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EmuX86: Implement SUB opcode

This commit is contained in:
Luke Usher 2017-09-12 22:18:30 +01:00 committed by PatrickvL
parent 5f60dddd8f
commit 1cd9cafb78
1 changed files with 37 additions and 0 deletions
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37
src/CxbxKrnl/EmuX86.cpp
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@ -911,6 +911,39 @@ bool EmuX86_Opcode_OR(LPEXCEPTION_POINTERS e, _DInst& info)
return true;
}
bool EmuX86_Opcode_SUB(LPEXCEPTION_POINTERS e, _DInst& info)
{
// Read value from Source and Destination
uint32_t src = 0;
if (!EmuX86_Operand_Read(e, info, 1, &src))
return false;
uint32_t dest = 0;
if (!EmuX86_Operand_Read(e, info, 0, &dest))
return false;
// SUB Destination with src
uint32_t result = dest - src;
// Write result back
EmuX86_Operand_Write(e, info, 0, result);
EmuX86_SetFlag(e, EMUX86_EFLAG_CF, (result >> 32) > 0);
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_TEST(LPEXCEPTION_POINTERS e, _DInst& info)
{
// TEST reads first value :
@ -1146,6 +1179,10 @@ bool EmuX86_DecodeException(LPEXCEPTION_POINTERS e)
break;
goto unimplemented_opcode;
case I_SUB:
if (EmuX86_Opcode_SUB(e, info))
break;
goto unimplemented_opcode;
case I_TEST:
if (EmuX86_Opcode_TEST(e, info))
break;