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Implement INC/DEC opcodes

This commit is contained in:
Luke Usher 2017-09-19 11:07:48 +01:00 committed by PatrickvL
parent e16468c83d
commit a4fa55519d
1 changed files with 63 additions and 0 deletions
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63
src/CxbxKrnl/EmuX86.cpp
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@ -876,6 +876,60 @@ bool EmuX86_Opcode_CMPXCHG(LPEXCEPTION_POINTERS e, _DInst& info)
return true;
}
bool EmuX86_Opcode_DEC(LPEXCEPTION_POINTERS e, _DInst& info)
{
uint32_t dest = 0;
if (!EmuX86_Operand_Read(e, info, 0, &dest))
return false;
// ADD Destination to src
uint64_t result = dest - 1;
// Write result back
EmuX86_Operand_Write(e, info, 0, result);
EmuX86_SetFlag(e, EMUX86_EFLAG_OF, (result >> 31) != (dest >> 31));
// TODO: Figure out how to calculate this EmuX86_SetFlag(e, EMUX86_EFLAG_AF, 0);
EmuX86_SetFlag(e, EMUX86_EFLAG_SF, result >> 31);
EmuX86_SetFlag(e, EMUX86_EFLAG_ZF, result == 0 ? 1 : 0);
// Set Parity flag, based on "Compute parity in parallel" method from
// http://graphics.stanford.edu/~seander/bithacks.html#ParityParallel
uint32_t v = 255 & dest;
v ^= v >> 4;
v &= 0xf;
EmuX86_SetFlag(e, EMUX86_EFLAG_PF, (0x6996 >> v) & 1);
return true;
}
bool EmuX86_Opcode_INC(LPEXCEPTION_POINTERS e, _DInst& info)
{
uint32_t dest = 0;
if (!EmuX86_Operand_Read(e, info, 0, &dest))
return false;
// ADD Destination to src
uint64_t result = dest + 1;
// Write result back
EmuX86_Operand_Write(e, info, 0, result);
EmuX86_SetFlag(e, EMUX86_EFLAG_OF, (result >> 31) != (dest >> 31));
// TODO: Figure out how to calculate this EmuX86_SetFlag(e, EMUX86_EFLAG_AF, 0);
EmuX86_SetFlag(e, EMUX86_EFLAG_SF, result >> 31);
EmuX86_SetFlag(e, EMUX86_EFLAG_ZF, result == 0 ? 1 : 0);
// Set Parity flag, based on "Compute parity in parallel" method from
// http://graphics.stanford.edu/~seander/bithacks.html#ParityParallel
uint32_t v = 255 & dest;
v ^= v >> 4;
v &= 0xf;
EmuX86_SetFlag(e, EMUX86_EFLAG_PF, (0x6996 >> v) & 1);
return true;
}
bool EmuX86_Opcode_OR(LPEXCEPTION_POINTERS e, _DInst& info)
{
// Read value from Source and Destination
@ -1152,11 +1206,20 @@ bool EmuX86_DecodeException(LPEXCEPTION_POINTERS e)
case I_CPUID:
EmuX86_Opcode_CPUID(e, info);
break;
case I_DEC:
if (EmuX86_Opcode_DEC(e, info))
break;
goto unimplemented_opcode;
case I_IN:
if (EmuX86_Opcode_IN(e, info))
break;
goto unimplemented_opcode;
case I_INC:
if (EmuX86_Opcode_INC(e, info))
break;
goto unimplemented_opcode;
case I_INVD: // Flush internal caches; initiate flushing of external caches.
// We can safely ignore this
break;