From 1039569b01af29472edff27ad8eacc5883abbfd0 Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Tue, 21 Feb 2017 01:07:11 -0800
Subject: [PATCH] DS: Improve step stability

---
 src/arm/arm.c | 10 ++++++----
 src/ds/ds.c   | 28 +++++++++++++++++-----------
 2 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/src/arm/arm.c b/src/arm/arm.c
index 372da1411..460e4228e 100644
--- a/src/arm/arm.c
+++ b/src/arm/arm.c
@@ -303,10 +303,12 @@ void ARMHalt(struct ARMCore* cpu) {
 	} \
 	\
 	void ARM ## VERSION ## Run(struct ARMCore* cpu) { \
-		if (cpu->executionMode == MODE_THUMB) { \
-			Thumb ## VERSION ## Step(cpu); \
-		} else { \
-			ARM ## VERSION ## Step(cpu); \
+		if (cpu->cycles < cpu->nextEvent) { \
+			if (cpu->executionMode == MODE_THUMB) { \
+				Thumb ## VERSION ## Step(cpu); \
+			} else { \
+				ARM ## VERSION ## Step(cpu); \
+			} \
 		} \
 		if (cpu->cycles >= cpu->nextEvent) { \
 			cpu->irqh.processEvents(cpu); \
diff --git a/src/ds/ds.c b/src/ds/ds.c
index e56e4c858..262c6c1e0 100644
--- a/src/ds/ds.c
+++ b/src/ds/ds.c
@@ -359,7 +359,7 @@ static void DSProcessEvents(struct DSCommon* dscore) {
 		int32_t cycles = cpu->cycles;
 
 		cpu->cycles = 0;
-		cpu->nextEvent = INT_MAX;
+		cpu->nextEvent = 0;
 
 #ifndef NDEBUG
 		if (cycles < 0) {
@@ -371,12 +371,12 @@ static void DSProcessEvents(struct DSCommon* dscore) {
 			nextEvent = mTimingTick(&dscore->timing, nextEvent);
 		} while (ds->cpuBlocked);
 
-		cpu->nextEvent = nextEvent;
-
 		if (ds->earlyExit) {
 			ds->earlyExit = false;
 			break;
 		}
+
+		cpu->nextEvent = nextEvent;
 		if (cpu->halted) {
 			cpu->cycles = nextEvent;
 		}
@@ -397,17 +397,23 @@ void DSRunLoop(struct DS* ds) {
 }
 
 void DS7Step(struct DS* ds) {
-	while (ds->activeCpu == ds->ds9.cpu) {
-		ARMv5RunLoop(ds->ds9.cpu);
-	}
-	ARMv4Run(ds->ds7.cpu);
+	int32_t pc = ds->ds7.cpu->gprs[ARM_PC];
+	do {
+		while (ds->activeCpu == ds->ds9.cpu) {
+			ARMv5RunLoop(ds->ds9.cpu);
+		}
+		ARMv4Run(ds->ds7.cpu);
+	} while (ds->ds7.cpu->halted || ds->ds7.cpu->gprs[ARM_PC] == pc);
 }
 
 void DS9Step(struct DS* ds) {
-	while (ds->activeCpu == ds->ds7.cpu) {
-		ARMv4RunLoop(ds->ds7.cpu);
-	}
-	ARMv5Run(ds->ds9.cpu);
+	int32_t pc = ds->ds9.cpu->gprs[ARM_PC];
+	do {
+		while (ds->activeCpu == ds->ds7.cpu) {
+			ARMv4RunLoop(ds->ds7.cpu);
+		}
+		ARMv5Run(ds->ds9.cpu);
+	} while (ds->ds9.cpu->halted || ds->ds9.cpu->gprs[ARM_PC] == pc);
 }
 
 void DSAttachDebugger(struct DS* ds, struct mDebugger* debugger) {