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626 lines
20 KiB
C++
626 lines
20 KiB
C++
//
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// x86.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 01/01/21.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#include "Decoder.hpp"
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#include <algorithm>
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#include <cassert>
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#include <utility>
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using namespace InstructionSet::x86;
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// Only 8086 is suppoted for now.
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Decoder::Decoder(Model) {}
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std::pair<int, InstructionSet::x86::Instruction> Decoder::decode(const uint8_t *source, size_t length) {
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const uint8_t *const end = source + length;
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// MARK: - Prefixes (if present) and the opcode.
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/// Helper macro for those that follow.
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#define SetOpSrcDestSize(op, src, dest, size) \
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operation_ = Operation::op; \
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source_ = Source::src; \
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destination_ = Source::dest; \
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operation_size_ = size
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/// Covers anything which is complete as soon as the opcode is encountered.
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#define Complete(op, src, dest, size) \
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SetOpSrcDestSize(op, src, dest, size); \
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phase_ = Phase::ReadyToPost
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/// Handles instructions of the form rr, kk and rr, jjkk, i.e. a destination register plus an operand.
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#define RegData(op, dest, size) \
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SetOpSrcDestSize(op, DirectAddress, dest, size); \
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source_ = Source::Immediate; \
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operand_size_ = size; \
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phase_ = Phase::AwaitingDisplacementOrOperand
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/// Handles instructions of the form Ax, jjkk where the latter is implicitly an address.
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#define RegAddr(op, dest, op_size, addr_size) \
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SetOpSrcDestSize(op, DirectAddress, dest, op_size); \
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operand_size_ = addr_size; \
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phase_ = Phase::AwaitingDisplacementOrOperand
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/// Handles instructions of the form jjkk, Ax where the former is implicitly an address.
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#define AddrReg(op, source, op_size, addr_size) \
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SetOpSrcDestSize(op, source, DirectAddress, op_size); \
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operand_size_ = addr_size; \
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destination_ = Source::DirectAddress; \
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phase_ = Phase::AwaitingDisplacementOrOperand
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/// Covers both `mem/reg, reg` and `reg, mem/reg`.
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#define MemRegReg(op, format, size) \
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operation_ = Operation::op; \
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phase_ = Phase::ModRegRM; \
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modregrm_format_ = ModRegRMFormat::format; \
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operand_size_ = 0; \
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operation_size_ = size
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/// Handles JO, JNO, JB, etc — jumps with a single byte displacement.
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#define Jump(op) \
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operation_ = Operation::op; \
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phase_ = Phase::AwaitingDisplacementOrOperand; \
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displacement_size_ = 1
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/// Handles far CALL and far JMP — fixed four byte operand operations.
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#define Far(op) \
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operation_ = Operation::op; \
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phase_ = Phase::AwaitingDisplacementOrOperand; \
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operand_size_ = 4; \
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while(phase_ == Phase::Instruction && source != end) {
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// Retain the instruction byte, in case additional decoding is deferred
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// to the ModRegRM byte.
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instr_ = *source;
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++source;
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++consumed_;
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switch(instr_) {
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default: {
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const auto result = std::make_pair(consumed_, Instruction());
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reset_parsing();
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return result;
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}
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#define PartialBlock(start, operation) \
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case start + 0x00: MemRegReg(operation, MemReg_Reg, 1); break; \
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case start + 0x01: MemRegReg(operation, MemReg_Reg, 2); break; \
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case start + 0x02: MemRegReg(operation, Reg_MemReg, 1); break; \
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case start + 0x03: MemRegReg(operation, Reg_MemReg, 2); break; \
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case start + 0x04: RegData(operation, AL, 1); break; \
