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jitasm.Backend.x86.h
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jitasm.Backend.x86.h
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#ifndef jitasm_Backend_x86_h__
#define jitasm_Backend_x86_h__
#include "jitasm.x86.h"
#include "jitasm.Backend.h"
namespace jitasm
{
namespace x86
{
struct Backend : jitasm::Backend$CRTP < Backend >
{
bool is64_;
Backend(bool is64, void * buffaddr = nullptr, size_t buffsize = 0)
: jitasm::Backend$CRTP< Backend >(buffaddr, buffsize), is64_(is64)
{
memset(buffaddr, 0xCC, buffsize);
}
size_t SizeOf(Instr & instr)
{
Backend backend(is64_);
backend.Assemble(instr);
return backend.GetSize();
}
static bool HasRIP(detail::Opd const & opd)
{
return opd.IsMem() && (opd.GetBase().type == R_TYPE_IP);
}
uint8 GetWRXB(int w, detail::Opd const & reg, detail::Opd const & r_m)
{
uint8 wrxb = w ? 8 : 0;
if (reg.IsReg())
{
if (!reg.GetReg().IsInvalid() && reg.GetReg().id >= R8) wrxb |= 4;
}
if (r_m.IsReg())
{
if (r_m.GetReg().id >= R8) wrxb |= 1;
}
if (r_m.IsMem())
{
if (!r_m.GetIndex().IsInvalid() && r_m.GetIndex().id >= R8) wrxb |= 2;
if (!r_m.GetBase().IsInvalid() && r_m.GetBase().id >= R8) wrxb |= 1;
}
return wrxb;
}
void EncodePrefixes(uint32 flag, detail::Opd const & reg, detail::Opd const & r_m, detail::Opd const & vex)
{
if (flag & (E_VEX | E_XOP))
{
// Encode VEX prefix
if (is64_ && r_m.IsMem() && r_m.GetAddressBaseSize() != O_SIZE_64) db(0x67);
uint8 vvvv = vex.IsReg() ? 0xF - (uint8)vex.GetReg().id : 0xF;
uint8 mmmmm = (flag & E_VEX_MMMMM_MASK) >> E_VEX_MMMMM_SHIFT;
uint8 pp = static_cast<uint8>((flag & E_VEX_PP_MASK) >> E_VEX_PP_SHIFT);
uint8 wrxb = GetWRXB(flag & E_VEX_W, reg, r_m);
if (flag & E_XOP)
{
db(0x8F);
db((~wrxb & 7) << 5 | mmmmm);
db((wrxb & 8) << 4 | vvvv << 3 | (flag & E_VEX_L ? 4 : 0) | pp);
}
else if (wrxb & 0xB || (flag & E_VEX_MMMMM_MASK) == E_VEX_0F38 || (flag & E_VEX_MMMMM_MASK) == E_VEX_0F3A)
{
db(0xC4);
db((~wrxb & 7) << 5 | mmmmm);
db((wrxb & 8) << 4 | vvvv << 3 | (flag & E_VEX_L ? 4 : 0) | pp);
}
else
{
db(0xC5);
db((~wrxb & 4) << 5 | vvvv << 3 | (flag & E_VEX_L ? 4 : 0) | pp);
}
}
else
{
uint8 wrxb = GetWRXB(flag & E_REXW_PREFIX, reg, r_m);
if (wrxb)
{
// Encode REX prefix
if (flag & E_REP_PREFIX) db(0xF3);
if (is64_ && r_m.IsMem() && r_m.GetAddressBaseSize() != O_SIZE_64) db(0x67);
if (flag & E_OPERAND_SIZE_PREFIX) db(0x66);
/**/ if (flag & E_MANDATORY_PREFIX_66) db(0x66);
else if (flag & E_MANDATORY_PREFIX_F2) db(0xF2);
else if (flag & E_MANDATORY_PREFIX_F3) db(0xF3);
db(0x40 | wrxb);
}
else
{
/**/ if (flag & E_MANDATORY_PREFIX_66) db(0x66);
