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thumb: initialise instruction formats

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Signed-off-by: Amneesh Singh <natto@weirdnatto.in>
This commit is contained in:
Amneesh Singh
2023-09-23 22:05:20 +05:30
parent 6822e1255a
commit 208527b7f8
4 changed files with 426 additions and 1 deletions
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191
src/cpu/thumb/instruction.cc Normal file
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#include "instruction.hh"
#include "util/bits.hh"
#include <iterator>
namespace matar {
namespace thumb {
Instruction::Instruction(uint16_t insn) {
// Format 1: Move Shifted Register
if ((insn & 0xE000) == 0x0000) {
uint8_t rd = bit_range(insn, 0, 2);
uint8_t rs = bit_range(insn, 3, 5);
uint8_t offset = bit_range(insn, 6, 10);
ShiftType opcode = static_cast<ShiftType>(bit_range(insn, 11, 12));
data = MoveShiftedRegister{
.rd = rd, .rs = rs, .offset = offset, .opcode = opcode
};
// Format 2: Add/Subtract
} else if ((insn & 0xF800) == 0x1800) {
uint8_t rd = bit_range(insn, 0, 2);
uint8_t rs = bit_range(insn, 3, 5);
uint8_t offset = bit_range(insn, 6, 8);
AddSubtract::OpCode opcode =
static_cast<AddSubtract::OpCode>(get_bit(insn, 9));
bool imm = get_bit(insn, 10);
data = AddSubtract{
.rd = rd, .rs = rs, .offset = offset, .opcode = opcode, .imm = imm
};
// Format 3: Move/compare/add/subtract immediate
} else if ((insn & 0xE000) == 0x2000) {
uint8_t offset = bit_range(insn, 0, 7);
uint8_t rd = bit_range(insn, 8, 10);
MovCmpAddSubImmediate::OpCode opcode =
static_cast<MovCmpAddSubImmediate::OpCode>(bit_range(insn, 11, 12));
data =
MovCmpAddSubImmediate{ .offset = offset, .rd = rd, .opcode = opcode };
// Format 4: ALU operations
} else if ((insn & 0xFC00) == 0x4000) {
uint8_t rd = bit_range(insn, 0, 2);
uint8_t rs = bit_range(insn, 3, 5);
AluOperations::OpCode opcode =
static_cast<AluOperations::OpCode>(bit_range(insn, 6, 9));
data = AluOperations{ .rd = rd, .rs = rs, .opcode = opcode };
// Format 5: Hi register operations/branch exchange
} else if ((insn & 0xFC00) == 0x4400) {
uint8_t rd = bit_range(insn, 0, 2);
uint8_t rs = bit_range(insn, 3, 5);
bool hi_2 = get_bit(insn, 6);
bool hi_1 = get_bit(insn, 7);
HiRegisterOperations::OpCode opcode =
static_cast<HiRegisterOperations::OpCode>(bit_range(insn, 8, 9));
data = HiRegisterOperations{
.rd = rd, .rs = rs, .hi_2 = hi_2, .hi_1 = hi_1, .opcode = opcode
};
// Format 6: PC-relative load
} else if ((insn & 0xF800) == 0x4800) {
uint8_t word = bit_range(insn, 0, 7);
uint8_t rd = bit_range(insn, 8, 10);
data = PcRelativeLoad{ .word = word, .rd = rd };
// Format 7: Load/store with register offset
} else if ((insn & 0xF200) == 0x5000) {
uint8_t rd = bit_range(insn, 0, 2);
uint8_t rb = bit_range(insn, 3, 5);
uint8_t ro = bit_range(insn, 6, 8);
bool byte = get_bit(insn, 10);
bool load = get_bit(insn, 11);
data = LoadStoreRegisterOffset{
.rd = rd, .rb = rb, .ro = ro, .byte = byte, .load = load
};
// Format 8: Load/store sign-extended byte/halfword
} else if ((insn & 0xF200) == 0x5200) {
