private static bool TryGetImmediate(ImageReader rdr, PrimitiveType type, out MachineOperand op)
{
if (type.Size == 1)
{
rdr.Offset += 1; // skip a byte so we get the appropriate lsb byte and align the word stream.
}
Constant imm;
if (!rdr.TryReadBe(type, out imm))
{
op = null; return(false);
}
else
{
op = new M68kImmediateOperand(imm);
return(true);
}
}
private bool TryParseOperandInner(ushort uInstr, byte addressMode, byte operandBits, PrimitiveType dataWidth, EndianImageReader rdr, out MachineOperand op)
{
Constant offset;
switch (addressMode)
{
case 0: // Data register direct.
op = DataRegisterOperand(operandBits, 0);
return(true);
case 1: // Address register direct
op = new RegisterOperand(AddressRegister(operandBits, 0));
return(true);
case 2: // Address register indirect
op = MemoryOperand.Indirect(dataWidth, AddressRegister(operandBits, 0));
return(true);
case 3: // Address register indirect with postincrement.
op = MemoryOperand.PostIncrement(dataWidth, AddressRegister(operandBits, 0));
return(true);
case 4: // Address register indirect with predecrement.
op = MemoryOperand.PreDecrement(dataWidth, AddressRegister(operandBits, 0));
return(true);
case 5: // Address register indirect with displacement.
if (!rdr.TryReadBe(PrimitiveType.Int16, out offset))
{
op = null;
return(false);
}
op = MemoryOperand.Indirect(dataWidth, AddressRegister(operandBits, 0), offset);
return(true);
case 6: // Address register indirect with index
return(TryAddressRegisterIndirectWithIndex(uInstr, dataWidth, rdr, out op));
case 7:
switch (operandBits)
{
case 0: // Absolute short address
ushort usAddr;
if (!rdr.TryReadBeUInt16(out usAddr))
{
op = null; return(false);
}
op = new M68kAddressOperand(usAddr);
return(true);
case 1: // Absolute long address
uint uAddr;
if (!rdr.TryReadBeUInt32(out uAddr))
{
op = null; return(false);
}
op = new M68kAddressOperand(uAddr);
return(true);
case 2: // Program counter with displacement
var off = rdr.Address - dasm.instr.Address;
short sOffset;
if (!rdr.TryReadBeInt16(out sOffset))
{
op = null; return(false);
}
off += sOffset;
op = new MemoryOperand(dataWidth, Registers.pc, Constant.Int16((short)off));
return(true);
case 3:
// Program counter with index
var addrExt = rdr.Address;
ushort extension;
if (!rdr.TryReadBeUInt16(out extension))
{
op = null; return(false);
}
if (EXT_FULL(extension))
{
if (EXT_EFFECTIVE_ZERO(extension))
{
op = new M68kImmediateOperand(Constant.Word32(0));
return(true);
}
Constant @base = null;
Constant outer = null;
if (EXT_BASE_DISPLACEMENT_PRESENT(extension))
{
@base = EXT_BASE_DISPLACEMENT_LONG(extension)
? rdr.ReadBe(PrimitiveType.Word32)
: rdr.ReadBe(PrimitiveType.Int16);
}
if (EXT_OUTER_DISPLACEMENT_PRESENT(extension))
{
outer = EXT_OUTER_DISPLACEMENT_LONG(extension)
? rdr.ReadBe(PrimitiveType.Word32)
: rdr.ReadBe(PrimitiveType.Int16);
}
RegisterStorage base_reg = EXT_BASE_REGISTER_PRESENT(extension)
? Registers.pc
: null;
RegisterStorage index_reg = null;
PrimitiveType index_width = null;
int index_scale = 0;
if (EXT_INDEX_REGISTER_PRESENT(extension))
{
index_reg = EXT_INDEX_AR(extension)
? Registers.AddressRegister((int)EXT_INDEX_REGISTER(extension))
: Registers.DataRegister((int)EXT_INDEX_REGISTER(extension));
index_width = EXT_INDEX_LONG(extension) ? PrimitiveType.Word32 : PrimitiveType.Int16;
index_scale = (EXT_INDEX_SCALE(extension) != 0)
? 1 << EXT_INDEX_SCALE(extension)
: 0;
}
op = new IndexedOperand(dataWidth, @base, outer, base_reg, index_reg, index_width, index_scale,
(extension & 7) > 0 && (extension & 7) < 4,
(extension & 7) > 4);
return(true);
}
op = new IndirectIndexedOperand(
dataWidth,
EXT_8BIT_DISPLACEMENT(extension),
Registers.pc,
EXT_INDEX_AR(extension)
? Registers.AddressRegister((int)EXT_INDEX_REGISTER(extension))
: Registers.DataRegister((int)EXT_INDEX_REGISTER(extension)),
EXT_INDEX_LONG(extension)
? PrimitiveType.Word32
: PrimitiveType.Int16,
1 << EXT_INDEX_SCALE(extension));
return(true);
case 4:
// Immediate
if (dataWidth.Size == 1) // don't want the instruction stream to get misaligned!
