From fa18382757d1934d465a3a6ee1ca508cac53094c Mon Sep 17 00:00:00 2001
From: tomcw <tomcw@users.noreply.github.com>
Date: Mon, 18 Oct 2021 21:45:45 +0100
Subject: [PATCH] Core emulation: simplify NMI & IRQ handling

---
 source/CPU.cpp        |  1 -
 source/CPU/cpu6502.h  | 14 ++++----------
 source/CPU/cpu65C02.h | 14 ++++----------
 3 files changed, 8 insertions(+), 21 deletions(-)

diff --git a/source/CPU.cpp b/source/CPU.cpp
index 865710a3..cd39707b 100644
--- a/source/CPU.cpp
+++ b/source/CPU.cpp
@@ -446,7 +446,6 @@ static __forceinline bool IRQ(ULONG& uExecutedCycles, BOOL& flagc, BOOL& flagn,
 							(g_bmIRQ & 8) ? "MOUSE" : "UNKNOWN";
 		LogOutput("IRQ (%08X) (%s)\n", (UINT)g_nCycleIrqStart, pSrc);
 #endif
-		CheckSynchronousInterruptSources(7, uExecutedCycles);
 		g_interruptInLastExecutionBatch = true;
 		irqTaken = true;
 	}
diff --git a/source/CPU/cpu6502.h b/source/CPU/cpu6502.h
index 96c7a58d..6887fbc2 100644
--- a/source/CPU/cpu6502.h
+++ b/source/CPU/cpu6502.h
@@ -50,18 +50,12 @@ static DWORD Cpu6502(DWORD uTotalCycles, const bool bVideoUpdate)
 		{
 			const UINT uZ80Cycles = z80_mainloop(uTotalCycles, uExecutedCycles); CYC(uZ80Cycles)
 		}
+		else if (NMI(uExecutedCycles, flagc, flagn, flagv, flagz) || IRQ(uExecutedCycles, flagc, flagn, flagv, flagz))
+		{
+			// Allow AppleWin debugger's single-stepping to just step the pending IRQ
+		}
 		else
 		{
-			if (IRQ(uExecutedCycles, flagc, flagn, flagv, flagz) || NMI(uExecutedCycles, flagc, flagn, flagv, flagz))
-			{
-				if (bVideoUpdate)
-				{
-					ULONG uElapsedCycles = uExecutedCycles - uPreviousCycles;
-					NTSC_VideoUpdateCycles(uElapsedCycles);
-				}
-				continue;	// Allow AppleWin debugger's single-stepping to just step the pending IRQ
-			}
-
 			HEATMAP_X( regs.pc );
 			Fetch(iOpcode, uExecutedCycles);
 
diff --git a/source/CPU/cpu65C02.h b/source/CPU/cpu65C02.h
index fa1b4ff7..f9eb55f2 100644
--- a/source/CPU/cpu65C02.h
+++ b/source/CPU/cpu65C02.h
@@ -50,18 +50,12 @@ static DWORD Cpu65C02(DWORD uTotalCycles, const bool bVideoUpdate)
 		{
 			const UINT uZ80Cycles = z80_mainloop(uTotalCycles, uExecutedCycles); CYC(uZ80Cycles)
 		}
+		else if (NMI(uExecutedCycles, flagc, flagn, flagv, flagz) || IRQ(uExecutedCycles, flagc, flagn, flagv, flagz))
+		{
+			// Allow AppleWin debugger's single-stepping to just step the pending IRQ
+		}
 		else
 		{
-			if (IRQ(uExecutedCycles, flagc, flagn, flagv, flagz) || NMI(uExecutedCycles, flagc, flagn, flagv, flagz))
-			{
-				if (bVideoUpdate)
-				{
-					ULONG uElapsedCycles = uExecutedCycles - uPreviousCycles;
-					NTSC_VideoUpdateCycles(uElapsedCycles);
-				}
-				continue;	// Allow AppleWin debugger's single-stepping to just step the pending IRQ
-			}
-
 			HEATMAP_X( regs.pc );
 			Fetch(iOpcode, uExecutedCycles);