fix: improve condition branch checks in loops (#2274)

jadx-core/src/main/java/jadx/core/dex/visitors/regions/IfMakerHelper.java

@@ -120,8 +120,12 @@ public class IfMakerHelper {
 		List<BlockNode> preds = block.getPredecessors();
 		List<BlockNode> ifBlocks = info.getMergedBlocks();
 		for (BlockNode pred : preds) {
+			if (pred.contains(AFlag.LOOP_END)) {
+				// ignore loop back edge
+				continue;
+			}
 			BlockNode top = BlockUtils.skipSyntheticPredecessor(pred);
-			if (!ifBlocks.contains(top) && !top.contains(AFlag.LOOP_END)) {
+			if (!ifBlocks.contains(top)) {
 				return false;
 			}
 		}

jadx-core/src/main/java/jadx/core/dex/visitors/regions/RegionMaker.java

@@ -182,7 +182,7 @@ public class RegionMaker {
 		Set<BlockNode> exitBlocksSet = loop.getExitNodes();
 
 		// set exit blocks scan order priority
-		// this can help if loop have several exits (after using 'break' or 'return' in loop)
+		// this can help if loop has several exits (after using 'break' or 'return' in loop)
 		List<BlockNode> exitBlocks = new ArrayList<>(exitBlocksSet.size());
 		BlockNode nextStart = getNextBlock(loopStart);
 		if (nextStart != null && exitBlocksSet.remove(nextStart)) {
@@ -299,10 +299,7 @@ public class RegionMaker {
 				// skip nested loop condition
 				continue;
 			}
-			BlockNode loopEnd = loop.getEnd();
-			boolean exitAtLoopEnd = block == loopEnd
-					|| (loopEnd.getInstructions().isEmpty() && ListUtils.isSingleElement(loopEnd.getPredecessors(), block));
-
+			boolean exitAtLoopEnd = isExitAtLoopEnd(block, loop);
 			LoopRegion loopRegion = new LoopRegion(curRegion, loop, block, exitAtLoopEnd);
 			boolean found;
 			if (block == loop.getStart() || exitAtLoopEnd
@@ -345,6 +342,18 @@ public class RegionMaker {
 		return null;
 	}
 
+	private static boolean isExitAtLoopEnd(BlockNode exit, LoopInfo loop) {
+		BlockNode loopEnd = loop.getEnd();
+		if (exit == loopEnd) {
+			return true;
+		}
+		BlockNode loopStart = loop.getStart();
+		if (loopStart.getInstructions().isEmpty() && ListUtils.isSingleElement(loopStart.getSuccessors(), exit)) {
+			return false;
+		}
+		return loopEnd.getInstructions().isEmpty() && ListUtils.isSingleElement(loopEnd.getPredecessors(), exit);
+	}
+
 	private boolean checkLoopExits(LoopInfo loop, BlockNode mainExitBlock) {
 		List<Edge> exitEdges = loop.getExitEdges();
 		if (exitEdges.size() < 2) {

jadx-core/src/test/java/jadx/tests/integration/loops/TestLoopRestore2.java

@@ -0,0 +1,18 @@
+package jadx.tests.integration.loops;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.RaungTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+public class TestLoopRestore2 extends RaungTest {
+
+	@Test
+	public void test() {
+		disableCompilation(); // unreachable statement
+		assertThat(getClassNodeFromRaung())
+				.code()
+				.containsOne("while (1 == 0) {");
+	}
+}

jadx-core/src/test/raung/loops/TestLoopRestore2.raung

@@ -0,0 +1,20 @@
+.version 45.3  # Java 1.1
+.class public super loops/TestLoopRestore2
+
+.method public test([I[I)V
+    .max stack 5
+    .max locals 6
+
+    iconst_0
+    istore 3
+    sipush 0
+    ifeq :L0
+    goto :L1
+  :L1
+    sipush 1
+    ifeq :L1
+    goto :L0
+  :L0
+    iinc 3 1
+    return
+.end method