uint8_t rd = bit_range(insn, 0, 2);
uint8_t rb = bit_range(insn, 3, 5);
uint8_t ro = bit_range(insn, 6, 8);
bool s = get_bit(insn, 10);
bool h = get_bit(insn, 11);
data = LoadStoreSignExtendedHalfword{
.rd = rd, .rb = rb, .ro = ro, .s = s, .h = h
};
// Format 9: Load/store with immediate offset
} else if ((insn & 0xF000) == 0x6000) {
uint8_t rd = bit_range(insn, 0, 2);
uint8_t rb = bit_range(insn, 3, 5);
uint8_t offset = bit_range(insn, 6, 10);
bool load = get_bit(insn, 11);
bool byte = get_bit(insn, 12);
data = LoadStoreImmediateOffset{
.rd = rd, .rb = rb, .offset = offset, .load = load, .byte = byte
};
// Format 10: Load/store halfword
} else if ((insn & 0xF000) == 0x8000) {
uint8_t rd = bit_range(insn, 0, 2);
uint8_t rb = bit_range(insn, 3, 5);
uint8_t offset = bit_range(insn, 6, 10);
bool load = get_bit(insn, 11);
data = LoadStoreHalfword{
.rd = rd, .rb = rb, .offset = offset, .load = load
};
// Format 11: SP-relative load/store
} else if ((insn & 0xF000) == 0x9000) {
uint8_t word = bit_range(insn, 0, 7);
uint8_t rd = bit_range(insn, 8, 10);
bool load = get_bit(insn, 11);
data = SpRelativeLoad{ .word = word, .rd = rd, .load = load };
// Format 12: Load address
} else if ((insn & 0xF000) == 0xA000) {
uint8_t word = bit_range(insn, 0, 7);
uint8_t rd = bit_range(insn, 8, 10);
bool sp = get_bit(insn, 11);
data = LoadAddress{ .word = word, .rd = rd, .sp = sp };
// Format 12: Load address
} else if ((insn & 0xF000) == 0xA000) {
uint8_t word = bit_range(insn, 0, 7);
uint8_t rd = bit_range(insn, 8, 10);
bool sp = get_bit(insn, 11);
data = LoadAddress{ .word = word, .rd = rd, .sp = sp };
// Format 13: Add offset to stack pointer
} else if ((insn & 0xFF00) == 0xB000) {
uint8_t word = bit_range(insn, 0, 6);
bool sign = get_bit(insn, 7);
data = AddOffsetStackPointer{ .word = word, .sign = sign };
// Format 14: Push/pop registers
} else if ((insn & 0xF600) == 0xB400) {
uint8_t regs = bit_range(insn, 0, 7);
bool pclr = get_bit(insn, 8);
bool load = get_bit(insn, 11);
data = PushPopRegister{ .regs = regs, .pclr = pclr, .load = load };
// Format 15: Multiple load/store
} else if ((insn & 0xF000) == 0xC000) {
uint8_t regs = bit_range(insn, 0, 7);
uint8_t rb = bit_range(insn, 8, 10);
bool load = get_bit(insn, 11);
data = MultipleLoad{ .regs = regs, .rb = rb, .load = load };
// Format 17: Software interrupt
} else if ((insn & 0xFF00) == 0xDF00) {
data = SoftwareInterrupt{};
// Format 16: Conditional branch
} else if ((insn & 0xF000) == 0xD000) {
uint8_t offset = bit_range(insn, 0, 7);
Condition condition = static_cast<Condition>(bit_range(insn, 8, 11));
data = ConditionalBranch{ .offset = offset, .condition = condition };
// Format 18: Unconditional branch
} else if ((insn & 0xF800) == 0xE000) {
uint16_t offset = bit_range(insn, 0, 10);
data = UnconditionalBranch{ .offset = offset };
// Format 19: Long branch with link
} else if ((insn & 0xF000) == 0xF000) {
uint16_t offset = bit_range(insn, 0, 10);
bool high = get_bit(insn, 11);
data = LongBranchWithLink{ .offset = offset, .high = high };
}
}
}
}