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poweropcodes: Fix lscbx. 

- Fix CR calculation. It depends on whether a match occurred and only the EQ flag is affected.
- Remove bytes_copied. We can subtract bytes_remaining from bytes_to_load to calculate that.
- Initialize ppc_result_d to zero so that bitmask is not needed to add new bytes to it. This is ok since the manual says that bytes that are not loaded are undefined.
This commit is contained in:
joevt 2024-04-09 01:54:28 -07:00 committed by dingusdev
parent df7ff76404
commit c71d856a08
1 changed files with 19 additions and 16 deletions
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35
cpu/ppc/poweropcodes.cpp
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@ -212,47 +212,50 @@ void dppc_interpreter::power_lscbx() {
ppc_grab_regsdab(ppc_cur_instruction);
ppc_effective_address = ppc_result_b + (reg_a ? ppc_result_a : 0);
uint8_t return_value = 0;
uint32_t bytes_to_load = (ppc_state.spr[SPR::XER] & 0x7F);
uint32_t bytes_copied = 0;
uint32_t bytes_remaining = bytes_to_load;
uint8_t matching_byte = (uint8_t)(ppc_state.spr[SPR::XER] >> 8);
uint32_t ppc_result_d = 0;
uint32_t ppc_result_d = 0;
bool is_match = false;
// for storing each byte
uint32_t bitmask = 0xFF000000;
uint8_t shift_amount = 24;
while (bytes_to_load > 0) {
return_value = mmu_read_vmem<uint8_t>(ppc_effective_address);
while (bytes_remaining > 0) {
uint8_t return_value = mmu_read_vmem<uint8_t>(ppc_effective_address);
ppc_result_d = (ppc_result_d & ~bitmask) | (return_value << shift_amount);
ppc_result_d |= return_value << shift_amount;
if (!shift_amount) {
if (reg_d != reg_a && reg_d != reg_b)
ppc_store_iresult_reg(reg_d, ppc_result_d);
reg_d = (reg_d + 1) & 0x1F;
bitmask = 0xFF000000;
ppc_result_d = 0;
shift_amount = 24;
} else {
bitmask >>= 8;
shift_amount -= 8;
}
ppc_effective_address++;
bytes_copied++;
bytes_to_load--;
bytes_remaining--;
if (return_value == matching_byte)
if (return_value == matching_byte) {
is_match = true;
break;
}
}
// store partiallly loaded register if any
// store partially loaded register if any
if (shift_amount != 24 && reg_d != reg_a && reg_d != reg_b)
ppc_store_iresult_reg(reg_d, ppc_result_d);
ppc_state.spr[SPR::XER] = (ppc_state.spr[SPR::XER] & ~0x7F) | bytes_copied;
ppc_state.spr[SPR::XER] = (ppc_state.spr[SPR::XER] & ~0x7F) | (bytes_to_load - bytes_remaining);
if (rec)
ppc_changecrf0(ppc_result_d);
if (rec) {
ppc_state.cr =
(ppc_state.cr & 0x0FFFFFFFUL) |
(is_match ? CRx_bit::CR_EQ : 0) |
((ppc_state.spr[SPR::XER] & XER::SO) >> 3);
}
}
template void dppc_interpreter::power_lscbx<RC0>();