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case start + 0x05: RegData(operation, AX, 2)
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PartialBlock(0x00, ADD); break;
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case 0x06: Complete(PUSH, ES, None, 2); break;
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case 0x07: Complete(POP, None, ES, 2); break;
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PartialBlock(0x08, OR); break;
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case 0x0e: Complete(PUSH, CS, None, 2); break;
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PartialBlock(0x10, ADC); break;
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case 0x16: Complete(PUSH, SS, None, 2); break;
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case 0x17: Complete(POP, None, SS, 2); break;
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PartialBlock(0x18, SBB); break;
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case 0x1e: Complete(PUSH, DS, None, 2); break;
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case 0x1f: Complete(POP, None, DS, 2); break;
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PartialBlock(0x20, AND); break;
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case 0x26: segment_override_ = Source::ES; break;
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case 0x27: Complete(DAA, AL, AL, 1); break;
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PartialBlock(0x28, SUB); break;
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case 0x2e: segment_override_ = Source::CS; break;
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case 0x2f: Complete(DAS, AL, AL, 1); break;
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PartialBlock(0x30, XOR); break;
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case 0x36: segment_override_ = Source::SS; break;
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case 0x37: Complete(AAA, AL, AX, 1); break;
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PartialBlock(0x38, CMP); break;
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case 0x3e: segment_override_ = Source::DS; break;
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case 0x3f: Complete(AAS, AL, AX, 1); break;
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#undef PartialBlock
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#define RegisterBlock(start, operation) \
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case start + 0x00: Complete(operation, AX, AX, 2); break; \
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case start + 0x01: Complete(operation, CX, CX, 2); break; \
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case start + 0x02: Complete(operation, DX, DX, 2); break; \
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case start + 0x03: Complete(operation, BX, BX, 2); break; \
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case start + 0x04: Complete(operation, SP, SP, 2); break; \
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case start + 0x05: Complete(operation, BP, BP, 2); break; \
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case start + 0x06: Complete(operation, SI, SI, 2); break; \
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case start + 0x07: Complete(operation, DI, DI, 2)
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RegisterBlock(0x40, INC); break;
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RegisterBlock(0x48, DEC); break;
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RegisterBlock(0x50, PUSH); break;
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RegisterBlock(0x58, POP); break;
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#undef RegisterBlock
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// 0x60–0x6f: not used.
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case 0x70: Jump(JO); break;
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case 0x71: Jump(JNO); break;
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case 0x72: Jump(JB); break;
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case 0x73: Jump(JNB); break;
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case 0x74: Jump(JE); break;
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case 0x75: Jump(JNE); break;
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case 0x76: Jump(JBE); break;
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case 0x77: Jump(JNBE); break;
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case 0x78: Jump(JS); break;
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case 0x79: Jump(JNS); break;
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case 0x7a: Jump(JP); break;
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case 0x7b: Jump(JNP); break;
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case 0x7c: Jump(JL); break;
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case 0x7d: Jump(JNL); break;
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case 0x7e: Jump(JLE); break;
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case 0x7f: Jump(JNLE); break;
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case 0x80: MemRegReg(Invalid, MemRegADD_to_CMP, 1); break;
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case 0x81: MemRegReg(Invalid, MemRegADD_to_CMP, 2); break;
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case 0x82: MemRegReg(Invalid, MemRegADC_to_CMP, 1); break;
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case 0x83: MemRegReg(Invalid, MemRegADC_to_CMP, 2); break;
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case 0x84: MemRegReg(TEST, MemReg_Reg, 1); break;
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case 0x85: MemRegReg(TEST, MemReg_Reg, 2); break;
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case 0x86: MemRegReg(XCHG, Reg_MemReg, 1); break;
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case 0x87: MemRegReg(XCHG, Reg_MemReg, 2); break;
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case 0x88: MemRegReg(MOV, MemReg_Reg, 1); break;
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case 0x89: MemRegReg(MOV, MemReg_Reg, 2); break;
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case 0x8a: MemRegReg(MOV, Reg_MemReg, 1); break;
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case 0x8b: MemRegReg(MOV, Reg_MemReg, 2); break;
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// 0x8c: not used.
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case 0x8d: MemRegReg(LEA, Reg_MemReg, 2); break;
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case 0x8e: MemRegReg(MOV, SegReg, 2); break;
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case 0x8f: MemRegReg(POP, MemRegPOP, 2); break;
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case 0x90: Complete(NOP, None, None, 0); break; // Or XCHG AX, AX?
