core: fix loop detection

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

@@ -244,7 +244,6 @@ public class RegionMaker {
 			}
 		}
 
-		stack.push(loopRegion);
 		curRegion.getSubBlocks().add(loopRegion);
 
 		exitBlocks.remove(condBlock);
@@ -290,9 +289,12 @@ public class RegionMaker {
 			out = (bThen == loopStart ? bElse : bThen);
 
 			loopStart.getAttributes().remove(AttributeType.LOOP);
+
+			stack.push(loopRegion);
 			stack.addExit(loop.getEnd());
 			loopRegion.setBody(makeRegion(loopStart, stack));
 			loopStart.getAttributes().add(loop);
+			stack.pop();
 		} else {
 			Set<BlockNode> loopBlocks = loop.getLoopBlocks();
 			BlockNode loopBody = null;
@@ -308,14 +310,18 @@ public class RegionMaker {
 			out = selectOther(loopBody, condBlock.getSuccessors());
 			AttributesList outAttrs = out.getAttributes();
 			if (outAttrs.contains(AttributeFlag.LOOP_START)
-					&& outAttrs.get(AttributeType.LOOP) != loop) {
+					&& outAttrs.get(AttributeType.LOOP) != loop
+					&& stack.peekRegion() instanceof LoopRegion
+					&& RegionUtils.isRegionContainsBlock(stack.peekRegion(), out)) {
 				// exit to outer loop which already processed
 				out = null;
 			}
+
+			stack.push(loopRegion);
 			stack.addExit(out);
 			loopRegion.setBody(makeRegion(loopBody, stack));
+			stack.pop();
 		}
-		stack.pop();
 		return out;
 	}
 

jadx-core/src/test/java/jadx/tests/internal/loops/TestLoopCondition.java

@@ -1,4 +1,4 @@
-package jadx.tests.internal;
+package jadx.tests.internal.loops;
 
 import jadx.api.InternalJadxTest;
 import jadx.core.dex.nodes.ClassNode;

jadx-core/src/test/java/jadx/tests/internal/loops/TestLoopDetection.java

@@ -0,0 +1,37 @@
+package jadx.tests.internal.loops;
+
+import jadx.api.InternalJadxTest;
+import jadx.core.dex.nodes.ClassNode;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.junit.Assert.assertThat;
+
+public class TestLoopDetection extends InternalJadxTest {
+
+	public static class TestCls {
+
+		private void test(int[] a, int b) {
+			int i = 0;
+			while (i < a.length && i < b) {
+				a[i]++;
+				i++;
+			}
+			while (i < a.length) {
+				a[i]--;
+				i++;
+			}
+		}
+	}
+
+	@Test
+	public void test() {
+		ClassNode cls = getClassNode(TestCls.class);
+		String code = cls.getCode().toString();
+		System.out.println(code);
+
+		assertThat(code, containsString("while (i < a.length && i < b) {"));
+		assertThat(code, containsString("while (i < a.length) {"));
+	}
+}

jadx-core/src/test/java/jadx/tests/internal/loops/TestNestedLoops.java

@@ -0,0 +1,51 @@
+package jadx.tests.internal.loops;
+
+import jadx.api.InternalJadxTest;
+import jadx.core.dex.nodes.ClassNode;
+
+import java.util.Iterator;
+import java.util.List;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.junit.Assert.assertThat;
+
+public class TestNestedLoops extends InternalJadxTest {
+
+	public static class TestCls {
+
+		private void test(List<String> l1, List<String> l2) {
+			Iterator<String> it1 = l1.iterator();
+			while (it1.hasNext()) {
+				String s1 = it1.next();
+				Iterator<String> it2 = l2.iterator();
+				while (it2.hasNext()) {
+					String s2 = it2.next();
+					if (s1.equals(s2)) {
+						if (s1.length() == 5) {
+							l2.add(s1);
+						} else {
+							l1.remove(s2);
+						}
+					}
+				}
+			}
+			if (l2.size() > 0) {
+				l1.clear();
+			}
+		}
+	}
+
+	@Test
+	public void test() {
+		ClassNode cls = getClassNode(TestCls.class);
+		String code = cls.getCode().toString();
+		System.out.println(code);
+
+		assertThat(code, containsString("while (it1.hasNext()) {"));
+		assertThat(code, containsString("while (it2.hasNext()) {"));
+		assertThat(code, containsString("if (s1.equals(s2)) {"));
+		assertThat(code, containsString("l2.add(s1);"));
+	}
+}

jadx-samples/src/main/java/jadx/samples/TestCF3.java

@@ -87,6 +87,23 @@ public class TestCF3 extends AbstractTest {
 		return j > 10;
 	}
 
+	private int testLoops(int[] a, int b) {
+		int i = 0;
+		while (i < a.length && i < b) {
+			a[i]++;
+			i++;
+		}
+		while (i < a.length) {
+			a[i]--;
+			i++;
+		}
+		int sum = 0;
+		for (int e : a) {
+			sum += e;
+		}
+		return sum;
+	}
+
 	public static boolean testLabeledBreakContinue() {
 		String searchMe = "Look for a substring in me";
 		String substring = "sub";
@@ -227,6 +244,8 @@ public class TestCF3 extends AbstractTest {
 		assertEquals(testComplexIfInLoop3(6), 6);
 		assertEquals(testComplexIfInLoop3(8), 24);
 
+		assertEquals(testLoops(new int[]{1, 2, 3, 4, 5, 6}, 2), 19);
+
 		assertTrue(testInline() > 20);
 		assertTrue(testInline2());
 		return true;