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Deferring ModRM work, proceeds to 0x9f.

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This commit is contained in:
Thomas Harte 2021-01-02 19:29:43 -05:00
parent 290972cedf
commit 9c5dc0ed29
2 changed files with 51 additions and 9 deletions
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57
Processors/Decoders/x86/x86.cpp
View File

@ -13,13 +13,13 @@ using namespace CPU::Decoder::x86;
Instruction Decoder::decode(uint8_t *source, size_t length) {
uint8_t *const limit = source + length;
#define MapPartial(value, op, sz, fmt, phs) \
case value: \
operation_ = Operation::op; \
operand_size_ = Size::sz; \
format_ = Format::fmt; \
phase_ = Phase::phs; \
break;
#define MapPartial(value, op, sz, fmt, phs) \
case value: \
operation_ = Operation::op; \
operand_size_ = Size::sz; \
format_ = Format::fmt; \
phase_ = Phase::phs; \
break
#define MapComplete(value, op, sz, src, dest) \
case value: \
@ -28,10 +28,13 @@ Instruction Decoder::decode(uint8_t *source, size_t length) {
source_ = Source::src; \
destination_ = Source::dest; \
phase_ = Phase::ReadyToPost; \
break;
break
while(phase_ == Phase::Instruction && source != limit) {
switch(*source) {
// Retain the instruction byte, in case additional decoding is deferred
// to the ModRM byte.
instr_ = *source;
switch(instr_) {
#define PartialBlock(start, operation) \
MapPartial(start + 0x00, operation, Byte, MemReg_Reg, ModRM); \
MapPartial(start + 0x01, operation, Word, MemReg_Reg, ModRM); \
@ -110,6 +113,42 @@ Instruction Decoder::decode(uint8_t *source, size_t length) {
MapPartial(0x7e, JLE, Byte, Disp, AwaitingOperands);
MapPartial(0x7f, JNLE, Byte, Disp, AwaitingOperands);
// TODO:
//
// 0x80, 0x81, 0x82, 0x83, which all require more
// input, from the ModRM byte.
MapPartial(0x84, TEST, Byte, MemReg_Reg, ModRM);
MapPartial(0x85, TEST, Word, MemReg_Reg, ModRM);
MapPartial(0x86, XCHG, Byte, Reg_MemReg, ModRM);
MapPartial(0x87, XCHG, Word, Reg_MemReg, ModRM);
MapPartial(0x88, MOV, Byte, MemReg_Reg, ModRM);
MapPartial(0x89, MOV, Word, MemReg_Reg, ModRM);
MapPartial(0x8a, MOV, Byte, Reg_MemReg, ModRM);
MapPartial(0x8b, MOV, Word, Reg_MemReg, ModRM);
/* 0x8c: not used. */
MapPartial(0x8d, LEA, Word, Reg_Addr, ModRM);
MapPartial(0x8e, MOV, Word, SegReg_MemReg, ModRM);
// TODO: 0x8f, which requires further selection from the ModRM byte.
MapComplete(0x90, NOP, Implied, None, None); // Or XCHG AX, AX?
MapComplete(0x91, XCHG, Word, AX, CX);
MapComplete(0x92, XCHG, Word, AX, DX);
MapComplete(0x93, XCHG, Word, AX, BX);
MapComplete(0x94, XCHG, Word, AX, SP);
MapComplete(0x95, XCHG, Word, AX, BP);
MapComplete(0x96, XCHG, Word, AX, SI);
MapComplete(0x97, XCHG, Word, AX, DI);
MapComplete(0x98, CBW, Implied, None, None);
MapComplete(0x99, CWD, Implied, None, None);
MapPartial(0x9a, CALL, Word, Disp, AwaitingOperands);
MapComplete(0x9b, WAIT, Implied, None, None);
MapComplete(0x9c, PUSHF, Implied, None, None);
MapComplete(0x9d, POPF, Implied, None, None);
MapComplete(0x9e, SAHF, Implied, None, None);
MapComplete(0x9f, LAHF, Implied, None, None);
}
++source;
++consumed_;

3
Processors/Decoders/x86/x86.hpp
View File

@ -109,6 +109,8 @@ struct Decoder {
Reg_MemReg,
Ac_Data,
MemReg_Data,
SegReg_MemReg,
Reg_Addr,
Disp
} format_ = Format::MemReg_Reg;
@ -118,6 +120,7 @@ struct Decoder {
Source source_ = Source::None;
Source destination_ = Source::None;
Source segment_override_ = Source::None;
uint8_t instr_ = 0x00;
};
}