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127 lines
3.9 KiB
C++
127 lines
3.9 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 1/1/21.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#include "x86.hpp"
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using namespace CPU::Decoder::x86;
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Instruction Decoder::decode(uint8_t *source, size_t length) {
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uint8_t *const limit = source + length;
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#define MapPartial(value, op, sz, fmt, phs) \
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case value: \
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operation_ = Operation::op; \
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operand_size_ = Size::sz; \
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format_ = Format::fmt; \
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phase_ = Phase::phs; \
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break;
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#define MapComplete(value, op, sz, src, dest) \
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case value: \
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operation_ = Operation::op; \
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operand_size_ = Size::sz; \
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source_ = Source::src; \
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destination_ = Source::dest; \
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phase_ = Phase::ReadyToPost; \
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break;
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while(phase_ == Phase::Instruction && source != limit) {
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switch(*source) {
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#define PartialBlock(start, operation) \
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MapPartial(start + 0x00, operation, Byte, MemReg_Reg, ModRM); \
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MapPartial(start + 0x01, operation, Word, MemReg_Reg, ModRM); \
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MapPartial(start + 0x02, operation, Byte, Reg_MemReg, ModRM); \
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MapPartial(start + 0x03, operation, Word, Reg_MemReg, ModRM); \
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MapPartial(start + 0x04, operation, Byte, Ac_Data, AwaitingOperands); \
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MapPartial(start + 0x05, operation, Word, Ac_Data, AwaitingOperands);
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PartialBlock(0x00, ADD);
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MapComplete(0x06, PUSH, Word, ES, None);
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MapComplete(0x07, POP, Word, ES, None);
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PartialBlock(0x08, OR);
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MapComplete(0x0e, PUSH, Word, CS, None);
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/* 0x0f: not used. */
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PartialBlock(0x10, ADC);
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MapComplete(0x16, PUSH, Word, SS, None);
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MapComplete(0x17, POP, Word, SS, None);
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PartialBlock(0x18, SBB);
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MapComplete(0x1e, PUSH, Word, DS, None);
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MapComplete(0x1f, POP, Word, DS, None);
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PartialBlock(0x20, AND);
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case 0x26: segment_override_ = Source::ES; break;
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MapComplete(0x27, DAA, Implied, None, None);
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PartialBlock(0x28, SUB);
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case 0x2e: segment_override_ = Source::CS; break;
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MapComplete(0x2f, DAS, Implied, None, None);
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PartialBlock(0x30, XOR);
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case 0x36: segment_override_ = Source::SS; break;
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MapComplete(0x37, AAA, Implied, None, None);
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PartialBlock(0x38, CMP);
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case 0x3e: segment_override_ = Source::DS; break;
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MapComplete(0x3f, AAS, Implied, None, None);
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#undef PartialBlock
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#define RegisterBlock(start, operation) \
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MapComplete(start + 0x00, operation, Word, AX, AX); \
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MapComplete(start + 0x01, operation, Word, CX, CX); \
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MapComplete(start + 0x02, operation, Word, DX, DX); \
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MapComplete(start + 0x03, operation, Word, BX, BX); \
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MapComplete(start + 0x04, operation, Word, SP, SP); \
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MapComplete(start + 0x05, operation, Word, BP, BP); \
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MapComplete(start + 0x06, operation, Word, SI, SI); \
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MapComplete(start + 0x07, operation, Word, DI, DI); \
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RegisterBlock(0x40, INC);
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RegisterBlock(0x48, DEC);
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RegisterBlock(0x50, PUSH);
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RegisterBlock(0x58, POP);
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#undef RegisterBlock
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/* 0x60–0x6f: not used. */
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MapPartial(0x70, JO, Byte, Disp, AwaitingOperands);
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MapPartial(0x71, JNO, Byte, Disp, AwaitingOperands);
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MapPartial(0x72, JB, Byte, Disp, AwaitingOperands);
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MapPartial(0x73, JNB, Byte, Disp, AwaitingOperands);
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MapPartial(0x74, JE, Byte, Disp, AwaitingOperands);
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MapPartial(0x75, JNE, Byte, Disp, AwaitingOperands);
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MapPartial(0x76, JBE, Byte, Disp, AwaitingOperands);
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MapPartial(0x77, JNBE, Byte, Disp, AwaitingOperands);
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MapPartial(0x78, JS, Byte, Disp, AwaitingOperands);
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MapPartial(0x79, JNS, Byte, Disp, AwaitingOperands);
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MapPartial(0x7a, JP, Byte, Disp, AwaitingOperands);
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MapPartial(0x7b, JNP, Byte, Disp, AwaitingOperands);
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MapPartial(0x7c, JL, Byte, Disp, AwaitingOperands);
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MapPartial(0x7d, JNL, Byte, Disp, AwaitingOperands);
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MapPartial(0x7e, JLE, Byte, Disp, AwaitingOperands);
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MapPartial(0x7f, JNLE, Byte, Disp, AwaitingOperands);
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}
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++source;
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++consumed_;
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}
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#undef MapInstr
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if(phase_ == Phase::ReadyToPost) {
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// TODO: construct actual Instruction.
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}
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return Instruction();
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}
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