else if (flag & E_MANDATORY_PREFIX_F2) db(0xF2);
else if (flag & E_MANDATORY_PREFIX_F3) db(0xF3);
if (flag & E_REP_PREFIX) db(0xF3);
if (is64_ && r_m.IsMem() && r_m.GetAddressBaseSize() != O_SIZE_64) db(0x67);
if (flag & E_OPERAND_SIZE_PREFIX) db(0x66);
}
}
}
void EncodeModRM(uint8 reg, detail::Opd const & r_m)
{
reg &= 0x7;
/**/ if (r_m.IsReg())
{
db(0xC0 | (reg << 3) | (r_m.GetReg().id & 0x7));
}
else if (r_m.IsMem())
{
int base = r_m.GetBase().id; if (base != INVALID) base &= 0x7;
int index = r_m.GetIndex().id; if (index != INVALID) index &= 0x7;
if (base == INVALID && index == INVALID)
{
if (is64_)
{
db(reg << 3 | 4);
db(0x25);
}
else
{
db(reg << 3 | 5);
}
dd(r_m.GetDisp());
}
else if (r_m.GetBase().type == R_TYPE_IP)
{
db(0 << 6 | reg << 3 | 5);
dd(r_m.GetDisp());
}
else
{
if (index == ESP)
{
index = base;
base = ESP;
}
bool sib = index != INVALID || r_m.GetScale() || base == ESP;
// ModR/M
uint8 mod = 0;
/**/ if (r_m.GetDisp() == 0 || (sib && base == INVALID)) mod = base != EBP ? 0 : 1;
else if (detail::IsInt8(r_m.GetDisp())) mod = 1;
else if (detail::IsInt32(r_m.GetDisp())) mod = 2;
db(mod << 6 | reg << 3 | (sib ? 4 : base));
// SIB
if (sib)
{
uint8 ss = 0;
if (r_m.GetScale() == 0) ss = 0;
else if (r_m.GetScale() == 2) ss = 1;
else if (r_m.GetScale() == 4) ss = 2;
else if (r_m.GetScale() == 8) ss = 3;
else JITASM_ASSERT(0);
if (index != INVALID && base != INVALID)
{
db(ss << 6 | index << 3 | base);
}
else if (base != INVALID)
{
db(ss << 6 | 4 << 3 | base);
}
else if (index != INVALID)
{
db(ss << 6 | index << 3 | 5);
}
}
// Displacement
if (mod == 0 && sib && base == INVALID) dd(r_m.GetDisp());
if (mod == 1) db(r_m.GetDisp());
if (mod == 2) dd(r_m.GetDisp());
}
}
}
void EncodeOpcode(uint32 opcode)
{
if (opcode & 0xFF000000) db((opcode >> 24) & 0xFF);
if (opcode & 0xFFFF0000) db((opcode >> 16) & 0xFF);
if (opcode & 0xFFFFFF00) db((opcode >> 8) & 0xFF);
/**********************/ db((opcode >> 0) & 0xFF);
}
void EncodeImm(detail::Opd const & imm)
{
auto const size = imm.GetSize();
/**/ if (size == O_SIZE_8) db(imm.GetImm());
else if (size == O_SIZE_16) dw(imm.GetImm());
else if (size == O_SIZE_32) dd(imm.GetImm());
else if (size == O_SIZE_64) dq(imm.GetImm());
}
void EncodeSource(detail::Opd const & imm)
{
AddBookmark(size_, uint64(imm.GetImm()));
}
void EncodeMultiNop(detail::Opd const & imm)
{
size_t align = 1ULL << size_t(imm.GetImm());
size_t bytes = ((size_ + align - 1) & size_t(-intptr_t(align))) - size_;
while (bytes > 0)
{
size_t size = bytes < 16 ? bytes : 16;
bytes -= size;
switch (size)
{
case 0: break;
