M CHANGES → CHANGES

@@ -64,6 +64,7 @@ - GBA Video: Implement green swap (fixes mgba.io/i/1609)
  - GBA Video: Emulate sprite cycle limits in OpenGL renderer (fixes mgba.io/i/1635)
  - GBA Video: Fix OBJWIN erratic rendering in OpenGL renderer
  - SM83: Emulate HALT bug
+ - SM83: Improve mid-M-cycle interrupts
 Other fixes:
  - 3DS: Fix thread cleanup
  - All: Improve export headers (fixes mgba.io/i/1738)

M src/sm83/sm83.c → src/sm83/sm83.c

@@ -153,11 +153,19 @@ bool running = true;
 	_SM83Step(cpu);
 	int t = cpu->tMultiplier;
 	if (cpu->cycles + t * 2 >= cpu->nextEvent) {
-		int32_t diff = cpu->nextEvent - cpu->cycles;
-		cpu->cycles = cpu->nextEvent;
-		cpu->executionState += diff >> (t - 1); // NB: This assumes tMultiplier is either 1 or 2
-		cpu->irqh.processEvents(cpu);
-		cpu->cycles += (SM83_CORE_EXECUTE - cpu->executionState) * t;
+		if (cpu->cycles >= cpu->nextEvent) {
+			cpu->irqh.processEvents(cpu);
+		}
+		cpu->cycles += t;
+		++cpu->executionState;
+		if (cpu->cycles >= cpu->nextEvent) {
+			cpu->irqh.processEvents(cpu);
+		}
+		cpu->cycles += t;
+		++cpu->executionState;
+		if (cpu->cycles >= cpu->nextEvent) {
+			cpu->irqh.processEvents(cpu);
+		}
 		running = false;
 	} else {
 		cpu->cycles += t * 2;