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case 0x91: Complete(XCHG, AX, CX, 2); break;
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case 0x92: Complete(XCHG, AX, DX, 2); break;
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case 0x93: Complete(XCHG, AX, BX, 2); break;
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case 0x94: Complete(XCHG, AX, SP, 2); break;
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case 0x95: Complete(XCHG, AX, BP, 2); break;
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case 0x96: Complete(XCHG, AX, SI, 2); break;
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case 0x97: Complete(XCHG, AX, DI, 2); break;
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case 0x98: Complete(CBW, AL, AH, 1); break;
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case 0x99: Complete(CWD, AX, DX, 2); break;
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case 0x9a: Far(CALLF); break;
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case 0x9b: Complete(WAIT, None, None, 0); break;
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case 0x9c: Complete(PUSHF, None, None, 2); break;
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case 0x9d: Complete(POPF, None, None, 2); break;
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case 0x9e: Complete(SAHF, None, None, 1); break;
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case 0x9f: Complete(LAHF, None, None, 1); break;
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case 0xa0: RegAddr(MOV, AL, 1, 1); break;
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case 0xa1: RegAddr(MOV, AX, 2, 2); break;
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case 0xa2: AddrReg(MOV, AL, 1, 1); break;
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case 0xa3: AddrReg(MOV, AX, 2, 2); break;
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case 0xa4: Complete(MOVS, None, None, 1); break;
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case 0xa5: Complete(MOVS, None, None, 2); break;
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case 0xa6: Complete(CMPS, None, None, 1); break;
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case 0xa7: Complete(CMPS, None, None, 2); break;
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case 0xa8: RegData(TEST, AL, 1); break;
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case 0xa9: RegData(TEST, AX, 2); break;
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case 0xaa: Complete(STOS, None, None, 1); break;
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case 0xab: Complete(STOS, None, None, 2); break;
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case 0xac: Complete(LODS, None, None, 1); break;
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case 0xad: Complete(LODS, None, None, 2); break;
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case 0xae: Complete(SCAS, None, None, 1); break;
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case 0xaf: Complete(SCAS, None, None, 2); break;
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case 0xb0: RegData(MOV, AL, 1); break;
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case 0xb1: RegData(MOV, CL, 1); break;
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case 0xb2: RegData(MOV, DL, 1); break;
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case 0xb3: RegData(MOV, BL, 1); break;
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case 0xb4: RegData(MOV, AH, 1); break;
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case 0xb5: RegData(MOV, CH, 1); break;
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case 0xb6: RegData(MOV, DH, 1); break;
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case 0xb7: RegData(MOV, BH, 1); break;
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case 0xb8: RegData(MOV, AX, 2); break;
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case 0xb9: RegData(MOV, CX, 2); break;
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case 0xba: RegData(MOV, DX, 2); break;
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case 0xbb: RegData(MOV, BX, 2); break;
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case 0xbc: RegData(MOV, SP, 2); break;
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case 0xbd: RegData(MOV, BP, 2); break;
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case 0xbe: RegData(MOV, SI, 2); break;
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case 0xbf: RegData(MOV, DI, 2); break;
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case 0xc2: RegData(RETN, None, 2); break;
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case 0xc3: Complete(RETN, None, None, 2); break;
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case 0xc4: MemRegReg(LES, Reg_MemReg, 2); break;
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case 0xc5: MemRegReg(LDS, Reg_MemReg, 2); break;
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case 0xc6: MemRegReg(MOV, MemRegMOV, 1); break;
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case 0xc7: MemRegReg(MOV, MemRegMOV, 2); break;
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case 0xca: RegData(RETF, None, 2); break;
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case 0xcb: Complete(RETF, None, None, 4); break;
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case 0xcc: Complete(INT3, None, None, 0); break;
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case 0xcd: RegData(INT, None, 1); break;
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case 0xce: Complete(INTO, None, None, 0); break;
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case 0xcf: Complete(IRET, None, None, 0); break;
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case 0xd0: case 0xd1:
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phase_ = Phase::ModRegRM;
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modregrm_format_ = ModRegRMFormat::MemRegROL_to_SAR;
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operation_size_ = 1 + (instr_ & 1);
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source_ = Source::Immediate;
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operand_ = 1;
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break;
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case 0xd2: case 0xd3:
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phase_ = Phase::ModRegRM;
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modregrm_format_ = ModRegRMFormat::MemRegROL_to_SAR;
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operation_size_ = 1 + (instr_ & 1);
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source_ = Source::CL;
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break;
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case 0xd4: RegData(AAM, AX, 1); break;
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case 0xd5: RegData(AAD, AX, 1); break;
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case 0xd7: Complete(XLAT, None, None, 1); break;
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case 0xd8: MemRegReg(ESC, MemReg_Reg, 0); break;
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case 0xd9: MemRegReg(ESC, MemReg_Reg, 0); break;
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case 0xda: MemRegReg(ESC, MemReg_Reg, 0); break;
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case 0xdb: MemRegReg(ESC, MemReg_Reg, 0); break;
