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necdsp: improve OV1/S1 flag calculations

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necdsp: improve OV1/S1 flag calculations
This commit is contained in:
Sharpy 2017-09-05 21:07:58 +01:00 committed by GitHub
parent 57d813f20e e93c847785
commit 8b547f1c5d
1 changed files with 12 additions and 13 deletions
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25
bsnes/snes/chip/necdsp/necdsp.cpp
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@ -100,6 +100,7 @@ void NECDSP::exec_op(uint24 opcode) {
flag.s0 = (r & 0x8000);
flag.z = (r == 0);
if (!flag.ov1) flag.s1 = flag.s0;
switch(alu) {
case 1: case 2: case 3: case 10: case 13: case 14: case 15: {
@ -111,17 +112,14 @@ void NECDSP::exec_op(uint24 opcode) {
case 4: case 5: case 6: case 7: case 8: case 9: {
if(alu & 1) {
//addition
flag.ov0 = (q ^ r) & ~(q ^ p) & 0x8000;
flag.ov0 = (q ^ r) & (p ^ r) & 0x8000;
flag.c = (r < q);
} else {
//subtraction
flag.ov0 = (q ^ r) & (q ^ p) & 0x8000;
flag.ov0 = (q ^ r) & (q ^ p) & 0x8000;
flag.c = (r > q);
}
if(flag.ov0) {
flag.s1 = flag.ov1 ^ !(r & 0x8000);
flag.ov1 = !flag.ov1;
}
flag.ov1 = (flag.ov0 & flag.ov1) ? (flag.s1 == flag.s0) : (flag.ov0 | flag.ov1);
break;
}
case 11: {
@ -146,15 +144,16 @@ void NECDSP::exec_op(uint24 opcode) {
exec_ld((idb << 6) + dst);
switch(dpl) {
case 1: regs.dp = (regs.dp & 0xf0) + ((regs.dp + 1) & 0x0f); break; //DPINC
case 2: regs.dp = (regs.dp & 0xf0) + ((regs.dp - 1) & 0x0f); break; //DPDEC
case 3: regs.dp = (regs.dp & 0xf0); break; //DPCLR
if (dst != 4) {
switch(dpl) {
case 1: regs.dp = (regs.dp & 0xf0) + ((regs.dp + 1) & 0x0f); break; //DPINC
case 2: regs.dp = (regs.dp & 0xf0) + ((regs.dp - 1) & 0x0f); break; //DPDEC
case 3: regs.dp = (regs.dp & 0xf0); break; //DPCLR
}
regs.dp ^= dphm << 4;
}
regs.dp ^= dphm << 4;
if(rpdcr) regs.rp--;
if(rpdcr && dst != 5) regs.rp--;
}
void NECDSP::exec_rt(uint24 opcode) {