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poweropcodes: Fix doz. 

Calculate overflow first before calculating condition codes because the overflow condition is copied from XER.
Fix OV calculation. Previously, it was using power_setsoov which I think is only for add and subtract operations. doz does a subtract but only if the result is supposed to be positive, therefore a negative result indicates an overflow.
This commit is contained in:
joevt 2024-04-09 01:37:20 -07:00 committed by dingusdev
parent 0d1ce68d19
commit df7ff76404
1 changed files with 9 additions and 4 deletions
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13
cpu/ppc/poweropcodes.cpp
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@ -175,13 +175,18 @@ template void dppc_interpreter::power_divs<RC1, OV1>();
template <field_rc rec, field_ov ov>
void dppc_interpreter::power_doz() {
ppc_grab_regsdab(ppc_cur_instruction);
uint32_t ppc_result_d = (int32_t(ppc_result_a) >= int32_t(ppc_result_b)) ? 0 :
ppc_result_b - ppc_result_a;
uint32_t ppc_result_d = (int32_t(ppc_result_a) < int32_t(ppc_result_b)) ?
ppc_result_b - ppc_result_a : 0;
if (ov) {
if (int32_t(ppc_result_d) < 0) {
ppc_state.spr[SPR::XER] |= XER::SO | XER::OV;
} else {
ppc_state.spr[SPR::XER] &= ~XER::OV;
}
}
if (rec)
ppc_changecrf0(ppc_result_d);
if (ov)
power_setsoov(ppc_result_a, ppc_result_b, ppc_result_d);
ppc_store_iresult_reg(reg_d, ppc_result_d);
}