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case 0xdc: MemRegReg(ESC, MemReg_Reg, 0); break;
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case 0xdd: MemRegReg(ESC, MemReg_Reg, 0); break;
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case 0xde: MemRegReg(ESC, MemReg_Reg, 0); break;
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case 0xdf: MemRegReg(ESC, MemReg_Reg, 0); break;
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case 0xe0: Jump(LOOPNE); break;
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case 0xe1: Jump(LOOPE); break;
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case 0xe2: Jump(LOOP); break;
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case 0xe3: Jump(JPCX); break;
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case 0xe4: RegAddr(IN, AL, 1, 1); break;
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case 0xe5: RegAddr(IN, AX, 2, 1); break;
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case 0xe6: AddrReg(OUT, AL, 1, 1); break;
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case 0xe7: AddrReg(OUT, AX, 2, 1); break;
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case 0xe8: RegData(CALLD, None, 2); break;
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case 0xe9: RegData(JMPN, None, 2); break;
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case 0xea: Far(JMPF); break;
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case 0xeb: Jump(JMPN); break;
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case 0xec: Complete(IN, DX, AL, 1); break;
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case 0xed: Complete(IN, DX, AX, 1); break;
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case 0xee: Complete(OUT, AL, DX, 1); break;
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case 0xef: Complete(OUT, AX, DX, 2); break;
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case 0xf4: Complete(HLT, None, None, 1); break;
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case 0xf5: Complete(CMC, None, None, 1); break;
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case 0xf6: MemRegReg(Invalid, MemRegTEST_to_IDIV, 1); break;
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case 0xf7: MemRegReg(Invalid, MemRegTEST_to_IDIV, 2); break;
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case 0xf8: Complete(CLC, None, None, 1); break;
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case 0xf9: Complete(STC, None, None, 1); break;
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case 0xfa: Complete(CLI, None, None, 1); break;
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case 0xfb: Complete(STI, None, None, 1); break;
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case 0xfc: Complete(CLD, None, None, 1); break;
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case 0xfd: Complete(STD, None, None, 1); break;
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case 0xfe: MemRegReg(Invalid, MemRegINC_DEC, 1); break;
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case 0xff: MemRegReg(Invalid, MemRegINC_to_PUSH, 1); break;
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// Other prefix bytes.
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case 0xf0: lock_ = true; break;
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case 0xf2: repetition_ = Repetition::RepNE; break;
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case 0xf3: repetition_ = Repetition::RepE; break;
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}
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}
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#undef Far
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#undef Jump
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#undef MemRegReg
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#undef AddrReg
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#undef RegAddr
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#undef RegData
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#undef Complete
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#undef SetOpSrcDestSize
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// MARK: - ModRegRM byte, if any.
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if(phase_ == Phase::ModRegRM && source != end) {
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const uint8_t mod = *source >> 6; // i.e. mode.
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const uint8_t reg = (*source >> 3) & 7; // i.e. register.
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const uint8_t rm = *source & 7; // i.e. register/memory.
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++source;
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++consumed_;
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Source memreg;
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constexpr Source reg_table[3][8] = {
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{},
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{
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Source::AL, Source::CL, Source::DL, Source::BL,
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Source::AH, Source::CH, Source::DH, Source::BH,
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}, {
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Source::AX, Source::CX, Source::DX, Source::BX,
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Source::SP, Source::BP, Source::SI, Source::DI,
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}
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};
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switch(mod) {
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case 0: {
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constexpr Source rm_table[8] = {
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Source::IndBXPlusSI, Source::IndBXPlusDI,
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Source::IndBPPlusSI, Source::IndBPPlusDI,
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Source::IndSI, Source::IndDI,
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Source::DirectAddress, Source::IndBX,
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};
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memreg = rm_table[rm];
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} break;
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default: {
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constexpr Source rm_table[8] = {
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Source::IndBXPlusSI, Source::IndBXPlusDI,
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Source::IndBPPlusSI, Source::IndBPPlusDI,
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Source::IndSI, Source::IndDI,
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Source::IndBP, Source::IndBX,
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};
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memreg = rm_table[rm];
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displacement_size_ = 1 + (mod == 2);
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} break;
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// Other operand is just a register.
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case 3:
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memreg = reg_table[operation_size_][rm];
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// LES and LDS accept a memory argument only, not a register.
