We are loading a new value into the PC, check if entering Thumb or ARM mode
extraCycles = 2;
//if the user mode flag is set and r15 is being loaded, we are executing
//LDM(3) and returning from an exception. We may be returning to Thumb mode or
//ARM mode. In each case, force align the returning address.
if (userModeLoad)
{ //we are returning from an exception, check if returning to ARM or Thumb mode
if ((CPSR.SPSR & 0x0020) != 0) //check thumb bit of saved CPSR
{
data = data & 0xfffffffe; //returning to thumb mode, force align HWord
}
else
{
data = data & 0xfffffffc; //returning to arm mode, force align Word
}
}
else if ((data & 0x01) != 0)
{ //Entering Thumb mode. Make sure destination address is HWord aligned
CPSR.tf = true;
data = data & 0xfffffffe;
} //if
else
{ //Entering ARM mode. Make sure destination address is Word aligned
CPSR.tf = false;
data = data & 0xfffffffc;
} //else
} //if
if (userModeLoad & !includesPC)
{
mGPR.SetUserModeRegister(reg, data);
}
else
{
mGPR[reg] = data;
}
address += 4;
} //if
reg_list >>= 1;
++reg;
} //while
//if the PC was loaded during this instruction and the user mode load was specified
//then we are returning from an exception.
if (includesPC && userModeLoad)
{
CPSR.RestoreCPUMode();
}
return(2 + count + extraCycles);
} //ldm
