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cpu/decoder - add function with shared code for 16-bit addition

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madmaurice 2023-08-30 13:20:57 +02:00
parent 317d22b8ab
commit 87b939c80e
1 changed files with 13 additions and 22 deletions
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35
cpu/decoder.cpp
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@ -7,6 +7,16 @@ static inline u16 make_u16(u8 msb, u8 lsb)
return (((u16)msb << 8) | (u16)lsb);
}
static inline void add16(Cpu& cpu, u16& out, u16 lhs, u16 rhs)
{
u16 res11 = (lhs & 0x0FFF) + (rhs & 0x0FFF);
cpu.state.halfcarry = (res11 & 0x1000);
u32 res32 = lhs + rhs;
cpu.state.carry = (res32 & 0x10000);
cpu.state.subtract = false;
lhs = (u16)res32;
}
void Cpu::executeInstruction()
{
u16 currentpc = state.PC;
@ -164,12 +174,7 @@ void Cpu::executeInstruction()
}
else if((op & 0xCF) == 0x09) // ADD HL, rr
{
u16 rhs = state.reg16((op >> 4) & 0x3);
u16 res12 = (state.HL & 0x0FFF) + (rhs & 0x0FFF);
state.halfcarry = (res12 & 0x1000);
u32 res32 = (u32)state.HL + (u32)rhs;
state.carry = (res32 & 0x10000);
state.subtract = false;
add16(*this, state.HL, state.HL, state.reg16((op >> 4) & 0x3));
mcycles = 2;
}
else if((op & 0xE7) == 0xC0) // RET cc
@ -490,29 +495,15 @@ void Cpu::executeInstruction()
case 0xE8: // ADD SP, e8
{
u32 lhs = state.SP;
s32 rhs = (s8)readPC8();
u32 low_add = (lhs & 0x0FFF) + (rhs & 0x0FFF);
state.halfcarry = (low_add & 0x1000);
u32 res32 = lhs + rhs;
state.carry = (res32 & 0x10000);
state.SP = (u16)res32;
state.subtract = false;
add16(*this, state.SP, state.SP, (s8)readPC8());
state.zero = false;
mcycles = 4;
}
break;
case 0xF8: // LD HL, SP + e8
{
u32 lhs = state.SP;
s32 rhs = (s8)readPC8();
u32 low_add = (lhs & 0x0FFF) + (rhs & 0x0FFF);
state.halfcarry = (low_add & 0x1000);
u32 res32 = lhs + rhs;
state.carry = (res32 & 0x10000);
state.HL = (u16)res32;
add16(*this, state.HL, state.SP, (s32)((s8)readPC8()));
state.zero = false;
state.subtract = false;
mcycles = 3;
}
break;