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if(operation_ == Operation::LES || operation_ == Operation::LDS) {
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const auto result = std::make_pair(consumed_, Instruction());
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reset_parsing();
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return result;
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}
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break;
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}
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switch(modregrm_format_) {
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case ModRegRMFormat::Reg_MemReg:
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case ModRegRMFormat::MemReg_Reg: {
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if(modregrm_format_ == ModRegRMFormat::Reg_MemReg) {
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source_ = memreg;
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destination_ = reg_table[operation_size_][reg];
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} else {
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source_ = reg_table[operation_size_][reg];
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destination_ = memreg;
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}
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} break;
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case ModRegRMFormat::MemRegTEST_to_IDIV:
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source_ = destination_ = memreg;
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switch(reg) {
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default: {
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const auto result = std::make_pair(consumed_, Instruction());
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reset_parsing();
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return result;
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}
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case 0: operation_ = Operation::TEST; break;
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case 2: operation_ = Operation::NOT; break;
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case 3: operation_ = Operation::NEG; break;
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case 4: operation_ = Operation::MUL; break;
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case 5: operation_ = Operation::IMUL; break;
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case 6: operation_ = Operation::DIV; break;
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case 7: operation_ = Operation::IDIV; break;
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}
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break;
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case ModRegRMFormat::SegReg: {
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source_ = memreg;
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constexpr Source seg_table[4] = {
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Source::ES, Source::CS,
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Source::SS, Source::DS,
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};
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if(reg & 4) {
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const auto result = std::make_pair(consumed_, Instruction());
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reset_parsing();
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return result;
|
||
}
|
||
|
||
destination_ = seg_table[reg];
|
||
} break;
|
||
|
||
case ModRegRMFormat::MemRegROL_to_SAR:
|
||
destination_ = memreg;
|
||
|
||
switch(reg) {
|
||
default: {
|
||
const auto result = std::make_pair(consumed_, Instruction());
|
||
reset_parsing();
|
||
return result;
|
||
}
|
||
|
||
case 0: operation_ = Operation::ROL; break;
|
||
case 2: operation_ = Operation::ROR; break;
|
||
case 3: operation_ = Operation::RCL; break;
|
||
case 4: operation_ = Operation::RCR; break;
|
||
case 5: operation_ = Operation::SAL; break;
|
||
case 6: operation_ = Operation::SHR; break;
|
||
case 7: operation_ = Operation::SAR; break;
|
||
}
|
||
break;
|
||
|
||
case ModRegRMFormat::MemRegINC_DEC:
|
||
source_ = destination_ = memreg;
|
||
|
||
switch(reg) {
|
||
default: {
|
||
const auto result = std::make_pair(consumed_, Instruction());
|
||
reset_parsing();
|
||
return result;
|
||
}
|
||
|
||
case 0: operation_ = Operation::INC; break;
|
||
case 1: operation_ = Operation::DEC; break;
|
||
}
|
||
break;
|
||
|
||
case ModRegRMFormat::MemRegINC_to_PUSH:
|
||
source_ = destination_ = memreg;
|
||
|
||
switch(reg) {
|
||
default: {
|
||
const auto result = std::make_pair(consumed_, Instruction());
|
||
reset_parsing();
|
||
return result;
|
||
}
|
||
|
||
case 0: operation_ = Operation::INC; break;
|
||
case 1: operation_ = Operation::DEC; break;
|
||
case 2: operation_ = Operation::CALLN; break;
|
||
case 3:
|
||
operation_ = Operation::CALLF;
|
||
operand_size_ = 4;
|
||
source_ = Source::Immediate;
|
||
break;
|
||
case 4: operation_ = Operation::JMPN; break;
|
||
case 5:
|
||
operation_ = Operation::JMPF;
|
||
operand_size_ = 4;
|
||
source_ = Source::Immediate;
|
||
break;
|
||
case 6: operation_ = Operation::PUSH; break;
|
||
}
|
||
break;
|
||
|
||
case ModRegRMFormat::MemRegPOP:
|
||
source_ = destination_ = memreg;
|
||
|
||
if(reg != 0) {
|
||
reset_parsing();
|
||
return std::make_pair(consumed_, Instruction());
|
||
}
|
||
break;
|
||
|
||
case ModRegRMFormat::MemRegMOV:
|
||
source_ = Source::Immediate;
|
||
destination_ = memreg;
|
||
operand_size_ = operation_size_;
|
||
break;
|
||
|
||
case ModRegRMFormat::MemRegADD_to_CMP:
|
||
destination_ = memreg;
|
||
operand_size_ = operation_size_;
|
||
|
||
switch(reg) {
|
||
default: operation_ = Operation::ADD; break;
|
||
case 1: operation_ = Operation::OR; break;
|
||
case 2: operation_ = Operation::ADC; break;
|
||
case 3: operation_ = Operation::SBB; break;
|
||
case 4: operation_ = Operation::AND; break;
|
||
case 5: operation_ = Operation::SUB; break;
|
||
case 6: operation_ = Operation::XOR; break;
|
||
case 7: operation_ = Operation::CMP; break;
|
||
}
|
||
break;
|
||
|
||
case ModRegRMFormat::MemRegADC_to_CMP:
|
||
destination_ = memreg;
|
||
source_ = Source::Immediate;
|
||
operand_size_ = 1; // ... and always 1; it'll be sign extended if
|
||
// the operation requires it.
