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DSPHLE: Return last mail with top bit cleared if there is no new mail

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This is an accuracy improvement, though I don't think it matters for anything in practice.
This commit is contained in:
Pokechu22 2022-06-16 14:51:59 -07:00
parent bdbb23fa1a
commit 3aeafcc70b
2 changed files with 15 additions and 7 deletions
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17
Source/Core/Core/HW/DSPHLE/MailHandler.cpp
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@ -41,10 +41,9 @@ u16 CMailHandler::ReadDSPMailboxHigh()
// check if we have a mail for the CPU core // check if we have a mail for the CPU core
if (!m_pending_mails.empty()) if (!m_pending_mails.empty())
{ {
u16 result = (m_pending_mails.front().first >> 16) & 0xFFFF; m_last_mail = m_pending_mails.front().first;
return result;
} }
return 0x00; return u16(m_last_mail >> 0x10);
} }
u16 CMailHandler::ReadDSPMailboxLow() u16 CMailHandler::ReadDSPMailboxLow()
@ -52,18 +51,22 @@ u16 CMailHandler::ReadDSPMailboxLow()
// check if we have a mail for the CPU core // check if we have a mail for the CPU core
if (!m_pending_mails.empty()) if (!m_pending_mails.empty())
{ {
u16 result = m_pending_mails.front().first & 0xFFFF; m_last_mail = m_pending_mails.front().first;
const bool generate_interrupt = m_pending_mails.front().second; const bool generate_interrupt = m_pending_mails.front().second;
m_pending_mails.pop_front(); m_pending_mails.pop_front();
if (generate_interrupt) if (generate_interrupt)
{ {
DSP::GenerateDSPInterruptFromDSPEmu(DSP::INT_DSP); DSP::GenerateDSPInterruptFromDSPEmu(DSP::INT_DSP);
} }
return result;
} }
return 0x00; // Clear the top bit of the high mail word after the mail has been read.
// The remaining bits read back the same as the previous mail, until new mail sent.
// (The CPU reads the high word first, and then the low word; since this function returns the low
// word, this means that the next read of the high word will have the top bit cleared.)
m_last_mail &= ~0x8000'0000;
return u16(m_last_mail & 0xffff);
} }
void CMailHandler::ClearPending() void CMailHandler::ClearPending()

5
Source/Core/Core/HW/DSPHLE/MailHandler.h
View File

@ -27,6 +27,8 @@ public:
// Clear any pending mail from the current uCode. This is called by DSPHLE::SetUCode and // Clear any pending mail from the current uCode. This is called by DSPHLE::SetUCode and
// DSPHLE::SwapUCode. Since pending mail is an abstraction for DSPHLE and not something that // DSPHLE::SwapUCode. Since pending mail is an abstraction for DSPHLE and not something that
// actually exists on real hardware, HLE implementations do not need to call this directly. // actually exists on real hardware, HLE implementations do not need to call this directly.
// Note that this function does not reset m_last_mail, which will continue to read the same value
// until the new uCode sends mail.
void ClearPending(); void ClearPending();
u16 ReadDSPMailboxHigh(); u16 ReadDSPMailboxHigh();
@ -37,5 +39,8 @@ private:
// mails. But for HLE, it's a lot easier to write all the mails that will be read ahead of time, // mails. But for HLE, it's a lot easier to write all the mails that will be read ahead of time,
// and then give them to the CPU in the requested order. // and then give them to the CPU in the requested order.
std::deque<std::pair<u32, bool>> m_pending_mails; std::deque<std::pair<u32, bool>> m_pending_mails;
// If no pending mail exists, the last mail that was read is returned,
// but with the top bit (0x80000000) cleared.
u32 m_last_mail = 0;
}; };
} // namespace DSP::HLE } // namespace DSP::HLE