From 7aa1af40fb0868f413cb1f73a31df163a0caa372 Mon Sep 17 00:00:00 2001
From: MadMaurice <madmaurice@zom.bi>
Date: Tue, 29 Aug 2023 13:45:17 +0200
Subject: [PATCH] cpu/cpu - Treat a call to an ISR as a step

---
 cpu/cpu.cpp | 14 +++++++++++---
 cpu/cpu.h   |  2 +-
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/cpu/cpu.cpp b/cpu/cpu.cpp
index 310a077..90784ce 100644
--- a/cpu/cpu.cpp
+++ b/cpu/cpu.cpp
@@ -1,4 +1,5 @@
 #include "cpu.h"
+#include "panic.h"
 
 void Cpu_state::setAF(u16 v)
 {
@@ -26,8 +27,10 @@ Cpu::Cpu(Mem_device* bus)
 
 void Cpu::step()
 {
-  handleInterrupts();
-  executeInstruction();
+  if(!handleInterrupts()) // if no isr has been called, decode an instruction
+    {
+      executeInstruction();
+    }
 }
 
 void Cpu::reset()
@@ -185,7 +188,7 @@ void Cpu::aluop8(AluOp op, u8 lhs, u8 rhs, u8& out, bool update_carry)
     out = res;
 }
 
-void Cpu::handleInterrupts()
+bool Cpu::handleInterrupts()
 {
   // servicable interrupts (assuming IME is on)
   u8 si = state.IE & state.IF & INT_MASK;
@@ -202,11 +205,16 @@ void Cpu::handleInterrupts()
       else if (si & INT_Timer)   { it = INT_Timer;   isr = 0x50; }
       else if (si & INT_Serial)  { it = INT_Serial;  isr = 0x58; }
       else if (si & INT_Joypad)  { it = INT_Joypad;  isr = 0x60; }
+      else panic("Can't find pending interrupt IE=%02x IF=%02x\n", state.IE, state.IF);
 
       state.IME = IME_OFF; // Disable IME
       state.IF &= ~it; // clear interrupt in IF
       doCall(isr);     // Call interrupt service routine
 
       processed_mcycles += 5;
+
+      return true;
     }
+
+  return false;
 }
diff --git a/cpu/cpu.h b/cpu/cpu.h
index 8aff385..a566f1f 100644
--- a/cpu/cpu.h
+++ b/cpu/cpu.h
@@ -119,7 +119,7 @@ private:
 
   bool decodeCond(u8 cc);
 
-  void handleInterrupts();
+  bool handleInterrupts();
   void executeInstruction();
 
   void reset();