|
||
|
||
switch(reg) {
|
||
default: {
|
||
const auto result = std::make_pair(consumed_, Instruction());
|
||
reset_parsing();
|
||
return result;
|
||
}
|
||
|
||
case 0: operation_ = Operation::ADD; break;
|
||
case 2: operation_ = Operation::ADC; break;
|
||
case 3: operation_ = Operation::SBB; break;
|
||
case 5: operation_ = Operation::SUB; break;
|
||
case 7: operation_ = Operation::CMP; break;
|
||
}
|
||
break;
|
||
|
||
default: assert(false);
|
||
}
|
||
|
||
phase_ = (displacement_size_ + operand_size_) ? Phase::AwaitingDisplacementOrOperand : Phase::ReadyToPost;
|
||
}
|
||
|
||
// MARK: - Displacement and operand.
|
||
|
||
if(phase_ == Phase::AwaitingDisplacementOrOperand && source != end) {
|
||
const int required_bytes = displacement_size_ + operand_size_;
|
||
|
||
const int outstanding_bytes = required_bytes - operand_bytes_;
|
||
const int bytes_to_consume = std::min(int(end - source), outstanding_bytes);
|
||
|
||
// TODO: I can surely do better than this?
|
||
for(int c = 0; c < bytes_to_consume; c++) {
|
||
inward_data_ = (inward_data_ >> 8) | (uint64_t(source[0]) << 56);
|
||
++source;
|
||
}
|
||
|
||
consumed_ += bytes_to_consume;
|
||
operand_bytes_ += bytes_to_consume;
|
||
|
||
if(bytes_to_consume == outstanding_bytes) {
|
||
phase_ = Phase::ReadyToPost;
|
||
|
||
switch(operand_size_) {
|
||
default: operand_ = 0; break;
|
||
case 1:
|
||
operand_ = inward_data_ >> 56; inward_data_ <<= 8;
|
||
|
||
// Sign extend if a single byte operand is feeding a two-byte instruction.
|
||
if(operation_size_ == 2 && operation_ != Operation::IN && operation_ != Operation::OUT) {
|
||
operand_ |= (operand_ & 0x80) ? 0xff00 : 0x0000;
|
||
}
|
||
break;
|
||
case 4: displacement_size_ = 2; [[fallthrough]];
|
||
case 2: operand_ = inward_data_ >> 48; inward_data_ <<= 16; break;
|
||
break;
|
||
}
|
||
switch(displacement_size_) {
|
||
default: displacement_ = 0; break;
|
||
case 1: displacement_ = int8_t(inward_data_ >> 56); break;
|
||
case 2: displacement_ = int16_t(inward_data_ >> 48); break;
|
||
}
|
||
} else {
|
||
// Provide a genuine measure of further bytes required.
|
||
return std::make_pair(-(outstanding_bytes - bytes_to_consume), Instruction());
|
||
}
|
||
}
|
||
|
||
// MARK: - Check for completion.
|
||
|
||
if(phase_ == Phase::ReadyToPost) {
|
||
const auto result = std::make_pair(
|
||
consumed_,
|
||
Instruction(
|
||
operation_,
|
||
source_,
|
||
destination_,
|
||
lock_,
|
||
segment_override_,
|
||
repetition_,
|
||
Size(operation_size_),
|
||
displacement_,
|
||
operand_)
|
||
);
|
||
reset_parsing();
|
||
return result;
|
||
}
|
||
|
||
// i.e. not done yet.
|
||
return std::make_pair(0, Instruction());
|
||
}
|