core: fix indexed loop checks

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

@@ -104,8 +104,10 @@ public class LoopRegionVisitor extends AbstractVisitor implements IRegionVisitor
 			return false;
 		}
 		// can't make loop if argument from increment instruction is assign in loop
-		for (InsnArg iArg : incrInsn.getArguments()) {
-			if (iArg.isRegister() && assignOnlyInLoop(mth, loopRegion, (RegisterArg) iArg)) {
+		List<RegisterArg> args = new LinkedList<RegisterArg>();
+		incrInsn.getRegisterArgs(args);
+		for (RegisterArg iArg : args) {
+			if (assignOnlyInLoop(mth, loopRegion, (RegisterArg) iArg)) {
 				return false;
 			}
 		}

jadx-core/src/test/java/jadx/tests/integration/arith/TestArith3.java

@@ -0,0 +1,43 @@
+package jadx.tests.integration.arith;
+
+import jadx.core.dex.nodes.ClassNode;
+import jadx.tests.api.IntegrationTest;
+
+import org.junit.Test;
+
+import static jadx.tests.api.utils.JadxMatchers.containsOne;
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.not;
+import static org.junit.Assert.assertThat;
+
+public class TestArith3 extends IntegrationTest {
+
+	public static class TestCls {
+		private int vp;
+
+		private void test(byte[] buffer) {
+			int n = ((buffer[3] & 255) + 4) + ((buffer[2] & 15) << 8);
+			while (n + 4 < buffer.length) {
+				int c = buffer[n] & 255;
+				int p = (buffer[n + 2] & 255) + ((buffer[n + 1] & 31) << 8);
+				int len = (buffer[n + 4] & 255) + ((buffer[n + 3] & 15) << 8);
+				switch (c) {
+					case 27:
+						this.vp = p;
+						break;
+				}
+				n += len + 5;
+			}
+		}
+	}
+
+	@Test
+	public void test() {
+		ClassNode cls = getClassNode(TestCls.class);
+		String code = cls.getCode().toString();
+
+		assertThat(code, containsOne("while (n + 4 < buffer.length) {"));
+		assertThat(code, containsOne("n += len + 5;"));
+		assertThat(code, not(containsString("; n += len + 5) {")));
+	}
+}

jadx-core/src/test/java/jadx/tests/integration/variables/TestVariables5.java

@@ -0,0 +1,56 @@
+package jadx.tests.integration.variables;
+
+import jadx.core.dex.nodes.ClassNode;
+import jadx.tests.api.IntegrationTest;
+
+import org.junit.Test;
+
+import static jadx.tests.api.utils.JadxMatchers.containsOne;
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.not;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+public class TestVariables5 extends IntegrationTest {
+
+	public static class TestCls {
+		public String f = "str//ing";
+		private boolean enabled;
+
+		private void testIfInLoop() {
+			int j = 0;
+			for (int i = 0; i < f.length(); i++) {
+				char ch = f.charAt(i);
+				if (ch == '/') {
+					j++;
+					if (j == 2) {
+						setEnabled(true);
+						return;
+					}
+				}
+			}
+			setEnabled(false);
+		}
+
+		private void setEnabled(boolean b) {
+			this.enabled = b;
+		}
+
+		public void check() {
+			setEnabled(false);
+			testIfInLoop();
+			assertTrue(enabled);
+		}
+	}
+
+	@Test
+	public void test() {
+		noDebugInfo();
+		ClassNode cls = getClassNode(TestCls.class);
+		String code = cls.getCode().toString();
+
+		assertThat(code, not(containsString("int i2++;")));
+		assertThat(code, containsOne("int i = 0;"));
+		assertThat(code, containsOne("i++;"));
+	}
+}