GBA: New idle loop detection metrics + Advance Wars 2 loops

src/gba/context/overrides.c

@@ -15,6 +15,10 @@ static const struct GBACartridgeOverride _overrides[] = {
 	{ "AWRE", SAVEDATA_FLASH512, HW_NONE, 0x8038810 },
 	{ "AWRP", SAVEDATA_FLASH512, HW_NONE, 0x8038810 },
 
+	// Advance Wars 2: Black Hole Rising
+	{ "AW2E", SAVEDATA_FLASH512, HW_NONE, 0x8036E08 },
+	{ "AW2P", SAVEDATA_FLASH512, HW_NONE, 0x803719C },
+
 	// Boktai: The Sun is in Your Hand
 	{ "U3IJ", SAVEDATA_EEPROM, HW_RTC | HW_LIGHT_SENSOR, IDLE_LOOP_NONE },
 	{ "U3IE", SAVEDATA_EEPROM, HW_RTC | HW_LIGHT_SENSOR, IDLE_LOOP_NONE },

src/gba/io.c

@@ -565,8 +565,34 @@ void GBAIOWrite32(struct GBA* gba, uint32_t address, uint32_t value) {
 	gba->memory.io[(address >> 1) + 1] = value >> 16;
 }
 
+bool GBAIOIsReadConstant(uint32_t address) {
+	switch (address) {
+	default:
+		return false;
+	case REG_BG0CNT:
+	case REG_BG1CNT:
+	case REG_BG2CNT:
+	case REG_BG3CNT:
+	case REG_WININ:
+	case REG_WINOUT:
+	case REG_BLDCNT:
+	case REG_BLDALPHA:
+	case REG_DMA0CNT_LO:
+	case REG_DMA1CNT_LO:
+	case REG_DMA2CNT_LO:
+	case REG_DMA3CNT_LO:
+	case REG_KEYINPUT:
+	case REG_IE:
+		return true;
+	}
+}
+
 uint16_t GBAIORead(struct GBA* gba, uint32_t address) {
-	gba->haltPending = false; // IO reads need to invalidate detected idle loops
+	if (!GBAIOIsReadConstant(address)) {
+		// Most IO reads need to disable idle removal
+		gba->haltPending = false;
+	}
+
 	switch (address) {
 	case REG_TM0CNT_LO:
 		GBATimerUpdateRegister(gba, 0);

src/gba/io.h

@@ -159,6 +159,8 @@ void GBAIOWrite8(struct GBA* gba, uint32_t address, uint8_t value);
 void GBAIOWrite32(struct GBA* gba, uint32_t address, uint32_t value);
 uint16_t GBAIORead(struct GBA* gba, uint32_t address);
 
+bool GBAIOIsReadConstant(uint32_t address);
+
 struct GBASerializedState;
 void GBAIOSerialize(struct GBA* gba, struct GBASerializedState* state);
 void GBAIODeserialize(struct GBA* gba, const struct GBASerializedState* state);

src/gba/memory.c

@@ -156,7 +156,7 @@ static void _analyzeForIdleLoop(struct GBA* gba, struct ARMCore* cpu, uint32_t a
 					} else {
 						loadAddress += offset;
 					}
-					if ((loadAddress >> BASE_OFFSET) == REGION_IO) {
+					if ((loadAddress >> BASE_OFFSET) == REGION_IO && !GBAIOIsReadConstant(loadAddress)) {
 						gba->idleDetectionStep = -1;
 						return;
 					}