libgambatte: simplify a bit

libgambatte/src/initstate.cpp

@@ -1194,7 +1194,7 @@ void gambatte::setInitState(SaveState &state, bool const cgb, bool const gbaCgbM
 		setInitialDmgIoamhram(state.mem.ioamhram.ptr);
 	}
 
-	state.mem.ioamhram.ptr[0x104] = 0x1C;
+	state.mem.ioamhram.ptr[0x104] = 0x00;
 	state.mem.ioamhram.ptr[0x140] = 0x91;
 	state.mem.ioamhram.ptr[0x144] = 0x00;
 
@@ -1202,7 +1202,7 @@ void gambatte::setInitState(SaveState &state, bool const cgb, bool const gbaCgbM
 	// This also applies to the TIMA and PSG frame sequencer, which may suggest
 	// that div reset could affect the other two.
 	// TODO: test whether div reset can affect other counters.
-	state.mem.divLastUpdate = 0;
+	state.mem.divLastUpdate = -0x1C00;
 	state.mem.timaLastUpdate = 0;
 	state.mem.tmatime = disabled_time;
 	state.mem.nextSerialtime = disabled_time;
@@ -1221,7 +1221,6 @@ void gambatte::setInitState(SaveState &state, bool const cgb, bool const gbaCgbM
 	state.mem.rambankMode = false;
 	state.mem.hdmaTransfer = false;
 
-
 	for (int i = 0x00; i < 0x40; i += 0x02) {
 		state.ppu.bgpData.ptr[i    ] = 0xFF;
 		state.ppu.bgpData.ptr[i + 1] = 0x7F;

libgambatte/src/memory.cpp

@@ -67,6 +67,7 @@ void Memory::setStatePtrs(SaveState &state) {
 
 unsigned long Memory::saveState(SaveState &state, unsigned long cc) {
 	cc = resetCounters(cc);
+	ioamhram_[0x104] = 0;
 	nontrivial_ff_read(0x05, cc);
 	nontrivial_ff_read(0x0F, cc);
 	nontrivial_ff_read(0x26, cc);
@@ -96,7 +97,7 @@ void Memory::loadState(SaveState const &state) {
 	cart_.loadState(state);
 	intreq_.loadState(state);
 
-	divLastUpdate_ = state.mem.divLastUpdate;
+	divLastUpdate_ = state.mem.divLastUpdate - 0x100l * state.mem.ioamhram.get()[0x104];
 	intreq_.setEventTime<intevent_serial>(state.mem.nextSerialtime > state.cpu.cycleCounter
 		? state.mem.nextSerialtime
 		: state.cpu.cycleCounter);
@@ -456,16 +457,9 @@ unsigned long Memory::resetCounters(unsigned long cc) {
 
 	updateIrqs(cc);
 
-	{
-		unsigned long divinc = (cc - divLastUpdate_) >> 8;
-		ioamhram_[0x104] = (ioamhram_[0x104] + divinc) & 0xFF;
-		divLastUpdate_ += divinc << 8;
-	}
-
-	unsigned long const dec = cc < 0x10000
+	unsigned long const dec = cc < 0x20000
 		? 0
-		: (cc & ~0x7FFFul) - 0x8000;
-	decCycles(divLastUpdate_, dec);
+		: (cc & -0x10000l) - 0x10000;
 	decCycles(lastOamDmaUpdate_, dec);
 	decEventCycles(intevent_serial, dec);
 	decEventCycles(intevent_oam, dec);
@@ -574,13 +568,7 @@ unsigned Memory::nontrivial_ff_read(unsigned const p, unsigned long const cc) {
 		updateSerial(cc);
 		break;
 	case 0x04:
-		{
-			unsigned long divcycles = (cc - divLastUpdate_) >> 8;
-			ioamhram_[0x104] = (ioamhram_[0x104] + divcycles) & 0xFF;
-			divLastUpdate_ += divcycles << 8;
-		}
-
-		break;
+		return (cc - divLastUpdate_) >> 8 & 0xFF;
 	case 0x05:
 		ioamhram_[0x105] = tima_.tima(cc);
 		break;
@@ -705,7 +693,6 @@ void Memory::nontrivial_ff_write(unsigned const p, unsigned data, unsigned long
 		data |= 0x7E - isCgb() * 2;
 		break;
 	case 0x04:
-		ioamhram_[0x104] = 0;
 		divLastUpdate_ = cc;
 		return;
 	case 0x05:

libgambatte/src/tima.cpp

@@ -19,9 +19,13 @@
 #include "tima.h"
 #include "savestate.h"
 
-static unsigned char const timaClock[4] = { 10, 4, 6, 8 };
+using namespace gambatte;
 
-namespace gambatte {
+namespace {
+
+unsigned char const timaClock[] = { 10, 4, 6, 8 };
+
+}
 
 Tima::Tima()
 : lastUpdate_(0)
@@ -47,8 +51,8 @@ void Tima::loadState(SaveState const &state, TimaInterruptRequester timaIrq) {
 	unsigned long nextIrqEventTime = disabled_time;
 	if (tac_ & 4) {
 		nextIrqEventTime = tmatime_ != disabled_time && tmatime_ > state.cpu.cycleCounter
-		                 ? tmatime_
-		                 : lastUpdate_ + ((256u - tima_) << timaClock[tac_ & 3]) + 3;
+			? tmatime_
+			: lastUpdate_ + ((256u - tima_) << timaClock[tac_ & 3]) + 3;
 	}
 
 	timaIrq.setNextIrqEventTime(nextIrqEventTime);
@@ -128,13 +132,10 @@ void Tima::setTac(unsigned const data, unsigned long const cc, TimaInterruptRequ
 		if (tac_ & 0x04) {
 			updateIrq(cc, timaIrq);
 			updateTima(cc);
-
 			// FIXME: this looks naive.
 			// TODO: more TIMA tests.
 			lastUpdate_ -= (1u << (timaClock[tac_ & 3] - 1)) + 3;
-			tmatime_ -= (1u << (timaClock[tac_ & 3] - 1)) + 3;
 			nextIrqEventTime -= (1u << (timaClock[tac_ & 3] - 1)) + 3;
-
 			if (cc >= nextIrqEventTime)
 				timaIrq.flagIrq();
 
@@ -167,5 +168,3 @@ void Tima::doIrqEvent(TimaInterruptRequester timaIrq) {
 	timaIrq.setNextIrqEventTime(timaIrq.nextIrqEventTime()
 	                          + ((256u - tma_) << timaClock[tac_ & 3]));
 }
-
-}