{
rdr.Offset += 1;
}
Constant coff;
if (!rdr.TryReadBe(dataWidth, out coff))
{
op = null; return(false);
}
op = new M68kImmediateOperand(coff);
return(true);
default:
op = null;
return(false);
}
default:
throw new NotImplementedException(string.Format("Address mode {0:X1} not implemented.", addressMode));
}
}
private bool TryAddressRegisterIndirectWithIndex(PrimitiveType dataWidth, EndianImageReader rdr, out MachineOperand op)
{
ushort extension;
if (!rdr.TryReadBeUInt16(out extension))
{
op = null; return(false);
}
if (EXT_FULL(extension))
{
if (M68kDisassembler.EXT_EFFECTIVE_ZERO(extension))
{
op = new M68kImmediateOperand(Constant.Zero(dataWidth));
return(true);
}
RegisterStorage base_reg = null;
RegisterStorage index_reg = null;
PrimitiveType index_reg_width = null;
int index_scale = 1;
Constant @base = null;
if (EXT_BASE_DISPLACEMENT_PRESENT(extension))
{
@base = rdr.ReadBe(EXT_BASE_DISPLACEMENT_LONG(extension) ? PrimitiveType.Word32 : PrimitiveType.Int16);
}
Constant outer = null;
if (EXT_OUTER_DISPLACEMENT_PRESENT(extension))
{
outer = rdr.ReadBe(EXT_OUTER_DISPLACEMENT_LONG(extension) ? PrimitiveType.Word32 : PrimitiveType.Int16);
}
if (EXT_BASE_REGISTER_PRESENT(extension))
{
base_reg = Registers.AddressRegister(opcode & 7);
}
if (EXT_INDEX_REGISTER_PRESENT(extension))
{
index_reg = EXT_INDEX_AR(extension)
? Registers.AddressRegister((int)EXT_INDEX_REGISTER(extension))
: Registers.DataRegister((int)EXT_INDEX_REGISTER(extension));
index_reg_width = EXT_INDEX_LONG(extension) ? PrimitiveType.Word32 : PrimitiveType.Word16;
if (EXT_INDEX_SCALE(extension) != 0)
{
index_scale = 1 << EXT_INDEX_SCALE(extension);
}
}
bool preindex = (extension & 7) > 0 && (extension & 7) < 4;
bool postindex = (extension & 7) > 4;
op = new IndexedOperand(dataWidth, @base, outer, base_reg, index_reg, index_reg_width, index_scale, preindex, postindex);
}
else
{
op = new IndirectIndexedOperand(
dataWidth,
EXT_8BIT_DISPLACEMENT(extension),
Registers.AddressRegister(opcode & 7),
EXT_INDEX_AR(extension)
? Registers.AddressRegister((int)EXT_INDEX_REGISTER(extension))
: Registers.DataRegister((int)EXT_INDEX_REGISTER(extension)),
EXT_INDEX_LONG(extension) ? PrimitiveType.Word32 : PrimitiveType.Int16,
EXT_INDEX_SCALE(extension));
}
return(true);
}