From 2d74062abb29c63eeccec700e7ff638d465ed3a4 Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <stenzek@gmail.com>
Date: Fri, 3 Jul 2020 00:57:22 +1000
Subject: [PATCH] CPU: Delay interrupts by one instruction/block

Fixes Gameshark Sampler Disc.
---
 src/core/cpu_core.cpp         | 10 ++++++++--
 src/core/cpu_core.h           |  1 +
 src/core/save_state_version.h |  2 +-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/core/cpu_core.cpp b/src/core/cpu_core.cpp
index 88b4afdac..6faf24ee8 100644
--- a/src/core/cpu_core.cpp
+++ b/src/core/cpu_core.cpp
@@ -1,7 +1,7 @@
 #include "cpu_core.h"
+#include "common/align.h"
 #include "common/log.h"
 #include "common/state_wrapper.h"
-#include "common/align.h"
 #include "cpu_disasm.h"
 #include <cstdio>
 Log_SetChannel(CPU::Core);
@@ -93,6 +93,8 @@ bool Core::DoState(StateWrapper& sw)
   sw.Do(&m_current_instruction_was_branch_taken);
   sw.Do(&m_next_instruction_is_branch_delay_slot);
   sw.Do(&m_branch_was_taken);
+  sw.Do(&m_exception_raised);
+  sw.Do(&m_interrupt_delay);
   sw.Do(&m_load_delay_reg);
   sw.Do(&m_load_delay_value);
   sw.Do(&m_next_load_delay_reg);
@@ -328,6 +330,7 @@ void Core::RaiseException(Exception excode, u32 EPC, bool BD, bool BT, u8 CE)
 void Core::SetExternalInterrupt(u8 bit)
 {
   m_cop0_regs.cause.Ip |= static_cast<u8>(1u << bit);
+  m_interrupt_delay = 1;
 }
 
 void Core::ClearExternalInterrupt(u8 bit)
@@ -341,7 +344,10 @@ bool Core::HasPendingInterrupt()
   const bool do_interrupt =
     m_cop0_regs.sr.IEc && (((m_cop0_regs.cause.bits & m_cop0_regs.sr.bits) & (UINT32_C(0xFF) << 8)) != 0);
 
-  return do_interrupt;
+  const bool interrupt_delay = m_interrupt_delay;
+  m_interrupt_delay = false;
+
+  return do_interrupt && !interrupt_delay;
 }
 
 void Core::DispatchInterrupt()
diff --git a/src/core/cpu_core.h b/src/core/cpu_core.h
index d91cf0dfd..ce07632be 100644
--- a/src/core/cpu_core.h
+++ b/src/core/cpu_core.h
@@ -155,6 +155,7 @@ private:
   bool m_next_instruction_is_branch_delay_slot = false;
   bool m_branch_was_taken = false;
   bool m_exception_raised = false;
+  bool m_interrupt_delay = false;
 
   // load delays
   Reg m_load_delay_reg = Reg::count;
diff --git a/src/core/save_state_version.h b/src/core/save_state_version.h
index b7cfb1c5b..ea9999566 100644
--- a/src/core/save_state_version.h
+++ b/src/core/save_state_version.h
@@ -2,7 +2,7 @@
 #include "types.h"
 
 static constexpr u32 SAVE_STATE_MAGIC = 0x43435544;
-static constexpr u32 SAVE_STATE_VERSION = 37;
+static constexpr u32 SAVE_STATE_VERSION = 38;
 
 #pragma pack(push, 4)
 struct SAVE_STATE_HEADER