case 1: PutBytes("\x90", 1); break;
case 2: PutBytes("\x66\x90", 2); break;
case 3: PutBytes("\x0f\x1f\x00", 3); break;
case 4: PutBytes("\x0f\x1f\x40\x00", 4); break;
case 5: PutBytes("\x0f\x1f\x44\x00\x00", 5); break;
case 6: PutBytes("\x66\x0f\x1f\x44\x00\x00", 6); break;
case 7: PutBytes("\x0f\x1f\x80\x00\x00\x00\x00", 7); break;
case 8: PutBytes("\x0f\x1f\x84\x00\x00\x00\x00\x00", 8); break;
case 9: PutBytes("\x66\x0f\x1f\x84\x00\x00\x00\x00\x00", 9); break;
case 10:
more_10: PutBytes("\x66\x2e\x0f\x1f\x84\x00\x00\x00\x00\x00", 10); break;
case 11:
case 12:
case 13:
case 14:
case 15:
default: PutBytes("\x66\x66\x66\x66\x66\x66", size - 10); goto more_10;
}
}
}
void Encode(Instr const & instr)
{
uint32 opcode = instr.opcode_;
auto const & opd0 = instr.GetOpd(0).IsDummy() ? detail::Opd() : instr.GetOpd(0);
auto const & opd1 = instr.GetOpd(1).IsDummy() ? detail::Opd() : instr.GetOpd(1);
auto const & opd2 = instr.GetOpd(2).IsDummy() ? detail::Opd() : instr.GetOpd(2);
auto const & opd3 = instr.GetOpd(3).IsDummy() ? detail::Opd() : instr.GetOpd(3);
// +rb, +rw, +rd, +ro
if (opd0.IsReg() && (opd1.IsNone() || opd1.IsImm()))
{
opcode += opd0.GetReg().id & 0x7;
}
if ((opd0.IsImm() || opd0.IsReg()) && (opd1.IsReg() || opd1.IsMem()))
{ // ModR/M
auto const & reg = opd0;
auto const & r_m = opd1;
auto const & vex = opd2;
EncodePrefixes(instr.encoding_flags_, reg, r_m, vex);
EncodeOpcode(opcode);
EncodeModRM((uint8)(reg.IsImm() ? reg.GetImm() : reg.GetReg().id), r_m);
// /is4
if (opd3.IsReg())
{
EncodeImm(Imm8(static_cast<uint8>(opd3.GetReg().id << 4)));
}
}
else
{
auto const & reg = detail::Opd();
auto const & r_m = opd0.IsReg() ? opd0 : detail::Opd();
auto const & vex = detail::Opd();
EncodePrefixes(instr.encoding_flags_, reg, r_m, vex);
EncodeOpcode(opcode);
}
if (opd0.IsImm() && !opd1.IsReg() && !opd1.IsMem()) EncodeImm(opd0);
if (opd1.IsImm()) EncodeImm(opd1);
if (opd2.IsImm()) EncodeImm(opd2);
if (opd3.IsImm()) EncodeImm(opd3);
}
void EncodeInstr(Instr & instr);
#ifdef JITASM_TEST
void TestInstr(InstrID id, std::vector< Instr > & list, bool is64);
#endif
void Assemble(Instr & instr)
{
if (0 == (instr.encoding_flags_ & E_ENCODED))
{
EncodeInstr(instr);
}
switch (instr.GetID())
{
case I_ALIGN: EncodeMultiNop(instr.GetOpd(0)); break;
case I_NULL: break;
case I_SOURCE: EncodeSource(instr.GetOpd(0)); break;
case I_DB: db(instr.GetOpd(0).GetImm()); break;
case I_DW: dw(instr.GetOpd(0).GetImm()); break;
case I_DD: dd(instr.GetOpd(0).GetImm()); break;
case I_DQ: dq(instr.GetOpd(0).GetImm()); break;
default: Encode(instr); break;
}
}
};
}
}
#endif // jitasm_Backend_x86_h__